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Tracheomalacia is an airway condition in which the trachea excessively collapses during breathing. Neonates diagnosed with tracheomalacia require more energy to breathe, and the effect of tracheomalacia can be quantified by assessing flow-resistive work of breathing (WOB) in the trachea using computational fluid dynamics (CFD) modeling of the airway. However, CFD simulations are computationally expensive; the ability to instead predict WOB based on more straightforward measures would provide a clinically useful estimate of tracheal disease severity. The objective of this study is to quantify the WOB in the trachea using CFD and identify simple airway and/or clinical parameters that directly relate to WOB. This study included 30 neonatal intensive care unit subjects (15 with tracheomalacia and 15 without tracheomalacia). All subjects were imaged using ultrashort echo time (UTE) MRI. CFD simulations were performed using patient-specific data obtained from MRI (airway anatomy, dynamic motion, and airflow rates) to calculate the WOB in the trachea. Several airway and clinical measurements were obtained and compared with the tracheal resistive WOB. The maximum percent change in the tracheal cross-sectional area (ρ = 0.560

What is the central question of this study? Increased work of breathing and the accumulation of metabolites have neural and cardiovascular consequences through a respiratory muscle-induced metaboreflex. The influence of the respiratory muscle-induced metaboreflex on splanchnic blood flow in humans remains unknown. What is the main finding and its importance? Coeliac artery blood flow decreased gradually during inspiratory resistive breathing, accompanied by a progressive increase in arterial blood pressure. It is possible that the respiratory muscle-induced metaboreflex contributes to splanchnic blood flow regulation.The purpose of this study was to clarify the effect of increasing inspiratory muscle work on coeliac artery blood flow. Eleven healthy young males completed the study. The subjects performed voluntary hyperventilation with or without inspiratory resistance (loading or non-loading trial; tidal volume of 40% of vital capacity and breathing frequency of 20 breaths/min). The loading trial was conducted with inspiratory resistance (40% of maximal inspiratory pressure) and was terminated when the subjects could no longer maintain the target tidal volume or breathing frequency. The non-loading trial was conducted without inspiratory resistance and was of the same duration as the loading trial. Arterial blood pressure was recorded using finger photoplethysmography, and coeliac artery blood flow was measured using Doppler ultrasound. Mean arterial blood pressure increased gradually during the loading trial (mean ± SD; from 89.0 ± 10.8 to 103.9 ± 17.3 mmHg) but not in the non-loading trial (from 88.7 ± 5.9 to 90.4 ± 9.9 mmHg). Coeliac artery blood flow and coeliac vascular conductance decreased gradually during the loading trial (from 601.2 ± 155.7 to 482.6 ± 149.5 mL/min and from 6.9 ± 2.2 to 4.8 ± 1.7 mL/min/mmHg, respectively) but were unchanged in the non-loading trial (from 630.7 ± 157.1 to 635.6 ± 195.7 mL/min and from 7.1 ± 1.8 to 7.2 ± 2.9 mL/min/mmHg, respectively). These results show that increasing inspiratory muscle work affects splanchnic blood flow regulation, and we suggest that this might be mediated by the inspiratory muscle-induced metaboreflex.

Congenital diaphragmatic hernia (CDH) results in varying degrees of pulmonary hypoplasia. Volume targeted ventilation (VTV) is a lung protective strategy but the optimal target tidal volume in CDH infants has not previously been studied. The aim of this study was to test the hypothesis that low targeted volumes would be better in CDH infants as determined by measuring the work of breathing (WOB) in CDH infants, at three different targeted tidal volumes. A randomised cross-over study was undertaken. Infants were eligible for inclusion in the study after surgical repair of their diaphragmatic defect. Targeted tidal volumes of 4, 5, and 6 ml/kg were each delivered in random order for 20-min periods with 20-min periods of baseline ventilation between. WOB was assessed and measured by using the pressure–time product of the diaphragm (PTPdi). Nine infants with a median gestational age at birth of 38 + 4 (range 36 + 4–40 + 6) weeks and median birth weight 3202 (range 2855–3800) g were studied. The PTPdi was higher at 4 ml/kg than at both 5, p = 0.008, and 6 ml/kg, p = 0.012.Conclusion: VTV of 4 ml/kg demonstrated an increased PTPdi compared to other VTV levels studied and should be avoided in post-surgical CDH infants. What is Known:• Lung injury secondary to mechanical ventilation increases the mortality and morbidity of infants with CDH.• Volume targeted ventilation (VTV) reduces ‘volutrauma’ and ventilator-induced lung injury in other neonatal intensive care populations. What is New:• A randomised cross-over trial was carried out investigating the response to different VTV levels in infants with CDH.• Despite pulmonary hypoplasia being a common finding in CDH, a VTV of 5ml/kg significantly reduced the work of breathing in infants with CDH compared to a lower VTV level.

This study examined the impact of aging on the elastic and resistive components of the work of breathing (W(b)) during locomotor exercise at a given 1) ventilatory rate, 2) metabolic rate, and 3) operating lung volume. Eight healthy younger (25 ± 4 yr) and 8 older (72 ± 6 yr) participants performed incremental bicycle exercise, from which retrospective analyses identified similar ventilatory rates (approximately 40, 70, and 100 L·min(−1)), similar metabolic rates (V̇o(2): approximately 1.2, 1.6, and 1.9 L·min(−1)), and similar lung volumes [inspiratory and expiratory reserve volumes (IRV/ERV: approximately 25/34%, 16/33%, and 13-34% of vital capacity]. W(b) at each level was quantified by integrating the averaged esophageal pressure-volume loop, which was then partitioned into elastic and resistive components of inspiratory and expiratory work using the modified Campbell diagram. IRV was smaller in the older participants during exercise at ventilations of 70 and 100 L·min(−1) and during exercise at the three metabolic rates (P < 0.05). Mainly because of a greater inspiratory elastic and resistive W(b) in the older group (P < 0.05), total W(b) was augmented by 40%–50% during exercise at matched ventilatory and matched metabolic rates. When examined during exercise evoking similar lung volumes, total W(b) was not different between the groups (P = 0.86). Taken together, although aging exaggerates total W(b) during locomotor exercise at a given ventilatory or a given metabolic rate, this difference is abolished during exercise at a given operating lung volume. These findings highlight the significance of operating lung volume in determining the age-related difference in W(b) during locomotor exercise. NEW & NOTEWORTHY This study evaluated the impact of aging on the work of breathing (W(b)) during locomotor exercise evoking similar ventilatory rates, metabolic rates, and operating lung volumes in young and older individuals. Mainly because of a greater inspiratory elastic and resistive W(b) in older participants, total W(b) was higher during exercise at any given ventilatory and metabolic rate with aging. However, this age-related difference was abolished during exercise evoking similar operating lung volumes in both age groups. These findings highlight the significance of lung volumes in determining the age-related difference in total W(b).

For infants with the most severe forms of chronic lung disease, regardless of etiology, chronic mechanical ventilation can provide stability, reduce acute respiratory events, and alleviate increased work of breathing. This approach prioritizes the baby's growth and development during early life. Once breathing comfortably, these infants can tolerate developmental therapies with the goal of achieving the best neurocognitive outcomes possible.

Introduction Respiratory muscle oxygen consumption increases with the work of breathing. We hypothesized that reducing excessive respiratory muscle activity during exercise may improve exercise tolerance. Method We developed a device to provide real-time visual feedback of thoracoabdominal movement and used it to examine the influence of visual feedback of thoracoabdominal movement during diaphragmatic breathing on oxygen consumption in eight healthy men. While sitting on a wheelchair with the backrest reclined at 60 degrees, oxygen consumption per body weight (VO 2 /BW), minute ventilation (VE), tidal volume (VT), and breathing frequency (fR) were measured, breath-by-breath, using an expired-gas analyzer. The breathing pattern was analyzed by inductance plethysmography, with transducer bands over the chest and abdomen recording thoracoabdominal movements. Results There was no significant difference in RatioTH-ABD and the ventilatory parameters between diaphragmatic breathing and diaphragmatic breathing with visual feedback. The average VO 2 /BW during diaphragmatic breathing with visual feedback was 0.6 ml/kg lower than that during diaphragmatic breathing without visual feedback (p= Conclusion When visual feedback was used during diaphragmatic breathing, the RatioTH-ABD remained essentially unchanged, but VO2/BW decreased significantly. This suggests that visual feedback of thoracoabdominal movement during diaphragmatic breathing may reduce respiratory muscle oxygen consumption.

