Introduction and objectives Cough frequency is increased in chronic cough (CC) compared to healthy subjects. It is not known if patients with CC cough more intensely. We investigated cough intensity in maximum voluntary cough (MVC) in patients with chronic cough and in healthy controls.
Methods 28 subjects with chronic cough and 21 healthy subjects underwent measurement of oesophageal pressure (Poes), gastric pressure (Pga), peak abdominal electromyographic activity (EMGabd) and peak cough flow rate (PCFR) during 10 maximum voluntary cough manoeuvres. Coughs were performed at functional residual capacity. Inspiratory volume (IV) preceding cough efforts was calculated by integration of flow. Expiratory muscle strength was assessed by measuring twitch gastric pressure (TwPga) in response to magnetic stimulation. EMGabd data was normalised to EMGabd twitch compound muscle action potential and PCFR data normalised to predicted peak flow rate (PEFRp). The analysis of data was restricted to gender and expressed per unit IV.
Results Subjects were matched for age, gender, BMI and had normal lung function. All measures of cough intensity were significantly higher in chronic cough compared to healthy controls, irrespective of gender (Table 1). However, this was not due to increased activation of the abdominal muscles since there were no significant differences in EMG (p>0.2) or due to increased expiratory muscle strength (p>0.36). There was no significant difference in Poes/IV and Pga/IV between male and female patients or controls (p>0.28), but female cough subjects produced significantly higher PCFR/IV compared to males (p<0.01).
Conclusions Cough intensity is increased in patients with chronic cough, during MVC. This raises the possibility that cough intensity in these patients may contribute to cough severity and health status. The mechanism is unclear and deserves further investigation in studies of VC and spontaneous cough.
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