Reproducibility of the 13C-octanoic acid breath test for assessment of gastric emptying in healthy preterm infants

Review of paediatric gastrointestinal physiology relevant to the absorption of orally administered medicines

Despite much progress in regulations to improve paediatric drug development, there remains a significant need to develop better medications for children. For the design of oral dosage forms, a detailed understanding of the specific gastrointestinal (GI) conditions in children of different age categories and how they differ from GI conditions in adults is essential. Several review articles have been published addressing the ontogeny of GI characteristics, including luminal conditions in the GI tract of children. However, the data reported in most of these reviews are of limited quality because (1) information was cited from very old publications and sometimes low quality sources, (2) data gaps in the original data were filled with textbook knowledge, (3) data obtained on healthy and sick children were mixed, (4) average data obtained on groups of patients were mixed with data obtained on individual patients, and (5) results obtained using investigative techniques that may have altered the outcome of the respective studies were considered. Consequently, many of these reviews draw conclusions that may be incorrect. The aim of the present review was to provide a comprehensive and updated overview of the available original data on the ontogeny of GI luminal conditions relevant to oral drug absorption in the paediatric population. To this end, the PubMed and Web of Science metadatabases were searched for appropriate studies that examined age-related conditions in the oral cavity, esophagus, stomach, small intestine, and colon. Maturation was observed for several GI parameters, and corresponding data sets were identified for each paediatric age group. However, it also became clear that the ontogeny of several GI traits in the paediatric population is not yet known. The review article provides a robust and valuable data set for the development of paediatric in vitro and in silico biopharmaceutical tools to support the development of age-appropriate dosage forms. In addition, it provides important information on existing data gaps and should provide impetus for further systematic and well-designed in vivo studies on GI physiology in children of specific age groups in order to close existing knowledge gaps and to sustainably improve oral drug therapy in children.

Development of a 13C Stable Isotope Assay for Dipeptidyl Peptidase-4 Enzyme Activity A New Breath Test for Dipeptidyl Peptidase Activity

Dipeptidyl peptidase-4 inhibitors (DPP4i) are a class of orally available, small molecule inhibitors for the management of Type-II diabetes. A rapid, real-time, functional breath test for DPP4 enzyme activity could help to define DPP4i efficacy in patients that are refractory to treatment. We aimed to develop a selective, non-invasive, stable-isotope ¹³C-breath test for DPP4. In vitro experiments were performed using high (Caco-2) and low (HeLa) DPP4 expressing cells. DPP gene expression was determined in cell lines by qRT-PCR. A DPP4 selective ¹³C-tripeptide was added to cells in the presence and absence of the DPP4 inhibitor Sitagliptin. Gas samples were collected from the cell headspace and ¹³CO₂ content quantified by isotope ratio mass spectrometry (IRMS). DPP4 was highly expressed in Caco-2 cells compared to HeLa cells and using the ¹³C-tripeptide, we detected a high ¹³CO₂ signal from Caco2 cells. Addition of Sitaglitpin to Caco2 cells significantly inhibited this ¹³CO₂ signal. ¹³C-assay DPP4 activity correlated positively with the enzyme activity detected using a colorimetric substrate. We have developed a selective, non-invasive, ¹³C-assay for DPP4 that could have broad translational applications in diabetes and gastrointestinal disease.

The Reproducibility of Blood Acid Base Responses in Male Collegiate Athletes Following Individualised Doses of Sodium Bicarbonate: A Randomised Controlled Crossover Study

BACKGROUND

Current evidence suggests sodium bicarbonate (NaHCO₃) should be ingested based upon the individualised alkalotic peak of either blood pH or bicarbonate (HCO₃^-) because of large inter-individual variations (10-180 min). If such a strategy is to be practical, the blood analyte response needs to be reproducible.

OBJECTIVE

This study aimed to evaluate the degree of reproducibility of both time to peak (TTP) and absolute change in blood pH, HCO₃^- and sodium (Na⁺) following acute NaHCO₃ ingestion.

METHODS

Male participants (n = 15) with backgrounds in rugby, football or sprinting completed six randomised treatments entailing ingestion of two doses of 0.2 g·kg^-1 body mass (BM) NaHCO₃ (SBC2a and b), two doses of 0.3 g·kg^-1 BM NaHCO₃ (SBC3a and b) or two control treatments (CON1a and b) on separate days. Blood analysis included pH, HCO₃^- and Na⁺ prior to and at regular time points following NaHCO₃ ingestion over a 3-h period.

RESULTS

HCO₃^- displayed greater reproducibility than pH in intraclass correlation coefficient (ICC) analysis for both TTP (HCO₃^- SBC2 r = 0.77, P = 0.003; SBC3 r = 0.94, P < 0.001; pH SBC2 r = 0.62, P = 0.044; SBC3 r = 0.71, P = 0.016) and absolute change (HCO₃^- SBC2 r = 0.89, P < 0.001; SBC3 r = 0.76, P = 0.008; pH SBC2 r = 0.84, P = 0.001; SBC3 r = 0.62, P = 0.041).

CONCLUSION

Our results indicate that both TTP and absolute change in HCO₃^- is more reliable than pH. As such, these data provide support for an individualised NaHCO₃ ingestion strategy to consistently elicit peak alkalosis before exercise. Future work should utilise an individualised NaHCO₃ ingestion strategy based on HCO₃^- responses and evaluate effects on exercise performance.

Enhanced Resistance to Several Abiotic Stresses in Vibrio cholerae during Starvation

In this study, we investigated whether Vibrio cholerae cells exposed to nutrient-limited conditions developed resistance to abiotic stresses because of which most, if not all, starved cells turn coccoid in shape and exhibited marked resistance to freezing, low pH, and chlorine, but not against bile.

Repeatability of gastric volume measurements and intragastric content using ultrasound in preterm infants

OBJECTIVES

The aim of the present study was to determine whether serial gastric volumes and intragastric curding are repeatable within individual preterm infants when given sequential feeds of the same volume and composition. Infant and feeding characteristics that may influence differences in measured gastric volumes, echogenicity, and intragastric curding were also explored.

