ABILITY OF ASTHMATICS TO DETECT ADDED RESISTIVE LOADS

Abstract

The ability to detect resistive loads added to inspiration was assessed in normal and asthmatic subjects. The threshold of detection of added loads and higher in the asthmatic (mean threshold, 0.87 cm H2O per l .cntdot. s) than normal subjects (mean, 0.52 cm H2O per l .cntdot. s), but the difference was not significant (P > 0.2). When the results were expressed as the ratio of the added resistance to the sum of the airway resistance and the minimal resistance of the apparatus, the mean values were similar in the 2 groups. There was a wide variation in both the threshold of detection and the ratio of the added resistance to the sum of the airway resistance and the minimal resistance of the apparatus in the asthmatic compared to the normal group. After bronchodilator therapy, in the normal subjects there was a decrease in the threshold value but not change in the ratio of added resistance to the sum of the airway resistance and the minimal resistance of the apparatus; however, in the asthmatics there was an increase in both values after bronchodilation. The wide variation in the threshold of detection in the asthmatics and the effects of bronchodilation on the detection threshold suggest that in the patients variation in the psychological response, and, perhaps, chronic adaptation to the increased airway resistance, are also involved in the detection process.