The effect of huffing and directed coughing on energy expenditure in young asymptomatic subjects

Coughing and huffing have been shown to be effective airway clearance techniques and some authors have anecdotally reported that a huff requires less energy than a series of coughs commencing and finishing at the same lung volume. The aim of this study was to determine whether there is a difference in the energy expenditure between periods of huffing and directed voluntary coughing commencing from the same initial lung volume in young asymptomatic subjects. Energy expenditure was measured using open-circuit indirect calorimetry equipment. Twenty-four non-smoking asymptomatic subjects (12 male, 12 female, aged 18-24 years), without any form of disease and within 10% of their predicted pulmonary function, completed the study. Energy expenditure was measured over three 10min, randomly ordered sessions of huffing, directed coughing and rest. The forced expiratory sessions comprised a single huff or double-barrel cough (both starting at total lung capacity) at the end of every two minutes. Each session was separated by a 5min washout period. No significant difference in energy expenditure was found between the huffing and directed coughing periods (mean difference 0.003 mL/kg/min (95% CI -0.160 to 0.114) and both produced significantly greater energy expenditure than rest (rest and huff mean difference 0.309 mL/kg/min (95% CI 0.080 to 0.549) and rest and cough mean difference 0.306 mL/kg/min (95% CI 0.074 to 0.508)). The suggested benefits of huffing versus coughing in terms of energy conservation are yet to be shown.