Physical activity and intestinal gas clearance in patients with bloating

BACKGROUND: Patients complaining of abdominal bloating have impaired tolerance and clearance of intestinal gas loads. Mild exercise enhances intestinal clearance and prevents retention of intestinal gas loads in healthy subjects. Our aim was to evaluate the putative beneficial effects of physical activity in patients with abdominal bloating. METHODS: In eight patients complaining of bloating, seven with irritable bowel syndrome, and one with functional bloating, according to Rome II criteria, a gas mixture was continuously infused (12 mL/min) into the jejunum for 120 min with simultaneous duodenal lipid perfusion (1 kcal/min). Gas evacuation, perception (0-6 scale), and abdominal girth were measured at 15-min intervals. Paired studies were randomly performed in the supine position during intermittent pedaling (5 min with 3-min rest intervals at 40 rpm and 0.15 kp load) versus rest (as control). RESULTS: During rest, a significant proportion of the gas infused was retained in the gut (45 +/- 9%, P < 0.01 vs basal), but retention was significantly lower during exercise (24 +/- 7%, P < 0.05 vs rest). Gas retention during rest was associated with significant abdominal symptoms (3.6 score; P < 0.01 vs basal), and symptoms also improved during exercise (2.8 score, P < 0.05 vs rest). During the test, patients developed abdominal distension, which was related to the volume of gas retained (r = 0.68, P < 0.05). CONCLUSION: Mild physical activity enhances intestinal gas clearance and reduces symptoms in patients complaining of abdominal bloating.     

Prokinetic effects in patients with intestinal gas retention

BACKGROUND & AIMS: We have previously shown that patients with irritable bowel syndrome (IBS) have impaired transit of intestinal gas loads. Because abnormal gas retention can be experimentally reproduced in healthy subjects by pharmacological inhibition of gut motility, we hypothesized that impaired gas transit and retention can be reciprocally corrected by pharmacologically stimulating intestinal propulsion. METHODS: In 28 patients with abdominal bloating (14 IBS, 14 functional bloating) and in 14 healthy subjects, gas evacuation and perception of jejunal gas infusion (12 mL/min) were measured. After 2 hours, in 20 patients we tested the effect of intravenous neostigmine (0.5 mg) vs. intravenous saline administered blindly and randomly at a 1-hour interval. RESULTS: After 2 hours of gas infusion, patients with IBS and functional bloating alike exhibited significant gas retention (418 +/- 86 mL), abdominal symptoms (2.7 +/- 0.5 score), and objective distention (8 +/- 2 mm girth increment), in contrast to healthy controls, who experienced none (46 +/- 102 mL retention, 0.4 +/- 0.3 symptom score, and 3 +/- 1 mm distention; P < 0.05 for all). Neostigmine produced immediate clearance of gas retained within the gut (603 +/- 53 mL/30 minutes vs. 273 +/- 59 mL/30 minutes after saline; P < 0.05) and by 1 hour reduced gas retention (by 373 +/- 57 mL), abdominal symptoms (by 1.1 +/- 0.5 score), and distention (by 6 +/- 1 mm; P < 0.05 for all), whereas intravenous saline produced no effects. CONCLUSIONS: In patients with intestinal gas retention, pharmacological stimulation of intestinal propulsion improves gas transit, abdominal symptoms, and distention.     

Impaired small bowel gas propulsion in patients with bloating during intestinal lipid infusion

