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Keywords:

  • antroduodenal;
  • manometry;
  • migrating motor complex;
  • pylorus;
  • solid-state catheter

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgment
  9. References

Abstract  Manometric recording from the pyloric channel is challenging and is usually performed with a sleeve device. Recently, a solid-state manometry system was developed, which incorporates 36 circumferential pressure sensors spaced at 1-cm intervals. Our aim was to use this system to determine whether it provided useful manometric measurements of the pyloric region. We recruited 10 healthy subjects (7 males : 3 females). The catheter (ManoScan360) was introduced transnasally and, in the final position, 15–20 sensors were in the stomach and the remainder distributed across the pylorus and duodenum. Patients were recorded fasting and then given a meal and recorded postprandially. Using pressure data and isocontour plots, the pylorus was identified in all subjects. Mean pyloric width was 2.1 ± 0.1 cm (95% CI: 1.40–2.40). Basal pyloric pressure during phase I was 9.4 ± 1.1 mmHg, while basal antral pressure was significantly lower (P = 0.003; 95% CI: 2.4–8.4). Pyloric pressure was always elevated relative to antral pressure in phase I. For phases II and III, pyloric pressure was 7.7 ± 2.3 mmHg and 9.4 ± 1.1 mmHg, respectively. Pyloric pressure increased similarly after both the liquid and solid meal. In addition, isolated pressure events and waves, which involve the pylorus, were readily identified.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgment
  9. References

Antropyloroduodenal (APD) manometry can identify specific abnormalities characteristic of neuropathic and myopathic disorders. Measurement of antroduodenal pressure is relatively straightforward.1–4 Incorporation of manometric data from the pyloric channel is significantly more challenging primarily due to migration of the sphincter during peristalsis.

An advancement in the field was the development of a sleeve device by Dent5 This water-perfused catheter system has a 4.5-cm sleeve that incorporates several closely spaced (3–5 mm) pressure transducers that can be positioned across the pylorus.6,7 The device is coupled with measurement of transmucosal potential difference (TMPD) to verify placement. Additional sensors are distributed on either side of the sleeve to perform complete APD manometry.8–20 The complexity of this system and the limitation in number of pressure ports have restricted its widespread clinical use.

Recently, a solid-state manometry system (ManoScan360, Sierra Scientific Instruments, Inc., Los Angeles, CA, USA) was developed primarily for oesophageal manometry.21 The system uses a soft, moulded catheter with an outer diameter of 4.2 mm. Incorporated within the catheter are 36 1-cm spaced transducers. The system uses TactArray (Press Profile Systems Inc., Los Angeles, CA, USA) pressure transduction technology that allows each transducer to detect pressure over a length of 2.5 mm in each of 12 radially dispersed sectors. The system eliminates the complexities of water-perfused systems, allows pressure wave interpretation simultaneously along a significant length and is small enough to not disrupt normal physiological function of the pylorus.22

The purpose of this study was to use this system to perform antroduodenal manometry and provide normative data for healthy subjects. An additional goal was to determine whether the catheter could provide useful manometric measurements of the pyloric region.

Materials and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgment
  9. References

Twelve12 healthy, symptom-free subjects were recruited. The protocol was approved by our Institutional Review Board. Catheter placement was performed using endoscopic guidance in a room equipped with fluoroscopy.

High-resolution manometry catheter placement

Prior to the use of the catheter, its transducers were calibrated at 0 and 100 mmHg using externally applied pressure. The transducers are capable of recording transient pressure values as high as 6000 mmHg s−1 and are accurate to within 1 mmHg of atmospheric pressure.23 During endoscopy, the ManoScan360 catheter was introduced transnasally and advanced into the proximal stomach. The catheter measures 140 cm in total length and the distal portion, just beyond the last transducer, was adapted with a plastic eyehook (Fig. 1). A 2-0 silk suture was threaded through the hook, knotted and excess thread removed. A forceps was used to grasp the knotted suture and advance the catheter across the pylorus into the duodenum. Once the catheter remained in a transpyloric position, the overall insertion length was adjusted to avoid looping in the mouth and stomach. In this position, approximately 15–20 manometric sensors remained in the stomach, and the remainder were distributed across the pylorus and proximal duodenum. Throughout the study, multiple supine fluoroscopic images (GE OEC 9800-Plus C-Arm, General Electric, Salt Lake City, UT, USA) were obtained.

image

Figure 1.  Photograph of Manoscan360 system. Catheter has an OD = 4.2 mm and length of 140 cm, and it has 36 circumferential pressure transducers and two metallic rings distally. The tip of our study catheter was modified to allow a tied suture, which was used to pass the catheter beyond the pylorus.

