Trajectories of Hypoxemia & Respiratory System Mechanics of COVID-19 ARDS in the NorthCARDS dataset

Rationale: The preliminary reports of COVID Acute Respiratory Distress Syndrome (COVIDARDS) suggest the existence of a subset of patients with higher lung compliance despite profound hypoxemia. Understanding heterogeneity seen in patients with COVIDARDS and comparing to non-COVIDARDS may inform tailored treatments. Objectives: To describe the trajectories of hypoxemia and respiratory compliance in COVIDARDS and associations with outcomes. Methods: A multidisciplinary team of frontline clinicians and data scientists created the Northwell COVIDARDS dataset (NorthCARDS) leveraging over 11,542 COVID-19 hospital admissions. Data was summarized to describe differences based on clinically meaningful categories of lung compliance, and compared to non-COVIDARDS reports. A sophisticated method of extrapolating PaO2 from SpO2, as well estimating FiO2 from non invasive oxygen delivery devices were utilized to create meaningful trends of derived PaO2 to FiO2 (P/F). Measurements and Main Results: Of the 1595 COVIDARDS patients in the NorthCARDS dataset, there were 538 (34.6%) who had very low lung compliance (<20ml/cmH2O), 982 (63.2%) with low-normal compliance (20-50ml/cmH2O), and 34 (2.2%) with high lung compliance (>50ml/cmH2O). The very low compliance group had double the median time to intubation compared to the low-normal group (107 hours(IQR 26.3, 238.3) vs. 37.9 hours(IQR 4.8, 90.7)). Oxygenation trends have improved in all groups after a nadir immediately post intubation. The P/F ratio improved from a mean of 109 to 155, with the very low compliance group showing a smaller improvement compared to low compliance group. The derived P/F trends closely correlated with blood gas analysis driven P/F trends, except immediately post intubation were the trends diverge as illustrated in the image. Overall, 67.5% (n=1049) of the patients died during the hospitalization. In comparison to non-COVIDARDS reports, there were less patients in the high compliance category (2.2%vs 12%, compliance equal or over 50mL/cmH20), and more patients with P/F less than 150 ( 57.8% vs. 45.6%). No correlation was apparent between lung compliance and P/F ratio. The Oxygenation Index was similar, (11.12(SD 5.67)vs 12.8(SD 10.8)). Conclusions: Heterogeneity in lung compliance is seen in COVIDARDS, without apparent correlation to degree of hypoxemia. Notably, time to intubation was greater in the very low lung compliance category. Understanding ARDS patient heterogeneity must include consideration of treatment patterns in addition to trajectories of change in patient-level data and demographics.