OBJECTIVE: In healthy individuals, intraluminal lipids delay intestinal gas clearance, and this reflex is exaggerated in patients with irritable bowel syndrome (IBS). Our aim was to determine the site of action of abnormal lipid-induced reflexes in IBS. METHODS: In six patients with (IBS) predominantly complaining of bloating and in six healthy subjects, a mixture of gas (N2, O2, and CO2 in venous proportions to minimize diffusion) was infused (12 mL/min) either into the jejunum or into the ileum for 2 h, with simultaneous perfusion of lipids (0.5 kcal/min) into the proximal duodenum. Rectal gas evacuation was measured by a barostat. Abdominal perception (by a 0-6 scale) and girth changes were measured at 15-min intervals. The effects of jejunal versus ileal gas infusion were compared by paired tests in random order on separate days. RESULTS: IBS patients exhibited significant gas retention during infusion of gas into the jejunum (398 +/- 90 mL vs-210 +/- 105 mL in health, p < 0.05) but not during ileal infusion (-79 +/- 87 mL vs-79 +/- 78 mL in health, NS; p < 0.05 vs jejunal infusion). Gas retention during jejunal gas infusion in IBS patients was associated with significant abdominal distension (11 +/- 3 mm girth increment vs 0 +/- 1 mm during ileal gas infusion and 1 +/- 1 mm in health, p < 0.05 for both) and abdominal symptoms (3.6 +/- 0.6 score vs 2.6 +/- 0.7 score during ileal gas infusion and 1.6 +/- 0.5 score in health, p < 0.05 for both). CONCLUSIONS: In IBS patients intraluminal lipids impair intestinal gas clearance because of upregulated reflex inhibition of small bowel transit, without appreciable colonic effects.     

Origin of gas retention and symptoms in patients with bloating

BACKGROUND & AIMS: Patients reporting abdominal bloating exhibit impaired tolerance to intestinal gas loads. The aim of this study was to identify the gut compartment responsible for gas retention. METHODS: In 30 patients predominantly reporting abdominal bloating (24 with irritable bowel syndrome and 6 with functional bloating) and 22 healthy subjects, gas (nitrogen, carbon dioxide, and oxygen) was infused into the intestine for 2 hours while measuring rectal gas outflow. First, in 12 patients and 10 healthy subjects, gas transit (24 mL/min jejunal infusion labeled with 74 MBq bolus of 133 Xe) was measured by scintigraphy. Second, in groups of patients and healthy subjects, the effects of gas infusion (12 mL/min) in the jejunum versus ileum, jejunum versus cecum, and jejunum versus sham infusion (n=6 each) were compared by paired tests. RESULTS: In patients, total gut transit of gas was delayed (50% clearance time, 33 +/- 4 min vs 23 +/- 4 min in healthy subjects; P <.05) owing to impaired small bowel transit (50% clearance time, 20 +/- 2 min vs 12 +/- 3 min in healthy subjects; P <.05), whereas colonic transit was normal (50% clearance time, 13 +/- 2 min vs 11 +/- 2 min in healthy subjects; not significant). Furthermore, jejunal gas infusion in patients was associated with gas retention (329 +/- 81 mL vs 88 +/- 79 mL in healthy subjects; P <.05), whereas direct ileal or colonic infusion was not (61 +/- 103 mL and -143 +/- 87 mL retention, respectively). CONCLUSIONS: In patients reporting bloating, the small bowel is the gut region responsible for ineffective gas propulsion.     

Lipid-induced intestinal gas retention in irritable bowel syndrome

BACKGROUND & AIMS: We hypothesized that lipids, which induce various motor and sensory effects on the gut, modulate intestinal gas dynamics and that alteration of this regulatory mechanism may result in impaired gas transit in patients with irritable bowel syndrome (IBS). METHODS: In 45 healthy subjects and 30 patients with IBS, evacuation of gas infused into the jejunum (at 12 mL/min) was measured for 2 hours. The effect of simultaneous duodenal perfusion of lipids at 0 kcal/min (saline), 0.5 kcal/min, and 1 kcal/min was tested in groups of 15 subjects each. RESULTS: In healthy subjects, duodenal lipids at 1 kcal/min but not at 0 kcal/min or 0.5 kcal/min produced significant gas retention (281 +/- 53 mL vs. 22 +/- 64 mL at 0 kcal/min and -65 +/- 72 mL at 0.5 kcal/min; P < 0.05 for both). Patients with IBS exhibited gas retention during saline perfusion (259 +/- 85 mL at 0 kcal/min; P < 0.05 vs. healthy subjects) and were hypersensitive to duodenal lipids (505 +/- 61 mL retention at 0.5 kcal/min; P < 0.05 vs. saline and vs. healthy subjects). The "gas plus lipids" challenge test discriminated patients with 100% sensitivity and 93% specificity. CONCLUSIONS: Physiologic concentrations of intestinal lipids exert an inhibitory control on intestinal gas transit, and this mechanism is up-regulated in patients with IBS. Hence, impaired gas propulsion, shown by the gas challenge test, may be useful as a diagnostic test if replicated in a larger series of patients.     

