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Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Background  Oesophageal manometry (OM) is used to diagnose oesophageal motor disorders. Normal values of OM among United States ethnic groups are only available for Hispanic Americans (HA).

Aim  To obtain normal values of OM in adult African American (AA) volunteers, compare these with those obtained in HA and non-Hispanic white (nHw) volunteers to determine if ethnic variation in normal oesophageal motor function exists.

Methods  Healthy AA, HA and nHw were recruited from the Jacksonville metropolitan area. Ethnicity was self-reported. Exclusion criteria were symptoms suggestive of oesophageal disease, medication use or concurrent illness affecting OM. All underwent OM using a solid-state system with wet swallows. Resting lower oesophageal sphincter (LOS) pressure and LOS length were measured at mid-expiration, while per cent peristaltic contractions, distal oesophageal contraction velocity, amplitude and duration were measured after 5 cc water swallows.

Results  Fifty-six AA, 20 HA and 48 nHw were enrolled. All completed OM. AA had significantly higher resting LOS pressure, LOS length and distal oesophageal contraction duration than nHw (< 0.05).

Conclusions  Significant ethnic exist in OM findings between AA and nHw. These underscore the need for ethnic specific reference values for OM to allow for correct diagnosis of oesophageal motor disorders in AA.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Oesophageal manometry (OM) is the gold standard examination for diagnosing motor function disorders of the lower oesophageal sphincter (LOS), oesophageal body and upper oesophageal sphincter. These disorders include gastro-oesophageal reflux disease, achalasia, ineffective oesophageal motility and hypertensive LOS. Presently accepted normal values of the US volunteers have been published previously.1–6 However, these normal data were obtained in either non-Hispanic white (nHw) or Hispanic American (HA) volunteers. Recently, NIH has recognized the need to include minorities and women in clinical investigation to define benefit and risk across ethnic and gender lines. Normal physiological parameters such as haemoglobin levels, white blood cell count, pulmonary function tests and prostate specific antigen levels are ethnic specific.7–12 Similarly, ethnic-specific criteria for the diagnosis of oesophageal motor disorders may improve evaluation and treatment of minority subjects. The aim of this study was to obtain normal values of OM in African American (AA) volunteers and compare them with those obtained from nHw and HA volunteers of the Jacksonville, Florida metropolitan area.

Methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Subjects

AA, HA and nHw volunteers from the Jacksonville metropolitan area were recruited by flyer and word of mouth for the study. All volunteers received a financial incentive for their participation. Inclusion criteria were self-described ethnicity as either AA, HA or nHw. Exclusion criteria included symptoms suggestive of oesophageal disease (dysphagia, regurgitation, chest pain, odynophagia, heartburn) occurring at least once per month, diseases that may affect oesophageal function (diabetes mellitus, Reynaud’s disease, scleroderma, autonomic neuropathies, cerebrovascular accidents, seizures, alcoholism, prior oesophageal surgery, gastro-oesophageal reflux disease, peptic ulcer disease) and medications that may affect oesophageal function (calcium channel blockers, antacids, proton pump inhibitors, prokinetics, theophylline). The study was approved by the Institutional Review Board of The University of Florida Health Science Center/Jacksonville, and informed consent was obtained from every volunteer.

Oesophageal manometry

Each volunteer underwent standard OM using a four-channel solid-state catheter (Medtronic Inc., Minneapolis, MN, USA). The most distal transducer of the catheter is circumferential with the remaining three evaluating 120° angles. The sensors, spaced 5 cm apart, were used to record the following data: (i) resting LOS pressure, (ii) distal oesophageal wave contraction amplitude, (iii) distal oesophageal wave contraction duration and (iv) distal oesophageal wave contraction velocity. All output from pressure sensors are connected to a multipurpose data acquisition device (Microdigitrapper; Medtronic Inc.) and a desktop computer system (Dell, Round Rock, TX, USA) using physiographic software for recording and data analysis.

All volunteers were studied in the supine position after an overnight fast. Swallows were detected by direct visualization. The catheter was introduced nasally after topical anaesthesia administration (Cetacaine spray; Cetylite industries, Pennsauken, NJ, USA) and positioned with all sensors in the stomach. Measurements were obtained after an acclimation period of 5 min. Resting intra-gastric pressure was used as a zero reference for all data acquired. Resting LOS pressure (LOSP) was measured at mid-expiration by three pull-throughs using increments of 0.2 cm/s until all sensors passed into the oesophagus. The volunteers were instructed not to swallow during this segment of the examination. The catheter was then immobilized with the distal oesophageal recording site 3 cm above the upper point of the LOS. Recording sites for evaluation of oesophageal peristalsis were located 3, 8, and 13 and 18 cm above the upper point of the LOS. Oesophageal peristalsis was assessed with 10 wet swallows of 5 cc of water at room temperature done a minimum of 30 s apart. All study procedures were completed by a registered nurse previously trained in performing OM.

