Mechanics of Abdomen and Thorax in Man during Natural Breathing

The intra‐gastric pressure fluctuation during natural breathing is presumed to indicate the pressure moving the abdomen and thoracic wall. The mechanics of the abdomen and thoracic wall were estimated in resting human subjects by means of intra‐gastric pressure tidal volume curves. Compliance was 0.06–0.23 l/cm water, resistance 0.5–6.5 cm water/ I/sec, and rate of aspiratory work 15–100 litre cm water/min (100 litre cm water = 1 kpm) for abdomen and thoracic wall together. Supine as compared to sitting position increased the compliance and decreased the resistance. The abdomen was calculated to have a higher compliance and a lower resistance than the thoracic wall and to account for more than 0.6 of resting ventilation.