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Biomedical subjects

R Vos

Publications and source records attributed to R Vos.

At least 19 recordsLinked to original sources
PubMed2005

Small doses of the unabsorbable substance polyethylene glycol 3350 accelerate oro-caecal transit, but slow gastric emptying in healthy subjects.

BACKGROUND: Polyethylene glycol 3350 increases stool frequency and accelerates colonic transit. Used as a laxative, it proved effective in patients with normal and slow transit. Although free of severe side effects, it may cause nausea and vomiting. The effect of this substance on upper gut transit has not been studied. AIM: To investigate the effect of polyethylene glycol 3350 on gastric emptying and oro-caecal transit in 12 healthy subjects. METHODS: In a randomised controlled study, isosmotic polyethylene glycol 3350 electrolyte balanced solution, in the maximal recommended dose or isosmotic electrolyte solution, was administered after breakfast and lunch on separate days. Gastric half-emptying time and oro-caecal transit time were measured using [13C]-octanoate and lactose-[13C] ureide breath tests. RESULTS: Isosmotic polyethylene glycol 3350 electrolyte solution, as compared to isosmotic electrolyte solution, decreased oro-caecal transit time from 424+/-28 to 314+/-17 min (P = 0.001). Gastric half-emptying time was significantly increased (84+/-6 min versus 127+/-14 min; P = 0.006). CONCLUSION: Polyethylene glycol 3350 accelerate oro-caecal transit in healthy subjects, but also cause an important delay in gastric emptying. The delay in gastric emptying may be of clinical significance in patients who have associated gastroparesis.

Adult↗
PubMed2005

Mechanisms underlying duodeno-gastric reflux in man.

BACKGROUND: Recent studies suggest that duodeno-gastro-oesophageal reflux (DGER) contributes to the occurrence of reflux oesophagitis and Barrett's oesophagus. The mechanisms underlying duodeno-gastric reflux (DGR), a prerequisite for DGER, are poorly understood. AIMS: To study the occurrence of DGR in relation to interdigestive and postprandial gastroduodenal motility. SUBJECTS AND METHODS: Ten healthy subjects underwent stationary gastroduodenal manometry with simultaneous duodenal and antral Bilitec recording 4 h before and 5 h after ingestion of a liquid meal. Eight volunteers underwent the same study, with administration of erythromycin postprandially. RESULTS: During the interdigestive phase II, all volunteers had short DGR episodes. Postprandially, DGR occurred in all subjects, on average 39 +/- 28 min after the start of the meal, and was cleared from the stomach after 242 +/- 23 min. Induction of increased antral motility and of a premature phase III, by administration of erythromycin, was associated with faster gastric DGR clearance. However, there was no direct temporal relationship between erythromycin-induced gastric phase III and erythromycin-induced DGR clearance. CONCLUSION: In healthy subjects, duodenogastric reflux occurs sporadically in the interdigestive state and is a normal phenomenon in the postprandial period. Erythromycin induces faster clearance of DGR from the stomach, which depends on enhanced antral contractile activity rather than premature phase III.

Adult↗
PubMed2005

Dyspeptic patients with visceral hypersensitivity: sensitisation of pain specific or multimodal pathways?

BACKGROUND AND AIMS: Patients with functional dyspepsia who have hypersensitivity to gastric distension have more prevalent pain, suggesting the presence of hyperalgesia. It is unclear whether this reflects activation of pain specific afferent pathways or multimodal afferent pathways that also mediate non-painful sensations. In the former case, hyperalgesia should occur when intensity of non-painful sensations is still low. The aim of the study was to analyse whether the symptom profile during gastric dissentions in functional dyspepsia patients with hyperalgesia reflects sensitisation of pain specific or multimodal pathways. METHODS: Forty eight consecutive dyspeptic patients (35 female) underwent gastric sensitivity testing with a barostat balloon using a double random staircase protocol. At the end of every distending step, patients scored perception of upper abdominal sensations on a graphic 0-6 rating scale and completed visual analogue scales (VAS 0-100 mm) for pain, nausea, satiety, and fullness. The end point was a rating scale of 5 or more. RESULTS: Hypersensitivity was present in 20 patients (40%); gastric compliance did not differ between normo- and hypersensitive patients. At maximal distension (score 5 or more), hypersensitive patients had significantly lower distending pressures and intra-balloon volumes, but similar VAS scores for pain, nausea, satiety, and fullness compared with normosensitive patients. In both normosensitive and hypersensitive patients, elevation of pain VAS scores with increasing distending pressures paralleled the elevation in VAS scores for nausea, satiety, and fullness. CONCLUSIONS: Hypersensitive dyspeptic patients reach the same intensity of painful and non-painful sensations as normosensitive patients but at lower distending pressures. Hyperalgesia occurs in hypersensitive dyspeptic patients at distending pressures that also induce intense non-painful sensations. These findings argue against isolated upregulation of pain specific afferents in functional dyspepsia patients with visceral hypersensitivity.

