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Background: The physiological and prognostical significance of accessory and expiratory muscles activation is unknown during a spontaneous breathing trial (SBT). We hypothesized that, in patients experiencing weaning failure, accessory and expiratory muscles are activated to cope with an increased respiratory workload. Purpose: To describe accessory and expiratory muscle activation non-invasively by surface electromyography (sEMG) during an SBT and to assess differences in electrical activity (EA) of the inspiratory and expiratory muscles in successful vs. failing weaning patients. Methods: Intubated patients on mechanical ventilation for more than 48 h undergoing an SBT were enrolled in a medical and surgical third-level ICU of the University Teaching Hospital. Baseline characteristics and physiological variables were recorded in a crossover physiologic prospective clinical study. Results: Of 37 critically ill mechanically ventilated patients, 29 (78%) patients successfully passed the SBT. Rapid shallow breathing index (RSBI) was higher in patients who failed SBT compared with the successfully weaned patients at baseline and over time (group-by-time interaction p < 0.001). EA of both the diaphragm (EAdisurf) and of accessory muscles (ACCsurf) was higher in failure patients compared with success (group-by-time interaction p = 0.0174 and p < 0.001, respectively). EA of expiratory muscles (ESPsurf) during SBT increased more in failure than in weaned patients (group-by-time interaction p < 0.0001). Conclusion: Non-invasive respiratory muscle monitoring by sEMG was feasible during SBT. Respiratory muscles EA increased during SBT, regardless of SBT outcome, and patients who failed the SBT had a higher increase of all the inspiratory muscles EA compared with the patients who passed the SBT. Recruitment of expiratory muscles-as quantified by sEMG-is associated with SBT failure.

Objective:to describe our clinical experience using Electrical Impedance Tomography (EIT) in the management of mechanical ventilation in patients with acute respiratory failure and to determine to which extent EIT-guided PEEP setting differed from clinically set values.Approach:a retrospective, observational cohort study performed in a hub centre for the treatment of acute respiratory failure and veno-venous Extracorporeal Membrane Oxygenation (ECMO).Main results:between January 2017 and December 2019, EIT was performed 54 times in 41 patients, not feasible only in one case because of signal instability. More than 50% was on veno-venous ECMO support. In 16 cases (30%) EIT was used for monitoring mechanical ventilation i.e. to evaluate recruitability or sigh setting. In 37 cases (70%) EIT was used to set PEEP both with incremental (11 cases in nine patients) and decremental (26 cases, 18 patients) PEEP trial. Clinical PEEP before decremental PEEP trial (PEEPPRE) was 14.1 ± 3.4 cmH2O and clinical PEEP set by clinicians after PEEP trial (PEEPPOST) was 13.6 ± 3.1 (p =ns). EIT analyses demonstrated that more hypoxic patients were higher derecruited when compared to less hypoxic patients that were, on the contrary, more overdistended (p < 0.05). No acute effects of PEEP adjustment based on EIT on respiratory mechanics or regional EIT parameters modification were observed.Significance:variability of EIT findings in our population confirmed the need to provide ventilation settings individually tailored and EIT confirmed to be an optimal useful clinical bedside noninvasive tool to provide real-time monitoring of the PEEP effect and ventilation distribution.

BACKGROUND: Lung ultrasound can be used to assess lung density and aeration at the bedside. A few authors have investigated scores based on the ultrasonographic interstitial syndrome for this purpose, but none have compared them with the gold standard computed tomography in children.METHODS: Children < 10 kilograms undergoing a chest computed tomography for clinical purposes at a tertiary hospital Pediatric Intensive Care Unit were enrolled in the study. An ultrasound scan was performed shortly after computed tomography. Each hemithorax was divided in 6 zones, and each zone was scored: 1 = no B lines; 2 = < 3 B lines; 3 > 3 well separated B lines; 4 = crowded, coalescent B lines; 5 = white lung; 6 = consolidation. The pediatric Lung Ultrasound Score was obtained by adding all zones. Interobserver variation for two separate operators was calculated.RESULTS: Ten children, median age 95 days (range 23 - 721), were enrolled. Mean pediatric Lung Ultrasound Score had a significant correlation with lung density (rho = 0.68) and percentage of hypoaerated lung (rho = 0.51). Median density and percentage of hypoaerated lung increased along the ultrasound patterns values (p < 0.05) although not all patterns were significantly different from adjacent ones in the pairwise comparison. Interobserver variability in scoring of ultrasonographic patterns was moderate.CONCLUSIONS: The pediatric Lung Ultrasound Score correlates with lung density and percentage of hypoaerated lung measured with computed tomography.

