A noninvasive technique for measurement of changes in specific airway resistance

A simple noninvasive technique for measuring specific airway resistance (airway resistance X thoracic gas volume) in unanesthetized guinea pigs is described. Specific airway resistances measured by this technique correlated well (r = 0.81) with the resistances obtained using a pleural catheter pressure measurement over a wide range of airway resistances. This range of resistances was generated by exposing the pigs to an aerosolized histamine bronchial challenge. The average specific airways resistance in unchallenged pigs was 1.24 +/- 3.47 cmH2O/s, somewhat lower than found by others, probably reflecting in part our larger pigs and in part some uncertainty in the absolute value of resistance inherent in our measurement technique. This technique is particularly useful in bronchial challenge experiments because of its sensitivity to acute changes in airway resistance.