METHODS

Ultrasound images were used to calculate gastric volumes and to rate echogenicity and intragastric curding for 20 infants. A total of 29 paired feeds of the same volume and composition were monitored prefeed and postfeed and at 30-minute intervals thereafter. Statistical comparisons of paired gastric volume measurements and agreement between echogenicity and curding ratings were made for each time point. Analyses of factors that influence discrepancies between volume measurements and between curding ratings were performed.

RESULTS

Paired gastric volume measurements were repeatable (intraclass correlation coefficient [ICC] = 0.971, 0.938 < ICC < 0.987). Most (75%) discrepancies were <2 mL and increased over time, although volume differences were small. Overall moderate levels of consistency were observed for ratings of echogenicity (κ = 0.44), and curd presence (κ ≤ 0.65), density (κ = 0.41), and volume (κ = 0.47). Gastric emptying during feed delivery is influenced with infant positioning, fortification of breast milk, and feeding frequency.

CONCLUSIONS

For preterm infants serial gastric volumes are repeatable and ratings of intragastric echogenicity and curding are moderately consistent when fed milk of the same volume and composition. Ultrasound has the potential to further explore factors that influence gastric emptying in the preterm infant.

Physiologically based pharmacokinetic models in the prediction of oral drug exposure over the entire pediatric age range-sotalol as a model drug

In recent years, the increased interest in pediatric research has enforced the role of physiologically based pharmacokinetic (PBPK) models in pediatric drug development. However, an existing lack of published examples contributes to some uncertainties about the reliability of their predictions of oral drug exposure. Developing and validating pediatric PBPK models for oral drug application shall enrich our knowledge about their limitations and lead to a better use of the generated data. This study was conducted to investigate how whole-body PBPK models describe the oral pharmacokinetics of sotalol over the entire pediatric age. Two leading software tools for whole-body PBPK modeling: Simcyp® (Simcyp Ltd, Sheffield, UK) and PK-SIM® (Bayer Technology Services GmbH, Leverkusen, Germany), were used. Each PBPK model was first validated in adults before scaling to children. Model input parameters were collected from the literature and clinical data for 80 children were used to compare predicted and observed values. The results obtained by both models were comparable and gave an adequate description of sotalol pharmacokinetics in adults and in almost all pediatric age groups. Only in neonates, the mean ratio_(Obs/Pred) for any PK parameter exceeded a twofold error range, 2.56 (95% confidence interval (CI), 2.10–3.49) and 2.15 (95% CI, 1.77–2.99) for area under the plasma concentration-time curve from the first to the last concentration point and maximal concentration (C_max) using SIMCYP® and 2.37 (95% CI, 1.76–3.25) for time to reach C_max using PK-SIM®. The two PBPK models evaluated in this study reflected properly the age-related pharmacokinetic changes and predicted adequately the oral sotalol exposure in children of different ages, except in neonates.

Evaluation of gastroesophageal function and mechanisms underlying gastroesophageal reflux in infants and adults born with esophageal atresia

PURPOSE

To evaluate the mechanisms underlying gastroesophageal reflux (GER) following esophageal atresia (EA) repair and gastroesophageal function in infants and adults born with EA.

METHODS

Ten consecutive infants born with EA as well as 10 randomly selected adult EA patients were studied during their first postoperative follow-up visit and a purposely planned visit, respectively. A (13)C-octanoate breath test and esophageal pH-impedance-manometry study were performed. Mechanisms underlying GER and esophageal function were evaluated.

RESULTS

Transient lower esophageal sphincter relaxation (TLESR) was the most common mechanism underlying GER in infants and adults (66% and 62%, respectively). In 66% of all GER episodes, no clearing mechanism was initiated. On EFT, normal motility patterns were seen in six patients (four infants, two adults). One of these adults had normal motility overall (>80% of swallows). Most swallows (78.8%) were accompanied by abnormal motility patterns. Despite this observation, impedance showed normal bolus transit in 40.9% of swallows. Gastric emptying was delayed in 57.1% of infants and 22.2% of adults.

CONCLUSIONS

TLESR is the main mechanism underlying GER events in patients with EA. Most infants and adults have impaired motility, delayed bolus clearance, and delayed gastric emptying. However, normal motility patterns were seen in a minority of patients.

Reproducibility of gastric emptying in overweight and obese males

BACKGROUND & AIM

To understand whether any change in gastric emptying (GE) is physiologically relevant, it is important to identify its variability. Information regarding the variability of GE in overweight and obese individuals is lacking. The aim of this study was to determine the reproducibility of GE in overweight and obese males.

METHODS

Fifteen overweight and obese males [body mass index 30.3 (4.9) kg/m(2)] completed two identical GE tests 7 days apart. GE of a standard pancake breakfast was assessed by (13)C-octanoic acid breath test. Data are presented as mean (±SD).

RESULTS

There were no significant differences in GE between test days (half time (t1/2): 179 (15) and 176 (19 min), p = 0.56; lag time (tlag): 108 (14) and 104 (8) min, p = 0.26). Mean intra-individual coefficient of variation for t1/2 was 7.9% and tlag 7.5%. Based on these findings, to detect a treatment effect in a paired design with a power of 80% and α = 0.05, minimum mean effect sizes for t1/2 would need to be ≥14.4 min and tlag ≥ 8.1 min.

CONCLUSIONS

These data show that GE is reproducible in overweight and obese males and provide minimum mean effect sizes required to detect a hypothetical treatment effect in this population.