Bedside measurement of respiratory mechanics allows to closely monitor the lung function in critically ill patients. The two fundamental parameters describing the respiratory system mechanics are resistance and compliance. Resistance of the respiratory system describes the opposition to gas flow during inspiration. During volume-controlled ventilation, resistance can be calculated as the ratio between the peak to plateau pressure drop and the resulting flow rate. Compliance describes the elastic property of the respiratory system, comprising the lung and the chest wall. It is the ratio between a change in volume (i.e. tidal volume) and the corresponding change in pressure, calculated as the difference between plateau pressure and total positive end-expiratory pressure, measured by end-inspiratory and end-expiratory manual occlusion, respectively. In this review, we describe how to measure respiratory mechanics at the bedside, starting from the physiological background of the equation of motion of the respiratory system.  (Intensive care)

Background: Positive end-expiratory pressure (PEEP) is a key element of mechanical ventilation. It should optimize recruitment, without causing excessive overdistension, but controversy exists on the best method to set it. The purpose of the study was to test the feasibility of setting PEEP with electrical impedance tomography in order to prevent lung de-recruitment following a recruitment maneuver. We enrolled 16 patients undergoing mechanical ventilation with PaO2/FiO2 <300 mmHg. In all patients, under constant tidal volume (6–8 ml/kg) PEEP was set based on the PEEP/FiO2 table proposed by the ARDS network (PEEPARDSnet). We performed a recruitment maneuver and monitored the end-expiratory lung impedance (EELI) over 10 min. If the EELI signal decreased during this period, the recruitment maneuver was repeated and PEEP increased by 2 cmH2O. This procedure was repeated until the EELI maintained a stability over time (PEEPEIT). Results: The procedure was feasible in 87% patients. PEEPEIT was higher than PEEPARDSnet (13 ± 3 vs. 9 ± 2 cmH2O, p < 0.001). PaO2/FiO2 improved during PEEPEIT and driving pressure decreased. Recruited volume correlated with the decrease in driving pressure but not with oxygenation improvement. Finally, regional alveolar hyperdistention and collapse was reduced in dependent lung layers and increased in non-dependent lung layers. Conclusions: In hypoxemic patients, a PEEP selection strategy aimed at stabilizing alveolar recruitment guided by EIT at the bedside was feasible and safe. This strategy led, in comparison with the ARDSnet table, to higher PEEP, improved oxygenation and reduced driving pressure, allowing to estimate the relative weight of overdistension and recruitment.

BACKGROUND: We previously described an index, defined as the ratio between the inspiratory muscle pressure (Pmus) and the electrical activity of the diaphragm (EAdi) (Pmus/EAdi index). In the present work, we describe the trend of Pmus/EAdi index over time, investigating whether it could be an indicator of muscular efficiency associated with risk factors for diaphragmatic injury and/or clinical outcomes. METHODS: This work is a retrospective analysis of subjects with measurements of Pmus/EAdi index obtained, on different days, during assisted ventilation. Effects of Pmus/EAdi index absolute value on clinical outcomes were investigated dividing subjects into those with Pmus/EAdi index higher or lower than the median. Effects of Pmus/EAdi index trend over time were analyzed, distinguishing between subjects with Pmus/EAdi index increasing or decreasing. RESULTS: Mean Pmus/EAdi index was 1.04 ± 0.67, and the median (interquartile range) was 1.00 (0.59 –1.34), without a systematic trend over the days. Demographic, ventilator, or outcome data did not significantly differ between subjects with Pmus/EAdi index higher or lower than the median. Similarly, we did not find relevant differences in subjects with Pmus/EAdi index increasing or decreasing over time. CONCLUSIONS: The Pmus/EAdi index value remained constant in each subject over time, although the inter-individual variability was high. Neither the Pmus/EAdi index nor its trends appeared to be associated with ventilatory variables or clinical outcome.

