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Rationale: Obesity is characterized by elevated pleural pressure (Ppl) and worsening atelectasis during mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). Objectives: To determine the effects of a lung recruitment maneuver (LRM) in the presence of elevated Ppl on hemodynamics, left and right ventricular pressure, and pulmonary vascular resistance. We hypothesized that elevated Ppl protects the cardiovascular system against high airway pressure and prevents lung overdistension. Methods: First, an interventional crossover trial in adult subjects with ARDS and a body mass index ≥ 35 kg/m2 (n = 21) was performed to explore the hemodynamic consequences of the LRM. Second, cardiovascular function was studied during low and high positive end-expiratory pressure (PEEP) in a model of swine with ARDS and high Ppl (n = 9) versus healthy swine with normal Ppl (n = 6). Measurements and Main Results: Subjects with ARDS and obesity (body mass index = 57 ± 12 kg/m2) after LRM required an increase in PEEP of 8 (95% confidence interval [95% CI], 7–10) cm H2O above traditional ARDS Network settings to improve lung function, oxygenation and V./Q. matching, without impairment of hemodynamics or right heart function. ARDS swine with high Ppl demonstrated unchanged transmural left ventricular pressure and systemic blood pressure after the LRM protocol. Pulmonary arterial hypertension decreased (8 [95% CI, 13–4] mm Hg), as did vascular resistance (1.5 [95% CI, 2.2–0.9] Wood units) and transmural right ventricular pressure (10 [95% CI, 15–6] mm Hg) during exhalation. LRM and PEEP decreased pulmonary vascular resistance and normalized the V./Q. ratio. Conclusions: High airway pressure is required to recruit lung atelectasis in patients with ARDS and class III obesity but causes minimal overdistension. In addition, patients with ARDS and class III obesity hemodynamically tolerate LRM with high airway pressure. Clinical trial registered with www.clinicaltrials.gov (NCT 02503241).

Rationale: Cyclic strain may be a determinant of ventilator-induced lung injury. The standard for strain assessment is the computed tomography (CT), which does not allow continuous monitoring and exposes to radiation. Electrical impedance tomography (EIT) is able to monitor changes in regional lung ventilation. In addition, there is a correlation between mechanical deformation of materials and detectable changes in its electrical impedance, making EIT a potential surrogate for cyclic lung strain measured by CT (StrainCT). Objectives: To compare the global StrainCT with the change in electrical impedance (ΔZ). Methods: Acute respiratory distress syndrome patients under mechanical ventilation (VT 6 mL/kg ideal body weight with positive end-expiratory pressure 5 [PEEP 5] and best PEEP according to EIT) underwent whole-lung CT at end-inspiration and end-expiration. Biomechanical analysis was used to construct 3D maps and determine StrainCT at different levels of PEEP. CT and EIT acquisitions were performed simultaneously. Multilevel analysis was employed to determine the causal association between StrainCT and ΔZ. Linear regression models were used to predict the change in lung StrainCT between different PEEP levels based on the change in ΔZ. Main results: StrainCT was positively and independently associated with ΔZ at global level (P < .01). Furthermore, the change in StrainCT (between PEEP 5 and Best PEEP) was accurately predicted by the change in ΔZ (R2 0.855, P < .001 at global level) with a high agreement between predicted and measured StrainCT. Conclusions: The change in electrical impedance may provide a noninvasive assessment of global cyclic strain, without radiation at bedside.

Secretion management in mechanically ventilated patients is a paramount task for clinicians. A better understanding of the mechanisms of flow bias and airway dynamic compression during airway clearance therapy may enable a more effective approach for this population. Ventilator hyperinflation, expiratory rib cage compression, a PEEP-ZEEP maneuver, and mechanical insufflation-exsufflation are examples of techniques that can be optimized according to such mechanisms. In addition, novel technologies, such as electric impedance tomography, may help improve airway clearance therapy by monitoring the consequences of regional secretion displacement on lung aeration and regional lung mechanics.

