Benefits of Incentive Spirometry: Still More Work to Do.

We read with interest the randomized clinical trial on incentive spirometry (IS) in patients undergoing coronary artery bypass grafting (CABG) by Eltorai and colleagues. 1 The authors demonstrated that adding an hourly audible reminder for IS increases compliance. This is an interesting use of a device developed by the authors and does seem to improve compliance with a therapy that many believe decreases respiratory complications and promotes rehabilitation and discharge following any operation. However, the remainder of the study does require caution when interpreting the claimed improvement in outcomes. For the clinical end point in the study (on which the initial power calculations were based), the authors use the modified Wilcox score for lung atelectasis. 2 Unfortunately, this is not routinely used in clinical evaluation and treatment of patients undergoing CABG. Furthermore, although there was a reported significant difference between the initial postoperative radiography results and the predischarge radiography results, the absolute difference may not necessarily reflect clinical significance. Using a somewhat obscure risk score as the basis for power calculation directly affects the next issues with this study: the differences in the control and intervention groups. After a review of the raw data presented in the tables and supplementary material, it is evident that the bell on and bell off groups may have clinically significant differences in their risk profiles that did not meet statistical significance because of the relatively small sample size. The authors chose not to report the well-validated Society of Thoracic Surgeons risk scores associated with isolated or concomitant CABG. 3 This would have provided insights into the true equipoise of the 2 groups. A variable that deserves attention was the significantly increased history of smoking in the control arm, which as a single factor may predict a more difficult postoperative respiratory recovery. The reported differences in length of stay (LOS) and intensive care unit LOS can be particularly affected by these For example, the duration of chest tube increased in the control groups. 1 These 2 care and several which can easily