Figure 6 - Upper esophageal sphincter pressure increases in response to gastroesophageal reflux events.

Examples of abrupt UES pressure increase in response to gastroesophageal reflux events accompanied by a clear secondary peristaltic pressure wave (SP; b) and absence of a recognizable SP (b). In both instances the intraesophageal pressure increase (IPI) encompasses the entire esophageal length, whereas a pH drop spares the proximal esophagus in b and does not reach 4.0 in a. The UES pressure increase lasts for 22 and 25 seconds, respectively. Note that although in the instance shown in a there is no change in respiration, in b there seems to be a shallow respiration at the onset of UES pressure increase and IPI. PE, proximal esophagus; ME; middle esophagus, DE, distal esophagus; EMG, electromyograph. (Source: Torrico et al.⁶⁰ with permission from the American Physiological Association)