Supplementing monosodium glutamate to partial enteral nutrition slows gastric emptying in preterm pigs(1-3)

Emerging evidence suggests that free glutamate may play a functional role in modulating gastroduodenal motor function. We hypothesized that supplementing monosodium glutamate (MSG) to partial enteral nutrition stimulates gastric emptying in preterm pigs. Ten-day-old preterm, parenterally fed pigs received partial enteral nutrition (25%) as milk-based formula supplemented with MSG at 0, 1.7, 3.0, and 4.3 times the basal protein-bound glutamate intake (468 mg·kg(-1)·d(-1)) from d 4 to 8 of life (n = 5-8). Whole-body respiratory calorimetry and (13)C-octanoic acid breath tests were performed on d 4, 6, and 8. Body weight gain, stomach and intestinal weights, and arterial plasma glutamate and glutamine concentrations were not different among the MSG groups. Arterial plasma glutamate concentrations were significantly higher at birth than after 8 d of partial enteral nutrition. Also at d 8, the significant portal-arterial concentration difference in plasma glutamate was substantial (∼500 μmol/L) among all treatment groups, suggesting that there was substantial net intestinal glutamate absorption in preterm pigs. MSG supplementation dose-dependently increased gastric emptying time and decreased breath (13)CO2 enrichments, (13)CO2 production, percentage of (13)CO2 recovery/h, and cumulative percentage recovery of (13)C-octanoic acid. Circulating glucagon-like peptide-2 (GLP-2) concentration was significantly increased by MSG but was not associated with an increase in intestinal mucosal growth. In contrast to our hypothesis, our results suggest that adding MSG to partial enteral nutrition slows the gastric emptying rate, which may be associated with an inhibitory effect of increased circulating GLP-2.

Nissen fundoplication in children with cerebral palsy: influence on rate of gastric emptying and postprandial symptoms in relation to protein source in caloric liquid meals

BACKGROUND & AIMS

The aim was to study the influence of Nissen fundoplication on rate of gastric emptying and postprandial symptoms in relation to protein source in liquid meals in children with cerebral palsy.

METHODS

Ten children with cerebral palsy and Nissen fundoplication and ten with cerebral palsy without Nissen fundoplication were studied. Patients had gastrostomy and received two meals, double-blinded, in random order, on separate days. Meals contained a standardised carbohydrate and fat base plus one of two protein modules (Meal A: 100% casein; Meal B: 40% casein/60% whey). The (13)C octanoic acid breath test was used to assess gastric emptying. Postprandial symptoms were recorded. Results are given as median.

RESULTS

For meal A and B, respectively, time until 50% of the meal had emptied (T1/2) was 110 in the Nissen fundoplication- and 181 min in the non-Nissen fundoplication group, (p = 0.35) and 50 and 85 min (p = 0.25). Seven in the Nissen fundoplication group reported postprandial symptoms to meal B, none in the non-Nissen fundoplication group (p < 0.01).

CONCLUSIONS

Compared with cerebral palsy-children without Nissen fundoplication, those with Nissen fundoplication have postprandial symptoms more frequently after receiving a rapid emptying meal. Gastric emptying alone, however, does not seem to explain the symptom occurrence. ClinicalTrials.gov: UUSKBK 28200706.

Whey- vs casein-based enteral formula and gastrointestinal function in children with cerebral palsy

OBJECTIVES

Children with severe cerebral palsy (CP) commonly have gastrointestinal (GI) dysfunction. Whey-based enteral formulas have been postulated to reduce gastroesophageal reflux (GOR) and accelerate gastric emptying (GE). The authors investigated whether whey-based (vs casein-based) enteral formulas reduce GOR and accelerate GE in children who have severe CP with a gastrostomy and fundoplication.

METHODS

Thirteen children received a casein-based formula for 1 week and either a 50% whey whole protein (50% WWP) or a 100% whey partially hydrolyzed protein (100% WPHP) formula for 1 week. Reflux episodes, gastric half-emptying time (GE t(1/2)), and reported pain and GI symptoms were measured.

RESULTS

Whey formulas emptied significantly faster than casein (median [interquartile range (IQR)] GE t(1/2), 33.9 [25.3-166.2] min vs 56.6 [46-191] min; P = .033). Reflux parameters were unchanged. GI symptoms were lower in children who received 50% WWP (visual analog symptom score, median [IQR], 0 [0-11.8]) vs 100% WPHP (13.0 [2.5-24.8]) (P = .035).

CONCLUSION

This pilot study shows that in children who have severe CP with a gastrostomy and fundoplication, GE of the whey-based enteral formula is significantly faster than casein. The acceleration in GE does not alter GOR frequency, and there appears to be no effect of whey vs casein in reducing acid, nonacid, and total reflux episodes. The results indicate that enteral formula selection may be particularly important for children with severe CP and delayed GE.

The effect of protein composition in liquid meals on gastric emptying rate in children with cerebral palsy

BACKGROUND & AIM

Dysmotility, nausea and vomiting are common among children with cerebral palsy. This study aimed to evaluate influence of protein composition on rate of gastric emptying and study the relation between gastric emptying and postprandial gastrointestinal symptoms.

METHODS

15 children with cerebral palsy, using gastrostomy, received four liquid test meals on separate days in random order. The meals contained a standard carbohydrate and fat base plus one of four protein modules (100% casein (A), hydrolysed whey (B), amino acids (C) and 40% casein/60% whey (D)) with a total energy of 1 kcal/ml. The (13)C octanoic acid breath test was applied to assess gastric emptying.

RESULTS

When comparing half emptying time (T(1/2)) of the fast emptying meals (meal B, C and D) with the slowest emptying meal (meal A), more rapid emptying was demonstrated for meal D (p < 0.001). For meal D, emptying was significantly faster in children with postprandial symptoms than in those without (p < 0.01).

CONCLUSION

In children with cerebral palsy using gastrostomy, gastric emptying is influenced by type of protein in the meal. The present results also suggest that there is a relation between rapid gastric emptying and postprandial gastrointestinal symptoms. CLINICALTRIALS.GOV: UUSKBK 28200706.

Evaluation of potential factors predicting attainment of full gavage feedings in preterm infants

BACKGROUND

The clinical measures of gastric residuals and abdominal distention are often used to guide feeding in preterm infants, but there are few data demonstrating their usefulness. Similarly, techniques are now available to investigate gastrointestinal (GI) function noninvasively and safely, but their ability to predict attainment of full gavage feedings and/or feeding volume in preterm infants is unclear.

OBJECTIVE

We sought to determine prospectively the potential relationships of attainment of full gavage feedings and feeding volume with clinical measures and noninvasive GI tests.

METHODS

Fifty preterm infants were followed prospectively. Daily tally was taken of gavage feeding intake, gastric residual volumes (GRVs; milliliters per day, number of GRVs >50% of the previous feeding volume, and number of GRVs >2 ml/kg), and abdominal distention. Infants underwent repeated measurement of lactase activity, GI permeability, fecal calprotectin concentration, and gastric emptying.

