Purpose: Abnormal skeletal muscle function is well documented in chronic obstructive pulmonary disease, but there is no information about the activity of muscle metabosensitive afferents. In this study, we tested the hypothesis that patients with chronic obstructive pulmonary disease would have abnormal reflex responses to stimulation of metabosensitive afferents in skeletal muscle when compared with healthy, matched subjects.
Methods: In 16 patients with moderate to severe chronic obstructive pulmonary disease and 13 healthy, age-matched control subjects, we evaluated heart rate, mean blood pressure, calf blood flow, and calf vascular resistance responses to static handgrip exercise at 30% of maximal voluntary contraction, followed by recovery with or without circulatory occlusion. Muscle metaboreflex control of calf vascular resistance was estimated by subtracting the area under the curve with circulatory occlusion from the area under the curve without circulatory occlusion.
Results: Mean blood pressure and heart rate responses were not significantly different in patients and controls during exercise and recovery. In the control group, calf vascular resistance increased significantly during exercise and remained elevated above baseline during circulatory occlusion, whereas in patients changes from rest were not significantly different in both trials. Estimated muscle metaboreflex control of calf vascular resistance was significantly reduced in the patients (controls: 31 ± 22 units, patients: 8 ± 31 units, P < 0.05).
Conclusion: Patients with chronic obstructive pulmonary disease have a reduced calf vascular resistance response to handgrip exercise and to selective activation of muscle metaboreflex when compared with healthy subjects.
1Exercise Pathophysiology Research Laboratory, 2Cardiology and 3Pulmonary Divisions, Hospital of Clinics of Porto Alegre, Porto Alegre, BRAZIL; and 4Department of Medicine, Faculty of Medicine, Federal University of Rio Grande Sul, Porto Alegre, BRAZIL
Address for correspondence: Jorge P. Ribeiro, M.D., ScD, Associate Professor and Chief on Noninvasive Cardiology, Hospital de Cli`nicas de Porto Alegre, Rua Ramiro Barcelos 2350, 90035-007, Porto Alegre, RS, Brazil; E-mail: firstname.lastname@example.org.
Submitted for publication July 2007.
Accepted for publication August 2007.