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Endoscopic clip placement

In one subject, two metal clips were attached within 1 cm proximal and distal to the endoscopically identified pyloric channel. A fluoroscopic image was then taken to precisely identify the sensor straddling the channel (Fig. 2). This patient was used as the standard for the identification of the manometric and isocontour plot profile of the pyloric sphincter.

image

Figure 2.  Fluoroscopic image of catheter placed with the tip in the duodenum. Distal transducer, no. 36, is labelled (short, heavy arrow). Two clips, both within 1 cm proximal and distal to the pylorus were placed prior to catheter insertion (thin, long arrow). Data from transducer no. 23 in the pyloric channel were used as the standard for other cases in the interpretation of pyloric manometric and isocontour image data.

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Manometry recording

After 30 min of recovery, the catheter leads were inserted into the ManoScan360 workstation for data acquisition. The system's software allows visualization of all the 36 pressure tracings simultaneously. The viewer also has the option of choosing a real-time colour isocontour plot of the manometric data. In that view, the computer represents the amplitude of each pressure wave by a colour and provides a colour key for interpretation. Interpolation of data between the sensors generates a smooth topographical image of the pressure cavity under study.

After obtaining fasting data, patients were given one of two standardized meals. In a random order, five subjects drank 250 cc (240 kcal, 4 g fat) of Boost® (Novartis Medical Nutrition, Freemont, MI, USA) over 10 min and another five ate a solid meal consisting of two large scrambled eggs, two slices of toasted white bread with 30 g of jam with 120 cc of tap water (345 kcal, 1.5 g fat) over 10 min. Postprandial pressure recordings continued for an additional 60 min. Thereafter, the catheter was removed and external thermal compensation was performed.

Data analysis

The ManoScan360 system utilizes an integrated software package (ManoView Analysis Program, Sierra Scientific Instruments, Los Angeles, CA, USA) to analyse the data. To begin the analysis, we integrated the thermal correction factor into our pressure data through an automated process. We selected the atmospheric mode from the pressure reference control to set the pressure baseline used for display. Each recording was first analysed for the number, duration and time between phase III migrating motor complex (MMC) events. For each MMC cycle, the duration of phases I and II activities was recorded. Attention was then focused on the pyloric region to determine its length and activity. The pylorus was localized with the use of the following criteria: (i) fluoroscopic correlation to individual pressure transducer in the channel; (ii) pressure tracing located between antral and small bowel pressure tracings during phase III; (iii) manometric morphology representing a hybrid of antral and duodenal morphology and (iv) persistence of the region as a high pressure zone. The pressure within the antrum and pylorus during all phases were calculated by taking the mean of multiple separate (between 10 and20) measurements during each period.

We recorded all pressure events (contractile events detected by a single transducer with an amplitude of ≥10 mmHg) and pressure waves (pressure events involving three or more successive transducers) during phase I. We also identified the following: (i) isolated pyloric pressure waves (IPPWs); (ii) isolated pressure wave bursts and (iii) small bowel discrete clustered contractile waves.

Data were first verified to be normally distributed with the use of histograms and P–P plots. Paired t-tests were used to compare pyloric and antral pressure data during each phase of the MMC and in the fed state. The spread of the mean was expressed as the standard error. Where appropriate, ranges and 95% CI were included to facilitate data presentation.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgment
  9. References

Catheter placement

Of the 12 healthy subjects who were enrolled, catheter placement was successful in only 10 (7 males, mean age 33 ± 2.6 years). In two patients, the catheter was placed into the small bowel but retracted into the stomach after withdrawal of the endoscope. Despite fluoroscopic guidance, the catheter still could not be properly positioned. In three patients, the catheter retracted into the stomach but was successfully repositioned.

