Table 3.
PaO2/FiO2 ratio and static respiratory system compliance responses after the first prone positioning session
| Entire group | PaO2/FiO2-matched | Compliance-matched | ||||
|---|---|---|---|---|---|---|
| N = 168 | P value | N = 46 | P value | N = 46 | P value | |
| PaO2/FiO2 ratio | ||||||
| Change at the end of the first prone positioning session, mmHg | ||||||
| COVID-19 ARDS, median (IQR) | 89.8 (35.3–135.2) | 0.003 | 89.8 (35.3–135.2) | 0.091 | 89.8 (35.3–135.2) | < 0.001 |
| Non-COVID ARDS, median (IQR) | 40.1 (7.0–77.5) | 48.7 (5.0–87.0) | 21.1 (0.0–43.8) | |||
| Regression coefficient (COVID vs. non-COVID) | ||||||
| Unadjusted (95% CI) | 46.7 (17.8–75.6) | 0.002 | 32.5 (− 14.7–79.8) | 0.172 | 69.7 (31.2–108.2) | 0.001 |
| Adjusted (95% CI)a | 39.3 (5.2–73.5) | 0.024 | 4.0 (− 62.9–71.0) | 0.903 | 58.4 (− 13.5–130.2) | 0.108 |
| Static respiratory system compliance | ||||||
| Change at the end of the first prone positioning session, mL/cmH2O | ||||||
| COVID-19 ARDS, median (IQR) | 3.7 (− 1.0–7.3) | < 0.001 | 3.7 (− 1.0–7.3) | 0.044 | 3.7 (− 1.0–7.3) | < 0.001 |
| Non-COVID ARDS, median (IQR) | − 0.3 (− 4.0–1.9) | 0.4 (− 1.2–2.3) | − 2.3 (− 7.2–0.0) | |||
| Regression coefficient (COVID vs. non-COVID) | ||||||
| Unadjusted (95% CI) | 4.2 (2.3–6.2) | < 0.001 | 2.7 (0.0–5.5) | 0.047 | 6.6 (3.8–9.3) | < 0.001 |
| Adjusted (95% CI)a | 3.4 (1.1–5.6) | 0.003 | 0.3 (− 3.3–3.8) | 0.883 | 2.2 (− 2.4–6.7) | 0.340 |
CI confidence interval, FiO2 fraction of inspired oxygen, IQR interquartile range, PaO2 partial pressure of oxygen
aFor multivariable linear regression, the following variables were adjusted: age, sex, body mass index, duration of mechanical ventilation before initiation of prone positioning, sequential organ failure assessment (SOFA) score, Charlson comorbidity index (CCI), baseline setting of mechanical ventilator (positive end-expiratory pressure and tidal volume), and baseline respiratory mechanics before initiation of prone positioning (PaO2/FiO2, static compliance, and ventilatory ratio)