Richard Kraemer,1,2 Hans-Jürgen Smith,3 Fabian Gardin,4 Jürg Barandun,4 Stefan Minder,3 Lukas Kern,5 Martin H Brutsche5 1Center of Pulmonary Medicine, Hirslanden Private Hospital Group, Salem-Hospital, Bern, Switzerland; 2Department of Biomedical Research, University of Bern, Bern, Switzerland; 3Medical Development, Research in Respiratory Diagnostics, Berlin, Germany; 4Center of Pulmonary Medicine, Hirslanden Private Hospital Group, Clinic Hirslanden, Zürich, Switzerland; 5Clinic of Pneumology, Cantonal Hospital St. Gallen, St. Gallen, SwitzerlandCorrespondence: Richard KraemerCenter of Pulmonary Medicine, Hirslanden Private Hospital Group, Schänzlistrasse 39, Berne, CH-3013, SwitzerlandTel +41 79 300 26 53Email richard.kraemer@hirslanden.chBackground: Airflow reversibility criteria in COPD are still debated – especially in situations of co-existing COPD and asthma. Bronchodilator response (BDR) is usually assessed by spirometric parameters. Changes assessed by plethysmographic parameters such as the effective, specific airway conductance (sGeff), and changes in end-expiratory resting level at functional residual capacity (FRCpleth) are rarely appreciated. We aimed to assess BDR by spirometric and concomitantly measured plethysmographic parameters. Moreover, BDR on the specific aerodynamic work of breathing (sWOB) was evaluated.Methods: From databases of 3 pulmonary centers, BDR to 200 g salbutamol was retrospectively evaluated by spirometric (∆FEV1 and ∆FEF25– 75), and plethysmographic (∆sGeff, ∆FRCpleth, and ∆sWOB) parameters in a total of 843 patients diagnosed as COPD (478 = 57%), asthma-COPD-overlap (ACO) (139 = 17%), or asthma (226 = 27%), encountering 1686 BDR-measurement-sets (COPD n = 958; ACO n = 276; asthma n = 452).Results: Evaluating z-score improvement taking into consideration the whole pre-test z-score range, highest BDR was achieved by combining ∆sGeff and ∆FRC detecting BDR in 62.2% (asthma: 71.4%; ACO: 56.7%; COPD: 59.8%), by ∆sGeff in 53.4% (asthma: 69.1%; ACO: 51.6%; COPD: 47.4%), whereas ∆FEV1 only distinguished in 10.6% (asthma: 21.8%; ACO: 18.6%; COPD: 4.2%). Remarkably, ∆sWOB detected BDR in 49.4% (asthma: 76.2%; ACO: 47.8%; COPD: 46.9%).Conclusion: BDR largely depends on the pre-test functional severity and, therefore, should be evaluated in relation to the pre-test conditions expressed as ∆z-scores, considering changes in airway dynamics, changes in static lung volumes and changes in small airway function. Plethysmographic parameters demonstrated BDR at a significant higher rate than spirometric parameters.Keywords: COPD, bronchodilator response, COPD and coexisting asthma, ACO, pulmonary hyperinflation, small airways dysfunction, aerodynamic work of breathing

A full-term male newborn presents with respiratory distress soon after delivery. ### Prenatal and Birth Histories ### Presentation (Newborn day) Soon after delivery, the neonate developed shallow breathing and increased work of breathing, for which high-flow nasal cannula was initiated at 3 L/min with fraction of inspired oxygen (Fio2) of 0.21. Empiric treatment with ampicillin and gentamicin was started for clinical pneumonia. ### Progression ### Vital Signs ### Physical Examination (Newborn Day)

Pressure support ventilation (PSV) should be titrated considering the pressure developed by the respiratory muscles (Pmusc) to prevent under- and over-assistance. The esophageal pressure (Pes) is the clinical gold standard for Pmusc assessment, but its use is limited by alleged invasiveness and complexity. The least square fitting method and the end-inspiratory occlusion method have been proposed as non-invasive alternatives for Pmusc assessment. The aims of this study were: (1) to compare the accuracy of Pmusc estimation using the end-inspiration occlusion (Pmusc,index) and the least square fitting (Pmusc,lsf) against the reference method based on Pes; (2) to test the accuracy of Pmusc,lsf and of Pmusc,index to detect overassistance, defined as Pmusc ≤ 1 cmH2O. We studied 18 patients at three different PSV levels. At each PSV level, Pmusc, Pmusc,lsf, Pmusc,index were calculated on the same breaths. Differences among Pmusc, Pmusc,lsf, Pmusc,index were analyzed with linear mixed effects models. Bias and agreement were assessed by Bland–Altman analysis for repeated measures. The ability of Pmusc,lsf and Pmusc,index to detect overassistance was assessed by the area under the receiver operating characteristics curve. Positive and negative predictive values were calculated using cutoff values that maximized the sum of sensitivity and specificity. At each PSV level, Pmusc,lsf was not different from Pmusc (p = 0.96), whereas Pmusc,index was significantly lower than Pmusc. The bias between Pmusc and Pmusc,lsf was zero, whereas Pmusc,index systematically underestimated Pmusc of 6 cmH2O. The limits of agreement between Pmusc and Pmusc,lsf and between Pmusc and Pmusc,index were ± 12 cmH2O across bias. Both Pmusc,lsf ≤ 4 cmH2O and Pmusc,index ≤ 1 cmH2O had excellent negative predictive value [0.98 (95% CI 0.94–1) and 0.96 (95% CI 0.91–0.99), respectively)] to identify over-assistance. The inspiratory effort during PSV could not be accurately estimated by the least square fitting or end-inspiratory occlusion method because the limits of agreement were far above the signal size. These non-invasive approaches, however, could be used to screen patients at risk for absent or minimal respiratory muscles activation to prevent the ventilator-induced diaphragmatic dysfunction.

INTRODUCTION In mechanically ventilated patients, driving pressure (ΔP) represents the dynamic stress applied to the respiratory system and is related to ICU mortality. An evolution of the Adaptive Support Ventilation algorithm (ASV® 1.1) minimizes inspiratory pressure in addition to minimizing the work of breathing. We hypothesized that ASV 1.1 would result in lower ΔP than the ΔP measured in APV-CMV (controlled mandatory ventilation with adaptive pressure ventilation) mode with physician-tailored settings. The aim of this randomized crossover trial was therefore to compare ΔP in ASV 1.1 with ΔP in physician-tailored APV-CMV mode. METHODS Pediatric patients admitted to the PICU with heterogeneous-lung disease were enrolled if they were ventilated invasively with no detectable respiratory effort, hemodynamic instability, or significant airway leak around the endotracheal tube. We compared two 60-min periods of ventilation in APV-CMV and ASV 1.1, which were determined by randomization and separated by 30-min washout periods. Settings were adjusted to reach the same minute ventilation in both modes. ΔP was calculated as the difference between plateau pressure and total PEEP measured using end-inspiratory and end-expiratory occlusions, respectively. RESULTS There were 26 patients enrolled with a median age of 16 (9-25 [IQR]) months. The median ΔP for these patients was 10.4 (8.5-12.1 [IQR]) and 12.4 (10.5-15.3 [IQR]) cmH2O in the ASV 1.1 and APV-CMV periods, respectively (p

ObjectiveDiagnosis of obstructive sleep apnoea (OSA) is made on overnight polysomnography (PSG). Given the widespread availability of smartphone video technology, we aimed to develop and test a standardised scoring system for smartphone videos and compare these scores to PSG results.MethodsChildren aged 1–16 years undergoing PSG for suspected OSA were included. Parents were asked to take 1–2 min videos of the breathing they were concerned about. Videos were scored using a newly developed and tested tool on five components: inspiratory obstructive noises (1–4), presence of obstructive events (0–1), increased work of breathing (0–1), mouth breathing (0–1) and neck extension (0–1). Video scores and the Obstructive Apnoea Hypopnoea Index (OAHI) were compared using Spearman correlation. Sensitivity, specificity, positive predictive value and negative predictive value were calculated for different cut-off scores to achieve the best results.ResultsVideos from 43 children (28 men (65.1%), median age 5.7 years (range 2.6–14.0 years), median OAHI 3.8/hour (range 0–82 events/hour) were included. Nine children (20.9%) had a video score of 5 events/hour) .ConclusionWe have developed and validated a simple clinical tool (the Monash Obstructive Sleep Apnoea Video Score) to quantify abnormalities in breathing seen on short video recordings made on a smartphone. A low score rules out moderate–severe OSA and may be valuable in the triage of children with symptoms of OSA.

