Background: ARDS incidence in patients with COVID-19 pneumonia varies from 15-42%; between 5-20% of patients with hospitalization criteria received mechanical ventilation (1-3). Prone positioning demonstrated mortality benefits for patients with Severe ARDS (sARDS) with lung injury, but its use in patient COVID-19 is not clear (4-6). ARDS protocol (ARDSp) is recommended by ATS and The Surviving Sepsis Campaign-COVID-19 guidelines, but its implementation should be evaluated case by case (7).
Methods: A retrospective cohort study that included patients with SARS-CoV2 positive by RT-PCR on Mechanical Ventilation from March-May 2020. Patients on ARDS by Berlin definition and PaO2/FiO2 ≤150 mmHg were included in our study. Death <24 hours followed endotracheal intubation, intubated in the field or other facilities, and transferred to our institution were exclusion criteria. Prone positing maneuver was performed by a multidisciplinary team based on our institutional protocol. ARDSnet protocol was followed at least 14 days if the patient was still alive. Kaplan-Maier curve and long-rank test were applied for survival analysis. Cox Proportional Hazzard Regression was conducted to determine risk factors for Mortality simultaneously. A significant p-value was considered as <0.05.
Results: Of 354 patients on mechanical ventilation, 239 (67.5%) met sARDS criteria. Mortality rate in sARDS subset was 77.4%. Kaplan-Meier survival analysis shows that subjects on ARDSp and Prone positioning intervention had a median time to survive of 32.0 (95%CI, [7.5-56.5]) days, which was longer than the nonintervention group 13.1 (95%CI, [11.1-15.1]) days. Significant differences were found by Long Rank tests (p=0.03). In our cohort, Proning positioning with ARDSp reduced mortality risk (adjusted HR, 0.48 [0.27-0.88], p=0.017). Other variables as Renal replacement therapy (aHR, 0.47, [0.32-0.70], p<0.000), LatinX (aHR, 0.68 [0.49-0.94], p=0.019) and Female (aHR, 0.69 [0.51-0.94], p=0.02) show independently reduction in mortality risk. Contrary, COPD (aHR, 1.9 [1.3-2.8], p=0.001), Sepsis syndrome defined by qSOFA (aHR, 2.23 [1.58-3.14], p<0.000), AKI on admission (aHR, 1.69 [1.20-2.38], p=0.003), and degree of Oxygen supplementation on admission (aHR, 1.01[1.004-1.016], p=0.001) increased Mortality risk.
Conclusions: Mortality in patients with sARDS on mechanical ventilation was high but did not differ from other studies in NYC (8). The WHO guidelines recommend mechanical ventilation support in COVID-19 infection for ARDS patients or need support for other dysfunctional organs (9). Covid-19 ARDS (cARDS) physiopathology, in contrast with ARDS from another virus, reveals ventilation-perfusion mismatch due to impairment in hypoxic pulmonary vasoconstriction and production of microemboli into the pulmonary circulation according to some mathematical model (10). Prone positioning is part of standard care for patients on sARDS with lung injury. It shows improved oxygenation parameters among awake non-intubated patients with hypoxemic respiratory failure due to COVID-19 infection (6). Patients mechanically ventilated with prone positioning maneuver improves ventilation and oxygenation parameters, but there is no effect on Mortality (11). ARDSp can be deleterious in cARDS for patients with good lung compliance (L-elastase phenotype) and can precipitate shock (7,12). In our cohort, prone positioning with ARDSp reduces mortality risk for patients that meet strict criteria for both interventions.