Effect of High- and Low-Caloric Mixed Liquid Meals on Intestinal Gas Dynamics

High-caloric meals can evoke postprandial abdominal complaints involving disturbances in intestinal gas balance. We aimed to determine the influence of the caloric content of meals on intestinal gas dynamics. Eight healthy subjects (five women, three men; age range, 25–43 years) underwent paired studies with low (1 kcal/min)- and high (3 kcal/min)-caloric meal infusion 35% fat, (45% carbohydrate, 20% protein) into the duodenum in random order and proximal jejunal gas infusion. Gas evacuation, perception, and abdominal girth were assessed. The low-caloric meal caused neither gas retention (–7 ± 58 ml) nor girth changes (0 ± 0 mm). In contrast, the high-caloric meal led to significant gas retention (705 ± 56 ml) and increased abdominal perimeter (7 ± 1 mm; P < 0.001 vs. the low-caloric meal for both). Thus, a high caloric load of nutrients arriving at the duodenum modulates both intestinal gas transit and abdominal perimeter. This work was supported by Research Fund of the Mannheim Faculty of Clinical Medicine Grant 098200/99-245, University of Heidelberg, and the Else-Kroener Fresenius Foundation.     

Duodenal infusion of different nutrients and the site of gaseous stimulation influence intestinal gas dynamics

OBJECTIVE: Excessive intestinal gas can be involved in postprandial abdominal symptom generation, but whether the small bowel influences intestinal gas dynamics, depending on the ingested meal, remains to be demonstrated. We compare the intestinal response to a proximal and distal small intestinal gas challenge during different duodenal nutrient components. MATERIAL AND METHODS: We randomly studied 32 healthy subjects, twice, on different days with a gas mixture infused at 12 ml/min either directly into the proximal jejunum or into the ileum; during duodenal lipids, amino acids, glucose, at 1 kcal/min each, or saline (n=8 for each group). Gas evacuation was monitored continuously and abdominal perception and girth changes were assessed. RESULTS: In response to the jejunal gas challenge, duodenal lipids delayed intestinal gas clearance more potently than amino acids (733+/-26 ml and 541+/-108 ml final gas retention; p<0.001), but when gas was directly infused into the ileum the retained volumes were much smaller (271+/-78 ml and 96+/-51 ml; p<0.001). During duodenal glucose, intestinal gas clearance following jejunal or ileal gas infusion was not significantly influenced. Abdominal perception in response to the jejunal and ileal gas challenge only increased slightly during duodenal lipids (2.0+/-0.3 score and 2.3+/-0.6 score; p<0.05 versus control). CONCLUSION: Postprandial intestinal gas clearance is hampered by duodenal lipids and amino acids but not by glucose. Specific inhibitory effects are more pronounced when gas is infused into the jejunum, which underlines the importance of the small intestine in postprandial gas retention.     

Modulation of intestinal gas dynamics in healthy human volunteers by the 5-HT receptor agonist tegaserod