Sleep disordered breathing (SDB) is common in adults with chronic heart failure (CHF), but its prevalence in children remains unclear. Continuous positive airway pressure (CPAP) is the treatment of SDB but deleterious hemodynamic effects have been reported.We prospectively analyzed SDB in children with CHF and the effect of CPAP on work of breathing (WOB) and cardiac index (CI). Children aged 6 months to 18 years old with CHF due to: 1) dilated cardiomyopathy (DM) with an ejection fraction 45%, 2) functional single ventricle (SV) or 3) aortic or mitral valve disease awaiting surgery (VD) were eligible for the study. A polysomnography (PSG), measurement of WOB and CI during spontaneous breathing (SB) and CPAP (6, 8 and 10 cmHThirty patients with mean age of 6.4 ± 5 years were included (16 DM 16, 10 SV, 4 LV). Twenty (73%) patients had a normal sleep efficiency. Median apnoeas hypopnea index (IAH) was within normal range at 1.6 events/h (0, 14) events/hour. Only one patient had central sleep apnoeas, none had Cheyne-Stokes respiration, and 3 patients had an obstructive AHI between 5 and 10 events/hour. Optimal CPAP level decreased WOB (p = 0.05) and respiratory rate (p = 0.01).Severe SDB was uncommon in children with CHF. However, CPAP may be beneficial by decreasing WOB and respiratory rate without deleterious effects on CI.

Background: While increased face mask use has helped reduce COVID-19 transmission, there have been concerns about its influence on thermoregulation during exercise in the heat, but consistent, evidence-based recommendations are lacking. Hypothesis: No physiological differences would exist during low-to-moderate exercise intensity in the heat between trials with and without face masks, but perceptual sensations could vary. Study Design: Crossover study. Level of Evidence: Level 2. Methods: Twelve physically active participants (8 male, 4 female; age = 24 ± 3 years) completed 4 face mask trials and 1 control trial (no mask) in the heat (32.3°C ± 0.04°C; 54.4% ± 0.7% relative humidity [RH]). The protocol was 60 minutes of walking and jogging between 35% and 60% of relative VO2max. Rectal temperature (Trec), heart rate (HR), temperature and humidity inside and outside of the face mask (Tmicro_in, Tmicro_out, RHmicro_in, RHmicro_out) and perceptual variables (rating of perceived exertion (RPE), thermal sensation, thirst sensation, fatigue level, and overall breathing discomfort) were monitored throughout all trials. Results: Mean Trec and HR increased at 30- and 60-minute time points compared with 0-minute time points, but no difference existed between face mask trials and control trials ( P > 0.05). Mean Tmicro_in, RHmicro_in, and humidity difference inside and outside of the face mask (ΔRHmicro) were significantly different between face mask trials ( P < 0.05). There was no significant difference in perceptual variables between face mask trials and control trials ( P > 0.05), except overall breathing discomfort ( P < 0.01). Higher RHmicro_in, RPE, and thermal sensation significantly predicted higher overall breathing discomfort ( r2 = 0.418; P < 0.01). Conclusion: Face mask use during 60 minutes of low-to-moderate exercise intensity in the heat did not significantly affect Trec or HR. Although face mask use may affect overall breathing discomfort due to the changes in the face mask microenvironment, face mask use itself did not cause an increase in whole body thermal stress. Clinical Relevance: Face mask use is feasible and safe during exercise in the heat, at low-to-moderate exercise intensities, for physically active, healthy individuals.

Background The physiological benefit of parent-infant skin-to-skin contact (SSC) is uncertain for preterm infants with ventilatory support. We aimed to investigate whether SSC stabilizes the respiration compared to incubator care in mechanically ventilated preterm infants. Methods The prospective observational study was performed in Turku University Hospital, Finland. Preterm infants were eligible if they were born before 36 weeks gestation and received respiratory support with either invasive or non-invasive neurally adjusted ventilatory assist (NAVA). SSC was applied as soon as possible after birth. Respiratory variables were collected from the ventilator log data, and SSC episodes were compared with matched control periods during incubator care. Results A total of 167 episodes of SSC were recorded from 17 preterm infants: 138 episodes during invasive NAVA and 29 episodes during non-invasive NAVA. During invasive NAVA, peak electrical activity of the diaphragm (Edi), minimum Edi, respiratory rate, time on backup ventilation, peak inspiratory pressure, and mean airway pressure were significantly lower in SSC than in incubator care. During non-invasive NAVA, peak Edi, minimum Edi, time on backup ventilation, and peak inspiratory pressure were significantly lower in SSC than in incubator care. Conclusions SSC stabilized and improved the respiratory physiology in mechanically ventilated preterm infants. Impact Skin-to-skin contact reduced work of breathing compared to incubator care in mechanically ventilated preterm infants. Skin-to-skin contact reduced the need for backup ventilation during neurally adjusted ventilatory assist in preterm infants. Skin-to-skin contact among ventilated preterm infants was not only safe but also stabilized and improved their respiratory physiology.

Background Ventilator liberation is one of the most challenging aspects in patients with respiratory failure. Most patients are weaned through a transition from full to partial respiratory support, whereas some advocate using a continuous spontaneous ventilation (CSV). However, there is little scientific evidence supporting the practice of pediatric ventilator liberation, including the timing of onset of and the approach to weaning mode. We sought to explore differences in patient effort between a pressure controlled continuous mode of ventilation (PC-CMV) [in this cohort PC assist/control (PC-A/C)] with a reduced ventilator rate and CSV, and to study changes in patient effort with decreasing PS. Methods In this prospective physiology cross-over study, we randomized children Campbell), and by pressure–rate-product (PRP) and pressure–time-product (PTP). Respiratory inductance plethysmography (RIP) was used to calculate the phase angle. Measurements were obtained at baseline, during PC-A/C and CPAP + PS, and during decreasing set PS (maximum -6 cmH2O). Results Thirty-six subjects with a median age of 4.4 (IQR 1.5–11.9) months and median ventilation time of 4.9 (IQR 3.4–7.0) days were included. Nearly all patients (94.4%) were admitted with primary respiratory failure. WOBCampbell during baseline [0.67 (IQR 0.38–1.07) Joules/L] did not differ between CSV [0.49 (IQR 0.17–0.83) Joules/L] or PC-A/C [0.47 (IQR 0.17–1.15) Joules/L]. Neither PRP, PTP, ∆Pes nor phase angle was different between the two ventilator modes. Reducing pressure support resulted in a statistically significant increase in patient effort, albeit that these differences were clinically negligible. Conclusions Patient effort during pediatric ventilation liberation was not increased when patients were in a CSV mode of ventilation compared to a ventilator mode with a ventilator back-up rate. Reducing the level of PS did not lead to clinically relevant increases in patient effort. These data may aid in a better approach to pediatric ventilation liberation. Trial registration clinicaltrials.gov NCT05254691. Registered 24 February 2022

We demonstrated that optoelectronic plethysmography (OEP) is a reliable tool to determine ventilatory volume changes during cycling and running, without restricting natural upper arm movements. Second, using OEP volumes coupled with pressure-derived measures, we calculated the work done by the rib cage and abdomen, respectively, during exercise. Collectively, our findings indicate that pulmonary mechanics can be accurately quantified using OEP, and abdominal work performed during ventilation contributes substantially to the overall work of the respiratory musculature.

The precise coordination of respiratory muscles during exercise minimizes work of breathing and avoids exercise intolerance. Fibrotic interstitial lung disease (f-ILD) patients are exercise-intolerant. We assessed whether respiratory muscle incoordination and thoracoabdominal asynchrony (TAA) occur in f-ILD during exercise, and their relationship with pulmonary function and exercise performance.We compared breathing pattern, respiratory mechanics, TAA and respiratory muscle recruitment in 31 f-ILD patients and 31 healthy subjects at rest and during incremental cycle exercise. TAA was defined as phase angle (PhAng)20°.During exercise, when compared with controls, f-ILD patients presented increased and early recruitment of inspiratory rib cage muscle (p 0.05), and an increase in PhAng, indicating TAA. TAA was more frequent in f-ILD patients than in controls, both at 50% of the maximum workload (42.3% vs. 10.7%, p = 0.01) and at the peak (53.8% vs. 23%, p = 0.02). Compared with f-ILD patients without TAA, f-ILD patients with TAA had lower lung volumes (forced vital capacity, p 0.01), greater dyspnoea (Medical Research Council 2 in 64.3%, p = 0.02), worse exercise performance (lower maximal work rate % predicted, p = 0.03; lower tidal volume, p = 0.03; greater desaturation and dyspnoea, p 0.01) and presented higher oesophageal inspiratory pressures with lower gastric inspiratory pressures and higher recruitment of scalene (p 0.05).Exercise induces TAA and higher recruitment of inspiratory accessory muscle in ILD patients. TAA during exercise occurred in more severely restricted ILD patients and was associated with exertional dyspnoea, desaturation and limited exercise performance.

