A.A.M. Masclee

The Role of the Barostat in Human Research and Clinical Practice

BACKGROUND The barostat is a recently developed device used to study the physiology and pathophysiology of the motor and sensory functions of the gastrointestinal tract. It can monitor volume changes while maintaining a set constant pressure and deliver controlled distensions of gastrointestinal organs. Simultaneously, motility and visceral perception may be assessed. The barostat has contributed to the understanding of physiological processes in the gastrointestinal tract with regard to regulation of tone, compliance, enteric reflexes, sensation and processing of signals to and from the gut. In addition, the barostat has been used to study various gastrointestinal disorders. In functional bowel disorders, objective abnormalities in visceral sensitivity and enteric reflexes have been demonstrated. Numerous other diseases, gastrointestinal in origin as well as systemic diseases affecting the gut, have been studied. In the near future, the barostat may become a clinically useful tool for the objective diagnosis of motor and sensitivity disorders of the gut and for monitoring the effectiveness of therapy.

Motor and Sensory Function of the Rectum in Different Subtypes of Constipation

Background: It is not known whether evaluation of motor and sensory function of the rectum using a barostat may help to distinguish subtypes of constipation. Methods: Motor and sensory function of the rectum have been evaluated using a barostat in 14 patients with slow transit constipation (STC), 12 patients with constipation-predominant irritable bowel syndrome (IBS) and 18 healthy controls. First minimal distending pressure was determined, after which spontaneous adaptive relaxation of the rectum was monitored. Then a step-wise isobaric distension procedure was performed, during which symptom perception was determined. The distension was followed by a 90-min barostat procedure: for 30 min in the basal state followed by ingestion of a semi-liquid meal (postprandial state). Results: Minimal distending pressure was not different between both patient groups and controls, neither was compliance different between constipated patients and controls. The degree of spontaneous adaptive relaxation was in the same range in all groups. During distensions with high pressures, the perception of urge was significantly reduced in STC patients compared to IBS and controls, while the perception of pain was significantly increased in IBS versus STC and controls. Postprandially, a small decrease of rectal volume was only observed in the control group, but not in the patients. Conclusions: Rectal motor characteristics are not different between patients with constipation-predominant IBS, patients with STC and healthy controls while during isobaric distensions, sensations of urge were reduced in STC and sensations of pain were increased in IBS. Rectal visceroperception testing may help distinguish groups of patients with different subtypes of constipation.BACKGROUND It is not known whether evaluation of motor and sensory function of the rectum using a barostat may help to distinguish subtypes of constipation. METHODS Motor and sensory function of the rectum have been evaluated using a barostat in 14 patients with slow transit constipation (STC), 12 patients with constipation-predominant irritable bowel syndrome (IBS) and 18 healthy controls. First minimal distending pressure was determined, after which spontaneous adaptive relaxation of the rectum was monitored. Then a step-wise isobaric distension procedure was performed, during which symptom perception was determined. The distension was followed by a 90-min barostat procedure: for 30 min in the basal state followed by ingestion of a semi-liquid meal (postprandial state). RESULTS Minimal distending pressure was not different between both patient groups and controls, neither was compliance different between constipated patients and controls. The degree of spontaneous adaptive relaxation was in the same range in all groups. During distensions with high pressures, the perception of urge was significantly reduced in STC patients compared to IBS and controls, while the perception of pain was significantly increased in IBS versus STC and controls. Postprandially, a small decrease of rectal volume was only observed in the control group, but not in the patients. CONCLUSIONS Rectal motor characteristics are not different between patients with constipation-predominant IBS, patients with STC and healthy controls while during isobaric distensions, sensations of urge were reduced in STC and sensations of pain were increased in IBS. Rectal visceroperception testing may help distinguish groups of patients with different subtypes of constipation.

Proximal Gastric Motor and Sensory Function in Slow Transit Constipation

BACKGROUND Slow transit constipation may be part of a more generalized gastrointestinal motility disorder. METHODS Gastric motor and sensory function were evaluated using a barostat in 17 patients with slow transit constipation and in 16 healthy controls. A step-wise isobaric distension procedure was performed, followed by a barostat procedure including a liquid meal. Symptoms were scored using visual analog scales. Plasma levels of gastrointestinal hormones were determined postprandially. RESULTS Proximal gastric compliance was significantly reduced in the patients. Basal gastric volume did not differ between patients and controls. Postprandial fundus relaxation was significantly reduced in the patients and correlated significantly with daily upper gastrointestinal symptoms. Postprandial secretion of cholecystokinin and gastrin was reduced in the patients. CONCLUSIONS In patients with slow transit constipation, proximal gastric compliance is reduced and postprandial fundus relaxation is impaired. These findings support the hypothesis that slow transit constipation may be part of a pan-enteric disorder.Background: Slow transit constipation may be part of a more generalized gastrointestinal motility disorder. Methods: Gastric motor and sensory function were evaluated using a barostat in 17 patients with slow transit constipation and in 16 healthy controls. A step-wise isobaric distension procedure was performed, followed by a barostat procedure including a liquid meal. Symptoms were scored using visual analog scales. Plasma levels of gastrointestinal hormones were determined postprandially. Results: Proximal gastric compliance was significantly reduced in the patients. Basal gastric volume did not differ between patients and controls. Postprandial fundus relaxation was significantly reduced in the patients and correlated significantly with daily upper gastrointestinal symptoms. Postprandial secretion of cholecystokinin and gastrin was reduced in the patients. Conclusions: In patients with slow transit constipation, proximal gastric compliance is reduced and postprandial fundus relaxation is impaired. These findings support the hypothesis that slow transit constipation may be part of a pan-enteric disorder.