OBJECTIVES: Bloating in irritable bowel syndrome (IBS) may result from impaired intestinal gas transit and is reduced by the 5-HT4 agonist tegaserod. Abnormal serotonergic function underlies many IBS symptoms, but the role of 5-HT4 pathways in regulating gas dynamics under healthy conditions is unexplored. We hypothesized that 5-HT4 activation by tegaserod stimulates gas transit in healthy individuals. METHODS: Sixteen normal volunteers underwent jejunal perfusion of gas mixtures (88% N2, 5.5% O2, 6.5% CO2) at 11.2 mL/min x 3 h under control conditions and 3 h after oral tegaserod 6 mg on separate days. Gas collected from an intrarectal catheter was quantified using a barostat. RESULTS: Under control conditions, gas evacuation after a lag period (1,959 +/- 428 s) was predominantly pulsatile with expulsion of 1,984 +/- 90 mL. A mean of 29 +/- 2 boluses with volumes of 72 +/- 5 mL were expelled. In 10 subjects with physiologic degrees of gas retention in control studies (248 +/- 73 mL), tegaserod increased expulsion from 1,768 +/- 73 to 1,973 +/- 37 mL and decreased retention to 43 +/- 37 mL (p < 0.05). Total volumes expelled as boluses were greater after tegaserod (1,708 +/- 73 vs 1,846 +/- 59 mL, p < 0.05) from increased bolus numbers in four subjects and increased bolus volumes in seven. Nonpulsatile continuous flow tended to increase with tegaserod (43 +/- 7 vs 126 +/- 43 mL, p= 0.10). Tegaserod did not increase evacuation in individuals without physiologic gas retention. CONCLUSIONS: The 5-HT4 agonist tegaserod promotes evacuation of jejunally perfused gas mixtures in healthy humans. These findings provide the foundation for future investigations into use of 5-HT4 agonists in conditions of pathologic gas retention.     

Impaired reflex control of intestinal gas transit in patients with abdominal bloating

BACKGROUND: Patients with abdominal bloating and distension exhibit impaired transit of intestinal gas which may lead to excessive gas retention and symptoms. Furthermore, we have previously shown that intestinal gas transit is normally accelerated by rectal distension. We hypothesise that in patients with functional bloating this modulatory mechanism fails and impairs gas transit. METHODS: In 12 healthy subjects and eight patients with abdominal bloating we compared, by paired studies, the effect of rectal versus sham distension on intestinal gas transit. Gas was infused into the jejunum (12 ml/min) for three hours with simultaneous perfusion of lipids into the duodenum (Intralipid 1 kcal/min) while measuring evacuation of gas per rectum. RESULTS: In healthy subjects, duodenal lipid infusion produced gas retention (409 (68) ml) which was prevented by rectal distension (90 (90) ml; p<0.05 v sham distension). In contrast, rectal distension in patients with abdominal bloating failed to reduce lipid induced gas retention (771 (217) ml retention during rectal distension v 730 (183) ml during sham distension; NS; p<0.05 v healthy controls for both). CONCLUSION: Failure of distension related reflexes impairs intestinal gas propulsion and clearance in patients with abdominal bloating.     

Gastric distension and duodenal lipid infusion modulate intestinal gas transit and tolerance in humans

OBJECTIVE: Patients with unexplained abdominal complaints often attribute their symptoms to intestinal gas and indicate that symptoms are exacerbated by ingestion of a meal. However, the mechanisms responsible are unknown. Our aim was to analyze the specific influence of two meal-related factors, gastric distension, and intestinal nutrients, on intestinal gas dynamics and tolerance. METHODS: In 35 healthy subjects, gas evacuation and perception of jejunal gas infusion (12 ml/min) were measured for 3 h, during simultaneous duodenal infusion of saline, as control, lipids at 1 Kcal/min, or gastric distension. RESULTS: Infusion of lipids into the duodenum induced gas retention (584 +/- 154 ml, p < 0.05 vs 161 +/- 86 ml after saline infusion) without perception (2.2 +/- 0.5 score), whereas gastric distension induced perception (score 5.6 +/- 0.4, p < 0.05 vs score 1.9 +/- 0.4 after saline) without gas retention (7 +/- 205 ml). CONCLUSIONS: Different meal-related factors exert specific effects on intestinal gas dynamics and tolerance, and these mechanisms may interact to produce postprandial gas symptoms.     