Data analysis

All studies were reviewed by a single investigator (KJV) without knowledge of the volunteer’s age, gender or ethnicity. Data collection was performed using a standardized data abstraction protocol created prior to the investigation. Resting LOSP was determined from gastric baseline to mid-expiratory sphincteric pressure. Resting LOSP values were expressed as the mean of LOS profiles obtained during pull-throughs. LOS length was determined by sensor entrance and exit from the high pressure zone. Oesophageal contraction amplitude was measured from the mean oesophageal baseline to the peak of the contraction for the distal two transducers. Duration of contraction was measured from the onset of wave upstroke to the return to oesophageal baseline. Velocity was calculated by measuring the distance between the on set of contractions, taking into account the distance (5 cm) between recording sites. Simultaneous contractions were defined as coincident onset of waves at two adjacent recording sites. Nontransmitted contractions were defined as a wave not transmitted along all three recording sites.

Statistical analysis

All values of LOSP, LOS length, per cent peristaltic contractions and distal oesophageal body contraction amplitude, duration and velocity are reported as means ± s.d. for each group of volunteers. Mean values for both groups represent the mean of individual values. Kolmogorov–Smirnov test of normality was used to assess distribution of the data. Student’s t-test was used for parametric comparisons between groups. Differences between groups will be considered significant if < 0.05. Data analysis was performed using jmp 5.0 for Windows (SAS Institute Inc., Cary, NC, USA).

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Demographics of study population

One hundred and twenty-four individuals meeting entry criteria volunteered for the study. All completed OM. Of the 124 volunteers, 56 (45%) described themselves as AA, 20 (16%) HA and 48 (39%) as nHw. Males comprised 48% of the AA and nHw groups and 50% of the HA group. The AA group was older than the nHw group (< 0.05, Table 1). Body mass index was elevated in the AA and HA groups in comparison to nHw (< 0.05, Table 1). No difference was noted between ethnic groups regarding smoking prevalence. Kolmogorov–Smirnov test confirmed that data for all manometric parameters were normally distributed.

Table 1.   Demographic data of the 124 healthy volunteers
 AA (= 56)HA (= 20)nHw (= 48)
  1. AA, African Americans; HA, Hispanic Americans; nHw, non-Hispanic whites.

  2. < 0.05 between AA and nHw only.

  3. † < 0.05 between AA/HA and nHw.

Male/female (%)48/5250/5048/52
Age range (years)18–5619–4718–57
Age (mean + s.d.), years34.9 ± 10.7*33.4 ± 8.330.5 ± 10.6
BMI31.7 ± 7.2131.2 ± 7.4425.9 ± 5.13†
Smokers (%)111010

Lower oesophageal sphincter

The mean resting LOSP at mid-expiration was significantly higher in AA than in nHw (resting LOSP, < 0.03). The difference observed in resting LOSP between AA and HA approached statistical significance only (resting LOSP, = 0.0685). LOS length in AA and HA were significantly longer than that seen in nHw (LOS length AA vs. nHw, < 0.04 and HA vs. nHw, < 0.002; Table 2). Gender and age had no effect on the LOS variables.

Table 2.   Oesophageal manometry parameters in healthy African Americans (= 56), Hispanic Americans (= 20) and non-Hispanic whites (= 48)
Oesophageal manometry parameter AA (mean ± s.d.) HA (mean ± s.d.) nHw (mean ± s.d.)P-value
  1. AA, African Americans; HA, Hispanic Americans; nHw, non-Hispanic whites; LOS, lower oesophageal sphincter.

Resting LOS pressure (mmHg)32.3 ± 13.926.1 ± 9.327.1 ± 9.6<0.03 (AA vs. nHw)
LOS length (cm)3.66 ± 0.854.05 ± 0.823.32 ± 0.83<0.04 (AA vs. nHw); <0.002 (HA vs. nHw)
% Peristaltic contraction95.1 ± 4.990 ± 1094.1 ± 5.9N.S.
Distal oesophageal contraction amplitude (mmHg)97.2 ± 43.899 ± 31.485.7 ± 31.2N.S.
Distal oesophageal contraction velocity (cm/s)3.59 ± 2.54.85 ± 2.24.73 ± 3.49N.S.
Distal oesophageal contraction duration (s)4.45 ± 1.754.27 ± 1.273.82 ± 1.260.04 (AA vs. nHw)

Oesophageal body function

The amplitude, duration and velocity of peristaltic waves increased distally along the oesophagus. Distal oesophageal body contraction duration was significantly higher in AA compared with nHw only (< 0.04). Oesophageal body contraction amplitude, velocity or per cent peristaltic contractions were similar in all groups. Age or gender did not influence the oesophageal body function results.