Role of Cholecystokinin in Relaxation of the Proximal Stomach

Ingestion of a meal causes proximal gastric relaxation (accommodation). The magnitude of accommodation is related to the fat content of the meal. A role for cholecystokinin (CCK) has been suggested. However, under fasting conditions intravenous CCK to postprandial levels does not induce a similar accommodation. This study further explores the role of CCK in accommodation. A gastric barostat was used in eight healthy persons to study accommodation in response to a carbohydrate meal with intravenous CCK (CH-CCK), carbohydrate meal with intravenous placebo (CH-placebo) and a fat rich meal with intravenous placebo (FAT). VAS scores for satiety and plasma CCK levels were obtained. In the first postprandial hour the FAT meal induced a relaxation of 112 +/- 29 ml, the CH-CCK meal 49 +/- 36 ml and the CH-placebo meal 12 +/- 32 ml (FAT versus CH-placebo P = 0.03; FAT versus CH-CCK P = 0.09). In the second postprandial hour, intragastric bag volume returned to baseline with all meals. The FAT meal had the most pronounced effect with respect to satiety, CH-placebo the least. In the first postprandial hour, plasma CCK levels increased with the CH-CCK and FAT meals but not with the CH-placebo meal; in the second postprandial hour, levels remained elevated with the CH-CCK meal. It is concluded that a carbohydrate meal with exogenous CCK does not induce fundic relaxation, whereas a fat-rich meal (endogenous CCK) does, despite similar plasma CCK levels.

Effect of cholecystokinin on rectal motor and sensory function in patients with irritable bowel syndrome and healthy controls

Aim  Ingestion of a meal frequently induces an urge to defaecate, the so‐called gastro‐colonic or gastro‐rectal reflex. In patients with irritable bowel syndrome (IBS), symptoms are often provoked by meals. Cholecystokinin (CCK), a proximal gut peptide released after ingestion of a meal, may mediate these postprandial changes. The potential role of CCK in rectal sensory and motor function was evaluated by a rectal barostat study in healthy controls and patients with IBS.

Effect of Somatostatin on Lower Esophageal Sphincter Characteristics in Man

Background: Somatostatin (SST) is known for its inhibitory effect on the gastrointestinal tract. Transient lower esophageal sphincter relaxations (TLESR), low or absent LES pressure (LESP) and swallowinduced LES relaxations are the most important reflux mechanisms. Methods: We have studied the effect of somatostatin on lower esophageal sphincter (LES) characteristics in man. Nine healthy volunteers participated in four experiments performed in random order and double-blind during continuous infusion of somatostatin (250 mg/h) or saline (control) under fasting and postprandial conditions. Esophageal motility was measured with sleeve manometry combined with pH metry. Results: Under fasting conditions LESP was not influenced by somatostatin. Ingestion of the carbohydrate meal significantly (P< 0.01) decreased LESP. During continuous somatostatin infusion the postprandial decrease in LESP did not occur; LESP was even significantly ( P< 0.05) increased over basal levels. Somatostatin did not significantly influence TLESR frequency, neither under basal conditions, nor postprandially. The residual pressure during swallow-induced LES relaxation was significantly ( P< 0.05) increased by somatostatin. Conclusion: In humans somatostatin prevents postprandial reduction in LESP, does not affect TLESR, but inhibits swallow-induced LES relaxation.BACKGROUND Somatostatin (SST) is known for its inhibitory effect on the gastrointestinal tract. Transient lower esophageal sphincter relaxations (TLESR), low or absent LES pressure (LESP) and swallow-induced LES relaxations are the most important reflux mechanisms. METHODS We have studied the effect of somatostatin on lower esophageal sphincter (LES) characteristics in man. Nine healthy volunteers participated in four experiments performed in random order and double-blind during continuous infusion of somatostatin (250 microg/h) or saline (control) under fasting and postprandial conditions. Esophageal motility was measured with sleeve manometry combined with pH metry. RESULTS Under fasting conditions LESP was not influenced by somatostatin. Ingestion of the carbohydrate meal significantly (P < 0.01) decreased LESP. During continuous somatostatin infusion the postprandial decrease in LESP did not occur; LESP was even significantly (P < 0.05) increased over basal levels. Somatostatin did not significantly influence TLESR frequency, neither under basal conditions, nor postprandially. The residual pressure during swallow-induced LES relaxation was significantly (P < 0.05) increased by somatostatin. CONCLUSION In humans somatostatin prevents postprandial reduction in LESP, does not affect TLESR, but inhibits swallow-induced LES relaxation.

