Repeated intermittent hypoxic stimuli reduce hypoxemia during one-lung ventilation

In patients undergoing one-lung ventilation, repeated intermittent hypoxic stimuli to the operative lung may help reduce hypoxemia by promoting hypoxic pulmonary vasoconstriction, a recent study has found.

Researchers conducted a parallel-group, double-blinded, randomized trial including two groups of 68 patients each; all participants were undergoing one-lung ventilation. The intervention arm received intermittent hypoxia before surgery, wherein the nondependent lung was not ventilated for 2 minutes before being ventilated for the same duration of time; the dependent lung was continuously ventilated.

Controls, on the other hand, were put under continuous normoxia, where both lungs were ventilated for 20 minutes. The primary study outcome was the number of hypoxemic patients, defined as oxygen saturation <95 percent during the procedure.

The researchers found that hypoxemia occurred less frequently in the hypoxemia vs normoxemia group (8.8 percent vs 25.0 percent), with the difference resulting in a statistically significant risk estimate (risk ratio [RR], 0.35, 95 percent confidence interval [CI], 0.15–0.84; p=0.012).

Similarly, 30- and 60-minute measurements for the partial pressure of oxygen (PaO₂; p=0.008 and p=0.007, respectively) as well as for the ratio between PaO₂ and the fractional inspired oxygen (p=0.008 for both) were significantly higher in patients receiving intermittent hypoxia. Inversely, the 30-minute alveolar-arterial pressure gradient (p=0.01) and shunt index (p=0.008) were significantly lowered in these patients.

In terms of safety, the researchers reported no significant difference in the rates of adverse events between arms.