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

The present study of oesophageal pressures in 124 volunteers is the largest group of healthy controls5, 6, 13 investigated using modern manometric techniques. This investigation was designed to obtain normal values of OM in AA and compare them with those obtained in nHw and HA volunteers of the Jacksonville, Florida metropolitan area to test the hypothesis that normal values of OM established in nHw/HA populations can be applied to AA. The results indicate that resting LOS pressure, LOS length and distal oesophageal contraction duration were significantly higher in normal AA compared with nHw. Comparing AA to HA, resting LOS pressure and distal oesophageal contraction duration were higher in AA, but LOS length and distal oesophageal contraction velocity were lower in AA. None of these differences achieved statistical significance between AA and HA, but could be because of the size of the HA sample. Oesophageal body contraction amplitude, velocity or per cent peristaltic contractions were similar between the two groups. The overall implication of these findings is that applying normal values of LOS pressure and length obtained from nHw/HA would underdiagnose LOS-related motility disorders in AA patients.

The difference in resting lower oesophageal pressure, LOS length and distal oesophageal contraction duration between healthy nHw/HA and AA has not been observed in previous studies as the ethnicity of the volunteers was not defined or only HA were compared with nHw.1–6,13 The normal values for resting LOS pressure, LOS length and distal oesophageal function obtained in nHw during this investigation differ from the reports by Richter and associates, Vega et al. as well as Grande et al. on normal/healthy subjects.5,6,13 This effect may be, in part, because of the manometric catheter systems used for measurement.

Other investigators have reported decreases in resting LOS pressure and oesophageal body function with increasing age.5,13,14 This was not observed in this study in either ethnic group. Unfortunately, the age distribution of our population did not allow for sub-analysis of age ranges performed in the previous investigations. However, the AA group was slightly yet significantly older that the nHw presently studied. On the basis of prior investigations, one would anticipate decreased function in the AA group as compared to nHw or HA. However, that was not observed in this study. Inclusion of volunteers greater than age 60 would allow for adequate assessment of oesophageal function across multiple age groups. Also, significantly higher body mass index was noted in both the AA and HA groups in comparison to nHw. However, Wu et al. recently did not observe differences in RLOSP at the indexes seen in the present investigation.15 Finally, no gender-related differences in resting LOSP were observed in the present investigation in accordance with previous evaluations of normal oesophageal function.5,13,14

The difference observed in resting LOSP between the groups has implication for the correct diagnosis of motility disorders in AA patients. Using normal values of only nHw or HA subjects would under diagnose LOS-related motor disorders in AA patients. Use of ethnic specific reference values would allow for correct diagnosis of such disorders.

The variation in LOS length and distal oesophageal contraction velocity between ethnic groups was small, yet significant. However, these findings may not have clinical implications in the healthy state. Investigations of bolus transit in healthy individuals, acid exposure and manometric function in disease states between ethnic groups could provide further insight into the clinical significance of these interesting observations.

Oesophageal manometry is the primary clinical examination to either diagnose or exclude the presence of motility disorders of the oesophagus. Johnston and associates clearly revealed that abnormal manometric findings lead to changes in the clinical management of patients studied for unexplained chest pain and dysphagia.16 Incorrect diagnosis and the resulting inappropriate recommendation for therapy can be minimized if ethnic-specific normal values of OM are applied. This investigation indicates that healthy AA compared to nHw and HA of north Florida have different OM parameters and appropriate diagnosis could not be made using such parameters obtained only from nHw or HA. This is in agreement with previous works evaluating physiological and laboratory values in ethnic groups, revealing differences between AA and nHw subjects.7–12

In summary, the results of this study suggest that presently accepted normal values of LOS pressure and length obtained from nHw or HA may not allow for the accurate diagnosis of LOS-related motility disorders in AA patients. Development of ethnic specific normal values for AA in clinical motility laboratories are needed for appropriate diagnosis of oesophageal motor disorders in these patients. Further studies to determine if age-related changes in oesophageal function in AA occurs in a similar fashion as reported in the literature among nHw would be desirable.

Acknowledgements

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

The authors would like to thank Myrna Mattos, RN, Sandra Canham MS, AHIP, Nancy Chaffin and Shannon Lloyd for their assistance in this investigation. Declaration of personal and funding interests: None.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References
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