[New methods for measurement of peripheral airway resistance]

We have developed two new methods to evaluate the peripheral resistance of the lung. The first is a method for continuous measurement of the frequency dependence of dynamic compliance (Cdyn, f.d.) and pulmonary resistance (RL) from a single-breath cycle by Fourier-series analysis. In this method, we have found that procaterol my first dilate the central airway and then gradually dilate the peripheral airway in bronchial asthma. The second is a method for the direct measurement of peripheral resistance by the anterograde catheter system using a catheter tip micromanometer. The catheter tip was inserted into the 3 mm diameter small airway anterogradely and intrabronchial pressure was measured simultaneously with transpulmonary pressure and mouth flow. We have found that the values of peripheral resistance in patients with COPD are four to seven times higher than that of normal subjects. These results suggest that the behavior of the peripheral and central airway may differ between patients and that the peripheral airway may be important to examine the pathogenesis of COPD.