Moderate-to-severe ARDS: COVID-19 patients compared to influenza patients for ventilator parameters and mortality

Background This study aimed to compare ventilatory parameters recorded in the first days of acute respiratory distress syndrome (ARDS) and mortality at day 60 between coronavirus disease 2019 (COVID19) and influenza ARDS patients with arterial oxygen tension (P-aO2)/inspiratory oxygen fraction (F-IO2)<= 150 mmHg. Methods We compared 244 COVID-19 ARDS patients with 106 influenza ARDS patients. Driving pressure, respiratory system compliance (Crs), ventilator ratio, corrected minute ventilation (V'(Ecorr)) and surrogate of mechanical power (index=(4xdriving pressure)+respiratory rate) were calculated from day 1 to day 5 of ARDS. A propensity score analysis and a principal component analysis (PCA) were performed. Results On day 1 of ARDS, COVID-19 patients had significantly higher P-aO2/F-IO2 (median (interquartile range) 97 (79-129.2) versus 83 (62.2-114) mmHg; p=0.001), and lower driving pressure (13.0 (11.0-16.0) versus 14.0 (12.0-16.7) cmH2O; p=0.01), ventilatory ratio (2.08 (1.73-2.49 versus 2.52 (1.97-3.03); p < 0.001), V' Ecorr (12.7 (10.2-14.9) versus 14.9 (11.6-18.6) L center dot min(-1); p < 0.001) and index (80 (70-89) versus 84 (75-94); p=0.004). PCA demonstrated an important overlap of ventilatory parameters recorded on day 1 between the two groups. From day 1 to day 5, repeated values of P-aO2/F-IO2, arterial carbon dioxide tension, ventilatory ratio and V' Ecorr differed significantly between influenza and COVID-19 patients in the unmatched and matched populations. Mortality at day 60 did not differ significantly after matching (29% versus 21.7%; p=0.43). Conclusions Ventilation was more impaired in influenza than in COVID-19 ARDS patients on the first day of ARDS with an important overlap of values. However, mortality at day 60 did not differ significantly in the matched population.