Respiratory system compliance at the same PEEP level is similar in COVID and non-COVID ARDS

Background The comparison of respiratory system compliance (Crs) between COVID and non-COVID ARDS patients has been the object of debate, but few studies have evaluated it when considering applied positive end expiratory pressure (PEEP), which is one of the known determinants of Crs itself. The aim of this study was to compare Crs taking into account the applied PEEP. Methods Two cohorts of patients were created: those with COVID-ARDS and those with non-COVID ARDS. In the whole sample the association between Crs and type of ARDS at different PEEP levels was adjusted for anthropometric and clinical variables. As secondary analyses, patients were matched for predicted functional residual capacity and the same association was assessed. Moreover, the association between Crs and type of ARDS was reassessed at predefined PEEP level of 0, 5, 10, and 15 cmH2O with a propensity score-weighted linear model. Results 367 patients were included in the study, 276 patients with COVID-ARDS and 91 with non-COVID ARDS. The association between Crs and type of ARDS was not significant in both the complete cohorts (p = 0.17) and in the matched cohorts (p = 0.92). This was true also for the propensity score weighted association at PEEP 5, 10 and 15 cmH2O, while it was statistically significant at PEEP 0 (with a median difference of 3 ml/cmH2O, which in our opinion is not clinically significant). Conclusions The compliance of the respiratory system is similar between COVID ARDS and non-COVID ARDS when calculated at the same PEEP level and while taking into account patients’ anthropometric characteristics.

Mechanical power in pediatric acute respiratory distress syndrome: a PARDIE study

Background Mechanical power is a composite variable for energy transmitted to the respiratory system over time that may better capture risk for ventilator-induced lung injury than individual ventilator management components. We sought to evaluate if mechanical ventilation management with a high mechanical power is associated with fewer ventilator-free days (VFD) in children with pediatric acute respiratory distress syndrome (PARDS). Methods Retrospective analysis of a prospective observational international cohort study. Results There were 306 children from 55 pediatric intensive care units included. High mechanical power was associated with younger age, higher oxygenation index, a comorbid condition of bronchopulmonary dysplasia, higher tidal volume, higher delta pressure (peak inspiratory pressure—positive end-expiratory pressure), and higher respiratory rate. Higher mechanical power was associated with fewer 28-day VFD after controlling for confounding variables (per 0.1 J·min−1·Kg−1 Subdistribution Hazard Ratio (SHR) 0.93 (0.87, 0.98), p = 0.013). Higher mechanical power was not associated with higher intensive care unit mortality in multivariable analysis in the entire cohort (per 0.1 J·min−1·Kg−1 OR 1.12 [0.94, 1.32], p = 0.20). But was associated with higher mortality when excluding children who died due to neurologic reasons (per 0.1 J·min−1·Kg−1 OR 1.22 [1.01, 1.46], p = 0.036). In subgroup analyses by age, the association between higher mechanical power and fewer 28-day VFD remained only in children < 2-years-old (per 0.1 J·min−1·Kg−1 SHR 0.89 (0.82, 0.96), p = 0.005). Younger children were managed with lower tidal volume, higher delta pressure, higher respiratory rate, lower positive end-expiratory pressure, and higher PCO2 than older children. No individual ventilator management component mediated the effect of mechanical power on 28-day VFD. Conclusions Higher mechanical power is associated with fewer 28-day VFDs in children with PARDS. This association is strongest in children < 2-years-old in whom there are notable differences in mechanical ventilation management. While further validation is needed, these data highlight that ventilator management is associated with outcome in children with PARDS, and there may be subgroups of children with higher potential benefit from strategies to improve lung-protective ventilation. Take Home Message: Higher mechanical power is associated with fewer 28-day ventilator-free days in children with pediatric acute respiratory distress syndrome. This association is strongest in children <2-years-old in whom there are notable differences in mechanical ventilation management.

Mechanical Ventilation with Dynamic Compliance-Guided Positive End-Expiratory Pressure in Laparoscopic Surgery with Trendelenburg Positioning: A Eandomised Controlled Study

