Utility of the 6-minute walk test following lung transplantation

Abstract

Background: The 6-minute walk test (6-MWT) has replaced standard cardiopulmonary exercises for the evaluation of lung disease. However, data on the utility and characteristics of the 6-MWT following lung transplant are lacking. This study aimed to determine if 6-MWT distance has a normal distribution at 6 months post-transplant and if lower 6-MWT distance was predictive of all-cause mortality.

Methods: We performed a retrospective chart review of 6-MWT data on all patients who were lung transplant recipients at Ochsner Medical Center between 2000 and 2005. Forty-nine lung transplant recipients completed a 6-MWT at 6 months following transplant. Of these 49 patients, 34 had completed both the 6-month and 12-month 6-MWT, and data from these were used to evaluate change in distance walked over time.

Results: The mean age was 46 ± 16 years, 57% were female, and 69% received a bilateral lung transplant. Normal distribution by Kolmogorov-Smirnov was demonstrated for 6-MWT distance at 6 months (P = 0.873). Mean distance walked improved from 348 ± 15 m to 478 ±14 m at 12 months (P = 0.0001). The 6-MWT distance at 6 months was not a predictor of survival (OR = 1.002).

Conclusions: Distance for the 6-MWT followed a normal distribution following lung transplant, and distances walked continued to improve for a year following transplant. Although 6-MWT distances are not a predictor of survival, other components of the test may strengthen the predictive value for morbidity and mortality post-transplant.

Keywords: 6-minute walk test; Cardiothoracic surgery; lung transplant; pulmonary.

Figure 1

Normal distribution by Kolmogorov-Smirnov for 6-minute walk test distance at 6 months (P  =  .873) following lung transplant.

Figure 2

Survival curves based on 6-minute walk test distance at 6 months following lung transplant analyzed by quartiles. 1 = below 1st quartile; 2 = between 1st and 2nd quartile; 3 = between 2nd and 3rd quartile; 4 = above 3rd quartile.

Figure 3

Survival curves based on 6-minute walk test distance at 6 months following lung transplant analyzed by median distance walked. 1 = below median; 2 =  above median.

Figure 4

Survival curves for patients with the 4 diagnostic categories. 1 = cystic fibrosis/bronchiectasis; 2 = pulmonary fibrosis; 3 = chronic obstructive pulmonary disease; 4 = other.