Impaired transit and tolerance of intestinal gas in the irritable bowel syndrome

BACKGROUND: Patients with irritable bowel syndrome (IBS) frequently complain of excessive gas but their fasting volume of intestinal gas is apparently normal. We hypothesised that the pathophysiological mechanism involved may be impairment of intestinal gas transit. AIM: To investigate intestinal gas transit and tolerance in IBS patients compared with healthy subjects. METHODS: A gas mixture (N(2), O(2), and CO(2) in venous proportions) was infused into the jejunum of 20 patients with IBS and 20 healthy controls at 12 ml/min for four hours. Gas evacuation, initially flatus from the anus (two hours) and then intrarectally (two hours), was continuously recorded. Symptom perception (0-6 scale) and abdominal distension were measured at 10 minute intervals. RESULTS: After two hours of external gas (flatus) collection, 18 of 20 IBS patients had developed gas retention (>400 ml), increased gastrointestinal symptoms (score >3), or abdominal distension (>3 mm girth increment) compared with only four of 20 control subjects. During intrarectal gas collection, 13 of 17 patients still exhibited abnormal responses. CONCLUSION: A large proportion of patients with IBS can be shown to have impaired transit and tolerance of intestinal gas loads. This anomaly may represent a possible mechanism of IBS symptoms, specifically pain and bloating.     

Impaired viscerosomatic reflexes and abdominal-wall dystony associated with bloating

BACKGROUND & AIMS: Abdominal bloating is a frequent complaint in irritable bowel syndrome (IBS), but its underlying mechanism remains uncertain. Our aim was to determine whether the abdominal wall, specifically its adaptation to intra-abdominal volumes, plays a role. METHODS: In 12 patients complaining of abdominal bloating (8 IBS and 4 functional bloating) and in 12 healthy controls, the effect of colonic gas load (24 mL/min rectal gas infusion for 1 hour) on perception (measured by a 0-6 scale), abdominal girth, and muscular activity was tested. With the participants sitting on an ergonomic chair and the trunk erect, multichannel electromyography was measured via bipolar surface electrodes located over the upper and lower rectus abdominis, and the external and internal oblique bilaterally. RESULTS: In healthy controls, colonic gas loads produced subjective symptoms (score, 3.0 +/- 0.3), objective abdominal distention (girth increment, 6 +/- 1 mm), and increased the activity of the abdominal muscles (external oblique activity, 11% +/- 3% in; P < .05 vs basal). At the same infused gas volumes, the patients developed significantly more symptoms (score, 4.5 +/- 0.4) and abdominal distention (11 +/- 1 mm; P < .05 vs healthy for both). These abnormal responses were associated with failed tonic contraction of the abdominal wall (external oblique activity change, -1% +/- 4%; P value not significant vs basal) and paradoxic relaxation of the internal oblique (activity reduction, 26% +/- 7%; P < .01 vs basal). CONCLUSIONS: In patients with bloating, abdominal perception and distention in response to intra-abdominal volume increments are exaggerated markedly and associated with muscular dystony of the abdominal wall.     

Assessment of symptoms and exercise capacity in cyanotic patients with congenital heart disease

OBJECTIVES: Patients with cyanotic congenital heart disease are generally thought to be limited by hypoxemia. To correlate exercise tolerance to the severity of the cardiac abnormality and to further characterize dyspnea in affected patients, we examined 25 adults with uncorrected cyanotic congenital heart disease. DESIGN AND SETTING: Cohort study at a university hospital. METHODS: Symptom-limited cardiopulmonary exercise testing (CPX) was performed on a treadmill. Expiratory gas was analyzed breath by breath for evaluation of maximal exercise performance, ventilation, and ventilatory efficiency in combination with blood gas analysis during rest and exercise. Symptoms were assessed by the ability index and New York Heart Association class, and the results were compared to 101 healthy volunteers. RESULTS: PaO(2) decreased by 26 +/- 8% (mean +/- SD) with exercise (from 49 +/- 12 to 36 +/- 10 mm Hg), while PaCO(2) was only slightly decreased compared to control subjects. Peak oxygen uptake (O(2)) was significantly reduced when compared to control subjects: 16.7 +/- 6.6 mL/kg/min vs 36.1 +/- 7.7 mL/kg/min. Ventilatory efficiency was markedly impaired at rest (minute ventilation [E]/carbon dioxide output [CO(2)] ratio of 70 +/- 18; control subjects, 53 +/- 11; p < 0.005) and during exercise (E vs CO(2) slope, 58 +/- 31; control subjects, 26 +/- 4; p < 0.005). At rest, ventilatory efficiency was correlated to resting pH and PaO(2), while during exercise it was linked to PaO(2). Ventilatory efficiency during exercise had the strongest correlation with observed symptoms, while hypoxemia and peak O(2) were not significantly associated with symptomatic state. CONCLUSION: CPX in patients with cyanotic congenital heart disease provides helpful parameters that better define the symptomatic state of these patients. The summation of disease-related factors is best reflected by ventilatory efficiency. This parameter offers additional and independent information when compared to peak O(2) and the extent of cyanosis alone.     

