Sensitive indices of improvement in a pulmonary rehabilitation program

It is often difficult to demonstrate objective evidence of physiologic improvement following a pulmonary rehabilitation program, despite subjective increases in exercise tolerance. In an attempt to identify sensitive indices of improvement, we studied resting and exercise lung function extensively in 15 patients (age range 45 to 73) with severe chronic obstructive lung disease before and after a pulmonary rehabilitation program. The six-week outpatient rehabilitation program consisted of exercise at 70 percent of the maximum predicted heart rate and diaphragmatic breathing for 20 minutes three times weekly. There were no significant changes in resting pulmonary function following exercise training. Exercise measurements were unchanged after completion of the program, with the exception of two parameters: heart rate and arterial lactate levels. The observed small but significant reductions in exercise heart rate and blood lactate levels following training may be due to conditioning of skeletal muscles, although respiratory muscle conditioning may be a contributing factor. Measurements of blood lactate may be a useful marker of conditioning in patients with chronic obstructive pulmonary disease who complete a pulmonary rehabilitation program.