The Characteristics of Bronchial Clearance in Humans and the Effects of Cigarette Smoking

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Abstract
The clearance of radioactive monodisperse ferric oxide aerosols ranging in diameter from 0.8μ to 7.9μ was studied in a total of 117 experiments on 36 subjects. In most normal subjects there were two discrete periods of bronchial clearance, with the first usually completed within one to two hours, and the second within four to ten hours after inhalation. The fraction cleared in each phase was strongly dependent on the size of the inhaled particles, with more first phase clearance for larger particles. The rates of bronchial clearance were expressed in terms of the time required for completion of 50% to 90% bronchial clearance. On the basis of the limited data thus far accumulated, bronchial clearance was impaired in eight out of fourteen cigarette smokers, three out of three former uranium miners, and two out of two emphysema cases.