OBJECTIVES It is not known how lung injury progression during mechanical ventilation modifies pulmonary responses to prone positioning. We compared the effects of prone positioning on regional lung aeration in late versus early stages of lung injury. DESIGN Prospective, longitudinal imaging study. SETTING Research imaging facility at The University of Pennsylvania (Philadelphia, PA) and Medical and Surgical ICUs at Massachusetts General Hospital (Boston, MA). SUBJECTS Anesthetized swine and patients with acute respiratory distress syndrome (acute respiratory distress syndrome). INTERVENTIONS Lung injury was induced by bronchial hydrochloric acid (3.5 mL/kg) in 10 ventilated Yorkshire pigs and worsened by supine nonprotective ventilation for 24 hours. Whole-lung CT was performed 2 hours after hydrochloric acid (Day 1) in both prone and supine positions and repeated at 24 hours (Day 2). Prone and supine images were registered (superimposed) in pairs to measure the effects of positioning on the aeration of each tissue unit. Two patients with early acute respiratory distress syndrome were compared with two patients with late acute respiratory distress syndrome, using electrical impedance tomography to measure the effects of body position on regional lung mechanics. MEASUREMENTS AND MAIN RESULTS Gas exchange and respiratory mechanics worsened over 24 hours, indicating lung injury progression. On Day 1, prone positioning reinflated 18.9% ± 5.2% of lung mass in the posterior lung regions. On Day 2, position-associated dorsal reinflation was reduced to 7.3% ± 1.5% (p < 0.05 vs Day 1). Prone positioning decreased aeration in the anterior lungs on both days. Although prone positioning improved posterior lung compliance in the early acute respiratory distress syndrome patients, it had no effect in late acute respiratory distress syndrome subjects. CONCLUSIONS The effects of prone positioning on lung aeration may depend on the stage of lung injury and duration of prior ventilation; this may limit the clinical efficacy of this treatment if applied late.

Background Inhaled nitric oxide (NO) is a selective pulmonary vasodilator. In-vitro studies report that NO donors can inhibit replication of SARS-CoV-2. This multicenter study evaluated the feasibility and effects of high-dose inhaled NO in non-intubated spontaneously breathing patients with Coronavirus disease-2019 (COVID-19). Methods This is an interventional study to determine whether NO at 160 parts-per-million (ppm) inhaled for 30 min twice daily might be beneficial and safe in non-intubated COVID-19 patients. Results Twenty-nine COVID-19 patients received a total of 217 intermittent inhaled NO treatments for 30 min at 160 ppm between March and June 2020. Breathing NO acutely decreased the respiratory rate of tachypneic patients and improved oxygenation in hypoxemic patients. The maximum level of nitrogen dioxide delivered was 1.5 ppm. The maximum level of methemoglobin (MetHb) during the treatments was 4.7%. MetHb decreased in all patients 5 min after discontinuing NO administration. No adverse events during treatment, such as hypoxemia, hypotension, or acute kidney injury during hospitalization occurred. In our NO treated patients, one patient of 29 underwent intubation and mechanical ventilation, and none died. The median hospital length of stay was 6 days [interquartile range 4–8]. No discharged patients required hospital readmission nor developed COVID-19 related long-term sequelae within 28 days of follow-up. Conclusions In spontaneous breathing patients with COVID-19, the administration of inhaled NO at 160 ppm for 30 min twice daily promptly improved the respiratory rate of tachypneic patients and systemic oxygenation of hypoxemic patients. No adverse events were observed. None of the subjects was readmitted or had long-term COVID-19 sequelae.

Made available in DSpace on 2021-06-25T11:13:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-28 Introduction and aim: Studies regarding asynchrony in patiients in the cardiac postoperative period are still only a few. The main objective of our study was to compare asynchronies incidence and its index (AI) in 3 different modes of ventilation (volume-controlled ventilation [VCV], pressure-controlled ventilation [PCV] and pressure-support ventilation [PSV]) after ICU admission for postoperative care. Methods: A prospective parallel randomised trialin the setting of a non-profitable hospital in Brazil. The participants were patients scheduled for cardiac surgery. Patients were randomly allocated to VCV or PCV modes of ventilation and later both groups were transitioned to PSV mode. Results: All data were recorded for 5 minutes in each of the three different phases: T1) in assisted breath, T2) initial spontaneous breath and T3) final spontaneous breath, a marking point prior to extubation. Asynchronies were detected and counted by visual inspection method by two independent investigators. Reliability, inter-rater agreement of asynchronies, asynchronies incidence, total and specific asynchrony indexes (AIt and AIspecific) and odds of AI ≥10% weighted by total asynchrony were analysed. A total of 17 patients randomly allocated to the VCV (n= 9) or PCV (n=8) group completed the study. High inter-rated agreement for AIt (ICC 0.978; IC95%, 0,963-0.987) and good reliability (r=0.945; p

Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background Intraoperative lung-protective ventilation has been recommended to reduce postoperative pulmonary complications after abdominal surgery. Although the protective role of a more physiologic tidal volume has been established, the added protection afforded by positive end-expiratory pressure (PEEP) remains uncertain. The authors hypothesized that a low fixed PEEP might not fit all patients and that an individually titrated PEEP during anesthesia might improve lung function during and after surgery. Methods Forty patients were studied in the operating room (20 laparoscopic and 20 open-abdominal). They underwent elective abdominal surgery and were randomized to institutional PEEP (4 cm H2O) or electrical impedance tomography–guided PEEP (applied after recruitment maneuvers and targeted at minimizing lung collapse and hyperdistension, simultaneously). Patients were extubated without changing selected PEEP or fractional inspired oxygen tension while under anesthesia and submitted to chest computed tomography after extubation. Our primary goal was to individually identify the electrical impedance tomography–guided PEEP value producing the best compromise of lung collapse and hyperdistention. Results Electrical impedance tomography–guided PEEP varied markedly across individuals (median, 12 cm H2O; range, 6 to 16 cm H2O; 95% CI, 10–14). Compared with PEEP of 4 cm H2O, patients randomized to the electrical impedance tomography–guided strategy had less postoperative atelectasis (6.2 ± 4.1 vs. 10.8 ± 7.1% of lung tissue mass; P = 0.017) and lower intraoperative driving pressures (mean values during surgery of 8.0 ± 1.7 vs. 11.6 ± 3.8 cm H2O; P < 0.001). The electrical impedance tomography–guided PEEP arm had higher intraoperative oxygenation (435 ± 62 vs. 266 ± 76 mmHg for laparoscopic group; P < 0.001), while presenting equivalent hemodynamics (mean arterial pressure during surgery of 80 ± 14 vs. 78 ± 15 mmHg; P = 0.821). Conclusions PEEP requirements vary widely among patients receiving protective tidal volumes during anesthesia for abdominal surgery. Individualized PEEP settings could reduce postoperative atelectasis (measured by computed tomography) while improving intraoperative oxygenation and driving pressures, causing minimum side effects.

Introduction: Noninvasive ventilation has been widely used to prevent pulmonary complications after cardiac surgery. Electrical Impedance Tomography(EIT) has been highlighted as a tool to monitor the distribution of regional pulmonary ventilation. However, there are few studies available on the use of this tool in evaluating the effects of noninvasive ventilation(NIV). Objectives: To compare the effects of noninvasive ventilation with oxygen therapy(OT) on pulmonary aeration and ventilation in patients in the immediate postoperative period of cardiac surgery; Hypothesis: the use of non-invasive ventilation in patients in the postoperative period of cardiac surgery results in greater ventilation and greater aeration during and after intervention compared to the control group. Methods: Patients were randomized into two groups: NIV and OT (control). The evaluation was performed through EIT. Results: 16 patients were randomized, 9 in NIV group and 7 in OT group. Greater global end expiratory lung impedance (pulmonary aeration) was observed during NIV when compared to OT group (0,20±0,08 and 0,23±0,10 vs. -0,14±0,01 and -0,21±0,02, p value 0,009 and 0,013 respectively); but there was no maintenance of this improvement after intervention. There was also a greater variation of global impedance (ventilation) change during intervention (7,96 vs. 4,17, p value 0,03). Conclusion: There was increased global aeration and ventilation during noninvasive ventilation in patients in post-operative cardiac surgery, but there was no maintenance of aeration improvement after its interruption. Grants: FACEPE, CNPq and CAPES.

Background: Floor and ceiling effects of functional status (FS) and peripheral muscle strength (PMS) assessment scales are reported in patients under mechanical ventilation at Intensive Care Unit (ICU) (Parry, S.M. et al. Critical Care 2015; 19:127). These effects can influence sensibility and responsiveness of those scales to clinical changes of different health conditions. Objective: To evaluate the frequency of floor and ceiling effects of FS and PMS scales in non-intubated patients during ICU stay. Methods: 40 patients (26 men). Functional Independence Measure (FIM), Functional Status Score for the Intensive Care Unit (FSS-ICU), Physical Function ICU Test Score (PFIT-s), Basic Mobility Scale (ICF-BMS) and Medical Research Council score (MRC-s) were assessed at ICU admission and discharge. Floor and ceiling effects were calculated by percentage frequency of highest and lowest scores, respectively. Results: Mean age was 55.1(19.2) years old and SAPSIII was 41.7(11.0) points. The following results are all in Table 1. Conclusion: High magnitude of ceiling effect for FIM, FSS-ICU, PFIT-s and MRC-s as well as floor effect for ICF-BMS suggest that using these tools may be insufficient to detect changes in the FS and PMS of non-intubated critically ill patients during ICU stay. Table 1. Floor and ceiling effects in FS and PMS scores at ICU admission and discharge.

