Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The effects of various distributions of regional ventilation, influenced by posture, respiratory rate, exercise, induced airway narrowing and pulmonary disease, on deposition of submicrometer particles have been investigated in 45 normal subjects (17 of whom smoked) and in 41 patients with pulmonary disease.;Regional ventilation was assessed using a rebreathing technique with Xenon-133. The test aerosol was Technetium-99m sulfur colloid generated by an air-drive nebulizer. Reservoir-settling bags, interposed between the nebulizer and the mouth, removed droplets larger than 2 (mu)m in diameter. The effective diameter of the aerosol within human lungs ranges from about 0.5 to 1 (mu)m, depending on the specifics of the delivery system and on the humidity and temperature of the respiratory tract. Particle deposition per unit long volume has been studied in both apical-basal and central-peripheral directions.;It has been shown that, in all circumstances, regional ventilation and aerosol deposition in the lung parenchyma are closely related, and that the greater the ventilation for a particular region, the greater the number of particles deposited in that region. These results indicate strongly that regional ventilation must be considered as a major factor determining particle deposition in the alveolar region of the lung. However, the character of this relation remains quite complex. Thus, the aerosol penetrance to damaged alveolar regions of the lung was reduced, compared to the penetrance of inspired radiogas, and the disparity increased with progressive impairment of ventilation (p < 0.001).;Despite the inherent differences between the two techniques, the present study has shown that aerosol imaging can be a sensitive and highly useful indicator of regional ventilatory abnormalities for clinical purposes. Consequently, the radioaerosol inhalation technique has been applied to 20 respirator-dependent ICU patients. Pulmonary embolus was judged highly probable in 10 of 16 patients after perfusion scanning alone, but this figure was reduced to 3 of the 16 after aerosol "ventilation" scanning was carried out. This demonstrates that this diagnostic procedure merits further attention.



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