AIRWAY DYNAMICS, ESOPHAGEAL PRESSURE AND COUGH

This study hypothesizes that: peak supramaximal airflow during cough r eflects expiratory muscle effort, and that expiratory muscle function during cough might be assessed from the airflow signal alone. We monit ored airflow and oesophageal pressure (Poes) in normal subjects during cough generated under two conditions: 1) voluntarily from functional residual capacity (FRC); and 2) involuntarily after inhalation of citr ic acid (CA). Maximal expiratory cough flow was quantified as the quot ient of maximal flow during a given cough divided by maximal flow at t he matched volume of thoracic gas (Vtg) as identified on the maximal e xpiratory flow-volume curve. We found: flow ratios correlated poorly w ith Poes; the variance of flow ratios associated with a series of volu ntary coughs was poorly explained by Poes. During CA inhalation, when the Vtg compressed during cough could not be controlled, correlation o f Foes with now Patio remained poor. We conclude that to study the mot or limb of the cough reflex, measurements of both airflow and oesophag eal pressure are required.