Regional Clearance of Ions from the Airways of the Lung1–3

Abstract

To understand the physiologic mechanisms of lung clearance and how soluble substances such as those deposited in the lung by inhalation therapy or air pollution are cleared, experiments were performed on 3 normal men to show clearance of the pertechnetate ion from 12 regions of the right lung. Each subject, seated in front of a gamma camera, inhaled 2 ml of 0.156 M sodium chloride mist containing 300 μc of sodium pertechnetate of approximately 5 μ mass median diameter. the clearance was followed for 5 hours by measuring regional count rates over the lung with a gamma camera, while activity in the blood was monitored by a scintillation probe over the thigh. to correct for radioactivity in the blood in the chest, an intravenous injection of 70 μc sodium pertechnetate in saline, given at another time, was monitored with the gamma camera and the thigh probe. Each clearance study was repeated with the subject in the supine position; the aerosol was always inhaled in the upright position. In the supine position, clearance half-times were uniform over the entire lung and ranged from 7 to 13 minutes in different subjects. Similar clearance times over the lower lung were found in the upright position; however, clearance half-times became longer near the apex. This suggests that the clearance of ions from the apex is affected by the reduced blood flow to this region. Pulmonary and bronchial blood flows appear to be the major mechanisms for the clearance of ions from the airways.