To minimize transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus responsible for coronavirus disease (COVID-19), the U.S. Centers for Disease Control and Prevention and the World Health Organization recommend wearing face masks in public. Some have expressed concern that these may affect the cardiopulmonary system by increasing the work of breathing, altering pulmonary gas exchange and increasing dyspnea, especially during physical activity. These concerns have been derived largely from studies evaluating devices intentionally designed to severely affect respiratory mechanics and gas exchange. We review the literature on the effects of various face masks and respirators on the respiratory system during physical activity using data from several models: cloth face coverings and surgical masks, N95 respirators, industrial respirators, and applied highly resistive or high–dead space respiratory loads. Overall, the available data suggest that although dyspnea may be increased and alter perceived effort with activity, the effects on work of breathing, blood gases, and other physiological parameters imposed by face masks during physical activity are small, often too small to be detected, even during very heavy exercise. There is no current evidence to support sex-based or age-based differences in the physiological responses to exercise while wearing a face mask. Although the available data suggest that negative effects of using cloth or surgical face masks during physical activity in healthy individuals are negligible and unlikely to impact exercise tolerance significantly, for some individuals with severe cardiopulmonary disease, any added resistance and/or minor changes in blood gases may evoke considerably more dyspnea and, thus, affect exercise capacity.

A 65-year-old man was admitted to the ICU for septic shock due to pneumonia. He remained on mechanical ventilation for 96 hours. His shock resolved, and he no longer required IV vasopressor therapy. His vital signs included a BP of 105/70 mm Hg, heart rate 85 beats/min, respiratory rate 22 breaths/min, and oxygen saturation 95%. His ventilator settings were volume control/assist control with a positive end-expiratory pressure of 5 and an Fio2 set to 40%. On these setting his blood gas showed an Pao2 of 75 mm Hg. He was following simple commands and had minimal tracheobronchial secretions. He was placed on a spontaneous breathing trial with a spontaneous mode of ventilation and pressure support of 7/5. He remained hemodynamically stable and showed no distress through the procedure, so he was extubated to 6 L oxygen by nasal cannula. Eighteen hours later, the patient was found to have increased work of breathing, with use of accessory respiratory muscles. A blood gas showed an elevated level of CO2, so the patient was reintubated. After intubation, the patient again appeared comfortable on minimal ventilator settings. Chest radiography before reintubation showed no new parenchymal process, but an elevated left diaphragm. After a thorough workup, it was determined that diaphragmatic weakness was the most likely reason for respiratory failure. The team questioned whether there was a way to have detected this before extubation.

Objective Monitoring work of breathing (WOB) is important to assess the pulmonary condition and adjust respiratory support in preterm infants. Conventional WOB measurement (esophageal pressure, tidal volume) is invasive and we hypothesized that monitoring diaphragm activity could be a noninvasive alternative to estimate WOB. The objective was to determine the correlation between conventional WOB measures and diaphragm activity, in preterm infants. Methods WOB and diaphragm activity, measured with transcutaneous electromyography (dEMG), were simultaneously recorded at different nasal continuous positive airway pressure (nCPAP) levels. During a 30-s recording at each nCPAP level, dEMG parameters, inspiratory WOB (WOBi ), and pressure time product (PTPin ) were calculated per breath. The correlation coefficient between WOB- and dEMG-measures was calculated using single breaths and after aggregating all breaths into deciles of incremental WOBi . Results Fifteen preterm infants were included (median gestational age, 28 weeks). Single-breath analysis showed a poor median correlation of 0.27 (interquartile range [IQR], 0.03 to 0.33) and 0.08 (IQR, -0.03 to 0.28), respectively, for WOBi and PTPin with peak diaphragmatic activity (dEMGpeak ). A modest median correlation coefficient of 0.65 (IQR, 0.13 to 0.79) and 0.43 (IQR, -0.33 to 0.69) was found for, respectively, WOBi and PTPin with dEMGpeak in the aggregated analysis. Conclusion Diaphragm activity showed a modest correlation with WOBi and PTPin in an aggregated analysis. This finding warrants further studies in infants with more significant lung disease.

ObjectivePatient’s work of breathing may vary between different neonatal nasal continuous positive airway pressure (NCPAP) devices. Therefore, we aimed to compare the inspiratory effort of three variable-flow NCPAP delivery systems used in preterm infants.DesignCross-over study.Patients/settingFrom June 2015 to August 2016, 20 preterm infants weighing ≤2500 g requiring NCPAP for mild respiratory distress syndrome were enrolled.InterventionsEach patient was successively supported by three randomly assigned variable-flow NCPAP systems (MedinCNO, Infant Flow and Servo-i) for 20 min while maintaining the same continuous positive airway pressure level as the patient was on before the study period.Main outcome measuresPatients’ inspiratory effort was estimated by calculating the sum of the difference between maximal inspiratory and baseline electrical activity of the diaphragm (∆EAdi) for 30 consecutive breaths, and after normalising this obtained value for the timing of the 30 breaths.ResultsPhysiological parameters (oxygen saturation measured by pulse oximetry, respiratory rate, heart beat, transcutaneous partial pressure CO2) and oxygen requirements remained identical between the three NCPAP systems. Although a wide variability in inspiratory effort could be observed, there were no statistically significant differences between the three systems for the sum of ∆EAdi for 30 breaths: CNO, 262 (±119) µV; IF, 352 (±262) µV; and SERVO-i, 286 (±126) µV, and the ∆EAdi reported on the timing of 30 breaths (sum ∆EAdi/s): CNO, 6.1 (±2.3) µV/s; IF, 7.9 (±4.9) µV/s; SERVO-i, 7.6 (±3.6) µV/s.ConclusionIn a neonatal population of preterm infants, inspiratory effort is comparable between the three tested modern variable-flow NCPAP devices.

Providing optimal care to patients with acute respiratory illness while preventing hospital transmission of COVID-19 is of paramount importance during the pandemic; the challenge lies in achieving both goals simultaneously. Controversy exists regarding the role of early intubation versus use of non-invasive respiratory support measures to avoid intubation. This review summarizes available evidence and provides a clinical decision algorithm with risk mitigation techniques to guide clinicians in care of the hypoxemic, non-intubated, patient during the COVID-19 pandemic. Although aerosolization of droplets may occur with aerosol-generating medical procedures (AGMP), including high flow nasal oxygen and non-invasive ventilation, the risk of using these AGMP is outweighed by the benefit in carefully selected patients, particularly if care is taken to mitigate risk of viral transmission. Non-invasive support measures should not be denied for conditions where previously proven effective and may be used even while there is suspicion of COVID-19 infection. Patients with de novo acute respiratory illness with suspected/confirmed COVID-19 may also benefit. These techniques may improve oxygenation sufficiently to allow some patients to avoid intubation; however, patients must be carefully monitored for signs of increased work of breathing. Patients showing signs of clinical deterioration or high work of breathing not alleviated by non-invasive support should proceed promptly to intubation and invasive lung protective ventilation strategy. With adherence to these principles, risk of viral spread can be minimized.

Background : Diaphragm dysfunction is a serious problem. However, a few management techniques exist for diaphragm dysfunction. Methods : Adult patients treated with high-flow nasal cannula (HFNC) in the intensive care unit were included in this study. The diaphragm function was evaluated using ultrasound measurement of thickening fraction before and after HFNC liberation. Normal diaphragm contraction was defined as thickening fraction ≥ 15% without HFNC, whereas decreased or paradoxical diaphragm contractions were 0%-15% or 0%, respectively. Results : Forty patients were enrolled, and 16 (40%) had normal diaphragm contraction, whereas 19 (48%) or 5 (13%) had decreased or paradoxical diaphragm contractions, respectively. Thickening fraction increased after HFNC liberation (27.0% ± 25.7% vs. 38.8% ± 34.5%, p = 0.03 in HFNC vs. no HFNC) in patients without diaphragm dysfunction. In patients with decreased diaphragm contraction, thickening fraction did not change with or without HFNC (8.9% ± 11.7% vs. 6.7% ± 5.2%, p = 0.35), whereas paradoxical contraction decreased with HFNC (1.0% ± 10.2% vs. -10.3% ± 2.7%, p = 0.04) in patients with paradoxical diaphragm contraction. Conclusions : The work of breathing decreased with HFNC in patients without diaphragm dysfunction, but did not decrease in patients with decreased diaphragm contraction. Paradoxical diaphragm contraction decreased with HFNC. J. Med. Invest. 68 : 159-164, February, 2021.