RESULTS

The number of GRVs >2 ml/kg tended to decrease with postnatal age (p = 0.06). Lactase activity and feeding volume in milliliters per kilogram per day prior to achieving full feedings were correlated (p = 0.007, β = 0.164). There was no correlation between feeding outcomes and GRV (ml/day), GRV >50%, GRV >2 ml/kg, small bowel, colonic, or whole bowel permeability, fecal calprotectin concentration, gastric emptying, or abdominal distention.

CONCLUSIONS

GRV is unreliable in predicting attainment of full gavage feeding. Lactase activity is related to feeding volume. However, other noninvasive GI tests utilized were not predictive. These data cast doubt upon the utility of GRV in guiding feeding therapy. Randomized trials of different GRV management protocols are needed.

Effect of body position changes on postprandial gastroesophageal reflux and gastric emptying in the healthy premature neonate

OBJECTIVE

To identify a body-positioning regimen that promotes gastric emptying (GE) and reduces gastroesophageal reflux (GER) by changing body position 1 hour after feeding.

STUDY DESIGN

Ten healthy preterm infants (7 male; mean postmenstrual age, 36 weeks [range, 33 to 38 weeks]) were monitored with combined esophageal impedance-manometry. Infants were positioned in the left lateral position (LLP) or right lateral position (RLP) and then gavage-fed. After 1 hour, the position was changed to the opposite side. Subsequently, all infants were restudied with the order of positioning reversed.

RESULTS

There was more liquid GER in the RLP than in the LLP (median, 9.5 [range, 6.0 to 22.0] vs 2.0 [range, 0.0 to 5.0] episodes/hour; P = .002). In the RLP-first protocol, the number of liquid GER episodes per hour decreased significantly after position change (first postprandial hour [RLP], 5.5 [2.0 to 13.0] vs second postprandial hour [LLP], 0.0 [0.0 to 1.0]; P = .002). GE was faster in the RLP-first protocol than in the LLP-first protocol (37.0 +/- 21.1 vs 61.2 +/- 24.8 minutes; P = .006).

CONCLUSIONS

A strategy of right lateral positioning for the first postprandial hour with a position change to the left thereafter promotes GE and reduces liquid GER in the late postprandial period and may prove to be a simple therapeutic approach for infants with GER disease.

13C-breath tests: current state of the art and future directions

13C-breath tests provide a non-invasive diagnostic method with high patient acceptance. In vivo, human and also bacterial enzyme activities, organ functions and transport processes can be assessed semiquantitatively using breath tests. As the samples can directly be analysed using non-dispersive isotope selective infrared spectrometers or sent to analytical centres by normal mail breath tests can be easily performed also in primary care settings. The 13C-urea breath test which detects a Helicobacter pylori infection of the stomach is the most prominent application of stable isotopes. Determination of gastric emptying using test meals labelled with 13C-octanoic or 13C-acetic acid provide reliable results compared to scintigraphy. The clinical use of 13C-breath tests for the diagnosis of exocrine pancreatic insufficiency is still limited due to expensive substrates and long test periods with many samples. However, the quantification of liver function using hepatically metabolised 13C-substrates is clinically helpful in special indications. The stable isotope technique presents an elegant, non-invasive diagnostic tool promising further options of clinical applications. This review is aimed at providing an overview on the relevant clinical applications of 13C-breath tests.

Reliability of the ICRP'S dose coefficients for members of the public: IV. basis of the human alimentary tract model and uncertainties in model predictions

The biokinetic and dosimetric model of the gastrointestinal (GI) tract applied in current documents of the International Commission on Radiological Protection (ICRP) was developed in the mid-1960s. The model was based on features of a reference adult male and was first used by the ICRP in Publication 30, Limits for Intakes of Radionuclides by Workers (Part 1, 1979). In the late 1990s an ICRP task group was appointed to develop a biokinetic and dosimetric model of the alimentary tract that reflects updated information and addresses current needs in radiation protection. The new age-specific and gender-specific model, called the Human Alimentary Tract Model (HATM), has been completed and will replace the GI model of Publication 30 in upcoming ICRP documents. This paper discusses the basis for the structure and parameter values of the HATM, summarises the uncertainties associated with selected features and types of predictions of the HATM and examines the sensitivity of dose estimates to these uncertainties for selected radionuclides. Emphasis is on generic biokinetic features of the HATM, particularly transit times through the lumen of the alimentary tract, but key dosimetric features of the model are outlined, and the sensitivity of tissue dose estimates to uncertainties in dosimetric as well as biokinetic features of the HATM are examined for selected radionuclides.

Effect of baclofen on esophagogastric motility and gastroesophageal reflux in children with gastroesophageal reflux disease: a randomized controlled trial

OBJECTIVE

To evaluate the effect of baclofen, a gamma-amino-butyric-acid B receptor agonist that inhibits transient lower esophageal sphincter relaxation (TLESR), on the rates of TLESR, gastroesophageal reflux (GER), and gastric emptying (GE) in children with GER disease.

STUDY DESIGN

The efficacy of 0.5 mg/kg baclofen was evaluated in a randomized, double-blinded, placebo-controlled trial in 30 children. Patients were intubated with a manometric/pH assembly and given 250 mL of cow's milk. Esophageal motility and pH were then measured for 2 hours (control period). Baclofen or placebo was then administered, and 1 hour later 250 mL of milk was given again and measurements performed for another 2 hours (test period). The GE rate was measured by the (13)C octanoate breath test.

RESULTS

Baclofen significantly reduced the incidence of TLESR (mean, 7.3 +/- 1.5 vs 3.6 +/- 1.2 TLESR/2 hours; P < .05) and acid GER (mean 4.2 +/- 0.7 vs 1.7 +/- 1.0 TLESR + GER/2 hours; P < .05) during the test period compared with the control period. Baclofen significantly accelerated the GE rate (median [interquartile range], GE(t1/2), 61 minutes [39, 81 minutes] vs 114 minutes [67, 170 minutes]; P < .05). Baclofen had no effect on the swallowing rate, pattern of esophageal peristalsis, or lower esophageal sphincter pressure.

