RELATIONSHIP BETWEEN REGIONAL VENTILATION AND AEROSOL DEPOSITION IN TIDAL BREATHING

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Abstract
The regional distribution of the deposition of 1.2 .mu.m particles of 99mTc sulfur colloid, inhaled by tidal breathing, was compared with the distribution of ventilation as measured by a 133Xe washout technique. Subjects (12) were studied, 6 with normal pulmonary function tests, 5 with air-flow limitation, and 1 with unilateral phrenic nerve paralysis. Both X and aerosol were inhaled at tidal vol by the subjects while seated upright. A large field .gamma. camera acquired posterior scans. Experiments (13) were also done on 7 dogs: 1 with extrathoracic obstruction of the airway to 1 lung, and 12 with bronchoconstriction from the instillation of methacholine chloride into the airways of a lower lobe. Two of these dogs were studied with a .gamma. camera system, and the others were studied with a Picker multi-probe system. Both in humans and in dogs, an increase in time constant, which indicated a decrease in ventilation, was associated with an increase in peripheral aerosol deposition when normalized for ventilation. Evidently, the increased residence time is responsible for the increased deposition in regions that received lesser ventilation.