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

The effect of the first cigarette in the morning on the airway resistance ( R) 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 8 min after smoking. A further study ( n = 16) showed that the fall in R 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)O and carbon dioxide difference P(A-a)CO was investigated in 12 inhaling cigarette smokers. Smoking gave rise to a significant ( P < 0.0005) fall in the partial pressure of oxygen ( PaO) with compensatory overventilation. At the same time, the P(A-a)O and the P(A-a)CO 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 ( $$\dot Q$$ ) 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 $$\dot Q$$ by an average of 11.3%. The decrease in the R the fall in the PaO with compensatory overventilation, the increase in P(A-a)O and P(A-a)O and the decrease in the $$\dot Q$$ are interpreted as manifestations of pronounced acute ventilation-perfusion mismatching induced by smoking. [ABSTRACT FROM AUTHOR]