The ventilatory response to muscle metaboreflex stimulation in patients with COPD

Abstract

The role of skeletal muscle metaboreceptive afferents in human cardiorespiratory control can be examined using post exercise circulatory occlusion (PECO). We have shown that the ventilatory responses to PECO are augmented in humans during concurrent hypercapnia. We now aim to determine whether PECO produces ventilatory responses in COPD patients who do and do not retain CO2.With Ethical approval, 18 COPD patients and 9 aged matched controls performed 2 trials. In both trials participants rested for 2 minutes followed by 2 minutes of rhythmic handgrip exercise. Upon cessation of exercise in the PECO trial a cuff around the upper arm was inflated to 200mmHg for 2 minutes before cuff deflation.PECO maintained blood pressure significantly above baseline levels in COPD patients and control participants (+ 7 mmHg and + 8 mmHg respectively). However ventilation during PECO was only maintained above baseline levels in COPD patients (+2–3 l.min‐1). There was no difference in this response between retainers and non‐retainers of CO2.These results suggest that metaboreflex activation causes ventilatory responses in patients with COPD but not in healthy aged matched controls. However as there was no difference in the ventilatory response to PECO in CO2 retainers and non‐retainers it appears that chronic hypercapnia is not the underlying mechanism behind the response.