Effects of Prone Positioning on Respiratory Mechanics and Oxygenation in Critically Ill Patients With COVID-19 Requiring Venovenous Extracorporeal Membrane Oxygenation

Background:The effect of prone positioning (PP) on respiratory mechanics remains uncertain in patients with severe acute respiratory distress syndrome (ARDS) requiring venovenous extracorporeal membrane oxygenation (VV-ECMO).Methods:We prospectively analyzed the effects of PP on respiratory mechanics from continuous data with over a thousand time points during 16-h PP sessions in patients with COVID-19 and ARDS under VV-ECMO conditions. The evolution of respiratory mechanical and oxygenation parameters during the PP sessions was evaluated by dividing each PP session into four time quartiles: first quartile: 0–4 h, second quartile: 4–8 h, third quartile: 8–12 h, and fourth quartile: 12–16 h.Results:Overall, 38 PP sessions were performed in 10 patients, with 3 [2–5] PP sessions per patient. Seven (70%) patients were responders to at least one PP session. PP significantly increased the PaO2/FiO2 ratio by 14 ± 21% and compliance by 8 ± 15%, and significantly decreased the oxygenation index by 13 ± 18% and driving pressure by 8 ± 12%. The effects of PP on respiratory mechanics but not on oxygenation persisted after supine repositioning. PP-induced changes in different respiratory mechanical parameters and oxygenation started as early as the first-time quartile, without any difference in PP-induced changes among the different time quartiles. PP-induced changes in driving pressure (−14 ± 14 vs. −6 ± 10%, p = 0.04) and mechanical power (−11 ± 13 vs. −0.1 ± 12%, p = 0.02) were significantly higher in responders (increase in PaO2/FiO2 ratio > 20%) than in non-responder patients.Conclusions:In patients with COVID-19 and severe ARDS, PP under VV-ECMO conditions improved the respiratory mechanical and oxygenation parameters, and the effects of PP on respiratory mechanics persisted after supine repositioning.

Maintenance of low driving pressure in patients with early acute respiratory distress syndrome significantly affects outcomes

Background Driving pressure (∆P) is an important factor that predicts mortality in acute respiratory distress syndrome (ARDS). We test the hypothesis that serial changes in daily ΔP rather than Day 1 ΔP would better predict outcomes of patients with ARDS. Methods This retrospective cohort study enrolled patients admitted to five intensive care units (ICUs) at a medical center in Taiwan between March 2009 and January 2018 who met the criteria for ARDS and received the lung-protective ventilation strategy. ∆P was recorded daily for 3 consecutive days after the diagnosis of ARDS, and its correlation with 60-day survival was analyzed. Results A total of 224 patients were enrolled in the final analysis. The overall ICU and 60-day survival rates were 52.7% and 47.3%, respectively. ∆P on Days 1, 2, and 3 was significantly lower in the survival group than in the nonsurvival group (13.8 ± 3.4 vs. 14.8 ± 3.7, p = 0.0322, 14 ± 3.2 vs. 15 ± 3.5, p = 0.0194, 13.6 ± 3.2 vs. 15.1 ± 3.4, p = 0.0014, respectively). The patients were divided into four groups according to the daily changes in ∆P, namely, the low ∆P group (Day 1 ∆P < 14 cmH2O and Day 3 ∆P < 14 cmH2O), decrement group (Day 1 ∆P ≥ 14 cmH2O and Day 3 ∆P < 14 cmH2O), high ∆P group (Day 1 ∆P ≥ 14 cmH2O and Day 3 ∆P ≥ 14 cmH2O), and increment group (Day 1 ∆P < 14 cmH2O and Day 3 ∆P ≥ 14 cmH2O). The 60-day survival significantly differed among the four groups (log-rank test, p = 0.0271). Compared with the low ΔP group, patients in the decrement group did not have lower 60-day survival (adjusted hazard ratio 0.72; 95% confidence interval [CI] 0.31–1.68; p = 0.4448), while patients in the increment group had significantly lower 60-day survival (adjusted hazard ratio 1.96; 95% CI 1.11–3.44; p = 0.0198). Conclusions Daily ∆P remains an important predicting factor for survival in patients with ARDS. Serial changes in daily ΔP might be more informative than a single Day 1 ΔP value in predicting survival of patients with ARDS.

