Influence of tracheobronchial smooth muscle on the mechanical properties of the lung in normal man

Historical background of the measuring, partitioning and correlating of resistance was reviewed, and the theory behind the indirect estimation of upstream resistance explained. The oscillator with volume plethysmograph enabled study of volume history effect on lower (obtained from a tracheal catheter) and total pulmonary resistance. An adaptation of the upstream resistance estimation was used. Each study was done both pre and post atropine. Each test showed inflation resistance greater than deflation. This hysteresis was greatly reduced after atropine. It was considered due to bronchomotor tone. Lower pulmonary resistance was found to be very low and much more sensitive to airway change than total pulmonary resistance, and showed an increase at TLC. Inflation partial expiratory flow volume curves were considered the best indicators of bronchodilation particularly due to their simplicity. All tests showed that airway calibre depended on the balance between elastic recoil pressure and smooth muscle tone