Effect of breathing pattern on esophageal pressure gradients in humans.

This study examines the hypothesis that respiratory muscle action alters regional pleural pressures. Seven normal volunteers were studied in the seated posture with three esophageal balloons positioned in the upper, middle, and lower esophagus. The intraesophageal pressure swings were recorded during natural breathing, enhanced rib cage, and enhanced diaphragmatic breathing. The pressures were also recorded at three frequencies ranging from 12 to 60 breaths/min. Data were processed with an ensemble average technique that largely removes cardiogenic artifact. During quiet natural breathing, the pressure swings in the lower esophagus were, on the average, 30% larger than the pressure swings in the upper esophagus but became nearly equal as the frequency increased to 60 breaths/min. Rib cage breathing nearly abolished the intraesophageal dynamic pressure differences, whereas abdominal breathing preserved the observed pressure difference even at 60 breaths/min. We concluded that muscle action can affect intrathoracic pressures in a regional way depending on the groups of muscles that are active. These results are discussed in terms of the topographical distribution of ventilation.