The effects of airway anesthesia on magnitude estimation of added inspiratory resistive and elastic loads.

The effects of airway anesthesia on the magnitude estimation of added inspiratory loads were studied in 5 healthy normal subjects. The subjects assessed the magnitude of a given load by means of a handgrip dynamometer; 5 suprathreshold resistive loads. (range, 2.9 to 21.0 cmH2O/L/s) and 7 suprathreshold elastic loads (range, 4.6 to 24.0 cmH2O/L) were used. Anesthesia of the upper and lower airways was obtained by gargling and inhalation of 4% lidocaine solution; the adequacy of airway anesthesia was assessed by the inhalation of 20% citric acid solution. Studies were performed in the control state and during the airway anesthetized state. The relationship between log added load and log handgrip response, represented by the regression coefficient between these two variables, was in accord with the psychophysical power law of Stevens in all the studies. The regression coefficient during the control state of resistive loads (mean = 0.566) and elastic loads (mean = 0.516) did not alter significantly (p greater than 0.05) during the airway anesthetized state. These results indicate that the magnitude estimation of added inspiratory loads is not primarily mediated through receptors in the upper or lower airways.