Table 1 Patient Characteristics, Blood Gas and Ventilatory Variables

Age (years)

54.0 (45.0–59.5)

Male (%)

90%

BMI (kg/m²)

36.0 (30.0–43.4)

SOFA score

8.0 (6.0–10.7)

Duration between onset of symptoms and admission to ICU (days)

10.5 (7.2–15.0)

Respiratory support prior to admission (NIV/HFNC), No. (%)

12 (60%) / 2 (10%)

Duration of first prone positioning session, hours

16.2 h (15.6–17.4)

Length of ICU stay prior to prone positioning

1 day (1–1.75)

Arterial blood gas variables

Pre-prone positioning

During prone positioning

 pH

7.30 (7.23–7.35

7.30 (7.22–7.36)

 PaO₂ (kPa)

12.5 (10.1–13.2)

14.3 (12.7–20.4)

 PaCO₂ (kPa)

7.0 (6.1–8.0)

7.3 (6.6–8.5)

Ventilatory variables

 Plateau airway pressure (cmH₂O)

26 (20–28)

26 (22–29)

 Tidal volume (mL)

426 (391–461)

436 (393–470)

 PEEP (cmH₂O)

14 (10–16)

14 (10–15)

 FiO₂ (%)

70 (60–95)

45 (36–55)

 PaO2/FiO2 (mmHg)

123 (100–154)

286 (195–348)

 Aa Gradient (mmHg)

342 (275–507)

114 (64–207)

 C_RS (ml/cmH2O)

33.7 (30.1–43.0)

32.5 (26.7–37.5)