Short of breath, short of benefit: Important considerations for the rehabilitation of IPF patients

Pulmonary rehabilitation is a multidisciplinary intervention that includes exercise training, disease specific education and behaviour modification techniques designed to reduce symptoms, improve functional capacity, enhance health-related quality of life (HRQL) and allow patients with respiratory disease to better self-manage their condition.1 Where pulmonary rehabilitation has been a standard of care for some time in patients with COPD, there is growing evidence to make the same recommendation for all patients with chronic lung disease. For patients with IPF, preliminary studies2–5 consistently demonstrate pulmonary rehabilitation can improve functional capacity, exertional dyspnoea and HRQL albeit to a lesser magnitude than in individuals with COPD6. With all of the documented benefits of pulmonary rehabilitation for patients with chronic lung disease, it is easy to become complacent and accept that pulmonary rehabilitation is working for all patients. Closer inspection of individual responses to any pulmonary rehabilitation program identifies that many patients do not achieve minimal clinically important improvements in dyspnoea, functional capacity or HRQL. This concept was highlighted by Vagaggini et al.,7 who demonstrated that following 8 weeks of pulmonary rehabilitation, only 45% and 53% of patients with COPD obtained the established minimally clinically important improvements in 6-minute walk distance (6MWD) 8 and HRQL9 (measured by the disease specific St Georges' Respiratory Questionnaire). These findings are not unique to COPD, as a recent retrospective study10 reported that only ≈50% of patients with interstitial lung disease (approximately half of whom had IPF) demonstrated minimal clinically important improvements in Borg dyspnoea11 and 6MWD following 6–8 weeks of pulmonary rehabilitation. There are many factors that could impact the benefits of pulmonary rehabilitation. Previously, we reported that the magnitude of improvements in exercise tolerance following a pulmonary rehabilitation program in patients with COPD was strongly associated with the volume and intensity of exercise performed during the program12. The finding that those who perform more exercise, or exercise at a higher intensity, get greater improvements is intuitive but reminds us that if exercise is not optimally prescribed or if a patient has multiple limitations to exercise, then gains could be greatly reduced. There are many factors that may contribute to a reduced ability to perform exercise for patients with IPF, including mechanical constraint to ventilation, diffusion limitation, ventilation–perfusion mismatching, cardiovascular limitation, neuromuscular disorders, and peripheral muscle dysfunction and weakness.13 However, the severity of exertional dyspnoea experienced by patients is often most critical in determining the type, intensity and volume of exercise that a patient can perform. In this issue of Respirology, Kozu and colleagues14 advance current understanding of how dyspnoea severity and the accompanying disability affects the benefits that can be gained from pulmonary rehabilitation in patients with IPF. Patients were grouped according to the Medical Research Council (MRC) dyspnoea scale, with those reporting MRC grades 2–4 performing 8 weeks of supervised comprehensive pulmonary rehabilitation twice weekly and those with the most severe disability (MRC grade 5) participating in an unsupervised, home-based program. A strength of the study was that the exercise prescriptions were individualized to each patient and progressed throughout the study in an attempt to optimize exercise, even for those exercising at home. Kozu reports improvements in 6MWD, HRQL (measured by the SF-36) and dyspnoea (transitional dyspnoea index), with those in MRC grades 2 and 3 having the greatest improvements in 6MWD and HRQL. Importantly, those in MRC grade 2 were the only group with a clinically important change in mean 6MWD for this population,15–17 suggesting that pulmonary rehabilitation may have a reduced clinical benefit for patients classified MRC grade 3–5. However, another encouraging finding of the study was the substantial reduction in the total number of hospital admissions and days in a hospital bed in the year following rehabilitation in the MRC grade 2, 3 and 4 groups, even though pulmonary rehabilitation did not greatly improve the more traditional outcomes for those in MRC grade 4. Kozu and colleagues14 appropriately suggest this unique finding may be related to the educational aspects of pulmonary rehabilitation improving the patient's ability to self-manage their condition. The investigation of Kozu et al.14 accentuates that, although patients are referred to pulmonary rehabilitation to reduce dyspnoea, it is often the severity of breathlessness that prevents patients gaining more from pulmonary rehabilitation. This dilemma encourages us to revisit a number of questions regarding the optimal duration and frequency of pulmonary rehabilitation programs, how to best prescribe exercise to minimize dyspnoea and how to optimize the volume and intensity of exercise for IPF patients with differing severities of dyspnoea. Kozu and colleagues suggest that IPF patients with grade 2 and 3 dyspnoea may be able to undertake exercise training similar to COPD patients. This may be true; however, it is becoming increasingly obvious that we cannot treat respiratory diseases as similar entities when it comes to pulmonary rehabilitation. It is highly possible that patients at any MRC grade may improve more if we were able to prescribe exercise to optimally balance patient comfort and exertional symptoms while still focusing on performing an appropriate intensity and volume of exercise for physiological adaptation. It is highly likely that patients with IPF may obtain greater benefits by having longer programs or more frequent visits to pulmonary rehabilitation that ease patients into exercise in smaller doses at lower intensities. This would allow individuals to build up the volume of exercise they can perform more slowly and would potentially lead to greater benefits, more successful behaviour changes and improved long-term activity adherence. Also, the use of adjunct therapies to exercise for ventilatory unloading and dyspnoea reduction in COPD has been promising and can improve the efficacy of pulmonary rehabilitation.12,18 Similar research is also needed in IPF, especially in those with the greatest disabilities (MRC 3–5), to try and alleviate dyspnoea, improve lung mechanics and maintain blood oxygen levels during exercise, with a goal of improving clinical outcomes for all patients. Kozu and colleagues should be commended for this important study demonstrating how dyspnoea in IPF impacts pulmonary rehabilitation. However, we now need to strive for ways to further optimize exercise and explore adjunct therapies in this heterogeneous condition to ensure that even those with the most severe shortness of breath can benefit as much as those with less severe disease.

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