Effect of changes in postoperative spirometry on survival after lung transplantation

Abstract

The decline in normalized forced 1-second expiratory volume after lung transplantation is inevitable; however, the effect of this change on survival is unknown. Additionally, the benefit of double versus single lung transplant is debated, particularly because pulmonary function is only slightly better after double lung transplant. Our goal was to determine the effect of the temporal pattern of post-transplant forced 1-second expiratory volume (percentage of predicted) on the risk of death after transplant and the differences in the sensitivity of single and double lung transplant to this relationship. From February 1990 to January 2008, 622 adults underwent lung transplantation, of whom 315 (51%) received 2 lungs. Of the 509 patients (82%) with available data, 9471 longitudinal evaluations of forced 1-second expiratory volume (percentage of predicted) were analyzed. The temporal pattern was characterized for each patient, and the resulting curve was evaluated as a time-varying covariable function in the survival analysis. Differences in sensitivity of single and double lung transplant were assessed by interaction. Forced 1-second expiratory volume (percentage of predicted) increased from 50% immediately postoperatively to 55% at 1 year after single lung transplant and then gradually declined to 47% by 3 years. Although the pattern was similar after double lung transplant, the corresponding forced 1-second expiratory volume (percentage of predicted) at these points was greater--60%, 75%, and 65%. Lower post-transplant forced 1-second expiratory volume (percentage of predicted) was associated with a substantially increased risk of death after single lung transplant (P < .0001); however, this increase was far less after double lung transplant (P < .0001). The results of our study have demonstrated the effect of changing lung function after lung transplantation on survival. Survival after single lung transplant proved more sensitive to declining pulmonary function, demonstrating an advantage of the increased pulmonary reserve provided by double lung transplant.