Gas exchange during maximal upper extremity exercise

STUDY OBJECTIVE: to characterize gas exchange and cardiopulmonary performance during maximal progressive arm crank exercise. DESIGN: Cardiopulmonary variables were measured and arterial blood gases were determined in blood samples obtained from an indwelling radial arterial catheter during arm crank exercise (34 watts/min). Arm crank exercise was compared to maximal leg exercise performed by a different but comparable group of subjects from a previous study. PARTICIPANTS: 19 healthy young (mean +/- SEM: 20 +/- 1 yr) black males. RESULTS: Peak arm crank exercise resulted in lower values compared to peak leg exercise for: power (129 +/- 2 vs 253 +/- 10 W), VO2 (2.17 +/- 0.04 vs 3.26 +/- 0.14 L/min); VCO2 (2.9 +/- 0.11 vs 4.32 +/- 0.17 L/min); HR (168 +/- 3 vs 189 +/- 3 beats/min); AT (1.15 +/- 0.05 vs 1.83 +/- 0.07 L/min); and VE (101 +/- 2 vs 144 +/- 8 L/min), respectively. Arm crank exercise (baseline vs peak) elicited an impressive improvement in PaO2 (85 +/- 1 to 97 +/- 1 mm Hg), no change in SaO2 (96 +/- 0.2 to 96 +/- 0.2 percent), no significant increase in P(A-a)O2 (3 +/- 0.7 to 5 +/- 0.9 mm Hg) and an appropriate trending decrease in VD/VT (0.22 +/- 0.01 to 0.17 +/- 0.01). Peak arm crank values were significantly different from peak cycle exercise for PaO2 (82 +/- 2.2 mm Hg), SaO2 (93 +/- 0.4 percent), P(A-a)O2 (21 +/- 1.9 mm Hg) and VD/VT (0.08 +/- 0.01). At comparable levels of VO2 for arm crank and cycle exercise (2.17 +/- 0.04 vs 2.26 +/- 0.08 L/min), significant differences were observed for PaO2 (97 +/- 1.4 vs 81 +/- 1.9 mm Hg); SaO2 (96 +/- 0.2 vs 94 +/- 0.4 percent); P(A-a)O2 (5 +/- 0.9 vs 14 +/- 1.5 mm Hg); and VD/VT (0.17 +/- 0.01 vs 0.08 +/- 0.01), respectively. CONCLUSIONS: Maximal arm crank exercise represents a submaximal cardiopulmonary stress compared to maximal leg exercise. The differences in gas exchange observed at peak exercise between arm crank and leg exercise for the most part reflect the lower VO2 achieved. However, the persistence of these gas exchange differences even at a comparable level of VO2 suggests that factors other than VO2 may be operative. These factors may include differences in alveolar ventilation, CO2 production, ventilation-perfusion inequality, diffusion, and control of breathing.     

