EFFECT OF ENTRAINMENT TIME ON PULMONARY DEPOSITION OF CIGARETTE-SMOKE IN DOGS

Chronic inhalation of tobacco smoke can produce a nonuniform pattern of lung disease, with apical (nondependent) areas affected more often and more severely than other lung regions. This localized tissue damage might be the result of uneven deposition of inhaled smoke aerosol. There is some evidence to suggest that the way in which an aerosol is inhaled can influence its deposition in the lung. This study sought to determine the effects of entrainment timing on the deposition of tobacco smoke in the lung. Anesthetized mechanically ventilated dogs (n = 14) inhaled 35-ml boluses of C-14-labeled mainstream cigarette smoke once per minute in either a supine or erect posture. Boluses were entrained at the start of inspiration (group 1) or at midinspiration (group 2). Lungs were removed, sectioned, and assayed for C-14. Group 1 lungs experienced deposition in regions distant from the tracheal axis, with peripheral lung units averaging twice the deposition of C-14 as central units. Group 2 lungs had a more uniform C-14 distribution pattern. Early smoke entrainment favored peripheral deposition. One explanation for this finding is that peripheral lung units may have shorter time constants, thus filling sooner and more completely than those located centrally.