The effect of directed vigorous coughing on energy expenditure and pulmonary function in normal subjects

Abstract

The aim of this study was to determine if directed vigorous coughing alters resting energy expenditure and pulmonary function in normal subjects. Energy expenditure was measured via open-circuit indirect calorimetry and pulmonary function was assessed via flow/volume manoeuvres. The subjects were 20 undergraduate students (10 males, 10 females, age 16-20 years) asymptomatic for respiratory disease. Energy expenditure was measured over three 20-min periods: during a rest period, a coughing regimen and a recovery phase. The coughing session involved three vigorous coughs at the end of every 2 min. Directed coughing in normal subjects was found to increase energy expenditure significantly when compared to rest. Lung function was not altered significantly 20-30 min after the direct coughing period, except for a significant drop in the forced expiratory flow at 25% forced vital capacity (FEF₂₅), indicating a mild narrowing of the larger airways. These results suggest that directed coughing demands increased oxygen consumption and irritates airways in asymptomatic subjects. The effects of directed coughing require further investigation if it is to be used as an alternative to other chest physiotherapy techniques in patients with suppurative lung conditions, patients who may already have increased metabolic demands and are more likely to experience complications from coughing.