Reproducibility of antroduodenal motility during prolonged ambulatory recording

Ambulatory recording of antroduodenal manometry is a novel technique with several advantages over standard stationary manometry recording. Although the feasibility of this technique in clinical practice has been demonstrated, reproducibility of antroduodenal motility recorded by means of ambulatory manometry has not been investigated. To test whether antroduodenal motility recorded by ambulatory manometry is reproducible, we performed two 24-h ambulatory antroduodenal manometry recordings in 18 healthy subjects according to an identical protocol with a 1-week interval. Motility was recorded with a five-channel solid-state catheter. Postprandial motility was recorded after consumption of two test meals and interdigestive motility was recorded nocturnally. Postprandial antroduodenal motor characteristics were identical between the separate recordings. The number and duration of nocturnal cycles of the interdigestive migrating motor complex were also in the same range. Phase III characteristics in general were not different between the two recordings. Only minor alterations were observed in the duration of phase III motor fronts with duodenal onset and in the number of interdigestive cycles concluded by duodenal onset phase III. Parameters obtained by qualitative analysis were comparable between the two recordings. The antroduodenal motility pattern, when measured by ambulatory recording with solid state catheters under standardized conditions, is very reproducible.

The role of 5HT3 receptors in mechanical and chemical stimulation of the duodenum

Stimulation of the duodenum, either mechanically or chemically, may induce upper abdominal sensations and may also induce proximal gastric relaxation. It is not clear which pathways mediate the motor and sensory responses. We studied the role of different types of duodenal stimuli and of 5HT3-antagonism on proximal gastric relaxation and visceral sensations. Methods: Nine healthy subjects (age 20-52 yr) were studied in a randomized double blind fashion at least one week apart. Either placebo i.v. or ondansetron 0.1 mglkg i.v. (bolus) was given. After an overnight fast, a catheter with an infinitely compliant bag was inserted into the horizontal part of the duodenum for stepwise increasing distensions (30-90 ml; 10 ml steps). A second catheter with an infinitely compliant bag was inserted into the proximal stomach and attached to a barostat device set at operating pressure to monitor changes in proximal gastric tone. After infusion of placebo or ondansetron, duodenal distensions were performed under fasting conditions. Next, Intralipid 2 kcal/min was continuously infused into the duodenum and duodenal distensions were repeated. Parameters: duodenal compliance, fundic relaxation and perception (pressure, nausea, fullness) scored on visual analog scales (VAS). Results: During duodenal distensions (mechanical stimulation), duodenal compliance was 3.0:!::0.1 ml/mmHg, the fundus relaxed (increment 41:!::19 mI, p<0.05) and VAS scores for all sensations increased significantly (p<O.OI). The motor and sensory responses to duodenal distensions were not different between placebo and ondansetron. Combined mechanical and chemical stimulation increased duodenal compliance to 4.4:!::0.3 ml/mmHg (p<0.05 vs fasting), further increased fundic relaxation (increment 279:!::80 ml, p<0.05 vs fasting) and increased VAS scores for nausea. The responses to combined mechanical and chemical stimulation of the duodenum were not different between ondansetron and placebo. Conclusions: 5HT3 antagonists do not alter motor and sensory responses of the stomach and duodenum after mechanical stimulation of the duodenum. Intraduodenallipid reduces tolerance for duodenal mechanical distension as manifested by an increase in nausea. This response is not modified by ondansetron. 5HT3-receptors do not have a major role in mediating sensations after mechanical and/or chemical stimulation of the duodenum.

Ileoanal pouch function is related to postprandialpouch tone

BACKGROUND Functional impairments are frequently observed in patients with an ileoanal pouch. Meal ingestion increases pouch tone and motility. Little is known, however, about the influence of meal-stimulated pouch characteristics on pouch function. The aim was to characterize basal and postprandial pouch motor and sensory characteristics in relation to clinical pouch function in patients with an ileoanal pouch. METHODS Nineteen patients with an ileoanal pouch, without faecal incontinence but with either a high stool frequency (n = 8) or an adequate stool frequency (n = 11), underwent pressure distension of the pouch, by which pouch compliance and sensitivity characteristics were assessed using an electronic barostat. A set pressure procedure was performed to assess the influence of a meal on pouch tone and motility. RESULTS Mean(s.d.) compliance was 10(6) and 11(4) ml/mmHg in the groups with poor and adequate pouch function respectively (P not significant). Mean(s.d.) visual analogue scale scores (0-10 cm) for urge at the highest pressure of 28 mmHg were 2.3(1.0) versus 2.3(2.4) cm respectively (P not significant); those for pain were 0.8(1.0) versus 0.5(0.7) (P not significant). Postprandially mean(s.d.) pouch volume decreased by 70(24) per cent in the group with poor pouch function and 29(25) per cent in the group with adequate pouch function (P < 0.01). The frequency and amplitude of phasic pouch contractions increased significantly postprandially, but no differences in motility characteristics were observed between the two groups. CONCLUSION In patients with uniform pouch design and follow-up after pouch construction, pouch compliance and sensitivity were no different between patients with normal and high stool frequency; however, postprandial pouch tone was increased significantly in patients with a high stool frequency.