Evidence for diminished visceral pain with aging: studies using graded intraesophageal balloon distension

Graded intraesophageal balloon distension (IEBD) has been utilized in the past to evaluate esophageal pain thresholds. With use of a technique that we have found to provide reproducible results for pain thresholds, two groups of normal individuals without esophageal symptoms or diabetes were studied. Group 1 included 10 "young" (age < 65 yr) individuals (mean age 27 yr, range 18-57 yr). Group 2 included 17 individuals age 65 yr or greater (mean age 72.5 yr, range 65-87 yr). Catheters with latex balloons (Wilson-Cook) were used in all 27 subjects with the balloon located 10 cm above the lower esophageal sphincter. Sequential inflations of 2-ml increments were performed until a total volume of 2 ml above the point of pain or to a maximum of 30 ml was reached. A series of two sequential inflations were performed on each subject on the day of the testing, and the mean value was taken to indicate pain threshold volumes for all 27 subjects. In the group of elderly volunteers, 5 subjects felt no pain even at the maximum inflatable volume of the balloon (30 ml) and were assigned a maximum threshold value of 30 ml. Mean pain threshold volumes for the young subjects was 17 +/- 0.8 ml of air (+/- SE) and for the elderly subjects was 27 +/- 1.4 ml (P < 0.01 and 95% confidence interval = 7.1-13.3). Our conclusion is that IEBD results in the esophagus indicate an age-related decrease in human visceral pain threshold.

Determinants of upper esophageal sphincter pressure in dogs

Chronic experiments were done on six dogs fitted with EMG electrodes on pharyngeal and esophageal musculature. Electromyographic activity of the cricopharyngeus was recorded in awake and sedated animals with and without manometric recordings as well as during esophageal distension. Intraluminal upper esophageal sphincter (UES) pressure had two distinct components; active contraction accompanied by cricopharyngeal EMG activity and passive elasticity that persisted in the absence of EMG activity. Between swallows, the cricopharyngeal EMG activity patterns observed were of either tonic activity, no activity, or phasic activity with inspiratory bursts. The activity level was markedly affected by anesthesia, phonating, whining, panting, level of alertness, or changes in head posture. A brisk UES contraction was elicited in response to passage of the manometric assembly and to intraesophageal balloon distension. Persistent EMG augmentation after stationing of the manometric sensor suggested that intraluminal manometry tends to exaggerate resting sphincter pressure. We conclude that electrical activity of the cricopharyngeus, and by inference UES pressure, is markedly affected by many variables that are difficult to control during clinical or experimental determinations of UES pressure.