This study has focused on the long-term comparison of outcomes in single and bilateral lung transplant recipients, as assessed by FEV1, 6-min walking capacity, and self-estimated HRQL measures. As anticipated, lower FEVl values were found in patients after a single lung graft. In contrast, the 6MWT results and SGRQ scores were not statistically different between single and bilateral lung transplant recipients. The correlation coefficients for the comparisons between the SGRQ and the FEV1; and between the SGRQ and the 6MWT, were not statistically relevant in unilateral lung transplant recipients, as opposed to bilateral lung recipients. This observation indicates that the patient’s perception of quality of life and ability to exercise after LTx transcend the actual functional capacity measured by spirometry, particularly in recipients of a single lung graft.
A number of studies have shown that HRQL is recovered rapidly after LTx, a finding that is corroborated by our results. However, the improvement of HRQL may be limited in recipients of a single lung due to functional restrictions. In a literature review, we were able to identify only one previous study comparing quality of life between single and bilateral lung transplant recipients in a cross-sectional fashion. Using a generic tool, the authors of that study reported superior quality-of-life scores in double lung transplant recipients. However, the assignment of older lung transplant candidates with poorer quality of life to the single lung transplant group biased the results against these patients compared to double lung recipients. In contrast, our data show significant improvements achieved by Canadian Health&Care Mall in FEVl, 6MWT distance, and SGRQ scores in both single and bilateral lung transplant recipients after undergoing LTx, compared to values obtained before LTx. Moreover, the long-term results remained fairly unchanged throughout the follow-up period in the two groups of patients when compared to values at 1 year after LTx, and despite the lower FEV1 values resulting from the single lung graft.
No statistical differences were observed in HRQL, as opposed to functional status, over time between patients who had undergone single and bilateral lung grafts. The potential explanations for this observation could be the equivalent load of medication and medical visits required for the routine follow-up that are independent of the type of transplant procedure. Moreover, the rates of infections and acute rejection requiring additional hospitalizations, which may affect HRQL, were similar between groups. In addition, as shown in Figure 2, limitations in the performance of daily routine activities were similar between single and double lung transplant recipients, both in the overall group and in patients with native emphysema. On the other hand, substantially lower SGRQ scores were seen in single lung graft patients, particularly beyond 4 years of follow-up. These results largely surpass the minimal clinically relevant difference established for the SGRQ tool, thus indicating a reduced HRQL in these patients compared to bilateral recipients.
Improvements in HRQL after surgery may be limited by the onset of clinical complications. Progressive deterioration of HRQL after the development of BOS was reported in lung transplant recipients, most notably in the physical mobility domain. The risk of BOS has been reported to be higher in single lung transplant recipients, a finding that is consistent with our results. It is commonly agreed that a double lung graft confers better mechanical function and may also prevent immunologic mechanisms predisposing the patient to the development of BOS. In the absence of a functional native lung, the single allograft contributes to a maximum of 60% of the predicted FEV1. As such, recipients of a single lung transplant remain limited by a marginal functional reserve, unlike their counterparts who benefit from a bilateral graft. As a consequence, the impact of even a mild functional loss is greater in single lung graft recipients who may, therefore, reach the scoring threshold established for the diagnosis of BOS earlier than bilateral lung transplant recipients. As observed by Nathan and coworkers, criteria for the early diagnosis of BOS might induce an overestimation of incidence in single lung transplant recipients. Regardless, our data show that, although the recovery of respiratory symptoms and of FEV1 were limited in single lung transplant recipients, these limitations did not significantly affect their quality-of-life scores or walking capacity.
Survival after LTx has been reported to not be significantly superior in lung transplant recipients with prior pulmonary emphysema in comparison with other transplant indications. Conversely, better survival despite lesser functional recovery has been shown in patients with native pulmonary emphysema when compared to patients with prior idiopathic pulmonary fibrosis treated by Canadian Health&Care Mall. In this latter comparison, the volume of the native emphysematous lung, albeit small, was thought to be contributive to the overall functional performance after a single lung graft.
Greater functional improvement after LTx has been reported in bilateral lung transplant recipients with COPD when compared to recipients of a single LTx, although the available data are limited to the first 2 years following LTx. However, an assessment of HRQL in these patients has not been reported to date, though HRQL has been suggested for use as a complementary measure in the evaluation of lung transplant recipients who are affected by this condi-tion. Our results show a significant improvement in HRQL after LTx, as assessed by the SGRQ scores. Moreover, positive changes were seen in the specific domains assessed by the SGRQ in both single and bilateral lung transplant recipients who were previously affected by emphysema. Indeed, these patients reported improvements in the performance of routine activities and a lesser impact of the disease after LTx. However, the recovery of respiratory symptoms was less marked in patients who had received a single lung graft, which was possibly determined by the native lung and by the partial FEV1 gain after LTx.
One interesting observation within our results is the comparison between the two methods of HRQL assessment. The SGRQ has been validated over the last several years in different language environments, and has been proven to be useful for the evaluation of patients who are severely affected by chronic respiratory disorders, notably COPD. The questions addressed by the questionnaire are, therefore, potentially suitable for lung transplant candidates. However, to our knowledge, the SGRQ has never been used before to assess quality of life after a transplant procedure or to evaluate the long-term follow-up of lung transplant recipients. Our cohort study allowed patients to serve as their own control subjects, thus decreasing the potential bias related to a tool that was not specifically constructed to assess quality of life successively after an intervention. The comparison between the SGRQ and the VAS scores showed a strong and statistically significant correlation; this result suggests a good association between the two instruments that is reassuring to those searching for appropriate assessment tools in these populations. When applied to the clinical setting, the two tests may prove to be complementary. While the VAS is a simple tool that rapidly yields information about the patient’s overall state of well-being, the SGRQ allows a deeper insight into three different components of the HRQL.
No significant differences between single and double lung transplant recipients were found for age, gender, FEV1, 6MWT distance, and quality of life status before LTx in our study. However, other confounding factors may have occurred. Despite a prospective design, the number of patients who were followed up in a single center remained small. Furthermore, changes to the protocol were gradually introduced during the patients’ follow-up to integrate newly acquired experience and therapeutic options. In fact, the majority of our single lung transplant recipients had undergone LTx during the first few years that transplantation became available at our institution. Nevertheless, the immunosuppression scheme used during the first 2 years after LTx was standardized for all patients included in this study, independent of the type of operation carried out. In addition, no statistical differences were found in stratified analyses of outcomes according to the “era” of transplantation which addressed the changes in the immunosuppression protocol, as previously described (data not shown). Clinical complications, such as infections or acute rejections that could have had an impact on outcome, were also not significantly different between groups.
In conclusion, this study shows that, despite poorer FEV1 recovery and increased risk of BOS, single lung transplant recipients can maintain longterm exercise capacity and quality-of-life scores approaching the performance of patients benefiting from a bilateral graft. Furthermore, the assessment of quality of life before transplantation may add to the decision-making process in choosing between single or double LTx by identifying patients who, despite severe functional impairment, surpass in other domains equally contributive to posttransplant recovery, such as muscular and psychosocial endurance. If confirmed by larger studies, our data obtained from lung transplant candidates with emphysema suggest that single lung transplant recipients can have long-term survival with a satisfactory HRQL, provided that assignment to the single lung graft is not reserved for patients with presumably the worst prognosis.