Adult↗
PubMed2004

Influence of a lipase inhibitor on gastric sensitivity and accommodation to an orally ingested meal.

BACKGROUND: Intraduodenal administration of lipids, through lipid digestion and release of cholecystokinin (CCK), induces viscero-visceral reflexes that affect gastric tone and sensitivity. It is unclear whether the same mechanisms control gastric function after an orally ingested meal. AIM: To evaluate the effect of orlistat, a selective lipase inhibitor, on gastric response to an orally administered meal. METHODS: Eighteen healthy volunteers participated in this study. They were treated for 5 days with orlistat (120 mg) or placebo t.d.s. in a double-blind randomized crossover design. During treatment, all subjects underwent a gastric barostat study, measurement of plasma CCK levels and a satiety drinking test. RESULTS: Although CCK plasma levels were significantly decreased, pre-treatment with orlistat failed to affect gastric compliance (72 +/- 6 mL/mm Hg and 64 +/- 6 mL/mm Hg, NS), gastric sensitivity (discomfort threshold 12.2 +/- 0.6 mm Hg vs. 10.9 +/- 0.6 mm Hg above minimal distending pressure, NS) or gastric accommodation (172 +/- 41 mL vs. 206 +/- 49 mL, NS) to an orally ingested meal. Furthermore, orlistat pre-treatment had no significant effect on the amount of calories ingested during a satiety drinking test (1329 +/- 88 kcal vs. 1217 +/- 115 kcal, NS). CONCLUSION: Administration of a lipase inhibitor does not affect gastric compliance, sensitivity to distension and accommodation to an orally ingested meal, and does not influence meal-induced satiety.

Adaptation, Physiological↗
PubMed2004

Effects of capsaicin on the sensorimotor function of the proximal stomach in humans.

BACKGROUND: Capsaicin-sensitive afferents have been implicated in the control of visceral sensorimotor functions. AIM: To study the effects of capsaicin on the sensorimotor function of the proximal stomach in humans. METHODS: In 10 healthy subjects, a gastric barostat was used to study the effect of saline or capsaicin-containing red pepper sauce on the sensitivity to gastric distension and on gastric accommodation to a meal. RESULTS: The administration of capsaicin was accompanied by a relaxation of the proximal stomach. After capsaicin, the compliance of the proximal stomach was increased and higher perception scores were reached for the same distending pressures. Dosing with capsaicin significantly decreased the pressures and corresponding wall tensions at the discomfort threshold. Gastric accommodation to a meal was not altered by capsaicin. CONCLUSION: The acute administration of capsaicin decreases proximal gastric tone, inhibits phasic contractility of the proximal stomach and increases sensitivity to proximal gastric distension. These data suggest the involvement of vanilloid receptor 1 in the modulation of gastric sensorimotor function in humans.

Adult↗
PubMed2004

Influence of continuous isobaric rectal distension on gastric emptying and small bowel transit in young healthy women.