Manometric data

The mean duration of recording was 234.4 ± 26.5 min (range 77–335.4 min) including a mean of 172.9 ± 21.8 min (range 62.7–267.1 min) fasting and 61.5 ± 7.6 min (range 13.6–92.5 min) postprandially. All subjects demonstrated all three phases of the MMC (Fig. 3). Overall, one subject had a single phase III complex, five5 had two phase III complexes and four4 had three phase III complexes. The duration of phases I, II and III were 103.6 ± 25.0 min (20.5–235.0), 25.9 ± 6.3 min (5.8–65.0) and 10.3 ± 0.9 min (5.8–15.1), respectively. Nine subjects were converted into the fed pattern after the study meal. One subject did not convert and was in the midst of a phase III complex at the initiation of a liquid meal and displayed only phase I activity during the entire fed period.

image

Figure 3.  Phase III of the MMC. Isocontour plot and manometry labelled from respective cavities. Phase III events were used to spatially identify the pylorus. Once pylorus was identified, region could be followed throughout the rest of the study. Pyloric position was periodically confirmed with fluoroscopy. The top panel represents the isocontour plot and below is the corresponding manometric tracing. Shown to the left of the isocontour plot is the pressure-colour key. Red spectrum represents higher pressures and blue spectrum lower pressures. To the right of the plot is a ruler to connect relationship between pressure wave and physical location along the length of the catheter.

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Pressure tracing data and isocontour plots identified a pylorus high-pressure zone in all 10 subjects. Isocontour data were utilized to estimate the width of the pyloric channel. The mean pyloric width was 2.1 ± 0.1 cm (95% CI: 1.40–2.40). Basal pyloric pressure (tonic pressure measured in the absence of phasic activity) during phase I was 9.4 ± 1.1 mmHg (95% CI: 2.8–14.4). Basal antral pressure was 4.0 ± 1.4 mmHg (95% CI: −5.1 to 9.1), significantly lower than the mean pyloric pressure (P = 0.003; 95% CI: 2.4–8.4) (Fig. 4).

image

Figure 4.  Boxplot of pyloric pressure data during the interdigestive phase. Plots demonstrate that tonic pyloric pressure (measured during intervals absent of phasic activity) was elevated relative to basal antral pressure. Peak pyloric pressure measured during phasic activity. The top and bottom ‘whiskers’ represent the lowest and highest values within 1.5 times the IQR. The three horizontal lines within the box represent the study group's 25%, 50% (heavy line) and 75% median, respectively. Outliers (>1.5 times the IQR) are represented by individual symbols beyond the whiskers.

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In phases II and III, the mean tonic pyloric pressures were 7.7 ± 2.3 and 9.4 ± 1.1 mmHg, respectively. Antral pressure was similar to pyloric pressure during phase II (mean difference 1.6 ± 2.9 mmHg; P = 0.61) and phase III (mean difference 2.0 ± 1.9 mmHg; P = 0.36). Pyloric pressure increased with both the liquid and solid meal. Basal postprandial pyloric pressures were similar for both groups (12.8 ± 2.6 vs 9.9 ± 1.8 mmHg; P = 0.39) as were peak pressures measured during phasic contractions (60.5 ± 8.9 vs 53.6 ± 8.4 mmHg; P = 0.59).

Pressure events and waves

There were 110 isolated antral events and 55 isolated duodenal events recorded. There were 54 APD waves, 15 pyloroduodenal waves, 11 retroperistaltic duodenopyloric waves, and 22 IPPWs (Fig. 5). One discrete cluster wave complex and one episode of isolated small intestinal burst activity were also observed.

image

Figure 5.  Isolated pyloric pressure wave as seen on isocontour plot and manometry. The pyloric region had previously been localized. Areas of pressure artefact labelled.

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Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgment
  9. References

This paper describes the use of a solid-state manometry system for the measurement of APD motor activity. A comparison between this manometry system and water-perfused sleeve device systems is shown in Table 1. Overall, the system provides detailed tracings for analysis and corresponding colour isocontour images. Our results confirm that the pylorus functions as a high-pressure zone during phase I with a pressure that is approximately 5 mmHg higher than the antral zone. These results agree with prior investigators who have suggested that the pylorus has intrinsic basal tone and primarily serves as a classic sphincter.7,24–26 During phases II and III, there are innumerable contractions and relaxations of the antrum, pylorus and duodenum, and the catheter was unable to identify a specific location as a relative high-pressure zone.