Relationship between Driving Pressure and Mortality in Ventilated Patients with Heart Failure: A Cohort Study

Background. Heart failure (HF) is a leading cause of mortality and morbidity worldwide, with an increasing incidence. Invasive ventilation is considered to be essential for patients with HF. Previous studies have shown that driving pressure is associated with mortality in acute respiratory distress syndrome (ARDS). However, the relationship between driving pressure and mortality has not yet been examined in ventilated patients with HF. We assessed the association of driving pressure and mortality in patients with HF. Methods. We conducted a retrospective cohort study of invasive ventilated adult patients with HF from the Medical Information Mart for Intensive Care-III database. We used multivariable logistic regression models, a generalized additive model, and a two-piecewise linear regression model to show the effect of the average driving pressure within 24 h of intensive care unit admission on in-hospital mortality. Results. Six hundred and thirty-two invasive ventilated patients with HF were enrolled. Driving pressure was independently associated with in-hospital mortality (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.06–1.18; P < 0.001 ) after adjusted potential confounders. A nonlinear relationship was found between driving pressure and in-hospital mortality, which had a threshold around 14.27 cmH2O. The effect sizes and CIs below and above the threshold were 0.89 (0.75 to 1.05) and 1.17 (1.07 to 1.30), respectively. Conclusions. There was a nonlinear relationship between driving pressure and mortality in patients with HF who were ventilated for more than 48 h, and this relationship was associated with increased in-hospital mortality when the driving pressure was more than 14.27 cmH2O.

Design, analysis and test of a novel cylinder-driven mode applied to microgripper

How to enlarge the output displacement is a key issue in the research field of microgrippers. It is difficult to further enlarge the output displacement for the traditional displacement transmission mechanism (DTM). In this research, a two-stage amplification cylinder-driven DTM based on the compliant mechanisms is designed to realize the displacement output expansion. The opening and closing of the clamping jaws is driven by the air cylinder to enlarge the output displacement of the microgripper. According to the analysis of statics model of the mechanism, the relationship between the output displacement of the microgripper and the driving pressure of the cylinder is established. The magnification of the microgripper is obtained using a dynamic model. Moreover, based on the finite element analysis, the mechanical structure parameters are optimized. The microgripper was fabricated by utilizing wire electro discharge machining (WEDM) technique, and then a series of experiments were carried out to obtain the relationship between the displacement and the driving pressure. It is found that the maximum output displacement measured is 1190.4μm under the pressure of 0-0.6 Mpa, corresponding to the magnification of 47.63. Compared with the results of finite element analysis and theoretical calculation, the test results have a discrepancy of 2.39% and 6.62%, respectively. The microgripper has successfully grasped a variety of micro-parts with irregular shapes, and parallel grasping can be achieved, demonstrating the potential application of this design in the field of micromanipulation.

A Retrospective Analysis of the Effects of TIME on Compliance and Driving Pressures in Acute Respiratory Distress Syndrome: The TIMED Study