Patients with slow transit constipation frequently have delayed gastric emptying. In animals rectal distensions inhibit gastrointestinal motility. In healthy volunteers isovolumetric rectal distensions delay upper gut transit. The purpose of this study was to determine the effect of continuous isobaric rectal distension on gastric emptying and oro-cecal transit in young females. Using validated 13C octanoic and lactose-[13C] ureide breath tests gastric half-emptying time and oro-cecal transit time for a meal were measured in 12 volunteers. The tests were repeated in randomized order: during isobaric balloon distension and during sham distension. Isobaric rectal distension was applied using a polyethylene bag connected to a barostat. Intraballoon pressure was kept just below the threshold for the urge sensation. Mean gastric half-emptying time during rectal distension (92.3 +/-5.1 min) was significantly higher than during sham distension (78.8 +/- 4 min; P = 0.015). Mean oro-cecal transit time during rectal distension (391.3 +/-29.1 min) and sham distension (328.8 +/- 38.4 min) were not significantly different. In conclusion, these findings indicate that isobaric rectal distension inhibits gastric emptying, but not small bowel transit in young healthy women. Studies in patients with constipation are indicated.

Adult↗
PubMed2004

Differences in the sensorimotor response to distension between the proximal and distal stomach in humans.

BACKGROUND: It is not known which region of the stomach is responsible for symptom generation or whether symptoms induced by gastric distension are region specific. Also, it is unclear whether low level gastric distension has a modulatory role on gastric tone and mechanosensitivity. AIMS: To define differences in the sensorimotor response to distension between proximal and distal gastric distension, and to determine the effects of low level gastric distension on gastric tone and mechanosensitivity. METHODS: In 14 healthy volunteers, a double barostat assembly incorporating a distal (antral) and proximal (fundic) bag was introduced into the stomach. Pressure sensitivity tests with either bag were performed with and without simultaneous background distension of the other bag in a randomised manner. Proximal gastric accommodation to a meal was measured with and without simultaneous distal gastric distension. RESULTS: The distal stomach was less compliant than the proximal stomach to low level distension. Thresholds for first perception and discomfort, and symptom profiles did not differ between distal and proximal gastric distension. Simultaneously applied low level gastric distension of one segment did not affect gastric mechanosensitivity of the other segment. Both the proximal and distal stomach relax after ingestion of a meal. Simultaneous low level antral distension decreases proximal gastric accommodation to a meal. CONCLUSIONS: Compared with the proximal stomach, the distal stomach is less compliant but its mechanosensitivity is not different. Symptoms induced by gastric distension are not region specific and no spatial summation occurred. Meal induced relaxation occurs both in the proximal and distal stomach.

Adult↗
PubMed2004

Oesophageal clearance of acid and bile: a combined radionuclide, pH, and Bilitec study.

BACKGROUND: Studies combining pH and Bilitec monitoring found a high prevalence of both acid and duodeno-gastro-oesophageal reflux in severe reflux disease. Clearance of refluxed material is a major defence mechanism against reflux. Several studies have been devoted to oesophageal acid clearance but oesophageal clearance of refluxed duodenal contents (DC) has rarely been addressed. AIM: To compare oesophageal acid and DC clearance. METHODS: Ten healthy volunteers (five women, mean age 23 (1) years) were studied. Firstly, a balloon tip catheter, positioned in the duodenum under fluoroscopy, was used to aspirate DC after stimulation by a high caloric liquid meal (200 ml, 300 kcal). During the second session, pH and Bilitec probes were positioned 5 cm above the lower oesophageal sphincter and a small infusion catheter was introduced into the proximal oesophagus. The subject was placed supine under a gamma camera. One of two different solutions (DC mixed with 0.2 mCi Tc99m pertechnetate or citric acid (pH 2) mixed with 0.2 mCi Tc99m pertechnetate) was infused into the proximal oesophagus and the subject was instructed to swallow at 20 second intervals. Clearance was assessed using scintigraphy (dynamic acquisition, one frame per second in the anterior view; calculation of time to clear peak counts to background level), pH (time to pH<4) or Bilitec (time absorbance >0.14) monitoring, with or without continuous saliva aspiration. Each condition was studied twice in a randomised design; measurement time was four minutes, interrupted by water flushing, with a two minute rest period. Results are given as mean (SEM) and were compared by Student's t test and Pearson correlation. RESULTS: Scintigraphic evaluation showed a volume clearance time of 29 (3) seconds for acid and 28 (9) seconds for DC (NS). Saliva aspiration had no significant influence on volume clearance of acid or DC (28 (4) and 30 (13) seconds, respectively; NS). pH monitoring showed an acid clearance time of 217 (15) seconds, which was significantly prolonged to 324 (30) seconds during saliva aspiration (p<0.05). Bilitec monitoring showed a DC clearance time of 131 (27) seconds, which was not significantly prolonged by saliva aspiration (176 (36) seconds; p = 0.08). DC clearance was faster than acid clearance, either without or with saliva aspiration (p<0.055 and p<0.05, respectively). CONCLUSIONS: Under experimental conditions, liquid acid and DC solutions have comparable volume clearances. Chemical clearance occurs slightly faster for DC than for acid, and saliva plays a major role in the clearance of acid only.