Table 1.   Comparison of solid-state vs water-perfused antropyloroduodenal (APD) catheter systems
TechnologyDescriptionAdvantagesDisadvantages
Solid-stateOD = 4.2 mm Incorporates 36 circumferential pressure sensors spaced at 1-cm intervals Real-time pressure tracings and topographic contour plotsSimple operation Highly portable Data displayed as traditional pressure tracings or contour plots. Pressure events and waves easily characterized in contour plot modeVery sensitive, frequent artefacts Requires mucosal clips to objectively verify that the sensor is in pyloric channel Expensive
Water-perfused4.5 cm sleeve, OD = 6.5 mm with transducers spaced (3–5 mm) Coupled with transmucosal potential difference (TMPD) Additional sensors on either side of sleeve to perform APD manometry Operates via continuous water perfusion through systemTime-honoured use with standard protocols Incorporates TMPD to validate sleeve position InexpensiveComplicated apparatus and operation Sleeve can underestimate pressures by 1–1.5 mmHg Subject to artefact from ‘air bubbles’ Contour plots unavailable

The catheter also provides the opportunity to measure pyloric length that has been disputed. One publication estimated the length to be 2 cm,27 while others have recorded measurements of only 0.6–1 cm.7,10,11 In this study, the pyloric length was determined to be 2.07 ± 0.13 cm (95% CI: 1.40–2.40). The difference between studies may be due to the sensitivity of the manometric system used. The Manoscan360 system is extremely sensitive and is able to detect very small pressure values. Less sensitive devices may detect only that portion of the pylorus with the highest pressure. A potential source of error in the Manoscan360 system is that it interpolates data between sensors to provide a continuous isocontour plot, which may result in the overestimation of sphincter length. Other types of recording devices may also have limitations. A sleeve sensor measures pressures over a 3–5 cm span, which may also include pressure profiles from the distal antrum and proximal duodenum. Thus, a sleeve may measure a mixture of pressures and not give true pyloric pressure measurements.

The catheter's 1-cm spaced transducers are ideally suited for detecting pressure events and short pressure waves that propagate over only a few centimetres. For example, Manoscan360 is capable of detecting IPPWs which our study confirms are rare events during phase I. They were frequent in phase II and the postprandial period (data not shown). This is in agreement with other studies showing that IPPWs decrease with fasting and increase with intraduodenal lipid or glucose infusions.10–12,20 Detection of IPPWs may be of clinical importance. A recent report identified a decrease in IPPWs after pyloric injection with botulinum toxin A (Botox; Allergen, Irvine, CA, USA) in a patient with gastroparesis.28 This correlated with symptom improvement, and IPPWs were hypothesized to have pathophysiological significance.

A potential weakness of our study is that we did not confirm our findings using a sleeve device as a comparator. Continuous measurement of TMPD with a sleeve device remains a valid technique for recording pyloric activity. Certainly the catheters could not be inserted simultaneously as this would have yielded erroneous data. It would have been possible to place separate catheters on separate days, but the daily variation in pyloric pressure would be an important confounder.9 Two lines of evidence indicate that this may not be a significant issue. Manometry of the oesophagus using this same system provides pressure profiles that are very similar to other catheter systems.29 Secondly, much data already exist on sleeve device measurements of pyloric pressure, which admittedly vary somewhat from study to study. Overall, our pressure numbers are actually quite consistent with the numbers generated from sleeve studies, which zero pyloric pressure to antral pressure.10

A similar concern is that of catheter migration. One study using a sleeve device confirmed successful transpyloric catheter positioning 75% of the time using a combination of TMPD and manometry.13 Unlike sleeve devices, this study relied on 1-cm spaced transducers without the use of mucosal potential difference to guide pyloric location. There were several mechanisms to account for migration and to identify the pyloric region. Firstly, frequent, magnified fluoroscopic examinations were performed throughout each study using state-of-the-art equipment. The transducers are sharply seen by fluoroscopy and therefore, within a small margin of error, the transducer lying within the pyloric channel can be identified. In a single patient, we used metal clips to fluoroscopically label the pylorus to confirm our radiographic impression of its location. After a phase III MMC event, manometric information demonstrating the precise location of the antrum and duodenum based on their characteristic slow wave frequency was utilized. The narrow region in between, best seen on the isocontour waves, must therefore be the pylorus. Analysis of corresponding pressure tracings allows for minor adjustments to ideally visualize/demonstrate pyloric waves. In this study, for all subjects, fluoroscopic images correlated very closely with phase III information. During phase I, the pyloric region usually persisted as a high-pressure zone that could be followed best by the isocontour plots. Occasionally, the pylorus relaxed and was ‘lost’. At other times, the pylorus was seen to migrate a short distance, but these episodes were easily identified (Fig. 6).

