Acute effects of continuous rotational therapy on ventilation-perfusion inequality in lung injury

Objective: To investigate ventilation-perfusion (V-A/Q) relationships, during continuous axial rotation and in the supine position, in patients with acute lung injury (ALI) using the multiple inert gas elimination technique, Design: Prospective investigation. Setting: Eighteen-bed intensive care unit in a university hospital. Patients and interventions: Ten patients with ALI (PaO2/FIO2 ratio < 300 mm Hg) were mechanically ventilated in a pressure controlled mode and placed on a kinetic treatment table. Measurements and results: Distributions of V-A/Q were determined 1) during rotation (after a period of 20 min) and 2) after a resting period of 20 min in the supine position. During axial rotation, intrapulmonary shunt (19.1 +/- 15 % of cardiac output) was significantly reduced in comparison with when in the supine position (23 +/- 14 %, p < 0.05), areas with "low" V-A/Q were not affected by the positioning maneuver. General V-A/Q mismatch (logarithmic distribution of pulmonary blood flow) was decreased during rotation (0.87 +/- 0.37) in comparison with when the patient was in the supine position (0.93 +/- 0.37, p < 0.05). Arterial oxygenation was significantly improved during continuous rotation (PaO2/FIO2 = 217 +/- 137 mm Hg) as compared with in the supine position (PaO2/ FIO2 = 174 +/- 82 mm Hg, p < 0.05), The positive response of the continuous rotation on arterial oxygenation was only demonstrated in patients with a Murray Score of 2.5 or less, indicating a "mild to moderate" lung injury, while in patients presenting with progressive ARDS (Murray Score > 2.5), the acute positive response was limited, Conclusions: Continuous axial rotation might be a method for an acute reduction of V-A/Q mismatch in patients with mild to moderate ALI, but this technique is not effective in late or progressive ARDS, Further studies including a large data collection are needed.