CONCLUSIONS

Baclofen reduces GER in children by inhibiting the triggering of TLESR. Baclofen also accelerates GE.

Factors regulating gastric emptying in preterm infants

OBJECTIVES

To determine whether osmolality, volume, or energy density affects gastric emptying rate (GE); whether simultaneously decreasing osmolality and increasing volume accelerates GE; and whether GE is related to any clinical and/or demographic characteristics.

STUDY DESIGN

GE was measured using the (13)C-octanoic acid breath test in 17 infants of 25 to 30 weeks gestation in a tertiary care children's hospital. In study 1, the independent effects of osmolality, volume, and nutrient density were evaluated in 10 infants. In study 2, the combined effects of decreasing osmolality and increasing volume were evaluated in 7 infants. Results from all infants were used to investigate the relationships between clinical and demographic characteristics and GE. The statistical analysis comprised analysis of covariance, the (paired) Student t-test, the 1-sample Wilcoxon test, and regression analysis.

RESULTS

Mean (+/- standard deviation) age was 27.7 +/- 14.6 days in study 1 and 34.1 +/- 14.0 days in study 2. Altering osmolality, volume, or energy density did not change GE, but simultaneously decreasing osmolality and increasing feeding volume accelerated GE by 18% versus standard feeding. GE correlated with gestational age at birth.

CONCLUSIONS

Unlike in adults, in preterm infants osmolality, volume, or energy density individually do not affect GE. Reducing osmolality and increasing feeding volume increases GE. GE is related to gestational age at birth even at age 1 month.

Variability of the 13C-octanoic acid breath test for gastric emptying of solids in healthy children

AIM

To assess the intra-individual variability of the 13C-octanoic acid breath test using non-dispersive infrared spectrometry for gastric emptying of solids in healthy children.

METHODS

A 13C-octanoic acid breath test was performed at least two times in 19 healthy children (age 12.4 +/- 2.7 years) 2-7 days apart to measure gastric emptying of solids. Breath samples were taken before eating a 13C-octanoic acid-labelled pancake and at 15-min intervals for the following 240 min. Breath samples were analysed using non-dispersive infrared spectrometry; 13C-recovery was used to calculate values for gastric half-emptying time (t(1/2)), gastric lag phase (t(lag)) and gastric emptying coefficient. Intra-individual variability of the parameters t(1/2), t(lag) and gastric emptying coefficient were expressed as coefficient of intrasubject variation.

RESULTS

The mean coefficient of intrasubject variation of t(1/2) was 13.3 +/- 7.9% (range 2.5-29.6%; interindividual range 99-204 min; intra-individual range 5-84 min for t(1/2)). The mean coefficient of intrasubject variation of t(lag) was 13.6 +/- 7.5% (range 0.8-27.8%) (interindividual range 65-146 min; intra-individual range 1-50 min for t(lag)). The mean coefficient of intrasubject variation of gastric emptying coefficient was 12.5 +/- 6.8% (range 3.4-30.2%; interindividual range 2.3-3.9; intra-individual range 0.17-1.4 for gastric emptying coefficient). The coefficient of intrasubject variations of t(1/2), t(lag) and gastric emptying coefficient were independent of the values of t(1/2), t(lag) and gastric emptying coefficient.

CONCLUSIONS

Gastric emptying in healthy children is characterized by a large inter- and intra-individual variability and is concordant with the results obtained with other techniques.

Variability of the 13C-acetate breath test for gastric emptying of liquids in healthy children

PURPOSE

Scintigraphy is considered as the "gold standard" for measuring gastric emptying (GE). The C-acetate breath test (C-ABT) offers an attractive alternative to measure GE of liquids as it is nonradioactive. The aim of this study was to assess the variability of the C-ABT for GE of liquids in healthy children using nondispersive infrared spectrometry (NDIRS).

METHODS

The C-ABT was repeated at least 2 times in 21 healthy children (6 girls and 15 boys), aged between 6.2 and 16.4 years, 2 to 7 days apart. After an overnight fast, a standardized milk drink, labeled with 50 or 100 mg C-acetate according to weight, was administered. Breath samples were taken before feeding, at 5-minute intervals for the first 40 minutes and at 10-minute intervals for the following 140 minutes after feeding. Breath samples were analyzed using NDIRS, and C recovery was used to calculate values for gastric half-emptying time (t1/2), time of peak C exhalation, or gastric lag phase (tlag) and gastric emptying coefficient (GEC). Intraindividual variabilities of the parameters t1/2, tlag, and GEC were expressed as coefficient of intrasubject variation (CV).

RESULTS

The median CV of t1/2 was 8.3% (CV range, 1.6%-16.2%; t1/2 interindividual range, 65-112 minutes; and t1/2 intraindividual range, 4-33 minutes). The median CV of tlag was 16.6% (CV range, 2.0%-26.6%; tlag interindividual range, 31-76 minutes; and tlag intraindividual range, 1-35 minutes). The median CV of GEC was 4.3% (CV range, 0.8%-15.7%; GEC interindividual range, 3.81-4.89; GEC intraindividual range, 0.08-1.31). The CVs of t1/2, tlag, and GEC were independent of age, sex, weight, height, and measured values of t1/2, tlag, and GEC.

CONCLUSIONS

The C-ABT using NDIRS is an easy, noninvasive, and nonradioactive procedure with a large intraindividual variation for measuring GE of liquids in healthy children, but comparable to the variation reported with other techniques.

Is the correction factor used in the breath test assessment of gastric emptying appropriate for use in infants?

OBJECTIVES

The gastric emptying breath test (GEBT) is now routinely used in many centers. Validation studies in adults have shown that although there is a linear correlation between the GEBT and scintigraphy, the GEBT overestimates gastric half emptying time (GEt1/2) by a constant of approximately 60 minutes because of postgastric processing. It is therefore conventional to apply a "correction factor" to the GEBT result. Because = no similar validation studies have been performed in infants, the aim of this study was to directly characterize the postgastric processing of 13C octanoic acid in infants to assess the suitability of the standard correction factor for use in infants.