Adult↗
PubMed2004

Coordinating the norms and values of medical research, medical practice and patient worlds-the ethics of evidence based medicine in orphaned fields of medicine.

Evidence based medicine is rightly at the core of current medicine. If patients and society put trust in medical professional competency, and on the basis of that competency delegate all kinds of responsibilities to the medical profession, medical professionals had better make sure their competency is state of the art medical science. What goes for the ethics of clinical trials goes for the ethics of medicine as a whole: anything that is scientifically doubtful is, other things being equal, ethically unacceptable. This particularly applies to so called orphaned fields of medicine, those areas where medical research is weak and diverse, where financial incentives are lacking, and where the evidence regarding the aetiology and treatment of disease is much less clear than in laboratory and hospital based medicine. Examples of such orphaned fields are physiotherapy, psychotherapy, medical psychology, and occupational health, which investigate complex syndromes such as RSI, whiplash, chronic low back pain, and chronic fatigue syndrome. It appears that the primary ethical problem in this context is the lack of attention to the orphaned fields. Although we agree that this issue deserves more attention as a matter of potential injustice, we want to argue that, in order to do justice to the interplay of heterogeneous factors that is so typical of the orphaned fields, other ethical models than justice are required. We propose the coordination model as a window through which to view the important ethical issues which relate to the communication and interaction of scientists, health care workers, and patients.

Allied Health Occupations↗
PubMed2003

Influence of tegaserod on proximal gastric tone and on the perception of gastric distension.

BACKGROUND: Tegaserod, a 5-hydroxytryptamine-4 receptor agonist, enhances gastric emptying, but its effects on proximal stomach function have not been studied. AIM: To study the effect of tegaserod on gastric compliance, accommodation and perception of distension in humans. METHODS: Nineteen healthy volunteers (10 females; mean age, 23.9 years) were studied on three separate occasions after 7 days of treatment with placebo, tegaserod 2 mg b.d. or tegaserod 6 mg b.d. in a double-blind, randomized, three-way cross-over design. After the introduction of a barostat bag, stepwise distensions were performed to determine gastric compliance and sensitivity, and a mixed liquid meal was administered in isobaric mode to assess accommodation. RESULTS: Tegaserod had no effect on the pressures or volumes inducing first perception or discomfort. Tegaserod 6 mg b.d. enhanced fasting gastric compliance compared with placebo. Pre-prandial and post-prandial intra-balloon volumes were significantly higher after 6 mg b.d. than after placebo. Both tegaserod 2 and 6 mg b.d. shortened the time to maximum post-prandial intra-balloon volume. The amplitude of meal-induced gastric relaxation (post-prandial minus pre-prandial volumes) did not differ between the treatment arms. CONCLUSION: In humans, tegaserod allows for larger intra-balloon volumes both before and after a meal. These findings warrant the investigation of the therapeutic potential of tegaserod in dyspeptic patients with impaired accommodation.

Adult↗
PubMed2003

Differential effects of baclofen on lower oesophageal sphincter pressure and proximal gastric motility in humans.