Introduction: Synchronization of non-invasive ventilation is challenging in extremely premature infants. We compared patient-ventilator synchrony between non-invasive neurally adjusted ventilatory assist (NIV-NAVA) using transdiaphragmatic (Edi) catheter and synchronized intermittent positive airway pressure (SiPAP) using an abdominal trigger. Methods: This study was a monocentric, randomized, crossover trial in premature infants born before 28 weeks of gestation, aged 3 days or more, and below 32 weeks postmenstrual age. NIV-NAVA and SiPAP were applied in a random order for 2 h with analysis of data from the second hour. The primary outcome was the asynchrony index. Results: Fourteen patients were included (median [IQR] gestational age at birth 25.6 (25.3–26.4) weeks, median [IQR] birth weight 755 [680–824] g, median [IQR] postnatal age 26.5 [19.8–33.8] days). The median (IQR) asynchrony index was significantly lower in NIV-NAVA versus SiPAP (49.9% [44.1–52.6] vs. 85.8% [74.2–90.9], p < 0.001). Ineffective efforts and auto-triggering were significantly less frequent in NIV-NAVA versus SiPAP (3.0% vs. 32.0% p < 0.001 and 10.0% vs. 26.6%, p = 0.004, respectively). Double triggering was significantly less frequent in SiPAP versus NIV-NAVA (0.0% vs. 9.0%, p < 0.001). No significant difference was observed for premature cycling and late cycling. Peak Edi and swing Edi were significantly lower in NIV-NAVA as compared to SiPAP (7.7 [6.1–9.9] vs. 11.0 [6.7–14.5] μV, p = 0.006; 5.4 [4.2–7.6] vs. 7.6 [4.3–10.8] μV, p = 0.007, respectively). No significant difference was observed between NIV-NAVA and SiPAP for heart rate, respiratory rate, COMFORTneo scores, apnoea, desaturations, or bradycardias. Discussion/Conclusion: NIV-NAVA markedly improves patient-ventilator synchrony as compared to SiPAP in extremely premature infants.

Background Patient–ventilator asynchrony is associated with increased morbidity and mortality. A direct causative relationship between Patient–ventilator asynchrony and adverse clinical outcome have yet to be demonstrated. It is hypothesized that during trigger errors excessive pleural pressure swings are generated, contributing to increased work-of-breathing and self-inflicted lung injury. The objective of this study was to determine the additional work-of-breathing and pleural pressure swings caused by trigger errors in mechanically ventilated children. Methods Prospective observational study in a tertiary paediatric intensive care unit in an university hospital. Patients ventilated > 24 h and Results Nine-hundred-and-fifty-nine trigger errors in 28 patients were identified. The additional work-of-breathing caused by trigger errors showed great variability among patients. The more asynchronous breaths were present the higher the work-of-breathing of these breaths. A higher spontaneous breath rate led to a lower amount of trigger errors. Patient–ventilator asynchrony was not associated with prolonged duration of mechanical ventilation or paediatric intensive care stay. Conclusions The additional work-of-breathing caused by trigger errors in ventilated children can take up to 30–40% of the total work-of-breathing. Trigger errors were less common in patients breathing spontaneously and those able to generate higher pressure–time–product and pressure swings. Trial registration Not applicable.

Objectives To determine the feasibility of having caregivers assist in recognition of clinical deterioration in children hospitalized with febrile illness in a resource-limited setting. Design Single-center, prospective, interventional pilot study. Setting General pediatric wards at Kenyatta National Hospital, Nairobi, Kenya's largest public tertiary-care hospital. Patients Children hospitalized with acute febrile illness, accompanied by caregivers available at the bedside for 24 hours soon after hospital admission. Interventions Caregivers were trained to recognize signs of critical illness using the Family-Assisted Severe Febrile Illness Therapy tool, which quantifies patients' work of breathing, mental status, and perfusion, producing color-coded flags to signal illness severity. Caregivers' Family-Assisted Severe Febrile Illness Therapy assessments were compared with healthcare professional assessments and to established Pediatric Early Warning Scores (PEWS). An initial study stage was followed by refinement of training and a larger second stage with intervention/control arms. Measurements and main results A total of 107 patient/caregiver pairs were enrolled in the interventional arm; 106 caregivers underwent Family-Assisted Severe Febrile Illness Therapy training and were included in the analysis. Patient characteristics included median age 1.1 years (0.2-10 yr), 55 (52%) female, and diagnoses: pneumonia (64 [60%]), meningitis (38 [36%]), gastroenteritis (24 [23%]), and malaria (21 [20%]). Most caregivers had primary (34 [32%]) or secondary (53 [50%]) school education. Fourteen of 106 patients (13%) died during their stay, six within 2 days. Across all severity levels, caregiver Family-Assisted Severe Febrile Illness Therapy assessments matched professionals in 87% and 94% for stages 1 and 2, respectively. Caregiver Family-Assisted Severe Febrile Illness Therapy assessments had a moderate to strong correlation with coinciding Pediatric Early Warning Scores and were sensitive to life-threatening deterioration: for all six patients who died within 2 days of admission, caregiver assessment reached the highest alert level. Conclusions Caregiver involvement in recognition of critical illness in hospitalized children in low-resource settings may be feasible. This may facilitate earlier detection of clinical deterioration where staffing is severely limited by constrained resources. Further validation of the Family-Assisted Severe Febrile Illness Therapy tool is warranted, followed by its application in a larger multisite patient population to assess provider response and associated clinical outcomes.

Rationale: Dynamic collapse of the tracheal lumen (tracheomalacia) occurs frequently in premature neonates, particularly in those with common comorbidities such as bronchopulmonary dysplasia. The tracheal collapse increases the effort necessary to breathe (work of breathing [WOB]). However, quantifying the increased WOB related to tracheomalacia has previously not been possible. Therefore, it is also not currently possible to separate the impact of tracheomalacia on patient symptoms from parenchymal abnormalities. Objectives: To measure the increase in WOB due to airway motion in individual subjects with and without tracheomalacia and with different types of respiratory support. Methods: Fourteen neonatal intensive care unit subjects not using invasive mechanical ventilation were recruited. In eight, tracheomalacia was diagnosed via clinical bronchoscopy, and six did not have tracheomalacia. Self-gated three-dimensional ultrashort-echo-time magnetic resonance imaging (MRI) was performed on each subject with clinically indicated respiratory support to obtain cine images of tracheal anatomy and motion during the respiratory cycle. The component of WOB due to resistance within the trachea was then calculated via computational fluid dynamics (CFD) simulations of airflow on the basis of the subject’s anatomy, motion, and respiratory airflow rates. A second CFD simulation was performed for each subject with the airway held static at its largest (i.e., most open) position to determine the increase in WOB due to airway motion and collapse. Results: The tracheal-resistive component of WOB was increased because of airway motion by an average of 337% ± 295% in subjects with tracheomalacia and 24% ± 14% in subjects without tracheomalacia (P

Noninvasive ventilation (NIV) is considered to be the standard of care for the management of acute hypercapnic respiratory failure in patients with chronic obstructive pulmonary disease exacerbation. It can be delivered safely in any dedicated setting, from emergency rooms to high dependency or intensive care units and wards. NIV helps improving dyspnea and gas exchange, reduces the need for endotracheal intubation, and morbidity and mortality rates. It is therefore recognized as the gold standard in this condition. High-flow nasal therapy helps improving ventilatory efficiency and reducing the work of breathing in patients with severe chronic obstructive pulmonary disease. Early studies indicate that some patients with acute hypercapnic respiratory failure can be managed with high-flow nasal therapy, but more information is needed before specific recommendations for this therapy can be made. Therefore, high-flow nasal therapy use should be individualized in each particular situation and institution, taking into account resources, and local and personal experience with all respiratory support therapies.

OBJECTIVES: To calculate imposed work of breathing during simulated spontaneous breathing at a given tidal volume across the range of normal length or shortened pediatric endotracheal tube sizes and endotracheal tubes with an intraluminal catheter in situ.DESIGN: In vitro study.SETTING: Research laboratory.INTERVENTIONS: A bench model (normal compliance, no airway resistance) simulating sinusoid flow spontaneous breathing used to calculate imposed work of breathing for various endotracheal tube sizes (3.0-7.5 mm). Imposed work of breathing was calculated by integrating inspiratory tidal volume over the end-expiratory difference between the positive end-expiratory pressure and the tracheal pressure. Measurements were taken at different combinations of set spontaneous tidal volume (2.5, 5.0, 7.5, and 10 mL/kg), age-appropriate inspiratory times, length of endotracheal tube, and presence of intraluminal catheter.MEASUREMENTS AND MAIN RESULTS: Overall median imposed work of breathing (Joules/L) was not significantly different between the four age groups: 0.047 Joules/L (interquartile range, 0.020-0.074 Joules/L) for newborns, 0.077 Joules/L (interquartile range, 0.032-0.127 Joules/L) for infants, 0.109 Joules/L (interquartile range, 0.0399-0.193 Joules/L) for small children, and 0.077 Joules/L (interquartile range, 0.032-0.132 Joules/L) for adolescents. Shortening the endotracheal tubes resulted in a significant difference in reduction in overall imposed work of breathing, but the absolute reduction was most notable in small children (0.030 Joules/L) and the least effect in neonates (0.016 Joules/L). Overall imposed work of breathing increased in each age group when an intraluminal catheter was in situ: 91.09% increase in imposed work of breathing in neonates to 0.168 Joules/L, 84.98% in infants to 0.142 Joules/L, 81.98% in small children to 0.219 Joules/L, and 55.45% in adolescents to 0.140 Joules/L.CONCLUSIONS: Calculated imposed work of breathing were not different across the range of endotracheal tube sizes. The low imposed work of breathing values found in this study might be appreciated as clinically irrelevant. Our findings add to the change in reasoning that it is appropriate to perform spontaneous breathing trials without pressure support. Nonetheless, our findings on the measured imposed work of breathing values need to be confirmed in a clinical study.