METHODS

The pattern of breath 13CO2 excretion after separate infusion of 13C octanoic acid into either the stomach or the duodenum was measured in 13 healthy preterm infants (6 male, 7 female). The raw 13CO2 half excretion time after intragastric (GEt1/2 raw) and intraduodenal (DEt1/2 raw) administration of C octanoic acid was calculated, and the difference between GEt1/2 raw and DEt1/2 raw (i.e., GEt1/2 raw - DEt1/2 raw) was directly compared with GEt1/2 corrected, derived by applying the standard correction factor to GEt1/2 raw.

RESULTS

Values for GEt1/2 raw - DEt1/2 raw correlated significantly with GEt1/2 corrected.

CONCLUSION

Our results show that the standard correction factor is appropriate for performing the GEBT in preterm infants.

Paradoxical impact of body positioning on gastroesophageal reflux and gastric emptying in the premature neonate

OBJECTIVES

To combine manometry and impedance to characterize the mechanisms of gastroesophageal reflux (GER) and to explore their relation to the rate of gastric emptying (GE) and body position.

STUDY DESIGN

Ten healthy preterm infants (35 to 37 weeks' postmenstrual age) were studied with the use of a micromanometric/impedance assembly. Episodes of GER were identified by impedance, and the mechanism(s) of GER triggering and GER clearance were characterized. GE was determined with a C13Na-octanoate breath test.

RESULTS

Gastroesophageal reflux episodes (n=89) were recorded, consisting of 74% liquid, 14% gas, and 12% mixed. Transient lower esophageal sphincter relaxation (TLESR) was the predominant mechanism of reflux, triggering 83% of GER. Of 92 TLESRs recorded, 27% were not associated with reflux. Infants studied in the right lateral position had significantly (P <.01) more GER, a higher proportion of liquid GER (P <.05), and faster GE (P <.005) when compared with infants studied in the left lateral position.

CONCLUSIONS

In healthy preterm infants, GER is predominantly liquid in nature. Right-side positioning is associated with increased triggering of TLESR and GER despite accelerating GE.

Delayed gastric emptying in the obese: an assessment using the non-invasive (13)C-octanoic acid breath test

AIM

Much of the controversy surrounding the correlation between obesity and gastric emptying lies in the inconsistency of methodology and analysis. This study was designed to overcome some of the discrepancies encountered in previous studies and to test the hypothesis that obese individuals have altered gastric emptying compared to lean individuals.

METHODS

Gastric emptying was measured using the (13)C-octanoic acid breath test in 16 lean and 16 obese women pair-matched for age. Following an overnight fast, subjects were given a standard 2 MJ egg meal labelled with 100 microl of [1-(13)C]-octanoic acid. Breath samples were collected at regular intervals over a 6-h period. (13)C-isotopic enrichment in the breath was analysed using isotope ratio mass spectrometry and the data fitted to the established gastric emptying model. The lag times (t(lag)), half excretion times (t(1/2)), latency phase (t(lat)) and ascension times (t(asc)) were calculated.

RESULTS

The mean t(1/2)-values (+/-standard error of the mean) were 3.67 +/- 0.14 h and 4.23 +/- 0.18 h for lean and obese respectively, indicating significantly delayed gastric emptying in the obese (p = 0.019). The obese group also showed a significantly slower lag time (t(lag), p = 0.005) and latency phase (t(lat), p = 0.005), but no significant difference was found in the ascension time (t(asc), p = 0.154). Within groups, no correlation was found between half excretion times and body weight or half excretion times and body mass index.

CONCLUSIONS

The present study demonstrated a prolonged lag phase and delayed gastric emptying in obese women when compared to lean women. This delay may be as a consequence of high-fat diets, a sedentary lifestyle and increased gastric distension associated with obesity, or a contributing factor in the pathogenesis of obesity resulting from the inactivation of gastrointestinal satiety signals and in an increase in food intake.

Measuring gastric emptying of semisolids in children using the 13C-acetate breath test: a validation study

BACKGROUND AND AIM

Radioscintigraphy is the gold standard for evaluation of gastric emptying in children, but requires exposure to ionising radiation. Therefore, the aim of the study was to validate the non-radioactive 13C-acetate breath test in children in comparison to radioscintigraphy as reference method.

PATIENTS

Twenty-nine children with dyspeptic or respiratory symptoms were tested for gastric emptying disorders simultaneously performing the 13C-acetate breath test and radioscintigraphy.

METHODS

A semisolid oatmeal was doubly labelled with 150 mg 13C-acetate and 50 MBq 99mTechnetium. Breath samples were collected every 5-10 min for 4 h. After mass spectrometrical 13C-analysis, curve fitting of the 13C-cumulative recovery to the modified power exponential function Y = m(1 - e(-kt) calculated the half emptying times of the breath test (t 1/2 (breath)). Scintigraphic image acquisition began immediately after the ingestion of the 99mTechnetium-labelled testmeal at a rate of one frame every 60 s for 1 h.

RESULTS

Six children showed delayed gastric emptying in scintigraphy (t 1/2(scinti) > 60 min). All these children had prolonged half emptying times t 1/2 (breath) in the 13C-acetate breath test. Using a cut-off t 1/2(breath) > 90 min, the 13C-acetate breath test had a sensitivity of 100% and a specificity of 85%. Scintigraphic and breath test half emptying times were linearly correlated (Y = 0.80x + 47.68, r = 0.76, P < 0.00001).

CONCLUSIONS

The 13C-acetate breath test proves to be a reliable, non-radioactive alternative for measuring gastric emptying in children.

Multipoint measurement of intragastric pH in healthy preterm infants

BACKGROUND

The diagnostic use of 24 hour oesophageal pH monitoring in infants is controversial because of the impact of feed buffering of gastric acidity.

AIM

To re-evaluate the effect of feeding on gastric pH and reflux using multipoint pH measurements.

SUBJECTS

Fifteen healthy premature infants fed every four hours.

METHODS

Oesophageal pH and intragastric pH at 3, 6, and 9 cm below the lower oesophageal sphincter were simultaneously measured using a four channel pH probe for four hours after bolus feeding. Parameters of pH were compared for the different levels within the stomach. During reflux episodes, the nadir pH was compared with intragastric pH at all levels.