Acute respiratory distress syndrome (ARDS) is a clinical entity that acutely affects the lung parenchyma, and is characterized by diffuse alveolar damage and increased pulmonary vascular permeability. Currently, computed tomography (CT) is commonly used for classifying and prognosticating ARDS. However, performing this examination in critically ill patients is complex, due to the need to transfer these patients to the CT room. Fortunately, new technologies have been developed that allow the monitoring of patients at the bedside. Electrical impedance tomography (EIT) is a monitoring tool that allows one to evaluate at the bedside the distribution of pulmonary ventilation continuously, in real time, and which has proven to be useful in optimizing mechanical ventilation parameters in critically ill patients. Several clinical applications of EIT have been developed during the last years and the technique has been generating increasing interest among researchers. However, among clinicians, there is still a lack of knowledge regarding the technical principles of EIT and potential applications in ARDS patients. The aim of this review is to present the characteristics, technical concepts, and clinical applications of EIT, which may allow better monitoring of lung function during ARDS.

Introduction: Upon admission into ICU service not requiring mechanical ventilation, patients are usually considered less serious by the health care staff, which may conceal physical deficits at ICU admission which may worsen due reduced mobility during their stay. Aim: To evaluate respiratory and peripheral muscle strengths and functionality of critically ill non-ventilated patients admitted to the ICU within 48 hours. Methods: An observational study. In 82 patients (47 men), the following parameters were analysed: age, gender, SAPS III, respiratory muscle strength (MIP and MEP), peripheral muscle strength by MRC score, hand grip strength (HGS) and functionality by the functional independence measure scale (FIM), and the scored Physical Function in Intensive Care Test (PFIT-s). Results: The mean age was 57.8±19.54 years and SAPSIII was 44.1±12.6 points. Regarding the status of respiratory muscle strength, values of MIP and MEP below normal occurred in 85.7% and 80% in women and 70.2% and 72.3% in men, respectively. The MRC score was normal in all participants, but for HGS (based on the reference values by Shlussel, MM. et al. Clin Nutri. 2008), 58.5% of the participants presented a reduction; of these, 51.4% were women and 63.8% men. Regarding functionality, the median for FIM was 58 (44-71) points, representing 75.3% of the maximum score, while PFIT-s had a median of 10 (8-11) points, representing 83.3% of the maximum score. Conclusion: In a short stay in an ICU, it is possible to identify already committed changes in either respiratory and peripheral muscle strengths that may compromise functionality evaluated in the first 48 hours of admission.

Objectives Atelectasis develops in critically ill obese patients when undergoing mechanical ventilation due to increased pleural pressure. The current study aimed to determine the relationship between transpulmonary pressure, lung mechanics, and lung morphology and to quantify the benefits of a decremental positive end-expiratory pressure trial preceded by a recruitment maneuver. Design Prospective, crossover, nonrandomized interventional study. Setting Medical and Surgical Intensive Care Units at Massachusetts General Hospital (Boston, MA) and University Animal Research Laboratory (Sao Paulo, Brazil). Patients/subjects Critically ill obese patients with acute respiratory failure and anesthetized swine. Interventions Clinical data from 16 mechanically ventilated critically ill obese patients were analyzed. An animal model of obesity with reversible atelectasis was developed by placing fluid filled bags on the abdomen to describe changes of lung mechanics, lung morphology, and pulmonary hemodynamics in 10 swine. Measurements and main results In obese patients (body mass index, 48 ± 11 kg/m), 21.7 ± 3.7 cm H2O of positive end-expiratory pressure resulted in the lowest elastance of the respiratory system (18.6 ± 6.1 cm H2O/L) after a recruitment maneuver and decremental positive end-expiratory pressure and corresponded to a positive (2.1 ± 2.2 cm H2O) end-expiratory transpulmonary pressure. Ventilation at lowest elastance positive end-expiratory pressure preceded by a recruitment maneuver restored end-expiratory lung volume (30.4 ± 9.1 mL/kg ideal body weight) and oxygenation (273.4 ± 72.1 mm Hg). In the swine model, lung collapse and intratidal recruitment/derecruitment occurred when the positive end-expiratory transpulmonary pressure decreased below 2-4 cm H2O. After the development of atelectasis, a decremental positive end-expiratory pressure trial preceded by lung recruitment identified the positive end-expiratory pressure level (17.4 ± 2.1 cm H2O) needed to restore poorly and nonaerated lung tissue, reestablishing lung elastance and oxygenation while avoiding increased pulmonary vascular resistance. Conclusions In obesity, low-to-negative values of transpulmonary pressure predict lung collapse and intratidal recruitment/derecruitment. A decremental positive end-expiratory pressure trial preceded by a recruitment maneuver reverses atelectasis, improves lung mechanics, distribution of ventilation and oxygenation, and does not increase pulmonary vascular resistance.