King's College London

Very few studies have addressed how coughing varies in intensity. We assessed the influence of cough effort and operating volume on the mechanics of coughing using respiratory muscle surface electromyography (EMG), oesophageal/gastric pressures and cough sounds recorded from 15 healthy subjects [8 female, median age 30(IQR 30–50)years] performing 120 voluntary coughs from controlled operating volume/effort and three cough peals. For single coughs, low operating volumes and high efforts were associated with the highest EMG activity (p < 0.001); the resultant pressures increased with effort but volume had little influence. In contrast, cough sounds increased with both volume and effort. During cough peals, EMG fell initially, increasing towards the end of peals, pressures remained stable and sound parameters fell steadily to the end of the peal. In conclusion, effort and operating volume have important influences on cough mechanics but modulate muscle activation, pressure and cough sound amplitude and energy differently. Consequently, these cough sound parameters poorly represent voluntary cough mechanics and have limited potential as a surrogate intensity measure.