Ventilatory Parameters Measured After One Week of Mechanical Ventilation and Survival in COVID-19–Related ARDS

BACKGROUND: Ventilatory parameters measured soon after initiation of mechanical ventilation have limited ability to predict outcome of COVID-19–related ARDS. We hypothesized that ventilatory parameters measured after one week of mechanical ventilation might differ between survivors and non-survivors.

METHODS: One hundred twenty-seven subjects with COVID-related ARDS had gas exchange and lung mechanics assessed on the day of intubation and one week later. The main parameters of interest were P_aO2/F_IO2, ventilatory ratio (VR), respiratory system compliance (C_RS), and a composite score that was calculated as (P_aO2/F_IO2/100) × C_RS/VR. The primary outcome was death in the ICU.

RESULTS: Of the 127 subjects, 42 (33%) died in the ICU and 85 (67%) were successfully extubated. On the day of intubation, P_aO2/F_IO2, C_RS, and composite score of survivors and non-survivors were similar, but survivors had a lower VR. At one week, as compared to survivors, non-survivors had a significantly higher VR (2.04 ± 0.76 vs 1.60 ± 0.43, P < .001), lower C_RS (27.4 ± 6.4 mL/cm H₂O vs 32.4 ± 9.3 mL/cm H₂O, P = .002), and lower composite score (20.6 ± 11.9 vs 34.5 ± 18.6, P < .001), with no statistically significant difference in P_aO2/F_IO2 (137 ± 49 vs 155 ± 48, P = .08).

CONCLUSIONS: In subjects with COVID ARDS, parameters that reflect dead space (VR), lung mechanics (C_RS), and a combined score that included P_aO2/F_IO2, VR, and C_RS differed between survivors and non-survivors after one week of mechanical ventilation but with considerable overlap of values between survivors and non-survivors.