To clarify whether the gas exchange response to prone position is associated with lung recruitability in mechanically ventilated patients with acute respiratory failure.Methods
In 32 patients, gas exchange response to prone position was investigated as a function of lung recruitability, measured by computed tomography in supine position.Results
No relationship was found between increased oxygenation in prone position and lung recruitability. In contrast, the decrease of PaCO2 was related with lung recruitability (R2 0.19; P = 0.01). Patients who decreased their PaCO2 more than the median value (-0.9 mmHg) had a greater lung recruitability (19 ± 16 vs. 8 ± 6%; P = 0.02), higher baseline PaCO2 (48 ± 8 vs. 41 ± 11 mmHg; P = 0.07), heavier lungs (1,968 ± 829 vs. 1,521 ± 342 g; P = 0.06) and more non-aerated tissue (1,009 ± 704 vs. 536 ± 188 g; P = 0.02) than those who did not.Conclusions
During prone position, changes in PaCO2, but not in oxygenation, are associated with lung recruitability which, in turn, is associated with the severity of lung injury.