Background:The evolution of compliance and driving pressure in acute respiratory distress syndrome (ARDS) and the effects of time spent on noninvasive respiratory support prior to intubation has not been well studied. We conducted this study to assess the effect of the duration of noninvasive respiratory support prior to intubation (i.e., Noninvasive ventilation (NIV), High flow nasal cannula (HFNC), or a combination of NIV and HFNC) on static compliance and driving pressure and retrospectively describe its trajectory over time for COVID-19 and non-COVID-19 ARDS while on mechanical ventilation. Methods: Retrospective analysis of prospectively collected data from one university-affiliated academic medical center, one a rural magnet hospital, and three suburban community facilities. A total of 589 patients were included: 55 COVID-19 positive, 137 culture positive, and 397 culture negative patients. Static compliance and driving pressure were calculated at each 8-hour ventilator check. Results:Days of pre-intubation noninvasive respiratory support was associated with worse compliance and driving pressure but did not moderate any trajectory. COVID-19 positive patients showed non-statistically significant worsening compliance by 0.08-units per ventilator check (p = .241), whereas COVID-19 negative patients who were either culture positive or negative patients showed statistically significant improvement (0.12 and 0.18, respectively; both p < .05); a statistically similar but inverse pattern was observed for driving pressure. ConclusionIn contrast to non-COVID-19 ARDS, COVID-19 ARDS was associated with a more ominous trajectory with no improvement in static lung compliance or driving pressures. Though there was no association between days of pre-intubation noninvasive respiratory support and mortality, its use was associated with worse overall compliance and driving pressure.

Venovenous Extracorporeal CO2 removal to support ultraprotective ventilation in moderate-severe ARDS: A systematic review and meta-analysis of the literature

BackgroundA strategy that limits tidal volumes and inspiratory pressures, improves outcomes in patients with the acute respiratory distress syndrome (ARDS). Extracorporeal carbon dioxide removal (ECCO2R) may facilitate ultra-protective ventilation. We conducted a systematic review and meta-analysis to evaluate the efficacy and safety of venovenous ECCO2R in supporting ultra-protective ventilation in moderate-to-severe ARDS.MethodsMEDLINE and EMBASE were interrogated for studies (2000-2021) reporting venovenous ECCO2R use in patients with moderate-to-severe ARDS. Studies reporting ≥10 adult patients in English language journals were included. Ventilatory parameters after 24 hours of initiating ECCO2R, device characteristics, and safety outcomes were collected. The primary outcome measure was the change in driving pressure at 24 hours of ECCO2R therapy in relation to baseline. Secondary outcomes included change in tidal volume, gas exchange, and safety data.ResultsTen studies reporting 421 patients (PaO2:FiO2 141.03mmHg) were included. Extracorporeal blood flow rates ranged from 0.35-1.5 L/min. Random effects modelling indicated a 3.56 cmH2O reduction (95%-CI: 3.22-3.91) in driving pressure from baseline (p<0.001) and a 1.89 ml/kg (95%-CI: 1.75-2.02, p<0.001) reduction in tidal volume. Oxygenation, respiratory rate and PEEP remained unchanged. No significant interactions between driving pressure reduction and baseline driving pressure, partial pressure of arterial carbon dioxide or PaO2:FiO2 ratio were identified in metaregression analysis. Bleeding and haemolysis were the commonest complications of therapy.ConclusionsVenovenous ECCO2R permitted significant reductions in ΔP in patients with moderate-to-severe ARDS. Heterogeneity amongst studies and devices, a paucity of randomised controlled trials, and variable safety reporting calls for standardisation of outcome reporting.Prospective evaluation of optimal device operation and anticoagulation in high quality studies is required before further recommendations can be made.Key MessagesWhat is the Key Question?In adult patients with moderate-to-severe acute respiratory distress syndrome (ARDS), can venovenous extracorporeal carbon dioxide removal (ECCO2R) support ultraprotective lung ventilation beyond the current standard for protective ventilation in ARDS?What is the bottom line?Systematic review of available data on venovenous ECCO2R shows that it can reduce driving pressure in ventilated patients with moderate-to-severe ARDS, supporting ultraprotective ventilation. Prospective measurement of mechanical power, and greater emphasis on safety and patient-centred outcomes is needed.Why read on?This is the first systematic review to exclusively address venovenous ECCO2R use in the moderate-to-severe ARDS cohort. We report the degree of lung protection achieved with venovenous ECCO2R devices, along with factors potentially limiting widespread adoption.