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Role of exercise diffusing capacity in the preoperative evaluation of patients for lung resection Wang, Jeng-Shing

Abstract

Introduction: Pulmonary diffusing capacity for carbon monoxide (DLCO) at rest has been shown to be useful in the preoperative evaluation of patients for lung resection. DLCO increases during exercise but may not increase adequately if the pulmonary vascular bed is reduced by emphysema. Objective: The purpose of this prospective study is to evaluate whether lack of an adequate increase in DLCO during exercise is associated with increased postoperative complications following lung resection. Methods: We used a modification of the single breath DLCO technique, the 3-equation method (3EQ-DLCO), to determine DLCO during exercise in 57 patients undergoing lung resection at Vancouver General Hospital since October 1998. 3EQ-DLCO was determined during steady state exercise at 35% and 70% of the maximal workload reached in a progressive exercise test. Postoperative complications occurring within 30 days after resection were classified into mortality, cardiovascular and pulmonary complications. Maximal oxygen uptake, DLCO at rest, and the increase in DLCO during exercise, were compared in relation to postoperative complications. Results: Complications occurred in 19 patients (33%) and included mortality in 2 (4%), cardiovascular morbidity in 12 (21%), and pulmonary morbidity in 13 (23%). Pneumonia in 12% and atrial fibrillation in 18% of patients, were the major pulmonary and cardiovascular complications. Patients with complications had lower resting DLCO (RDLCO), lower increase in DLCO from rest to 70% of maximal workload expressed as % of predicted DLCO at rest ((70%-R)DLCO%), and lower maximal oxygen uptake, than patients without complications. Results suggested (70%-R)DLCO% was the best preoperative predictor of postoperative complications; a cut-off limit of 10% was the best index to identify complications, with a complication rate of 100% in patients with (70%-R)DLCO% < 10%, compared with a complication rate of 10% in patients with (70%-R)DLCO% > 10% (sensitivity = 78%, specificity = 100%). Conclusions: Patients who do not increase their DLCO sufficiently during exercise ((70%- R)DLCO% < 10%) have higher complication rates following lung resection. The strong correlation between exercise diffusing capacity and postoperative complications is likely due to the contribution of a reduced pulmonary capillary bed to cardiopulmonary complications. Exercise DLCO appear to be useful as an additional test to improve the prediction of postoperative morbidity following lung resection.

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