BACKGROUND: The intraoperative cardiorespiratory effect of ventilation with individualised positive end-expiratory pressure guided by dynamic compliance (Cdyn) remains undefined. We investigated whether individualised protective ventilation would protect the heart and lung more efficiently than standard protective ventilation during abdominal laparoscopic surgery with Trendelenburg positioning.METHODS: Forty patients undergoing abdominal laparoscopic surgery were randomly divided into two groups: Group T (titrimetric PEEP) and Group I (intentional PEEP, 5 cmH2O). Parameters of right ventricular function were measured via transoesophageal echocardiography, including tricuspid annular plane systolic excursion (TAPSE), early filling-to-late filling ratio of the right ventricle, and right ventricular end-diastolic area/left ventricular end-diastolic area (RVEDA/LVEDA) ratio. Cdyn, driving pressure (∆P), ratio of dead space to tidal volume (VD/VT), and partial pressure of arterial oxygen to inspiratory oxygen fraction (PF) ratio were measured during mechanical ventilation.RESULTS: The RVEDA/LVEDA ratio in all patients increased significantly at T2 compared with T0, but there were no significant differences in TAPSE or E/A ratio between groups during the whole procedure (P>0.05). Cdyn, ∆P, and VD/VT ratios in Group T were significantly improved compared to those in Group I at T2 (P<0.05). There was no significant difference in the PF ratio between groups (P>0.05).CONCLUSIONS: Intraoperative lung-protective ventilation with Cdyn-guided PEEP improved Cdyn, ∆P, and VD/VT ratio without obvious side effects on right ventricular function compared to standard protective ventilation during laparoscopic surgery with Trendelenburg positioning, which suggests that it is a circulation-friendly way to titrate PEEP for intraoperative lung protective ventilation.TRIAL REGISTRATION: Trial registration date: 13/09/2020; Trial registration number: ChiCTR2000038212.

Case Report: Respiratory Management With a 47-Day ECMO Support for a Critical Patient With COVID-19

This paper reports a complete case of severe acute respiratory distress syndrome (ARDS) caused by coronavirus disease 2019 (COVID-19), who presented with rapid deterioration of oxygenation during hospitalization despite escalating high-flow nasal cannulation to invasive mechanical ventilation. After inefficacy with lung-protective ventilation, positive end-expiratory pressure (PEEP) titration, prone position, we administered extracorporeal membrane oxygenation (ECMO) as a salvage respiratory support with ultra-protective ventilation for 47 days and finally discharged the patient home with a good quality of life with a Barthel Index Score of 100 after 76 days of hospitalization. The purpose of this paper is to provide a clinical reference for the management of ECMO and respiratory strategy of critical patients with COVID-19-related ARDS.

A more gradual positive end-expiratory pressure increase reduces lung damage and improves cardiac function in experimental acute respiratory distress syndrome

Increases in positive end-expiratory pressure (PEEP) or recruitment maneuvers may increase stress in lung parenchyma, extracellular matrix, and lung vessels; however, adaptative responses may occur. We evaluated the effects of PEEP on lung damage and cardiac function when increased abruptly, gradually, or more gradually in experimental mild/moderate acute respiratory distress syndrome (ARDS) induced by Escherichia coli lipopolysaccharide intratracheally. After 24h, Wistar rats (n=48) were randomly assigned to four mechanical ventilation strategies according to PEEP levels: (1) 3 cmH2O for 2-h (control); (2) 3 cmH2O for 1-h followed by an abrupt increase to 9 cmH2O for 1-h (no adaptation time); (3) 3 cmH2O for 30 min followed by a gradual increase to 9 cmH2O over 30 min then kept constant for 1-h (shorter adaptation time); and (4) more gradual increase in PEEP from 3 cmH2O to 9 cmH2O over 1-h and kept constant thereafter (longer adaptation time). At the end of the experiment, oxygenation improved in the shorter and longer adaptation time groups compared to the no-adaptation and control groups. Diffuse alveolar damage and expressions of interleukin-6, club cell protein-16, vascular cell adhesion molecule-1, amphiregulin, decorin, and syndecan were higher in no adaptation time compared to other groups. Pulmonary arterial pressure was lower in longer adaptation time than in no adaptation (p=0.002) and shorter adaptation time (p=0.025) groups. In this model, gradually increasing PEEP limited lung damage and release of biomarkers associated with lung epithelial/endothelial cell and extracellular matrix damage, as well as the PEEP-associated increase in pulmonary arterial pressure.

