Lobar Alveolar Gas Concentrations: Effect of Reduced Lung Volumes

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Abstract
Alveolar gas concns. may vary due to differences in pulmonary perfusion or pulmonary ventilation. We have previously shown lobar alveolar gas values vary with body position. Erect man has higher O2 and R. Q. values and lower CO2 values in the upper lobe than in lower. Supine man has lower O2 and higher CO2 concns. in the upper than in the lower lobe, with no difference statistically between lobes in R. Q. Changing from the erect to the supine position reduces lung volume with relative increase in the tidal air/functional residual air ratio. This provides more uniform ventilation of the lungs. A pneumoperitoneum in the erect subject causes a reduction in the lung volume as does recumbency. If changes in lobar alveolar air with body position were due to ventilation, the erect subject with pneumoperitoneum might be expected to have values similar to the recumbent normal. The 12 paired samples on 7 pneumoperitoneum subjects reveal no statistically significant difference between these subjects and normals. A pneumoperitoneum does not protect the ambulant erect subject from higher upper lobe O2 concns. which may provide a better environment for growth of the tubercle bacillus.

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