Comparison of mouth and oesophageal pressure fluctuations during panting against an occlusion

In four normal volunteers, differences between oesophageal pressure fluctuations (delta Pes) in the upper and lower parts of the oesophagus and mouth pressure fluctuations (delta Pm), simultaneously measured during panting against an occlusion, were evaluated. Averaged quasi static pressure-volume curves were obtained by measuring pressure in the upper and lower thirds of the oesophagus. The differences between delta Pes and delta Pm during panting, due to elastic recoil changes, were predicted from an exponential relationship fitted to the pressure-volume curves. The calculated errors were compared with those observed experimentally. In the lower part of the oesophagus, delta Pes was similar to delta Pm at lung volumes in the range of 50 to 70% of Vmax. Vmax was deduced from the asymptote of the exponential curve. Mean delta Pes/delta Pm was 0.98 +/- 0.08 (SD). In the upper oesophagus, delta Pes was lower than delta Pm. Mean delta Pes/delta Pm was 0.87 in the range of 50 up to 90% of Vmax with an SD +/- 0.15. At lung volumes above 90% of Vmax for the upper oesophagus and above 70% of Vmax for the lower oesophagus, the ratio of delta Pes to delta Pm exceeded 1 and progressively increased. The measured values were often higher than those predicted from the fitted curves, presumably due to a narrowed glottic aperture. We concluded that in normals both the positioning of the oesophageal balloon in the lower oesophagus and a lung volume near functional residual capacity (FRC) are prerequisites for the use of delta Pm as a control for delta Pes, or vice versa, during panting against an occlusion.