Lung recruitment, positive airway pressure do not avert atelectasis
MedWire News: Lung recruitment maneuver followed by positive airway pressure until extubation does not reduce the risk for atelectasis, show results of a small randomized trial.
The two techniques are effective for preventing atelectasis during anesthesia, but M. Simpson (Leeds Teaching Hospitals NHS Trust, UK) and colleagues found that they did not improve patients’ alveolar-to-arterial oxygen partial pressure difference (A-a)DO2 on emergence from anesthesia.
The researchers speculated that the critical period for developing atelectasis at the end of anesthesia would be after discontinuation of intermittent positive pressure ventilation and positive end-expiratory pressure (PEEP), but before extubation.
They therefore randomly assigned 22 patients to undergo a lung recruitment maneuver of 40 cm H2O for 15 seconds, 15 minutes before the end of anesthesia, followed by 10 cm H2O PEEP. On return to spontaneous breathing, patients received 10 cm H2O continuous positive airway pressure (CPAP) until extubation. The other 22 patients received only PEEP at up to 5 cm H2O.
The average (A-a)DO2 for all patients was 12.3 kPa at 30 minutes before the end of anesthesia, rising to 14.1 kPa at 1 hour after extubation. The average change in (A–a)DO2 was 1.52 in the intervention group and 1.98 in the control group; these were not significantly different.
Simpson and team conclude that lung recruitment followed by positive airway pressure “has not been shown to improve oxygenation after operation when used on emergence from anesthesia and therefore cannot be recommended.”
However, they note in the British Journal of Anaesthesia that the patients’ general condition may have contributed to the poor oxygenation.
“All patients were required to have an arterial line inserted on clinical grounds and so were mostly American Society of Anesthesiologists class II or III having major and prolonged surgery, and therefore care should be taken when applying our results to other patient populations.”
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By Eleanor McDermid