Correlation between mild hypoxaemia and limb skeletal muscle function in chronic obstructive pulmonary disease – Pilot study

Abstract Rationale Exercise capacity in COPD patients depends on the degree of airflow obstruction, the severity of the hypoxaemia and skeletal muscle function. Muscle atrophy and weakness are considered systemic consequences of COPD and are associated with reduced exercise capacity. Aims To investigate the correlation between mild hypoxaemia and muscular strength, muscular fatigue and functional capacity in COPD patients. Methods Ten patients enrolled on a PRP at the Hospital Universitario de Brasilia – HUB were included in this study. Lung function was evaluated by spirometry and arterial blood gas analysis. Functional evaluation was made using the 6MWT and using isometric contraction of deltoid and quadriceps muscles. Results There were positive correlations between PaO 2 , quadriceps strength (r 2  = 0.61 and p = 0.007) and PaO 2 and the 6MWT (r 2  = 0.96, p = 0.001). There were negative correlations between PaO 2 and median frequency of quadriceps (r 2  = -0.42 and p = 0.04). We observed significant correlation between quadriceps strength and the 6MWT (r 2  = 0.67 and p = 0.001). There was negative correlation between median frequency of quadriceps and the 6MWT (r 2 = -0.42 and p = 0.04). We did not observe any correlation between PaO 2 and strength or median frequency of deltoid muscle. Conclusions PaO 2 has important correlations with muscular function variables. The main negative impact of mild hypoxaemia and precocious limb muscular disability on COPD patients is decreased functional capacity.