Prediction of postoperative dyspnea and chronic respiratory failure

Even among patients considered to be functionally eligible for major lung resection, some experience postoperative dyspnea. Based on our previous study with quantitative computed tomography (CT), we hypothesized that postoperative dyspnea is associated with the collapse of the remaining lung, and thus, prediction of the postoperative lung volume may contribute to risk assessment for postoperative dyspnea.

We measured the emphysematous lung volume and functional lung volume (FLV) separately on whole lung CT using an image analysis software in 290 patients undergoing major lung resection for cancer between January 2006 and December 2012. The postoperative FLV was predicted by a stepwise multiple regression analysis.

Fourteen patients complained of postoperative dyspnea (complicated group), five of them presented with chronic respiratory failure. The postoperatively measured FLV was significantly lower in the complicated group than in the control group (P < 0.01). The postoperative FLV could be calculated using preoperative variables, including the forced vital capacity, number of resected segments, FLV, and emphysematous lung volume. The predicted postoperative FLV was significantly lower in the complicated group than in the control group (P < 0.01, area under the curve = 0.78; sensitivity 86%; specificity 73%). The predicted postoperative FLV was also useful in distinguishing complicated patients from matched-control patients who had similar preoperative pulmonary function (P = 0.02).

Postoperative dyspnea is likely accompanied by a collapse of the remaining lung. Quantitative assessment of the lung morphology on preoperative CT is useful to screen for patients at risk of postoperative dyspnea.