RESULTS

The proximal stomach was more significantly buffered by feeding and slower to re-acidify postprandially than the mid and distal stomach (42.2% of the time at pH < 4 compared with 58.7% and 55.7% respectively). During 27 of 62 gastro-oesophageal reflux episodes, nadir oesophageal pH was lower than the pH of the proximal stomach but always equal to or higher than the pH of the distal stomach.

CONCLUSIONS

These data indicate that previous studies may have overestimated the effect of feeding on gastric acidity and reflux.

Development of gastric emptying in premature infants. Use of the (13)C-octanoic acid breath test

OBJECTIVE

The non-invasive (13)C-octanoic acid breath test ((13)C-OABT) has recently been used to monitor gastric emptying. We evaluated (13)C-OABT as a method for assessing gastric emptying in relation to the amount of milk ingested in preterm neonates during their first days of life.

METHODS

The (13)C-OABT was performed in 16 stable preterm neonates born between weeks 31 and 37 of gestation (mean +/- standard deviation: 34.0 +/- 1.5 wk). Birth weight was 1400 to 2680 g (2076 +/- 350 g); four newborns were small for gestational age. The newborns underwent (13)C-OABT three times according to the amount of (13)C-primed breast milk being fed to them (<7 mL/kg, 7-13 mL/kg, and 10-19 mL/kg per dose). (13)C-primed breast milk (the test meal) was prepared by adding (13)C-octanoic acid to pasteurized breast milk to achieve a concentration of 1 microL of (13)C-octanoic acid/mL of milk. Exhaled air samples were taken through an original nasal mask. Amounts of (13)C and (12)C in the exhaled air samples were measured by mass spectrometry. Results were expressed as delta over baseline and related to the international standard of Pee Dee Belemnite Limestone. To assess the half-life of elimination (t(1/2)E), we modeled the process of elimination with the incomplete gamma-function, which has a convenient form for the empiric plotting of breath test data. We estimated the parameters of the function, f(x) = A x(b) e(-cx), by using the moment method. The curves were determined by the t(1/2)E of (13)CO(2) and characterized by the shape of the elimination curve. The half-time of gastric emptying (t(1/2)GE) was calculated as t(1/2)E reduced by the mean metabolic half-time of octanoic acid.

RESULTS

Forty-eight (13)C-OABT results from 16 premature newborns were analyzed. The mean and median of t(1/2)GE calculated from all three tests were 50.3 (+/-29.9) and 43.7 min, respectively. The t(1/2)GE did not change significantly (P = 0.6811) with the administered dose of (13)C-primed breast milk in the stomach. The coefficient of variation among the studied infants was 4.0% to 33.6% (mean, 11.5%). In 12 infants, the characteristic type of elimination curve was the same for all three tests.

CONCLUSIONS

In the first hours of gastric feeding, neither the age of the neonate nor the amount of administered (13)C-primed breast milk had any effect on t(1/2)GE. The gastric emptying rate and the evacuation curve shape for individual neonates were similar and independent of milk amount.

Patterns of antropyloric motility in fed healthy preterm infants

BACKGROUND

Antropyloric motility is important for regulation of gastric emptying and has not been adequately characterised in premature infants.

AIM

To evaluate fed patterns of antropyloric motility in premature infants.

SUBJECTS

Forty three healthy premature infants, 30-38 weeks of postmenstrual age.

METHODS

Postprandial antropyloric motility was measured using a micromanometric feeding assembly (outer diameter 1.8 mm) incorporating a pyloric sleeve sensor. The occurrence of isolated pyloric pressure waves (IPPWs) and antral pressure wave sequences (PWSs) was characterised. Sequences were further classified as being antegrade, synchronous, antegrade-synchronous, and retrograde according to the direction of propagation.

RESULTS

A total of 7289 pressure wave events were recorded, 48% IPPWs and 52% PWSs (18% antegrade, 12% synchronous, 13% antegrade-synchronous, 2% retrograde, and 7% undefined). IPPWs predominated in the first postprandial hour, peaking at 30-60 minutes. PWSs predominated in the period after one hour postprandially. Mean (SEM) half gastric emptying time was 42 (4) minutes.

CONCLUSIONS

Monitoring of antropyloric motor patterns in healthy premature infants indicates that the neuroregulatory mechanisms responsible for the coordination of antropyloric motility and gastric emptying are well developed by 30 weeks of postmenstrual age.

Acute ingestion of a meal rich in n-3 polyunsaturated fatty acids results in rapid gastric emptying in humans

BACKGROUND

n-3 Polyunsaturated fatty acids (PUFAs) have proven benefits for both the development of atherosclerosis and inflammatory conditions. The effects on atherosclerosis may be partly mediated by the observed reduction in fasting and postprandial triacylglycerol concentrations after both acute and chronic n-3 PUFA ingestion.

OBJECTIVE

The aim of this study was to assess gastric emptying and gastrointestinal hormone release after the consumption of mixed meals rich in n-3 PUFAs or other classes of fatty acids.

DESIGN

Ten healthy women (aged 50-62 y) completed 4 separate study visits in a single-blind, randomized design. On each occasion, subjects consumed 40 g oil rich in either saturated fatty acids, monounsaturated fatty acids, n-6 PUFAs, or n-3 PUFAs as part of a mixed meal. [1-(13)C]Octanoic acid (100 mg) was added to each oil. Gastric emptying was assessed by a labeled octanoic acid breath test, and concentrations of gastrointestinal hormones and plasma lipids were measured.

RESULTS

Recovery of (13)C in breath was enhanced after n-3 PUFA ingestion (P < 0.005). The cholecystokinin response after the n-3 PUFA meal was significantly delayed (P < 0.001), and the glucagon-like peptide 1 response was significantly reduced (P < 0.05).

CONCLUSION

The inclusion of n-3 PUFAs in a meal alters the gastric emptying rate, potentially as the result of changes in the pattern of cholecystokinin and glucagon-like peptide 1 release.

