VOLUNTARY COUGH SUPPRESSION AS AN INDICATION OF SYMPTOM SEVERITY IN UPPER RESPIRATORY-TRACT INFECTIONS

The aim of the present study was to determine whether the ability to s uppress cough voluntarily is an index of cough severity in upper respi ratory tract infection. Cough was measured by means of a microphone li nked to a pen recorder and subjects were instructed to voluntarily sup press cough in order to determine cough suppression time. Subjective s cores of symptom severity, mood and psychological parameters were made prior to cough measurements. The baseline frequency of cough showed a distribution towards the higher frequencies, with a median of 2.1 (lo wer quartile 1.2, upper quartile 3.2) coughs.min-1. The results for co ugh suppression fell into two distinct groups, one group reaching a br eaking point within 12.6 min; and another group which did not cough du ring the 20 min cough suppression period. In the group of subjects whi ch broke from the cough suppression, there was an inverse relationship between the cough suppression time and the baseline frequency of coug h. The median frequency of cough following cough suppression was signi ficantly greater than the baseline median frequency of cough. The subj ects who reached a breaking point had a greater baseline frequency of cough and a greater symptom severity score, and they also felt more fe eble, clumsy, sad and antagonistic than the group which did not reach a breaking point. The subjects who reached a breaking point had signif icantly greater scores for the psychology parameter of obsessional sym ptoms than the group which did not reach a breaking point. These resul ts demonstrate that there is considerable ability to voluntarily suppr ess cough, and that the degree of voluntary suppression is related to the severity of cough and to psychological factors such as obsessional symptoms.