image

Figure 6.  Completion of a phase III MMC cycle as shown by isocontour plot. Gastric and pyloric phasic activities cease prior to duodenal activity. The pyloric region remains an area of basal high pressure and is shown to migrate slightly. Fluoroscopic images correlated with manometric localization of the sphincter, which varied between 17 and 18 cm from the most proximal transducer. To the left of the isocontour image is a colour code with corresponding pressure. Numbers to right represent transducer site along the catheter where pressure originates. Data from only 32 of 36 transducers are shown.

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A potential limitation of this technology is that it readily identified physiological artefacts such as respiratory activity and pulsations from nearby major vessels, which may be confusing when first using the system (Fig. 3). Catheter angulation can theoretically produce artefactual high-pressure zones, but this should be minimized by the circumferential distribution of the TactArray pressure acquisition technology.

Although endoscopy was used to place the catheter, it is not necessary. This was performed for patient comfort, to limit radiation exposure and to ensure that immediate transpyloric placement was achieved. This study used only midazolam and diphenhydramine and avoided narcotics due to their known effect on motility. There are insufficient data to be completely sure that the medications given would significantly affect motility; however, it is suspected that their impact would be transient. One potential advantage of sedation is that there is less stimulation of sympathetic activity.

Conclusion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgment
  9. References

Our study demonstrates the results of using a solid-state catheter system to perform APD manometry. The system was consistently able to identify the pyloric sphincter. A pressure of approximately 5 mmHg above antral pressure was shown during phase I. Replication of this study in additional healthy subjects and those with neuropathic and myopathic gastroduodenal disorders is now being studied by our group.