Positive End-Expiratory Pressure Setting in COVID-19-Related Acute Respiratory Distress Syndrome: Comparison Between Electrical Impedance Tomography, PEEP/FiO2 Tables, and Transpulmonary Pressure

Introduction: The best way to titrate the positive end-expiratory pressure (PEEP) in patients suffering from acute respiratory distress syndrome is still matter of debate. Electrical impedance tomography (EIT) is a non-invasive technique that could guide PEEP setting based on an optimized ventilation homogeneity.Methods: For this study, we enrolled the patients with 2019 coronavirus disease (COVID-19)-related acute respiratory distress syndrome (ARDS), who required mechanical ventilation and were admitted to the ICU in March 2021. Patients were monitored by an esophageal catheter and a 32-electrode EIT device. Within 48 h after the start of mechanical ventilation, different levels of PEEP were applied based upon PEEP/FiO2 tables, positive end-expiratory transpulmonary (PL)/ FiO2 table, and EIT. Respiratory mechanics variables were recorded.Results: Seventeen patients were enrolled. PEEP values derived from EIT (PEEPEIT) were different from those based upon other techniques and has poor in-between agreement. The PEEPEIT was associated with lower plateau pressure, mechanical power, transpulmonary pressures, and with a higher static compliance (Crs) and homogeneity of ventilation.Conclusion: Personalized PEEP setting derived from EIT may help to achieve a more homogenous distribution of ventilation. Whether this approach may translate in outcome improvement remains to be investigated.

Portal Vein Pulsatility as a Dynamic Marker of Venous Congestion Following Cardiac Surgery: An Interventional Study Using Positive End-Expiratory Pressure

We aimed to assess variations in the portal vein pulsatility index (PI) during mechanical ventilation following cardiac surgery. Method. After ethical approval, we conducted a prospective monocentric study at Amiens University Hospital. Patients under mechanical ventilation following cardiac surgery were enrolled. Doppler evaluation of the portal vein (PV) was performed by transthoracic echography. The maximum velocity (VMAX) and minimum velocity (VMIN) of the PV were measured in pulsed Doppler mode. The PI was calculated using the following formula (VMAX − VMIN)/(VMax). A positive end-expiratory pressure (PEEP) incremental trial was performed from 0 to 15 cmH2O, with increments of 5 cmH2O. The PI (%) was assessed at baseline and PEEP 5, 10, and 15 cmH2O. Echocardiographic and hemodynamic parameters were recorded. Results. In total, 144 patients were screened from February 2018 to March 2019 and 29 were enrolled. Central venous pressure significantly increased for each PEEP increment. Stroke volumes were significantly lower after PEEP incrementation, with 52 mL (50–55) at PEEP 0 cmH2O and 30 mL (25–45) at PEEP 15 cmH2O, (p < 0.0001). The PI significantly increased with PEEP incrementation, from 9% (5–15) at PEEP 0 cmH2O to 15% (5–22) at PEEP 5 cmH2O, 34% (23–44) at PEEP 10 cmH2O, and 45% (25–49) at PEEP 15 cmH2O (p < 0.001). Conclusion. In the present study, PI appears to be a dynamic marker of the interaction between mechanical ventilation and right heart pressure after cardiac surgery. The PI could be a useful noninvasive tool to monitor venous congestion associated with mechanical ventilation.

Effects of an open lung ventilatory strategy on lung gas exchange during laparoscopic surgery

In general anaesthesia, early collapse of poorly ventilated lung segments with low alveolar ventilation–perfusion ratios occurs and may lead to postoperative pulmonary complications after abdominal surgery. An ‘open lung’ ventilation strategy involves lung recruitment followed by ‘individualised’ positive end-expiratory pressure titrated to maintain recruitment of low alveolar ventilation–perfusion ratio lung segments. There are limited data in laparoscopic surgery on the effects of this on pulmonary gas exchange. Forty laparoscopic bowel surgery patients were randomly assigned to standard ventilation or an ‘open lung’ ventilation intervention, with end-tidal target sevoflurane of 1% supplemented by propofol infusion. After peritoneal insufflation, stepped lung recruitment was performed in the intervention group followed by maintenance positive end-expiratory pressure of 12–15 cmH2O adjusted to maintain dynamic lung compliance at post-recruitment levels. Baseline gas and blood samples were taken and repeated after a minimum of 30 minutes for oxygen and carbon dioxide and for sevoflurane partial pressures using headspace equilibration. The sevoflurane arterial/alveolar partial pressure ratio and alveolar deadspace fraction were unchanged from baseline and remained similar between groups (mean (standard deviation) control group = 0.754 (0.086) versus intervention group = 0.785 (0.099), P = 0.319), while the arterial oxygen partial pressure/fractional inspired oxygen concentration ratio was significantly higher in the intervention group at the second timepoint (control group median (interquartile range) 288 (234–372) versus 376 (297–470) mmHg in the intervention group, P = 0.011). There was no difference between groups in the sevoflurane consumption rate. The efficiency of sevoflurane uptake is not improved by open lung ventilation in laparoscopy, despite improved arterial oxygenation associated with effective and sustained recruitment of low alveolar ventilation–perfusion ratio lung segments.