ABSTRACT
UNLABELLED: The purpose of this study was to examine the possibility that body position influences inspiratory airflow of submerged subjects. Our previous studies have suggested that for a given (negative) inspired gas pressure, exercising divers experience more dyspnea in the prone than in the upright position. METHODS: Six subjects performed maximal inspiratory efforts recorded as esophageal pressure (balloon catheter); simultaneously inspiratory flow and lung volumes were recorded. To standardize static lung load, the subjects' chest pressure centroids (representing the average water pressure on the chest) were held at a constant depth (0.33m) throughout the experiments. RESULTS: Recordings of peak inspiratory flow (PIF) showed a decrease of 25.56 +/- 4.14% (mean +/- SD, P = 0.01) from the submerged upright position mean flow of 6.19 +/- 1.48 (l/s) to the submerged prone mean flow of 4.37 +/- 0.69 (l/s). Nadiral esophageal pressure exhibited no significant differences: 5.40 +/- 4.32% (mean +/- SD, P = 0.512), from the upright mean pressure of (-) 51.70 +/- 24.09 (cm H2O) to the prone mean pressure of (-) 48.53 +/- 25.86 (cm H2O). CONCLUSIONS: The significant decrease in PIF when changing from the upright to the prone position, suggests a difference in the patency of the extra-thoracic airways. The higher water pressure exerted on the neck in the prone position may explain this difference. The similarity of pleural pressures in the two positions indicates that the differences in PIF were not due to differences in inspiratory effort.