Background Bedside measures of patient effort are essential to properly titrate the level of pressure support ventilation. We investigated whether the tidal swing in oesophageal (ΔPes) and transdiaphragmatic pressure (ΔPdi), and ultrasonographic changes in diaphragm (TFdi) and parasternal intercostal (TFic) thickening are reliable estimates of respiratory effort. The effect of diaphragm dysfunction was also considered. Methods Twenty-one critically ill patients were enrolled: age 73 (14) yr, BMI 27 (7) kg m−2, and Pao2/Fio2 33.3 (9.2) kPa. A three-level pressure support trial was performed: baseline, 25% (PS-medium), and 50% reduction (PS-low). We recorded the oesophageal and transdiaphragmatic pressure–time products (PTPs), work of breathing (WOB), and diaphragm and intercostal ultrasonography. Diaphragm dysfunction was defined by the Gilbert index. Results Pressure support was 9.0 (1.6) cm H2O at baseline, 6.7 (1.3) (PS-medium), and 4.4 (1.0) (PS-low). ΔPes was significantly associated with the oesophageal PTP (R2=0.868; P Conclusions ΔPes and ΔPdi are adequate estimates of inspiratory effort. Diaphragm ultrasonography is a reliable indicator of inspiratory effort in the absence of diaphragm dysfunction. Additional measurement of parasternal intercostal thickening may discriminate a low inspiratory effort or a high effort in the presence of a dysfunctional diaphragm.

Introduction The patient-ventilator relationship is dynamic as the patient's health fluctuates and the ventilator settings are modified. Spontaneously breathing patients respond to mechanical ventilation by changing their patterns of breathing. This study measured the physiologic response when pressure support (PS) settings were modified during mechanical ventilation. Methods Subjects were instrumented with a non-invasive pressure, flow, and carbon dioxide airway sensor to estimate tidal volume, respiratory rate, minute ventilation, and end-tidal CO2. Additionally, a catheter was used to measure esophageal pressure and estimate effort exerted during breathing. Respiratory function measurements were obtained while PS settings were adjusted 569 times between 5 and 25 cmH2O. Results Data was collected on 248 patients. The primary patient response to changes in PS was to adjusting effort (power of breathing) followed by adjusting tidal volume. Changes in respiratory rate were less definite while changes in minute ventilation and end-tidal CO2 appeared unrelated to the change in PS. Conclusion The data indicates that patients maintain a set minute ventilation by adjusting their breathing rate, volume, and power. The data indicates that the subjects regulate their Ve and PetCO2 by adjusting power of breathing and breathing pattern.

Ventilator graphic monitoring is common in ICUs. The graphic information provides clinicians with immediate clues regarding patient-ventilator interaction and ventilator function. These display tools are aimed at reducing complications associated with mechanical ventilation, such as patient-ventilator asynchrony. It is also useful to assess respiratory mechanics in mechanically ventilated patients using both scalar and plot displays on the ventilator. Additional information can be gained by observing secondary ventilator measures including stress index, inflection points, and work of breathing. Ventilator graphics impact mechanical ventilation management through optimizing effectiveness of patient care and enhancing promptness of clinician response. Despite being a valuable asset in providing high-quality patient care, many bedside clinicians do not have a thorough understanding of ventilator graphics. Mastery of ventilator graphics interpretation is key in managing patients who are receiving ventilatory support.

OBJECTIVES To compare the imposed work of breathing by means of pressure-time product of the diaphragm in newborn infants receiving different modes of mechanical ventilation. DESIGN Prospective observational crossover study. SETTING Tertiary care neonatal unit. PATIENTS Forty preterm newborns (gestational age ≤ 37 wk) in the phase of weaning from mechanical ventilation. INTERVENTIONS Participants were ventilated in assist control, synchronized intermittent mandatory ventilation, and intermittent mandatory ventilation mode, in a crossover manner. The combination synchronized intermittent mandatory ventilation-pressure support (SIMV-PS) at 50% (SIMV-PS50) and 75% (SIMV-PS75) of the difference between peak inflating and positive end-expiratory pressure, was also applied in a subset of infants (n = 11). Each mode was maintained for 30 minutes. Transdiaphragmatic pressure was obtained by digital subtraction of esophageal from gastric pressure (both measured using a dual pressure-tipped catheter), and pressure-time product of the diaphragm was computed by integration of transdiaphragmatic pressure over inspiratory time. MEASUREMENTS AND MAIN RESULTS The pressure-time product of the diaphragm was 224.2 ± 112.8 in the intermittent mandatory ventilation mode, 165.8 ± 58.8 in the synchronized intermittent mandatory ventilation mode, and 125.5 ± 61.8 cm H2O × s × min in the assist control mode; all values were significantly different to each other (p < 0.0001). The pressure-time product of the diaphragm difference between assist control and intermittent mandatory ventilation, and assist control and synchronized intermittent mandatory ventilation was negatively related to postmenstrual age (regression coefficient, -0.365; p = 0.020 and -0.341; p = 0.031, respectively). In the SIMV-PS subcohort, the pressure-time product of the diaphragm was significantly higher in the intermittent mandatory ventilation mode as compared with assist control (p < 0.0001) or SIMV-PS75 (p = 0.0027), and in the synchronized intermittent mandatory ventilation mode as compared with assist control (p = 0.0301). CONCLUSIONS In preterm infants, patient-triggered ventilation modalities result in lower work of breathing than intermittent mandatory ventilation, while the assist control mode is also associated with lower pressure-time product of the diaphragm compared with synchronized intermittent mandatory ventilation. The difference in the imposed diaphragmatic workload between these ventilation modalities was inversely related to postmenstrual age, implying that less mature infants benefit more from assist control-based ventilation strategies.

Purpose To develop an equation to calculate the bedside dynamic mechanical power (MPdyn) for modern ventilators using the Work of Breathing ventilator (WOBv) parameter. Materials and methods We developed an equation based on mechanical power values, which is equal to WOBv x minute volume. To measure mechanical power with this equation forty adult patients, hospitalized with the diagnosis of Acute Respiratory Distress Syndrome and underwent invasive mechanical ventilation, were used. To be able compare our results with Gattinoni's standart mechanical power equation (MPstd) the contribution of the PEEP was included in our equation. Then results obtained from MPdyn and MPstd were compared using univariable regression and Bland-Altman analysis. This comparison was performed at different I:E ratios, PEEP levels and tidal volumes. Results Analysis of the results for each condition showed that MPdyn and MPstd equation correlated with R2 ≥ 0.98. Additionally, there was no statistically significant difference between MPdyn and MPstd for patient power means were 0.04 J/min (p = .42) using Bland-Altman analysis. Conclusions Physicians can easily calculate mechanical power by using MPdyn at the bedside of patients on volume control mode.

Objectives To describe the long-term effects of ivacaftor (Kalydeco®) in individuals with cystic fibrosis (CF) on body mass index (BMI), body composition (BC), pulmonary function (PF), resting energy expenditure (REE), and exercise capacity (EC) after ≥12 months of treatment. Working hypothesis BMI, lean and fat mass, PF, and EC will increase and REE will decrease after treatment. Study design Observational study. Methodology Seven individuals with CF (mean age 15.4 ± 5.8 years) heterozygous for S1251N mutation, starting with ivacaftor, were included. Paired t tests were performed to assess the effects of ivacaftor. Height and weight were used to calculate BMI and BMI Z-scores. Dual-energy X-ray absorptiometry was used to assess BC. Spirometry and body plethysmography were used to assess PF. Indirect calorimetry was used to measure REE and cardiopulmonary exercise testing (CPET) was used to measure oxygen uptake (VO2peak ), peak work rate (Wpeak ), and other CPET variables. Results After a median of 15 (interquartile range: 13-16) months of treatment, BMI increased significantly (P = .03), but not BMI Z-score (P = .23) or BC. Significant improvements were found for several PF variables, especially measures of hyperinflation (P = .02). Absolute VO2peak (P = .01), VO2peak related to body weight (P = .00), and oxygen cost of work (P = .01) decreased. Absolute Wpeak (P = .59) and Wpeak related to body weight (P = .31) remained stable. Conclusions The results showed that long-term treatment of ivacaftor is associated with improvement of BMI and PF, but not of BC and REE. Oxygen uptake reduced after treatment, which may be due to a decrease in work of breathing.