BACKGROUND: The gamma-aminobutyric acid receptor type B agonist, baclofen, inhibits transient lower oesophageal sphincter relaxations by influencing a vagal pathway. Although post-prandial proximal gastric function, which is vagally mediated, is important in the occurrence of transient lower oesophageal sphincter relaxations, the effects of baclofen on post-prandial proximal gastric motility in humans remains undetermined. AIM: To determine the effects of baclofen on post-prandial lower oesophageal sphincter function and proximal gastric motility in healthy subjects. METHODS: In 11 healthy volunteers, a barostat bag and an oesophageal manometric catheter with a sleeve were simultaneously positioned; 40 mg of oral baclofen or placebo was then given in a randomized, double-blind manner. Subsequently, the intragastric bag volume, oesophageal and lower oesophageal sphincter pressure and oesophageal pH were recorded during the 90 min before and 120 min after a meal. RESULTS: During the post-prandial period, unlike the fasting period, baclofen decreased the rate of transient lower oesophageal sphincter relaxations and increased the basal lower oesophageal sphincter pressure compared with placebo. However, the meal-induced decrease in the tone and phasic contractility of the fundus was not affected by baclofen. CONCLUSION: The gamma-aminobutyric acid receptor type B agonist, baclofen, has a potent effect on post-prandial lower oesophageal sphincter motility without altering post-prandial proximal gastric motility, suggesting differential effects of baclofen on different signals of gastrointestinal vagal afferents.

Adult↗
PubMed2003

Monitoring hyperhydration during high-dose chemotherapy: body weight or fluid balance?

Body weight and fluid input/output are usually monitored for checking fluid balance in case of intravenous hyperhydration during nephrotoxic chemotherapy. The reliability of measuring fluid input/output is uncertain. Moreover, this measurement is redundant, complex, labour-intensive and represents an occupational hazard for nurses and other health-care workers handling fluids or body excreta. In a prospective cohort study, we determined the concordance between body weight and fluid intake/output. We also examined the clinical consequences with respect to the safety of selecting only body weight measurement as a parameter for fluid overload. A total of 591 combined observations of fluid balances and body weights were collected. We observed a higher increase in body weight than in fluid balance. The Pearson correlation between fluid balance and body weight was relatively low (r = 0.28). With regard to the safety of measuring body weight only, we found 4 cases (0.6%) who might not have received furosemide if the fluid input/output had not been measured, without clinical consequences, however. After standardization, body weight can safely be used as the only parameter for monitoring fluid retention in case of hyperhydration during chemotherapy.

Adolescent↗
PubMed2001

Comparative trials in registration files of cardiovascular drugs: comparator drugs and dosing schemes.

Registration files of 13 cardiovascular drugs were analysed with respect to the number of double-blind phase-III clinical trials, the use of placebo and active comparator drugs and their dosing schemes. Half of the 146 double-blind trials used active comparator drugs. The majority of files included first-choice reference drugs, but we also found trials in three files with lower dosing schemes of comparator drugs and four files which included only placebo or active controlled double-blind trials. To allow a better interpretation of the information provided in European Public Assessment Reports, which are published for every product approved for marketing in the European Union, uniform reporting is recommended on basic details of trial design, such as comparator drugs used and dosing schemes.

Cardiovascular Agents↗
PubMed2001

Reproducibility of gastric barostat studies in healthy controls and in dyspeptic patients.

OBJECTIVES: Gastric barostat studies are increasingly being performed, but their reproducibility and the most suitable study protocol have not been determined. The aim of this study was to verify the reproducibility of gastric sensitivity and accommodation testing in healthy and in dyspeptic subjects, and to compare stepwise and double random staircase distensions. METHODS: A total of 13 dyspeptic patients and 25 healthy control subjects underwent two successive studies. Sensory thresholds were assessed on a same-day/different-days protocol, using a stepwise (11/14 healthy subjects and 11/13 patients) or a double random staircase inflation (11/21 healthy subjects). In 10 healthy subjects, both methods were compared. Gastric accommodation was measured on different days in 13 patients and nine healthy subjects. Data (mean +/- SEM) were compared using the paired t test, and individual variability was expressed as the percent coefficient of variation. RESULTS: In healthy subjects, the thresholds for first perception and for discomfort were highly reproducible (p > 0.05) and the pressure thresholds showed a lower degree of variability than the volumes. Pressure thresholds quantified by stepwise showed lower variability than double random staircase inflation. In the patients, the sensory thresholds were unchanged between the sessions on the same and on different days (p > 0.05). Gastric accommodation also showed excellent reproducibility for both dyspeptic patients and healthy control subjects (p > 0.05). CONCLUSIONS: Both in dyspeptic patients and in healthy control subjects, gastric sensitivity and accommodation quantified by isobaric distensions show excellent reproducibility. Pressure and volume thresholds both are well reproducible, but the former shows less variability. Finally, the simplest stepwise protocol is better than the double random staircase to assess the gastric sensitivity to distension.

