Relationship between gas exchange response to prone position and lung recruitability during acute respiratory failure

Abstract

Purpose: 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 (R 2 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. © 2009 Springer-Verlag.