BACKGROUND: Double-triggering is a well-recognized form of patient-ventilator asynchrony in noninvasive ventilation (NIV). This benchtop simulated lung study aimed to determine under which patient and device-specific conditions double-triggering is more prevalent, and how this influences the delivery of NIV. METHODS: Two commonly used proprietary NIV devices were tested using a benchtop lung model. Lung compliance, airway resistance, respiratory effort, and breathing frequency were manipulated, and the frequency of double-triggering was assessed. A lung model of very low lung compliance (15 mL/cm H2O) was then used to assess the frequency of double-triggering when breathing frequency and respiratory effort were varied, along with basic NIV settings, including inspiratory pressure and expiratory pressure. Minute ventilation and total inspiratory work (as calculated by the simulated lung model) were also correlated with frequency of double-triggering. RESULTS: In both devices, double-triggering was observed with reduced lung compliance (P = .02 and P CONCLUSIONS: Both simulated-patient and device characteristics influenced the frequency of double-triggering in NIV, resulting in meaningful consequences in a simulated lung model.

Background Diaphragm atrophy and dysfunction are consequences of mechanical ventilation and are determinants of clinical outcomes. We hypothesize that partial preservation of diaphragm function, such as during assisted modes of ventilation, will restore diaphragm thickness. We also aim to correlate the changes in diaphragm thickness and function to outcomes and clinical factors. Methods This is a prospective, multicentre, observational study. Patients mechanically ventilated for more than 48 h in controlled mode and eventually switched to assisted ventilation were enrolled. Diaphragm ultrasound and clinical data collection were performed every 48 h until discharge or death. A threshold of 10% was used to define thinning during controlled and recovery of thickness during assisted ventilation. Patients were also classified based on the level of diaphragm activity during assisted ventilation. We evaluated the association between changes in diaphragm thickness and activity and clinical outcomes and data, such as ventilation parameters. Results Sixty-two patients ventilated in controlled mode and then switched to the assisted mode of ventilation were enrolled. Diaphragm thickness significantly decreased during controlled ventilation (1.84 ± 0.44 to 1.49 ± 0.37 mm, p p p = 0.004) and higher PEEP levels (12.6 ± 4 versus 10.4 ± 4 cmH2O, p = 0.034). An increase in diaphragm thickness of more than 10% during assisted ventilation was not associated with any clinical outcome but with lower respiratory rate (16.7 ± 3.2 versus 19.2 ± 4 bpm, p = 0.019) and Rapid Shallow Breathing Index (37 ± 11 versus 44 ± 13, p = 0.029) and with higher Pressure Muscle Index (2 [0.5, 3] versus 0.4 [0, 1.9], p = 0.024). Change in diaphragm thickness was not related to diaphragm function expressed as diaphragm thickening fraction. Conclusion Mode of ventilation affects diaphragm thickness, and preservation of diaphragmatic contraction, as during assisted modes, can partially reverse the muscle atrophy process. Avoiding a strenuous inspiratory work, as measured by Rapid Shallow Breathing Index and Pressure Muscle Index, may help diaphragm thickness restoration.

BackgroundThe original bubble continuous positive airway pressure (bCPAP) design has wide-bore tubing and a low-resistance interface. This creates a stable airway pressure that is reflected by the submersion depth of the expiratory tubing. Several systems with alterations to the original bCPAP design are now available. Most of these are aimed for use in low-income and middle-income countries and have not been compared with the original design.ObjectiveWe identified three major alterations to the original bCPAP design: (1) resistance of nasal interface, (2) volume of dead space and (3) diameter of expiratory tubing. Our aim was to study the effect of these alterations on CPAP delivery and work of breathing in a mechanical lung model. Dead space should always be avoided and was not further tested.MethodsThe effect of nasal interface resistance and expiratory tubing diameter was evaluated with simulated breathing in a mechanical lung model without interface leakage. The main outcome was delivered CPAP and imposed work of breathing.ResultsHigh-resistance interfaces and narrow expiratory tubing increased the work of breathing. Additionally, narrow expiratory tubing resulted in higher CPAP levels than indicated by the submersion depth.ConclusionOur study shows the significant effect on CPAP delivery and imposed work of breathing when using high-resistance interfaces and narrow expiratory tubing in bCPAP systems. New systems should include low-resistance interfaces and wide-bore tubing and be compared with the original bCPAP. Referring to all systems that bubble as bCPAP is misleading and potentially hazardous.

In newborns, it is unclear how nasal high flow (NHF) generates positive airway pressure. In addition, the reported benefits of NHF such as reduction in work of breathing may be independent of airway pressure. The authors hypothesized that during NHF the area of leak and the flow determine airway pressure and that NHF can reduce the required minute ventilation to maintain gas exchange. In response to NHF, pressure was measured in the upper airways of 9 newborns and ventilation was measured in another group of 17 newborns. In a bench model, airway pressures were measured during NHF with different prong sizes, nare sizes, and flows. The airway pressures during 8 L/min NHF were greater when a larger cannula versus a smaller cannula was used ( P < 0.05). NHF reduced minute ventilation in 16 of 17 neonates, with a mean decrease of 24% from a baseline of 0.66 L/min (SD 0.21) ( P < 0.001), and was unrelated to changes in airway pressure; arterial oxygen saturation by pulse oximetry ([Formula: see text]) and tissue CO2were unchanged. In the bench model, the airway pressure remained 2O when NEW & NOTEWORTHY In healthy newborns, nasal high flow (NHF) with room air reduced minute ventilation by one-fourth without affecting gas exchange but, in contrast to adults, produced variable response in respiratory rate during sleep. During NHF, pressure in the upper airways did not exceed 2 cmH2O at 8 L/min (3.4 L·min−1·kg−1) and was unaffected by opening of the mouth. NHF can generate higher pressure with larger prongs that decrease the leak around the cannula or by increasing the flow rate.

This study’s objective was the generation of a standardized geometry of the healthy nasal cavity. An average geometry of the healthy nasal cavity was generated using a statistical shape model based on 25 symptom-free subjects. Airflow within the average geometry and these geometries was calculated using fluid simulations. Integral measures of the nasal resistance, wall shear stresses (WSS) and velocities were calculated as well as cross-sectional areas (CSA). Furthermore, individual WSS and static pressure distributions were mapped onto the average geometry. The average geometry featured an overall more regular shape that resulted in less resistance, reduced WSS and velocities compared to the median of the 25 geometries. Spatial distributions of WSS and pressure of the average geometry agreed well compared to the average distributions of all individual geometries. The minimal CSA of the average geometry was larger than the median of all individual geometries (83.4 vs. 74.7 mm²). The airflow observed within the average geometry of the healthy nasal cavity did not equal the average airflow of the individual geometries. While differences observed for integral measures were notable, the calculated values for the average geometry lay within the distributions of the individual parameters. Spatially resolved parameters differed less prominently.

Purpose: Some patients with respiratory failure fail initial weaning attempts and need prolonged mechanical ventilation (MV). Prolonged MV is associated with many complications and consumption of heathcare resources. Objective weaning indices help staffs to identify high-potential patients for weaning from the MV. Traditional weaning indices are not reliable in clinical practice. Transitional percentage of minute volume (TMV%) is a new index of the work of breathing. This study aimed to investigate the utility of TMV% in the prediction of weaning potential. Methods: This study was prospectively performed including all patients with prolonged MV. Researchers recorded their demographics, TMV%, respiratory parameters, Acute Physiology and Chronic Health Evaluation II score, and laboratory data upon arrival at the respiratory care center. The factors associated with successful weaning were analyzed. Results: Out of the 120 patients included, 84 (70.0%) were successfully weaned from MV. Traditional weaning indices such as rapid shallow breathing index could not predict the weaning outcome. TMV% was a valuable parameter as patients with a lower TMV%, higher tidal volume, higher hemoglobin, lower blood urea nitrogen, and lower Acute Physiology and Chronic Health Evaluation II scores had a higher rate of successful weaning. TMV%, tidal volume, and HCO3- levels were independent predictors of successful weaning, and the area under the curve was .79 in the logistic regression model. Conclusion: TMV% is a novel and effective predictor of successful weaning. Patients with lower TMV% had a higher MV weaning outcome. Once patients with a high potential for successful weaning are identified, they should be aggressively weaned from MV as soon as possible. Clinical Trials Government Identifier: NCT033480. Keywords: respiratory insufficiency, ventilators, mechanical, work of breathing

Purpose The PSVPro mode is increasingly being used for surgeries under laryngeal mask airway owing to improved ventilator-patient synchrony and decreased work of breathing. We hypothesized that PSVPro ventilation mode would reduce consumption of anesthetic agents compared with pressure control ventilation (PCV). Methods Seventy children between three and eight years of age undergoing elective lower abdominal and urological surgery were randomized into PCV group (n = 35) or PSVPro group (n = 35). General anesthesia was induced with sevoflurane and a Proseal LMA™ was inserted. Anesthesia was maintained with propofol infusion to maintain the entropy values between 40 and 60. In the PCV mode, the inspiratory pressure was adjusted to obtain an expiratory tidal volume of 8 mL·kg−1 and a respiratory rate of 12–20/min. In the PSVPRO group, the flow trigger was set at 0.4 L·min−1 and pressure support was adjusted to obtain expiratory tidal volume of 8 mL·kg−1. Consumption of anesthetic agent was recorded as the primary outcome. Emergence time and discharge time were recorded as secondary outcomes. Results The PSVPro group showed significant reduction in propofol consumption compared with the PCV group (mean difference, 33.3 µg−1·kg−1·min−1; 95% confidence interval [CI], 24.2 to 42.2). There was decrease in the emergence time in the PSVPro group compared with the PCV group (mean difference, 3.5 min; 95% CI, 2.8 to 4.2) and in time to achieve modified Aldrete score > 9 (mean difference, 3.6 min; 95% CI, 1.9 to 5.2). Conclusion The PSVPro mode decreases propofol consumption and emergence time, and improves oxygenation index in children undergoing ambulatory surgery. Trial registration Clinical Trial Registry of India (CTRI/2017/12/010942); registered 21 December, 2017.

