Objective: Non-univocal conclusions have been published regarding the definition of oxygen desaturation in relation to postoperative outcome. We aimed to verify whether oxygen desaturation during a maximal stair-climbing test was associated with postoperative cardiopulmonary complications and to assess which definition of oxygen desaturation (oxygen saturation <90% or desaturation >4% with respect to rest level) discriminated better between complicated and uncomplicated patients.
Methods: Five hundred and thirty-six patients performing a maximal stair-climbing test prior to major lung resection were analyzed. All patients performed the test on room air. Patients with and without cardiopulmonary complications were compared in terms of several preoperative and operative characteristics by univariate analysis, including the presence of oxygen desaturation at peak exercise (saturation <90% or desaturation >4%). Logistic regression analysis was then performed and validated by bootstrap procedure to identify predictors of complications and to see whether the exercise oxygen desaturation retained its significancy after multivariable adjustment.
Results: Twenty-seven patients had an exercise oxygen saturation below 90%, but this parameter was not significantly associated with complications. Seventy-five patients experienced an exercise desaturation greater than 4%, which was a significant result associated with postoperative complications at univariate analysis (p=0.008) (36% complication rate). After adjusting for age, ppoFEV1, ppoDLCO, type of operation, height reached at stair-climbing test and cardiac co-morbidity, a desaturation greater than 4% retained its significance at logistic regression and proved to be stable at bootstrap.
Conclusions: A stair-climbing test is an intense constant workload exercise, challenging a large amount of muscle mass, and appears particularly appropriate to elicit oxygen desaturation, which in turn may be a reliable marker of deficits in the oxygen transport system. A desaturation >4% appears a better cut-off definition than a saturation level <90% in predicting the occurrence of complications. The risk of complications was approximately two-fold higher in patients with oxygen desaturation >4% at peak exercise.