Acute ventilation-perfusion mismatching resulting from inhalative smoking of the first cigarette in the morning

Abstract

The effect of the first cigarette in the morning on the airway resistance (R,w) which can be measured by body-plethysmography was investigated in 70 inhaling cigarette smokers. The test population showed a significant (P<0.0005) fall in R,w 8 rain after smoking. A further study (n = 16) showed that the fall in R~w was most likely to be attributable to a decrease in the trapped air. The effect of the first cigarette in the morning on the arterial blood gases and on the alveolar-arterial oxygen difference P(A-a)O2 and carbon dioxide difference P(A-a)CO2 was investigated in 12 inhaling cigarette smokers. Smoking gave rise to a significant (P < 0.0005) fall in the partial pressure of oxygen (PaO2) with compensatory overventilation. At the same time, the P(A-a)O2 and the P(A-a)CO2 increased significantly (P<0.01 and P<0.05, respectively). This effect could be observed for up to 24 min after smoking. In addition, the flow of blood in the pulmonary capillaries was measured in 28 test subjects with the nitrous oxide method ((~N2o) before, and 18-22 min after, smoking the first cigarette in the morning. After smoking, there was a significant (P < 0.0005) fall in the 0N2o by an average of 11.3%. The decrease in the Raw, the fall in the PaO2 with compensatory overventilation, the increase in P(A-a)O2 and P(A-a)CO2 and the decrease in the 0N2o are interpreted as manifestations of pronounced acute ventilation-perfusion mismatching induced by smoking.Abbreviations: Cdyn = dynamic compliance; Cdyn 40 = dynamic compliance at 40 breaths/min; QN~o =pulmonary capillary blood flow measured by the N/O method; P(A-a)= alveolararterial pressure difference; Pa=arterial partial pressure; APAo=alveolar pressure difference measured in the pressureflow curve at zero flow; Raw = airway resistance; sGaw = specific airway conductance; SVI=stroke volume index; TGV= thoracic gas volume; BSA = body surface area

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