Gastric emptying characteristics of a novel (13)C-octanoate-labeled muffin meal

GOALS

Determine the gastric emptying characteristics of a novel, 350-kcal test meal consisting of two muffins, using scintigraphy and the 13C-octanoate breath test (OBT).

STUDY

Healthy volunteers underwent three studies on separate days within a 1-week period. On day 1, we measured emptying of the 350-kcal muffin test meal labeled simultaneously with 99mTc sulfur colloid and 13C-octanoate. On day 2, reproducibility of the OBT using a single-labeled 350-kcal test meal was assessed. On day 3, the effect of erythromycin on the 350-kcal OBT was determined.

RESULTS

The mean (+/-SD) half-emptying time (T1/2) as measured by scintigraphy was 104 +/- 24 minutes, versus 212 +/- 52 minutes by OBT. There was a strong correlation between T1/2 determined by scintigraphy and the breath test (r = 0.83). Multiple linear regression analysis identified a significant relationship between T1/2 determined by scintigraphy and the 90-and 180-minute breath samples. There was a strong correlation (r = 0.830, slope = 0.732 +/- 0.120 [SE], intercept = 26.4 +/- 12.7) between the T1/2 obtained using the regression equation and the actual T1/2 obtained by scintigraphy. The mean T1/2 (+/-SD) for replicate determinations using the OBT was 209 +/- 52 minutes, compared with 196 +/- 42 minutes on days 1 and 2, respectively (not significant, p = 0.28, paired Student t test). Treatment with erythromycin on day 3 produced a significant decrease in T1/2 (155 +/- 49 minutes, p = 0.002).

CONCLUSIONS

The 350-kcal muffin meal OBT provides a convenient, nonscintigraphic way of measuring solid-phase gastric emptying. Multiple linear regression appears promising as a method of analyzing OBT data and may allow for an abbreviated breath test protocol.

Improved use of the [13C]octanoic acid breath test as intra-individual parameter to study the effect of a prokinetic drug on gastric emptying in preterm infants with oral feeding intolerance

The [13C]octanoic acid breath test was used for the measurement of differences in gastric emptying in preterm infants for the evaluation of pharmacological therapy. In order to perform a good intra-individual comparison of the gastric emptying in preterm infants under non-standardisable test conditions, we adjusted t1/2 for variations in non-recovered label (=label retention) and introduced an "effective half 13CO2 breath excretion time" t1/2eff = t1/2/m expressed as min per percentage of the cumulative dose recovered. In a pilot study, we investigated the action of the gastrointestinal prokinetic drug cisapride on gastric emptying in seven premature infants, of whom four suffered from gastric stasis and three had constipation. The postnatal age and weight at the start of treatment ranged from 15 to 64 days and from 815 to 1635 g, respectively. All infants received the standard formula for premature infants (Nenatal, Nutricia). Cisapride was administered orally 0.2 mg/kg, four times daily. The changes in gastrointestinal motility were studied using the total bowel transit time of carmine red. After 7 days of treatment in all children, the gastric emptying coefficient and the half 13CO2 breath excretion time adjusted for label retention were improved (n=7, the gastric emptying coefficient range before treatment was 1.69-3.34 (mean 2.59 +/- 0.80) and after treatment it was 2.79-3.76 (mean 3.28 +/- 0.30); the half 13CO2 breath excretion time adjusted for label retention range before treatment was 3.0-14.7 min/% dose (mean 7.0 +/- 5.0) and after treatment 2.6-4.0 min/% dose (mean 3.1 +/- 0.6). The total bowel transit time was only slightly improved in two patients (n=7, mean total bowel transit time before: 23.7 h compared to mean total bowel transit time after 7 days of treatment: 35.5 h). Side effects during cisapride treatment were not seen. We conclude that in premature infants cisapride is effective in shortening gastric emptying time and reducing gastric stasis; the therapeutic role in constipation has to be further investigated.

Gastroduodenal disorders in children

Studies within the past year examining the mechanisms underlying infantile hypertrophic stenosis at the cellular and molecular level are reviewed. A number of new modalities, including electrogastrography, and the 13C octanoid acid breath test have been used in the study of normal and abnormal gastrointestinal motility, as well as for the characterization of patterns of development of gastric motility in early infancy. Several studies pertaining to the natural outcome, the mode of transmission, and the associated symptomatology of Helicobacter pylori were published, attesting that, despite the tremendous progress achieved in our understanding of H. pylori, important gaps remain in our knowledge of this microorganism. Newly described clinical presentations of eosinophilic gastroenteritis and food allergy will also be of interest to the reader.

Reflux in children

Gastro-oesophageal reflux (GOR) is an extremely common paediatric problem that often runs a harmless and self-limited course. Physiological GOR however can lead to marked parental anxiety, many unnecessary investigations and often unwarranted and potentially harmful therapeutic interventions. Our ability to better define GOR and gastro-oesophageal reflux disease (GORD) has improved in the past 15 years with a better understanding of the pathophysiology in infants and children due to the development and wider use of flexible endoscopy, 24-hour oesophageal pH monitoring and, more recently, the use of micromanometric methods for studying oesophageal motility. This will be further enhanced in the future with the development of non-invasive breath testing to study gastrointestinal motility and the use of electrical impedance to study fluid movement. Our therapeutic interventions have also improved particularly in the areas of acid suppression, improved surgical techniques and most recently laparoscopic fundoplication. This chapter reviews these advances in the paediatric area especially with regard to pathophysiology, diagnostic testing and therapeutic intervention.

Gastric emptying of liquid meals measured noninvasively in humans with [13C]acetate breath test

The aim of the present study was to develop a breath test to measure liquid gastric emptying rates that would be without radiation exposure and applicable to field testing. Four different test meals were investigated: a glucose meal, an amino acid meal, a fat meal, and a mixed meal (Ensure). The test meals were labeled with two markers, [13C]acetate and PEG-4000 (polyethylene glycol 4000). Gastric emptying rates were measured simultaneously by both breath test and the double-indicator technique in eight healthy male subjects. The appearance of 13CO2 in the breath closely reflected gastric emptying of the four test meals as measured by the double-indicator technique. It is concluded that the [13C]acetate breath test is a reliable, noninvasive test to measure gastric emptying rates of liquid test meals.