Effect of betaxolol on the hemodynamic, gas exchange, and cardiac output response to exercise in chronic atrial fibrillation

BACKGROUND: beta-blockade controls the ventricular response to exercise in chronic atrial fibrillation (AF), but the effects of beta-blockers on exercise capacity in AF have been debated. METHODS: Twelve men with AF (65+/-8 years) participated in a randomized, double-blind, placebo-controlled study of betaxolol (20 mg daily). Patients underwent maximal exercise testing with ventilatory gas exchange analysis, and a separate, submaximal test (50% of maximum) during which cardiac output was measured by a CO2 rebreathing technique. RESULTS: After betaxolol therapy, heart rate was reduced both at rest (92+/-27 vs 62+/-12 beats/min; p < 0.001) and at peak exercise (173+/-22 vs 116+/-24 beats/min; p < 0.001). Maximal oxygen uptake (VO2) was reduced by 19% after betaxolol (21.8+/-5.3 with placebo vs 17.6+/-5.1 mL/kg/min with betaxolol; p < 0.05), with similar reductions observed for maximal exercise time, minute ventilation, and CO2 production. VO2 was reduced by a similar extent (19%) at the ventilatory threshold. Submaximal cardiac output was reduced by 15% during betaxolol therapy (12.9+/-2.3 vs 10.9+/-1.3 L/min; p < 0.05), and stroke volume was higher (88.0+/-21 vs 105.6+/-19 mL/beat; p < 0.05). CONCLUSION: Betaxolol therapy in patients with AF effectively controlled the ventricular rate at rest and during exercise, but also caused considerable reductions in maximal VO2 and cardiac output during exercise. The observed increase in stroke volume could not adequately compensate for reduced heart rate to maintain VO2 during exercise.     

Gas distribution within the human gut: effect of meals

BACKGROUND AND AIMS: Patients frequently complain of gas symptoms precipitated by meals, but the effect of early digestion on intestinal gas content remains unknown. Our aim was to determine the influence of meals on intestinal gas volume and distribution. METHODS: First, we developed a CT image analysis program, based on independent software modules, to measure gas content within the gut. The system was validated in nine healthy subjects by taking helical abdominal CT scans before and after rectal infusion of known volumes of air (100-400 mL). In 15 healthy subjects, intestinal gas distribution was measured in fast and early postcibal CT scans. The postcibal scan was taken 99 +/- 22 minutes after a 597 +/- 57 kcal meal. RESULTS: The volume of gas infused per rectum was detected with an accuracy of 100.4 +/- 3.0%. During fasting, intestinal gas volume was 94 +/- 7 mL (excluding two extreme outliers). After the meal, gas content within the gut increased by 64.7% (up to 149 +/- 21 mL, P < 0.01 vs fast) and the increment occurred in the colon (59 +/- 9 mL precibal vs 121 +/- 20 mL postcibal, P < 0.001), while other gut compartments remained unchanged. CONCLUSION: Ingestion of a meal activated gas metabolism and increased gas content within the gut. The increment occurred early, presumably prior to colonic fermentation of food substrates and was localized in the distal gut, suggesting that gas had a proximal origin and was propelled caudally.     

轻中度哮喘患者提高运动耐量可行性研究

目的 比较同等日常运动水平的轻、中度哮喘患者与健康志愿者的运动心肺功能;探讨静息深吸气量与大运动功率的关系。方法 轻、中度哮喘患者１９例和健康志愿者１９例接受了运动心肺功能试验。试验采用负荷递增运动方案,运动前测一秒钟用力呼气容积（ＦＥＶ１）、深吸气量（ＩＣ）,运动后监测ＦＥＶ１。运动中监测心率、氧耗量（ＶＯ２）、每分钟通气量（ＶＥ）、氧脉搏（Ｏ２－ｐｕｌｓｅ）、呼吸频率等。结果 哮喘患者运动后Ｆ     

Intestinal gas distribution determines abdominal symptoms

BACKGROUND: Patients with functional gut disorders manifest poor tolerance to intestinal gas loads but the mechanism of this dysfunction is unknown. AIM: Our aims were firstly, to explore the relative importance of the amount of intestinal gas versus its distribution on symptom production, and secondly, to correlate gut motility and perception of gas loads. SUBJECTS: Fourteen healthy subjects with no gastrointestinal symptoms. METHODS: In each subject a gas mixture was infused (12 ml/min) either into the jejunum or rectum for one hour during blocked rectal gas outflow, and subsequently gas clearance was measured over one hour of free rectal evacuation. We measured abdominal perception, distension, and gut tone by duodenal and rectal barostats. RESULTS: Similar magnitude of gas retention (720 ml) produced significantly more abdominal symptoms with jejunal compared with rectal infusion (perception score 4.4 (0.4) v 1.5 (0.5), respectively; p<0.01) whereas abdominal distension was similar (15 (2) mm and 14 (1) mm girth increment, respectively). Jejunal gas loads were associated with proximal contraction (by 57 (5)%) and colonic loads with distal relaxation (by 99 (20)%). CONCLUSION: The volume of gas within the gut determines abdominal distension whereas symptom perception depends on intraluminal gas distribution and possibly also on the gut motor response to gas loads.     

