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Acute effects of continuous rotational therapy on ventilation-perfusion inequality in lung injury
Objective:
To investigate ventilation-perfusion (VA/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 VA/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" VA/Q were not affected by the positioning maneuver. General VA/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 VA/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.