Background: Early after intubation, a layer of biofilm covers the inner lumen of the endotracheal tube (ETT). Cleaning the ETT might prevent airways colonization by pathogens, reduce resistance to airflow, and decrease sudden ETT obstruction. We investigated the effectiveness of a cleaning closed suction system in maintaining the endotracheal tube free from secretions. Methods: We conducted a single center, randomized controlled trial, in the general intensive care unit of a tertiary-level university hospital. We enrolled 40 adult critically ill patients expected to remain intubated for more than 48 h, within 24 h from intubation. Patients were randomized to receive three ETT cleaning maneuvers/day using a novel device (Airway Medix Closed Suction System™, cleaning group) or to standard care (no ETT cleaning, standard closed suction, control group). After extubation, the amount of secretions in the ETTs was measured by micro-computed tomography. Results: The volume of secretions in the ETTs from the cleaning group was lower than controls (0.081 [0.021–0.306] vs. 0.568 [0.162–0.756] mL, p = 0.001), corresponding to a cross-sectional area reduction six times lower (1[0–3] vs. 6 [2–10] %, p = 0.001). In a subset of 16 patients, the resistance to airflow tended to be lower after 1 day of treatment (p = 0.063) and was lower after 2 days (0.024), while no difference was present at enrollment (p = 0.922). ETT colonization did not differ between the two groups. Conclusions: The use of a novel cleaning closed suction system proved to be effective in reducing secretions present in the ETT after extubation, possibly reducing resistance to airflow during intubation. Trial registration: clinicaltrials.gov NCT01912105

Objective: Use of external ventricular drains and lumbar catheters is associated with a risk of ventriculitis and meningitis ranging from 2% to 24% because of lack of standardized diagnostic criteria. We evaluated the prevalence of ventriculitis or meningitis in 13 Italian ICUs. Design: Multicenter, prospective study. Setting: Thirteen Italian ICUs. Patients: Two hundred seventy-one patients (mean age, 57 yr) receiving a total number of 311 catheters. Two hundred fifty patients (92.2%) had an external ventricular drain, 17 patients (6.3%) had a lumbar catheter, and four patients (1.5%) had both external ventricular drain and lumbar catheter. Interventions: ICUs enrolled at least 10 consecutive adult patients with an external ventricular drain or lumbar catheter in place for more than 24 hours. Confirmed cerebrospinal fluid infection was defined by presence of a positive cerebrospinal fluid culture, a cerebrospinal fluid/blood glucose ratio less than 0.5, a neutrophilic cerebrospinal fluid pleocytosis (> 5 cells/?L), and fever. Abnormal cerebrospinal fluid findings with negative cultures were defined as suspected infection. Measurements and Main Results: Median duration of device use was 13 days (interquartile range, 8-19). Fifteen patients (5.5%) had a confirmed ventriculitis or meningitis, and 15 patients (5.5%) had a suspected ventriculitis or meningitis. Cerebrospinal fluid glucose and cerebrospinal fluid/blood glucose ratio were lower in patients with confirmed ventriculitis or meningitis and suspected ventriculitis or meningitis; proteins and lactates were significantly higher in confirmed ventriculitis or meningitis. Gram-negative and Gram-positive bacteria were equally cultured. Risk factors for infection were a concomitant extracranial infection (odds ratio, 2.34; 95% CI, 1.01-5.40; p = 0.05) and placement of catheters outside the operation room (odds ratio, 4.01; 95% CI, 0.98-16.50; p = 0.05). Conclusions: Ventriculitis or meningitis remains a problem in It