Adult↗
PubMed2001

Assessment of new cardiovascular drugs. Relationships between considerations, professional characteristics, and prescribing.

OBJECTIVES: To study considerations used by professional and academic leaders to assess the position of new cardiovascular drugs in the therapeutic regimen in relationship to professional characteristics and the level of prescribing. METHODS: Interviews with 39 internists, cardiologists, general practitioners, and hospital pharmacists about considerations regarding the therapeutic position and prescribing of a new cardiovascular drug (losartan or atorvastatin) and professional characteristics. Considerations were classified according to Rogers' characteristics of an innovation, i.e., referring to the drug's relative advantage, compatibility, or complexity. Proportions of respondents mentioning advantageous, comparable, and/or disadvantageous characteristics were used to construct patterns to analyze an overall evaluation of the drugs in relation to professional characteristics and level of prescribing. RESULTS: The majority of considerations referred to the degree of relative advantage, but different subjects were emphasized for both drugs. Overall patterns of evaluation were generally intermediate and negative. The respondents' profession, mentioning commercial sources of information and self-qualification as a (moderately) early adopter of new drugs differentiated the overall evaluation of the drugs, in contrast to expertness and academic affiliation. The level of prescribing differentiated the overall evaluation only in the case of losartan. CONCLUSIONS: These professional and academic leaders critically evaluated the claims when assessing the position of the drugs in the therapeutic regimen but did not show consensus in their considerations. Accepted principles for prescribing were considered when assessing the therapeutic position of the drugs but resulted in varied tendencies for prescribing.

Cardiovascular Agents↗
PubMed2000

Co-morbidity of 'clinical trial' versus 'real-world' patients using cardiovascular drugs.

PURPOSE: To examine discrepancies between co-morbidity of patients included in pre-marketing clinical trials of cardiovascular drugs and patients from daily practice, representing the actual users after marketing, and to investigate the availability of data regarding co-morbidity in registration files. METHODS: Data were collected from phase III trials of registration files of 16 drugs, registered in the Netherlands in the period 1985 through 1994 for the indications hypertension, angina pectoris or hypercholesterolemia, and from a general practitioners database. Patients were selected who used drugs from the same therapeutic classes for the same indication as the patients in the pre-marketing trials. Prevalences of concomitant cardiovascular, endocrine and metabolic diseases were compared between pre- and postmarketing populations. Discrepancies were defined as more than 10% difference in prevalences. RESULTS: Data regarding co-morbidity were present in 13 out of 16 registration files and differed in format of reporting. For all indications, coexisting cardiovascular, endocrine and metabolic diseases were less prevalent in the pre-marketing populations, except ischemic heart disease, which was more prevalent coexisting with angina pectoris and hypercholesterolemia. Discrepancies were found for hypertensive disease, heart failure, diabetes mellitus and myocardial infarction. CONCLUSIONS: Phase III trials testing cardiovascular drugs included patients with concomitant cardiovascular, endocrine and metabolic diseases, but discrepancies were present with patients in daily practice. Development of guidelines for uniform collection and reporting of co-morbidity data in pre-marketing trials is recommended, as well as further utilization of data.

Angina Pectoris↗
PubMed2000

Technology in medicine: ontology, epistemology, ethics and social philosophy at the crossroads.

In reference to the different approaches in philosophy (of medicine) of the nature of (medical) technology, this article introduces the topic of this special issue of Theoretical Medicine and Bioethics, that is, the way the different forms of medical technology function in everyday medical practice. The authors elaborate on the active role technology plays in shaping our views on disease, illness, and the body, whence in shaping our world.

Biomedical Technology↗