Inspiratory and expiratory resistive load detection in normal and asthmatic subjects. A sensory decision theory...

The ability to detect added external inspiratory and expiratory resistive loads was studied in normal and asthmatic subjects using sensory decision theory as a psychophysical method. Performances P(A)/delta R [where P(A) represents the index of sensitivity and delta R the additional resistor] were similar in normal and asthmatic subjects, but when sensitivity was expressed in relation to airway resistance [P(A)/delta R/Raw], asthmatics showed higher inspiratory and expiratory performances than normal subjects. After bronchodilation the relative sensitivity in the asthmatic group was impaired and approached that of normal subjects. Comparing inspiratory and expiratory load detection, normal subjects showed a higher sensitivity for expiratory than for inspiratory loads. In contrast, there was no difference in the asthmatic group. The response bias remained the same across conditions. If one accepts the assumption that the variability of sensitivity presented by asthmatic and normal subjects might be related to the variable state of their pulmonary function, our results can be interpreted as demonstrating a relationship between sensitivity and pulmonary distension or airway obstruction. These results are in agreement with the hypothesis that the site of perception for respiratory load detection is the chest wall.