Lung transplant candidates' quadriceps strength is a modifiable predictor of recovery in exercise capacity after transplantation.

Background: Defining a transplant candidate's suitable functional status and potential for rehabilitation is complex. Six-minute walk distance (6MWD) criteria are used in candidacy assessment and pre-transplant quadriceps strength may be a predictor of rehabilitation potential. The study aims were to determine if candidates pre-transplant 6MWD and quadriceps strength are independent factors associated with post-transplant 6MWD and, compare the trajectory in 6MWD and quadriceps strength in candidates from initial assessment to waitlisting and from waitlisting to transplanted (or delisted/died).

Methods: An observational repeated measures design was used. 6MWD and QS% were recorded at initial assessment, waitlisting, bi-monthly reassessments until transplanted/delisted/died and 2-, 6- 13- 26- and 52-weeks following transplantation.

Results: 342 (192 males; mean (±SD) age 51±14 years; 119 COPD, 93 IIP, 72 cystic fibrosis and 58 other) were studied. Recipients had a mean increase in 6MWD of 170±127 m (p<0.001) at 52-weeks post. Weekly 6MWD recovery was greater during the 2- and 6-week period (β 21.73, p<0.001) compared to the 6- to 52-week period (β 1.28, p<0.001). In the 2- to 6-weeks after transplantation, greater pre-transplant 6MWD (p<0.001), stronger pre-transplant QS% (p=0.001), shorter post-operative hospital admission (p<0.001) and cystic fibrosis (vs other) were factors associated with a greater 6MWD. In the 6- to 52-weeks after transplantation, stronger QS% value at corresponding time (p<0.001), younger recipients (p<0.001) and greater 2-week post-transplant 6MWD (p<0.001) were factors associated with a greater 6MWD. Pre-transplant 6MWD decreased by -0.059m (p<0.001) and QS% increased by 0.014% (p<0.001) per day between initial assessment to waitlisting (n=287).

Conclusions: Pre-transplant 6MWD and quadriceps strength are independent factors associated with recovery in exercise capacity after lung transplantation. However, candidates had a marked deterioration in 6MWD, but quadriceps strength had improved while being worked up for waitlisting. Quadriceps strength along with 6MWD should be considered when determining a candidate's lung transplant suitability.