Relationship between 6MWT distance and VO2max and Wmax in lung transplant candidates undergoing pulmonary rehabilitation

Introduction: Impaired exercise in lung transplant candidates (LTC) often reflects the end-stage of several lung diseases. While on the waiting list, pulmonary rehabilitation (PR) may help keep exercise capacity, in spite of clinical decline. Aims: Study the relationship between distance in the six minutes walk test (6MWD) at the start and at the end of PR, and the maximum work rate (Wmax) and maximal oxygen uptake (VO2max) in a cardiopulmonary exercise test (CPET) in a cycle ergometer at the start of PR in LTC. Methods: Retrospective evaluation of LTC records regarding initial CPET findings and 6MWT at the start of PR and: before transplant, ending PR for other reasons or this study, if still on the waiting list. Spearman9s rank test was used. Results: 37 patients were included, median age 56 years, 28 were male. Eleven had pneumoconiosis, 7 COPD, 6 interstitial lung diseases, 5 bronchiectasis, 8 other chronic lung diseases. PR median duration was 47 weeks. At start, median values were: 6MWD 400 m (IQR 182m), Wmax 53 Watts (IQR 35 Watts) and VO2max 12.2 ml/min/kg (IQR 6.2 ml/min/kg). Median 6MWD at the end was maintained: 400m. Positive correlation was found between 6MWD before PR and VO2max (rs=0.748, p 47 weeks did not show significant correlations between final 6MWD and CPET values. Conclusion: In this group of patients higher VO2max and Wmax seem to predict a longer 6MWD at the start of PR as well as at the end. This may not be the case in longer PR programs and clinical decline may be a reason.