Abstract
A method to measure airway resistance was invented by DuBois and his coworkers. With this method, airway resistances are measured during panting respiration. However the measurements are very difficult to make, not only in patients with respiratory diseases, but also in normal subjects. Furthermore, the method has another disadvantage in that the measurements are not obtained during natural breathing. For these reasons we have developed a new plethysmograph with which we are able to measure airway resistance continuously during spontaneous breathing. With the apparatus we measured airway resistances of 7 normal persons and 8 patients with chronic obstrucitve pulmonary disease. We were able to record alveolar pressure curves and airway resistances along with respiratory volume curves. Maximal airway resistances during each inspiration and expiration were measured. Maximal expiratory resistances were higher than inspiratory resistances especially in patients with chronic obstructive pulmonary disease. Airway resistances measured with our plethysmograph correlated well with values obtained with the DuBois' method (r=0.905). We think that this method is a very easy and useful one for measuring airway resistance in patients with respiratory disease.
