Over the years, respiratory medicine researchers have found that underweight COPD patients seem to exhibit the worst dyspnea (shortness of breath), report the lowest quality of life and experience the highest mortality rate among the general COPD population.
Pulmonary rehabilitation (PR) has been shown in many studies to improve both dyspnea and quality of life in the general COPD population but most PR studies have not distinguished between low body weight patients and those considered either normal weight or obese in reporting their findings. This raises the question – are their differences in PR outcomes among these three body weight classifications and if so, should PR programs be adapted to address the differing outcomes?
With those questions in mind, two recently published studies provide some insight into PR’s effectiveness for low body weight COPD patients in comparison to those of either normal weight or those considered obese.
To take a step back, the cornerstone element of pulmonary rehabilitation is observed, guided exercise where patients start at modest levels of intensity and duration and over the course of 8-12 weeks increase both intensity and duration. The goal of the exercise program is to boost aerobic endurance/stamina and to build muscle strength. By doing so, research has convincingly shown that upon program completion, PR participants demonstrate improved physical conditioning, reduced shortness of breath, lower incidence of COPD exacerbations (shortness of breath attacks), fewer hospitalizations and higher self-reported quality of life. PR programs include other elements that support this mission including breathing training, nutrition counseling and other self-management techniques.
The first of two recent pulmonary rehab studies distinguishing outcomes based on body weight classifications showed notable differences in self-reported quality of life measures depending on whether a COPD patient was considered low weight, normal weight or overweight. In the study, the Brown University based researchers examined the records of 61 male veterans who completed a pulmonary rehabilitation program at a Rhode Island based Veterans Administration medical center between October 2006 and January 2008. Fourteen of the 61 patients were considered underweight (body mass index lower than 23), 30 patients were considered middle-weight (BMI 23-33), and the remaining 17 patients were considered obese (BMI over 33). (Velasco R, et al. Influence of Body Mass Index on Changes in Disease-Specific Quality of Life of Veterans Completing Pulmonary Rehabilitation. J Cardiopulm Rehab and Prev. 2010; 30; 334-339.)
To assess the differences in PR outcomes, the Brown University study team looked at quality of life survey answers provided by the study participants prior to starting the PR program and again at the end of the PR program. They found that all three BMI groups did report improvement on all categories (mastery, fatigue, emotion and dyspnea) as a result of participating in the PR program, but that COPD patients who were obese (those in the highest weight category) experienced the greatest absolute gains across the four rated categories. By contrast, low BMI patients in the study experienced the smallest absolute gains in quality of life measures post-rehab. This led the researchers to conclude that higher BMI patients got more out of the PR program than the lower BMI patients – even though both groups achieved improvements.
In the second recent study examining PR outcomes based on weight classifications, a China-based research team evaluated low and normal weight COPD patients with regard to exercise capacity as well as quality of life ratings.
One wrinkle in this study was that all the study subjects (both low weight and normal weight patients) received supplemental oxygen during their rehab exercise sessions (3 liters/minute). Since the Chinese researchers didn’t evaluate the study subjects exercise performance without supplemental oxygen it’s difficult to discern how much of the absolute benefits were derived from the rehab program versus the use of supplemental oxygen. However, since both low body weight and normal body weight COPD patients received supplemental oxygen their relative PR outcomes to one another can be evaluated.
The Chinese study involved 44 COPD patients (22 considered underweight with a BMI lower than 20, and 22 considered normal weight with BMI greater than 20 – note that the split between weight groups in this study was significantly different than in the Brown University study described above). All 44 patients underwent a 12 week hospital based pulmonary rehab program. Diagnostic readings of exercise capacity and lung function were taken at the outset of the program and again at the end, as were quality of life surveys. (Lin CC, et al. Pulmonary rehabilitation improves exercise capacity and quality of life in underweight patients with chronic obstructive pulmonary disease. Respirology. Accepted article published online ahead of print. doi:10.1111/j.1440-1843.2010.01895)
Their results showed the low BMI group started at lower levels of physical conditioning/exercise capacity on most measures compared to the normal BMI group, but that the low BMI group achieved greater percentage gains post-rehab on a number of the exercise performance measures. For example, the low BMI group achieved a 13% increase in peak exercise work load from readings taken at the beginning of the PR program. By comparison, the normal BMI group increased peak work load by 9%. Maximum oxygen uptake during peak exercise also increased by a greater percentage in the low BMI group (9%) compared to the normal weight group (6%). On most other exercise performance measures there was little difference in improvement levels between the two groups.
In the quality of life survey results, both groups showed marked improvement post-rehab in comparison with their pre-program ratings and there were no significant differences in quality of life improvements based on body weight. However, the low BMI group did report absolute quality of life scores (both pre and post rehab) that were notably lower than the normal weight group.
The results of these two studies seem to indicate that even though low BMI COPD patients enter rehab programs at lower levels of conditioning and perceived quality of life, they do achieve meaningful gains from PR and in some cases these gains are relatively higher in comparison with normal-to-overweight COPD patients.
Given that upwards of 40% of COPD patients are considered underweight, it seems worthwhile for researchers and practitioners to take a harder look at tailoring rehab program elements for COPD patients of different body weight classifications to improve the gains of all rehab participants. To learn more about pulmonary rehabilitation, please visit www.breathebetterforlife.com.
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