Intraesophageal pressure gradient in man

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Abstract
The effect of vertical height in the thorax on intraesophageal pressure was studied in 13 normal men in the upright position by usine saline-filled catheters. In six of seven subjects, pressures recorded via a Teflon catheter (od, 1.7 mm) introduced through a Sawyer tube (od, 4.7 mm) were approximately zero and did not vary systematically with the vertical position in the thorax. Roentgenograms and aspirations of air indicated that the esophagus was open to ambient pressure. In six other subjects, a polyethylene catheter (od, 1.3 mm) recorded pressure gradients of about 1.0 cm H2O/cm below the superior heart border in the upright position. Above this border, small or no gradients were obtained and no air was detected at any site in the esophagus. Intraesophageal pressure was highest in the supine position. Lung pressure-volume curves obtained at different heights in the esophagus revealed no systematic differences in a given position. These results are consistent with the hypothesis that differences in intraesophageal pressure at different heights in the thorax are due to the weight of the thoracic contents.