Prognostic value of computed tomographic findings in acute respiratory distress syndrome and the response to prone positioning

Factors associated with a nonresponse to prone positioning in patients with severe acute respiratory distress syndrome due to SARS-CoV-2

OBJECTIVE

To identify risk factors for nonresponse to prone positioning in mechanically ventilated patients with COVID-19-associated severe acute respiratory distress syndrome and refractory hypoxemia in a tertiary care hospital in Colombia.

METHODS

Observational study based on a retrospective cohort of mechanically ventilated patients with severe acute respiratory distress syndrome due to SARS-CoV-2 who underwent prone positioning due to refractory hypoxemia. The study considered an improvement ≥ 20% in the PaO2/FiO2 ratio after the first cycle of 16 hours in the prone position to be a 'response'. Nonresponding patients were considered cases, and responding patients were controls. We controlled for clinical, laboratory, and radiological variables.

RESULTS

A total of 724 patients were included (58.67 ± 12.37 years, 67.7% males). Of those, 21.9% were nonresponders. Mortality was 54.1% for nonresponders and 31.3% for responders (p < 0.001). Variables associated with nonresponse were time from the start of mechanical ventilation to pronation (OR 1.23; 95%CI 1.10 - 1.41); preintubation PaO2/FiO2 ratio (OR 0.62; 95%CI 0.40 - 0.96); preprone PaO2/FiO2 ratio (OR 1.88. 95%CI 1.22 - 2.94); and radiologic multilobe consolidation (OR 2.12; 95%CI 1.33 - 3.33) or mixed pattern (OR 1.72; 95%CI 1.07 - 2.85) compared with a ground-glass pattern.

CONCLUSION

This study identified factors associated with nonresponse to prone positioning in patients with refractory hypoxemia and acute respiratory distress syndrome due to SARS-CoV-2 receiving mechanical ventilation. Recognizing such factors helps identify candidates for other rescue strategies, including more extensive prone positioning or extracorporeal membrane oxygenation. Further studies are needed to assess the consistency of these findings in populations with acute respiratory distress syndrome of other etiologies.

Effect of prone positioning on gas exchange according to lung morphology in patients with acute respiratory distress syndrome

Background: There are limited data on the clinical effects of prone positioning according to lung morphology. We aimed to determine whether the gas exchange response to prone positioning differs according to lung morphology.Methods: This retrospective study included adult patients with moderate-to-severe acute respiratory distress syndrome (ARDS). The lung morphology of ARDS was assessed by chest computed tomography scan and classified as “diffuse” or “focal.” The primary outcome was change in partial pressure of arterial oxygen to fraction of inspired oxygen (PaO2/FiO2) ratio after the first prone positioning session: first, using the entire cohort, and second, using subgroups of patients with diffuse ARDS matched 2 to 1 with patients with focal ARDS at baseline.Results: Ninety-five patients were included (focal ARDS group, 23; diffuse ARDS group, 72). Before prone positioning, the focal ARDS group showed worse oxygenation than the diffuse ARDS group (median PaO2/FiO2 ratio, 79.9 mm Hg [interquartile range (IQR)], 67.7–112.6 vs. 104.0 mm Hg [IQR, 77.6–135.7]; P=0.042). During prone positioning, the focal ARDS group showed a greater improvement in the PaO2/FiO2 ratio than the diffuse ARDS group (median, 55.8 mm Hg [IQR, 11.1–109.2] vs. 42.8 mm Hg [IQR, 11.6–83.2]); however, the difference was not significant (P=0.705). Among the PaO2/FiO2-matched cohort, there was no significant difference in change in PaO2/FiO2 ratio after prone positioning between the groups (P=0.904).Conclusions: In patients with moderate-to-severe ARDS, changes in PaO2/FiO2 ratio after prone positioning did not differ according to lung morphology. Therefore, prone positioning can be considered as soon as indicated, regardless of ARDS lung morphology.

COVID-19 Lessons Learned: Prone Positioning With and Without Invasive Ventilation

Prone positioning (PP) has been used extensively for patients requiring invasive mechanical ventilation for hypoxemic respiratory failure during the COVID-19 pandemic. Evidence suggests that PP was beneficial during the pandemic, as it improves oxygenation and might improve chances of survival, especially in those with a continuum of positive oxygenation responses to the procedure. Additionally, the pandemic drove innovation regarding PP, as it brought attention to awake PP (APP) and the value of an interdisciplinary team approach to PP during a pandemic. APP appears to be safe and effective at improving oxygenation; APP may also reduce the need for intubation in patients requiring advanced respiratory support like high-flow nasal cannula or noninvasive ventilation. Teams specifically assembled for PP during a pandemic also appear useful and can provide needed assistance to bedside clinicians in the time of crisis. Complications associated with PP can be mitigated, and a multidisciplinary approach to reduce the incidence of complications is recommended.