Influence of body posture on intestinal transit of gas

BACKGROUND: Patients describe that body posture may affect their abdominal bloating, distension, and flatulence, but whether changes in position have objectively demonstrable effects, either beneficial or deleterious, has not been investigated. Aim: To determine the effect of body posture, upright versus supine, on intestinal transit of gas loads. SUBJECTS: Eight healthy subjects without gastrointestinal symptoms. METHODS: In each subject a gas mixture was continuously infused into the jejunum (12 ml/min) for three hours, and gas evacuation, clearance of a non- absorbable gaseous marker, perception, and abdominal girth were measured. Paired studies were randomly performed in each subject on separate days in the upright and supine positions. RESULTS: In the upright position, intestinal gas retention was much smaller than when supine (13 (52) ml v 146 (75) ml retention at 60 minutes, respectively; p<0.05), and clearance of the gas marker was expedited (72 (10)% clearance v 49 (16)% at 60 minutes, respectively; p<0.05). The gas challenge test was well tolerated both in the upright and supine positions without abdominal distension. CONCLUSION: Body posture has a significant influence on intestinal gas propulsion: transit is faster in the upright position than when supine.     

Use of arm crank exercise in the detection of abnormal pulmonary gas exchange in patients at low altitude.

BACKGROUND: The measurement of arterial blood gases, P(A-a)O2 and VD/VT, during cycle ergometry is the "gold standard" for the assessment of pulmonary gas exchange. However, some patients are unable to perform cycle ergometry because of other medical problems. STUDY OBJECTIVE: To determine whether arm crank exercise could be used to reliably detect gas exchange abnormalities compared to cycle ergometry. PARTICIPANTS: Fifteen patients with a variety of pulmonary disorders, who were referred for exertional dyspnea. DESIGN: All patients performed maximal arm crank and cycle exercise. Arterial blood gases, VO2, VCO2, and VE were measured at rest and during exercise. RESULTS: Compared to peak cycle exercise (mean +/- SD), PaO2 (85 +/- 14 vs 75 +/- 13 mm Hg), SaO2 (94 +/- 2 vs 91 +/- 4 percent), VD/VT (0.21 +/- 0.07 vs 0.19 +/- 0.08), and pH (7.37 +/- 0.04 vs 7.34 +/- 0.03) were significantly higher during peak arm crank exercise. The P(A-a)O2 (18 +/- 13 vs 29 +/- 12 mm Hg) was narrower, and PaCO2 (29 +/- 3 vs 29 +/- 4 mm Hg) and PAO2 (104 +/- 4 vs 103 +/- 4 mm Hg) were similar. Six patients had normal gas exchange during cycle exercise at low altitude (P[A-a]O2 less than or equal to 27 mm Hg, PaO2 greater than or equal to 65 mm Hg, VD/VT less than or equal to 0.18) and nine were abnormal. Utilizing criteria specific for arm crank at low altitude, the same six patients had normal gas exchange (P[A-a]O2 less than or equal to 13 mm Hg, PaO2 greater than or equal to 85 mm Hg, VD/VT less than or equal to 0.26), and the remaining nine were abnormal. The P(A-a)O2 during peak arm crank was the most useful criterion in identifying patients with abnormal gas exchange. CONCLUSION: Proposed criteria for arm crank exercise testing accurately identified all patients with normal and abnormal pulmonary gas exchange during cycle exercise. The data from the present study suggest that arm crank can be an acceptable alternative exercise testing modality for the assessment of pulmonary gas exchange.