Pulmonary Rehabilitation in Interstitial Lung Disease: Benefits and Predictors of Response

Alicia Ferreira, MD; Chris Garvey, FNP; Gerilynn L. Connors, RRT; Lana Hilling, RCP; Julia Rigler, RRT; Susan Farrell, RRT; Cindy Cayou, RCP; Cyrus Shariat, MD; Harold R. Collard, MD, FCCP

Disclosures

CHEST. 2009;135(2):442-447. 

In This Article

Discussion

This study represents the largest study of PR in ILD published to date and is novel in its analysis of potential clinical predictors of response. These data strongly suggest that PR is beneficial for patients with ILD and that it should become the standard of care in this population, particularly for those with poor baseline functional status. Our results show a clinically significant improvement in both functional status (as measured by 6MWT distance) and dyspnea (as measured by Borg score and, in a subset of patients, the UCSD shortness of breath questionnaire) after 6 to 8 weeks of outpatient PR. This benefit was seen regardless of age, baseline pulmonary function, or center, but was more pronounced in the patients with the worst baseline walk distances. Whether improving dyspnea and 6MWT distance prolongs survival in ILD patients is unknown, but studies in both COPD and ILD patients have suggested that dyspnea level and 6MWT distance are predictors of mortality.[23,24,25,26,27,28]

PR is widely available in the United States due to its recognition as an important intervention in patients with COPD.[5] There are an estimated 446 certified PR programs nationwide. However, many pulmonologists do not refer patients with ILD for PR because of limited evidence demonstrating a benefit in this population.[29]

There is good rationale for the use of PR in patients with ILD. PR involves aerobic conditioning, strength and flexibility training, educational lectures, nutritional interventions, and psychosocial support. Exercise training improves aerobic capacity (cardiovascular performance), muscle strength and flexibility, and mechanical efficiency, all of which should contribute to lessening of dyspnea on exertion and improvement in functional status. In addition, PR is known to have positive psychosocial benefits that help patients understand their disease and mitigate anxiety and depression.[11,30]

There have been several small studies of PR in patients with ILD published to date.[12,13,14,15,16,17] These are summarized in Table 3 . Recently, Holland et al[12] randomized 57 patients with ILD to 8 weeks of exercise training (a component of PR) or weekly telephone support. They found a statistically significant improvement in 6MWT distance and dyspnea. Nishiyama et al[13] randomized 30 patients with idiopathic pulmonary fibrosis to a 10-week outpatient PR program or standard therapy. They observed a significant change in both the 6MWT distance and the St. Georges Respiratory Questionnaire with PR. The results of these published reports are consistent with our findings.

Importantly, the improvements we found in functional status and dyspnea after PR are both statistically and clinically significant. The minimal clinically significant difference for 6MWT distance, Borg dyspnea score, and the UCSD shortness of breath questionnaire have all been established.[18,19,22,31] Our data show that, on average, patients with ILD who undergo PR achieve improvements equal to or greater than the minimal clinically significant difference in all three of these variables. While the clinically significant difference for these measurements has not been validated in patients with ILD, it seems reasonable to assume similar degrees of change are relevant.

Baseline 6MWT distance had a significant impact on the change in 6MWT distance after PR. Interestingly, the lower a patient's baseline 6MWT distance was, the more likely the patient was to improve. Lower baseline 6MWT distance was associated with lower baseline FVC, DLCO, and the use of LTOT, suggesting that even those patients who are severely impaired can substantially improve their functional status; although enrollment shortly after an acute illness could also influence this finding. While the improvement in 6MWT distance was less pronounced in patients with better baseline values, PR remained important even in patients with relatively preserved function. Whether there is an upper limit to who should be referred for PR is unanswered by this study and should be investigated in future studies.

There are several limitations to this study. First, there was no control group of patients who had not undergone PR. Although controlled trials are the "gold standard" for evaluating an intervention, recently published trials have made this approach ethically questionable. Uncontrolled cohort studies can provide important evidence in certain situations, particularly when the outcome measured (in this case 6MWT distance) is known not to change dramatically over short periods of time in untreated patients.[32] Another limitation, inherent to all retrospective studies, is ensuring adequate data quality. The data available did not include information on comorbidities, the onset of a respiratory exacerbation or an acute illness during the PR program, current medications, and specific ILD diagnosis, all of which could potentially influence the results. Intention-to-treat analysis was not possible because data were only available for a few patients that did not successfully complete the PR program. While the anecdotal dropout rate for PR is quite low, it is possible that the benefits shown in this study would be less dramatic if intention-to-treat analysis could be performed. Also, detailed data on the level of oxygen used during walk testing were not available for all patients. While standard practice was to use a stable level of oxygen throughout the period of PR, it is possible that some patients could have received varying levels. Finally, important differences between participating centers could be present that were missed due to inadequate numbers.

In summary, this study demonstrates that patients with ILD have statistically and clinically significant improvements in functional status and dyspnea with PR, and that this benefit is more pronounced in patients with poor functional status. While emphasizing the need for further research, we strongly suggest that PR should be considered as a standard of care for patients with ILD.

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