Acknowledgment

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgment
  9. References

This work was supported by the Temple University Faculty Development Research Award funded by AstraZeneca to Frank K. Friedenberg.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgment
  9. References
  • 1
    Summer RW, Soffer EE. Evaluation of intestinal motility. In: AnurasS, ed. Motility Disorders of the Gastrointestinal Tract. New York: Raven Press, 1992: 89124.
  • 2
    Soffer EE, Summers RW. Ambulant manometry. In: KumarD, WingateDL, eds. An Illustrated Guide to Gastrointestinal Motility, 2nd edn. Edinburgh: Churchill Livingstone, 1993: 20010.
  • 3
    Camilleri M. Study of human gastroduodenaljejunal motility. Dig Dis Sci 1993; 38: 78594.
  • 4
    Husebye E. The patterns of small bowel motility: physiology and implication in organic disease and functional disorders. Neurogastroenterol Motil 1999; 11: 14161.
  • 5
    Dent J. A new technique for continuous sphincter pressure measurement. Gastroenterology 1976; 71: 2637.
  • 6
    Heddle R, Dent J, Toouli J, Read NW. Topography and measurement of pyloric pressure waves and tone in humans. Am J Physiol 1988; 255: G4907.
  • 7
    Faas H, Hebbard GS, Feinle C et al. Pressure–geometry relationship in the antroduodenal region in humans. Am J Physiol Gastrointest Liver Physiol 2001; 281: G121420.
  • 8
    Castedal M, Abrahamsson H. High-resolution analysis of the duodenal interdigestive phase III in humans. Neurogastroenterol Motil 2001; 13: 47381.
  • 9
    Dooley CP, Reznick JB, Valenzuela JE. A continuous manometric study of the human pylorus. Gastroenterology 1985; 89: 8216.
  • 10
    Heddle R, Dent J, Read NW et al. Antropyloroduodenal motor responses to intraduodenal lipid infusion in healthy volunteers. Am J Physiol 1988; 254: 6719.
  • 11
    Tougas G, Anvari M, Dent J, Somers S, Richards D, Stevenson GW. Relation of pyloric motility to pyloric opening and closure in healthy subjects. Gut 1992; 33: 46671.
  • 12
    Verhagen MAMT, Samsom M, Smout JPM. Effects of intraduodenal glucose infusion on gastric myoelectrical activity and antropyoloroduodenal motility. Am J Physiol Gastrointest Liver Physiol 2005; 274: 103844.
  • 13
    Jones K, Edelbroek M, Horowitz M, Sun WM, Dent J, Muecke T. Evaluation of antral motility in humans using manometry and scintigraphy. Gut 1985; 37: 6438.
  • 14
    Andrews JM, O'Donovan DG, Hebbard GS, Malbert CH, Doran SM, Dent J. Human duodenal phase III migrating motor complex activity is predominantly antegrade, as revealed by high-resolution manometry and colour pressure plots. Neurogastroenterol Motil 2002; 14: 3318.
  • 15
    Calvert EL, Whorwell PJ, Houghton LA. Inter-digestive and post-prandial antro-pyloro-duodenal motor activity in humans: effects of 5-hydroxytryptamine 1 receptor agonism. Aliment Pharmacol Ther 2004; 19: 80515.
  • 16
    Feinle C, O'Donovan D, Doran S, Andrews JM, Wishart J, Chapman I, Horowitz M. Effect of fat digestion on appetite, APD motility, and gut hormones in response to duodenal fat infusion in humans. Am J Physiol Gastrointest Liver Physiol 2003; 284: G798807.
  • 17
    Andrews JM, Doran SM, Hebbard GS, Malbert CH, Horowitz M, Dent J. Nutrient-induced spatial patterning of human duodenal motor function. Am J Physiol Gastrointest Liver Physiol 2001; 280: G5019.
  • 18
    Verhagen MAMT, Samson M, Smout AJPM. Effects of intraduodenal glucose infusion on gastric myoelectric activity and antropyloroduodenal motility. Am J Physiol Gastrointest Liver Physiol 1998; 37: G103844.
  • 19
    Heddle R, Dent J, Toouli J, Read NW. Topography and measurement of pyloric pressure waves and tone in humans. Am J Physiol Gastrointest Liver Physiol 1988; 255: G4907.
  • 20
    Feltrin KL, Little TJ, Meyer JH et al. Effects of intraduodenal fatty acids on appetite, antropylorduodenal motility, and plasma CCK and GLP-1 in humans vary with their chain length. Am J Physiol Regul Integr Comp Physiol 2004; 287: R52433.
  • 21
    Clouse RE, Parks T, Haroian LR, Zakko SF. Development and clinical validation of a solid-state high-resolution pressure measurement system for simplified and consistent esophageal manometry. Am J Gastroenterol 2003; 98 (Suppl.): S323.
  • 22
    Savoye-Collet C, Savoye G, Smout A. Determinants of transpyloric fluid transport: a study using combined real-time ultrasound, manometry, and impedance recording. Am J Physiol Gastrointest Liver Physiol 2003; 285: G114752.
  • 23
    Pandolfino JE, El-Serag HB, Zhang Q, Shah N, Ghosh S, Kahrilas PJ. Obesity: a challenge to esophagogastric junction integrity. Gastroenterology 2006; 130: 63949.
  • 24
    Fisher RS, Cohen S. Physiologic characteristics of the human pyloric sphincter. Gastroenterology 1973; 64: 6777.
  • 25
    Valenzuela JE, Defilippi C, Csendes A. Manometric studies on the human pyloric sphincter. Effect of cigarette smoking, metoclopramide and atropine. Gastroenterology 1976; 70: 4813.
  • 26
    Ehrlein HJ. Gastric and duodenal motility in relation to duodenagastric reflux in healthy dogs. Scand J Gastroenterol 1981; 16 (Suppl. 67): 237.
  • 27
    Anderson S, Grossman MI. Profile of pH, pressure and potential difference at gastroduodenal junction in man. Gastroenterology 1965; 49: 36471.
  • 28
    Gupta P, Rao SSC. Attenuation of isolated pyloric pressure waves in gastroparesis in response to botulinum toxin injection: a case report. Gastrointest Endosc 2002; 56: 7702.
  • 29
    Pandolfino JE, Ghosh SK, Zhang Q, Jarosz A, Shah N, Kahrilas PJ. Quantifying EGJ morphology and relaxation with high-resolution manometry: a study of 75 asymptomatic volunteers. Am J Physiol Gastrointest Liver Physiol 2006; 290: G103340.