Quality of life in severe chronic obstructive pulmonary disease: correlation with lung and muscle function

Chronic obstructive pulmonary disease (COPD) patients suffer from significant impairment in quality of life (QL), but the variables related to this impairment are not well known. The aim of this study has been to identify physiological parameters related to QL in severe COPD patients undergoing long-term oxygen therapy. Materials and methods. We studied 47 COPD patients using long-term oxygen therapy (43 men/four women, 65.17 SD 8.21 years, 3.17 SD 2.61 years on oxygen). The Nottingham Health Profile (NHP) and activities of daily living (ADL) questionnaire were used to measure QL. Subjective assessment of dyspnoea was performed using a visual analogue scale. The physiological parameters determined were lung function (spirometry, arterial blood gases, lung volumes and carbon monoxide diffusing capacity), muscle function (maximum inspiratory and expiratory pressures, deltoid muscle and handgrip strength), and nutrition status (tricipital skin fold and mid-arm muscle circumference). Results. High ADL (8.32 SD 6.97) and NHP scores (energy 63.3 SD 40.43, pain 35.11 SD 31.56, emotional reactions 43.03 SD 25.13, sleep 51.91 SD 32.75, social isolation 30.64 SD 26.98, physical mobility 49.73 SD 24.93) demonstrated clinically significant QL impairment in the severe COPD patients studied. Stepwise multiple regression analysis found a correlation between lung function and QL. Low FEV1% was associated with impairment in energy, physical mobility and social isolation NHP scores and ADL score (r = -0.3, P<0.05). RV/TLC also correlated with ADL and social isolation scores (r=0.3, P<0.05). Lung function explained 39-45% of the variation in these QL dimensions. QL did not correlate with other lung function parameters, muscle function or nutrition status. Conclusion. COPD patients using long-term oxygen suffer from severe QL impairment affecting not only energy and mobility but also emotional reactions, social isolation and sleep. Lung function is related to energy, mobility and social isolation dimensions, but muscle function is unrelated to QL in these patients.