Effects of shape changes of the chest wall on distribution of inspired gas.

The configuration of the chest wall was measured with magnetometers applied at various levels of the rib cage and abdomen. Distribution of ventilation was measured in the supine position using a bolus of xenon-133 inspired at a flow rate of 0.1 liter per sec. Measurements were made during spontaneous breathing, during augmented abdominal breathing, after manual lateral compression of the lower part of the rib cage followed by a predominantly abdominal motion, and after similar compression followed only by increase of the lateral basal rib cage diameter. Basal compression gave a decrease in lateral diameter of 5 to 7 per cent. During spontaneous breathing, apical ventilation exceeded basal ventilation. During an inspiration with an increase of the lateral basal rib cage diameter after compression, the ventilation of basal peripheral regions increased somewhat. No other systematic effects of the changes in either chest wall diameter at the start of inspiration or the type of inspiration were found on distribution of inspired boli.