Abstract
BackgroundQuadriceps muscle dysfunction is well confirmed in chronic obstructive pulmonary disease (COPD) and reported to be related to a higher risk of mortality. Factors contributing to quadriceps dysfunction have been postulated, while not one alone could fully explain it and there are few reports on it in China. This study was aimed to investigate the severity of quadriceps dysfunction in patients with COPD, and to compare quadriceps muscle function in COPD and the healthy elderly.MethodsQuadriceps strength and endurance capabilities were investigated in 71 COPD patients and 60 age-matched controls; predicted values for quadriceps strength and endurance were calculated using regression equations (incorporating age, gender, anthropometric measurements and physical activities), based on the data from controls. Potential parameters related to quadriceps dysfunction in COPD were identified by stepwise regression analysis.ResultsMean values of quadriceps strength was 46% and endurance was 38% lower, in patients with COPD relative to controls. Gender, physical activities and anthropometric measurements were predictors to quadriceps function in the controls. While in COPD, forced expiratory volume in 1 second percentage of predicted value (FEV1% pred), nutritional depletion, gender and physical inactivity were identified as independent factors to quadriceps strength (R2 = 0.72); FEV1%pred, thigh muscle mass, serum levels of tumor necrosis factor-alpha (TNF-α) and gender were correlated to quadriceps endurance variance, with each p<0.05.ConclusionQuadriceps strength and endurance capabilities are both substantially impaired in Chinese COPD patients, with strength most affected. For the controls, physical activity is most important for quadriceps function. While for COPD patients, quadriceps dysfunction is related to multiple factors, with airflow limitation, malnutrition and muscle disuse being the main ones.
Highlights
Skeletal muscle dysfunction is well documented as an important systemic manifestation of chronic obstructive pulmonary disease (COPD) and has been recognized as a contributing factor in reduced exercise capacity, impaired quality of life and higher health-care utilization
Age and height were comparable between the two groups, while differences were observed for body mass index (BMI)
Spirometry tests showed that COPD patients had, on average, severe airflow limitation as defined by the GOLD criteria, with FEV1 less than 50% predicted
Summary
Skeletal muscle dysfunction is well documented as an important systemic manifestation of chronic obstructive pulmonary disease (COPD) and has been recognized as a contributing factor in reduced exercise capacity, impaired quality of life and higher health-care utilization. Improved quadriceps muscle strength and endurance are recognized to underlie much of the increased exercise capacity observed following multidisciplinary pulmonary rehabilitation for COPD [7]. Better understanding of the severity and the factors associated with impairment of quadriceps muscle function in patients with COPD would help develop new preventive interventions in quadriceps dysfunction and therapeutic approaches in the rehabilitation of these patients. This study was aimed to investigate the severity of quadriceps dysfunction in patients with COPD, and to compare quadriceps muscle function in COPD and the healthy elderly
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