Table 2.
Changes in respiratory mechanics, blood gas analysis and VDalv in PP
| Parameters | Supine | PP H3 | PP H6 | PP H9 | PP H12 | PP H15 | P value |
|---|---|---|---|---|---|---|---|
| PaO2/FiO2, mmHg | 70 (51 to 77) | 91 (81 to 103) | 87 (73 to 139) | 90 (81 to 111) | 93 (83 to 137) | 99 (83 to 139) | < 0.0001 |
| PaCO2, mmHg | 58 (52 to 60) | 54 (51 to 58) | 54 (45 to 59) | 50 (47 to 59) | 54 (47 to 56) | 52 (47 to 56) | 0.04 |
| Pplat, cmH2O | 27 (26 to 28) | 25 (23 to 27) | 25 (22 to 26) | 25 (23 to 26) | 25 (21 to 26) | 25 (24 to 26) | 0.0004 |
| Crs, mL/cmH2O | 16 (13 to 30) | 18 (14 to 36) | 17 (15 to 40) | 18 (15 to 38) | 19 (15 to 38) | 18 (15 to 30) | 0.02 |
| VDalv/VT | 0.42 (0.35 to 0.47) | 0.31 (0.28 to 0.41) | 0.35 (0.22 to 0.39) | 0.35 (0.26 to 0.39) | 0.39 (0.28 to 0.44) | 0.40 (0.26 to 0.45) | 0.007 |
aCrs: compliance of the respiratory system; PP: prone position, Pplat: plateau pressure, VDalv/VT: ratio of alveolar dead space to tidal volume. H3, H6, H9, H12 and H15: 3, 6, 9, 12 and 15 hours of PP, respectively. P value is between supine position and PP. Data are expressed as medians (1st to 3rd interquartile range).