Relationship between expired lung volume, peak flow rate and peak velocity time during a voluntary cough manoeuvre.

Tussometry is a new non-invasive method of assessing laryngeal function by analysing the airflow waveform produced by a voluntary cough. Ten healthy male volunteers performed five (n = 6) or six (n = 4) voluntary cough manoeuvres at varying lung volumes from total lung capacity to functional residual capacity. During each manoeuvre, airflow (litre min-1) was plotted against time (ms) to record the peak flow generated by the cough (CPFR) and the time taken to achieve this (PVT). In addition, expired volume (CEV) was measured during each manoeuvre. Highly significant (P < 0.001) correlations existed between CPFR and PVT (r = 0.81), CPFR and CEV (r = 0.78) and PVT and CEV (r = 0.71). We conclude that PVT may vary with CPFR which in turn bears a direct relationship to expired lung volume during a cough manoeuvre. These relationships among different variables should be considered when interpreting the results of tussometry.