Inspiratory Muscle Responses to Sudden Airway Occlusion in Chronic Obstructive Pulmonary Disease

Abstract

Brief airway occlusion produces a potent reflex inhibition of inspiratory muscles that is thought to protect against aspiration. Its duration is prolonged in asthma and obstructive sleep apnea. We assessed this inhibitory reflex (IR) in chronic obstructive pulmonary disease (COPD). Reflex responses to brief (250 ms) inspiratory occlusions were measured in 18 participants with moderate to severe COPD (age 73±11) and 17 healthy age-matched controls (age 72±6). We compared the incidence and properties of the IR between groups. Median eupneic pre-occlusion electromyographic activity was higher in the COPD group than controls (9.4 vs. 5.2 μV, P = 0.001). Incidence of the short-latency IR was higher in the COPD group compared to controls (15 vs. 7 participants, P = 0.010). IR duration for scalenes was similar for the COPD and control groups (73±37 [mean±SD] and 90±50 ms, respectively) as was the magnitude of inhibition. IRs in the diaphragm were not detected in the controls but were present in 9 of the COPD group (P = 0.001). The higher incidence of the IR in the COPD group than in the age-matched controls may reflect the increased inspiratory neural drive in the COPD group. This higher drive counteracts changes in chest wall and lung mechanics. However, when present, the reflex was similar in size and duration in the two groups. The relation between the IR in COPD and swallowing function could be assessed.