Supplemental Digital Content is available in the text., OBJECTIVES: Lung- and diaphragm-protective ventilation is a novel concept that aims to limit the detrimental effects of mechanical ventilation on the diaphragm while remaining within limits of lung-protective ventilation. The premise is that low breathing effort under mechanical ventilation causes diaphragm atrophy, whereas excessive breathing effort induces diaphragm and lung injury. In a proof-of-concept study, we aimed to assess whether titration of inspiratory support based on diaphragm effort increases the time that patients have effort in a predefined “diaphragm-protective” range, without compromising lung-protective ventilation. DESIGN: Randomized clinical trial. SETTING: Mixed medical-surgical ICU in a tertiary academic hospital in the Netherlands. PATIENTS: Patients (n = 40) with respiratory failure ventilated in a partially-supported mode. INTERVENTIONS: In the intervention group, inspiratory support was titrated hourly to obtain transdiaphragmatic pressure swings in the predefined “diaphragm-protective” range (3–12 cm H2O). The control group received standard-of-care. MEASUREMENTS AND MAIN RESULTS: Transdiaphragmatic pressure, transpulmonary pressure, and tidal volume were monitored continuously for 24 hours in both groups. In the intervention group, more breaths were within “diaphragm-protective” range compared with the control group (median 81%; interquartile range [64–86%] vs 35% [16–60%], respectively; p < 0.001). Dynamic transpulmonary pressures (20.5 ± 7.1 vs 18.5 ± 7.0 cm H2O; p = 0.321) and tidal volumes (7.56 ± 1.47 vs 7.54 ± 1.22 mL/kg; p = 0.961) were not different in the intervention and control group, respectively. CONCLUSIONS: Titration of inspiratory support based on patient breathing effort greatly increased the time that patients had diaphragm effort in the predefined “diaphragm-protective” range without compromising tidal volumes and transpulmonary pressures. This study provides a strong rationale for further studies powered on patient-centered outcomes.

To quantify the mechanical work of breathing (Wb) during an indoor rowing test in men and women. Additionally, to compare sex-based differences in the Wb and its components through a rowing test. Fifteen collegiate rowers were recruited (8 women/7 men) and performed a 2000 m rowing test on a rowing ergometer. Esophageal pressure was measured during exercise via balloon catheterization, after which pressure–volume curves were used to calculate total, inspiratory resistive and elastic, and total expiratory Wb. Men had significantly higher values of instantaneous and cumulative total Wb at and beyond 37.5% (430.4 ± 42.5 vs. 282.1 ± 45.1 J min−1, P

The energy needed to drive airflow through the trachea normally constitutes a minor component of the work of breathing. However, with progressive tracheal compression, patient subjective symptoms can include severe breathing difficulties. Many patients suffer multiple respiratory co-morbidities and so it is important to assess compression effects when evaluating the need for surgery. This work describes the use of computational prediction to determine airflow resistance in compressed tracheal geometries reconstructed from a series of CT scans. Using energy flux analysis, the regions that contribute the most to airway resistance during inhalation are identified. The principal such region is where flow emerging from the zone of maximum constriction undergoes breakup and turbulent mixing. Secondary regions are also found below the tongue base and around the glottis, with overall airway resistance scaling nearly quadratically with flow rate. Since the anatomical extent of the imaged airway varied between scans—as commonly occurs with clinical data and when assessing reported differences between research studies—the effect of sub-glottic inflow truncation is considered. Analysis shows truncation alters the location of jet breakup and weakly influences the pattern of pressure recovery. Tests also show that placing a simple artificial glottis in the inflow to a truncated model can replicate patterns of energy loss in more extensive models, suggesting a means to assess sensitivity to domain truncation in tracheal airflow simulations. Electronic supplementary material The online version of this article (10.1007/s10439-019-02410-1) contains supplementary material, which is available to authorized users.

Objectives Postoperative pulmonary complications increase mortality, length, and cost of hospitalization. A better diaphragmatic strength may help face an increased work of breathing postoperatively. We, therefore, sought to determine if a low preoperative diaphragm thickening fraction (TFdi) determined by ultrasonography helped predict the occurrence of postoperative pulmonary complications after cardiac surgery independently of indicators of frailty, sarcopenia, and pulmonary function. Design Prospective observational cohort study. Setting Montreal Heart Institute, an academic cardiac surgery center in Canada. Patients Adults undergoing nonemergency cardiac surgery. Interventions We measured the preoperative thickness of the right and left hemidiaphragms at their zone of apposition at end-expiration (Tdi,ee) and peak-inspiration (Tdi,ei) with ultrasonography. Maximal thickening fraction of the diaphragm during inspiration (TFdi,max) was calculated using the following formula: TFdi,max = (Tdi,ei-Tdi,ee)/Tdi,ee. We also evaluated other potential risk factors including demographic parameters, comorbidities, Clinical Frailty Scale, grip strength, 5-meter walk test, and pulmonary function tests. We repeated TFdi,max measurements within 24 hours of extubation. The primary composite outcome of this study was the occurrence of postoperative pulmonary complications, defined as pneumonia, clinically significant atelectasis, or prolonged mechanical ventilation (> 24 hr). Measurement and main results Of the 115 patients included, 34 (29.6%) developed postoperative pulmonary complications, including two with pneumonia, four with prolonged mechanical ventilation, and 32 with clinically significant atelectasis. Those with postoperative pulmonary complications had prolonged ICU and hospital length of stays. They had a lower TFdi,max (37% [interquartile range, 31-45%] vs 44% [interquartile range, 33-58%]; p = 0.03). In multiple logistic regression, a TFdi,max less than 38.1% was associated with postoperative pulmonary complications (odds ratio, 4.9; 95% CI, 1.81-13.50; p = 0.002). All patients who developed pneumonia or prolonged mechanical ventilation had a TFdi,max less than 38.1%. Respiratory rate and diabetes were also independently associated with postoperative pulmonary complications, while pulmonary function tests and the assessed indicators of frailty and sarcopenia were not. Conclusions A low preoperative TFdi,max can help to identify patients at increased risk of postoperative pulmonary complications after cardiac surgery.

Background Reverse triggering (RT) is a dyssynchrony defined by a respiratory muscle contraction following a passive mechanical insufflation. It is potentially harmful for the lung and the diaphragm, but its detection is challenging. Magnitude of effort generated by RT is currently unknown. Our objective was to validate supervised methods for automatic detection of RT using only airway pressure (Paw) and flow. A secondary objective was to describe the magnitude of the efforts generated during RT. Methods We developed algorithms for detection of RT using Paw and flow waveforms. Experts having Paw, flow and esophageal pressure (Pes) assessed automatic detection accuracy by comparison against visual assessment. Muscular pressure (Pmus) was measured from Pes during RT, triggered breaths and ineffective efforts. Results Tracings from 20 hypoxemic patients were used (mean age 65 ± 12 years, 65% male, ICU survival 75%). RT was present in 24% of the breaths ranging from 0 (patients paralyzed or in pressure support ventilation) to 93.3%. Automatic detection accuracy was 95.5%: sensitivity 83.1%, specificity 99.4%, positive predictive value 97.6%, negative predictive value 95.0% and kappa index of 0.87. Pmus of RT ranged from 1.3 to 36.8 cmH20, with a median of 8.7 cmH20. RT with breath stacking had the highest levels of Pmus, and RTs with no breath stacking were of similar magnitude than pressure support breaths. Conclusion An automated detection tool using airway pressure and flow can diagnose reverse triggering with excellent accuracy. RT generates a median Pmus of 9 cmH2O with important variability between and within patients. Trial registration BEARDS, NCT03447288.

We hypothesized that the higher resistive work of breathing in females compared with males during high-intensity exercise is due to smaller airways. In vivo measures of the fourth to eighth airway generations made using optical coherence tomography show that females tend to have smaller airway luminal areas of the fourth to sixth airway generations. Sex differences in airway luminal area result in a greater resistive work of breathing during exercise in females compared with males.