- Email: [email protected]
Lower esophageal sphincter position in premature infants cannot be correctly estimated with current formulas
L
Lower esophageal sphincter position in premature infants cannot be correctly estimated with current formulas
Taher I. Omari, BSc, PhD, Marc A. Benninga, MD, PhD, Ross R. Haslam, MBBS, FRACP, Christopher P. Barnett, MBBS, FRACP, Geoff P. Davidson, MBBS, MD, FRACP, and John Dent, MBBChir, PhD, FRACP, FRCP Objectives: Strobel’s formula (Esophageal length = 5 + 0.252 × Height) is frequently used as a guide for determining the distance from the nares to the lower esophageal sphincter (LES) in term infants. The aim of this study was to examine this relationship in premature infants. Study design: The distance from nares to LES was manometrically determined in 156 premature infants (26-40 weeks’ postmenstrual age; body weights of 610-3050 g). The ability of body weight, height (body length), head circumference, and postmenstrual age to predict the manometrically determined LES position was evaluated with linear and non-linear regression analyses. Results: Body weight and body length were the most predictive of distance from nares to LES (r 2 = 0.848 and 0.802, respectively). These relationships were non-linear and, in the case of body length, deviated substantially from Strobel’s model. Conclusions: In premature neonates, a different formula is needed for prediction of the distance between nares and LES than that applied to term infants and children. (J Pediatr 1999;135:522-5)
Twenty-four–hour esophageal pH monitoring is used in the diagnosis of gastroesophageal reflux disease and to evaluate the effectiveness of anti-re-
flux therapy.1-3 The performance of reliable pH monitoring studies is critically dependent on accurate positioning of the pH sensor at a fixed distance
above the lower esophageal sphincter. Various methods, including manometry,4,5 fluoroscopy,6-10 endoscopy,11,12 and the identification of the gastroesophageal pH “step up”13-15 have been used to enable pH probe positioning. Of these, manometry and fluoroscopy are the most accurate. See related article, p. 517. Strobel et al16 and, more recently, Staiano and Clouse17 used manometric techniques to measure the distance from the nares to the proximal margin of the LES in human subjects of term age and older. Both studies described a highly significant linear correlation between body length and esophageal length and derived mathematical formulas, which are now used extensively to estimate the distance from the nares to the LES for the purposes of pH monitoring without performing manometry or fluoroscopy.18-24 LES PMA
Lower esophageal sphincter Postmenstrual age
From the Gastroenterology Unit and the Neonatal Medicine Unit, Women’s and Children’s Hospital, North Adelaide, Australia; and the Department of Gastrointestinal Medicine, Royal Adelaide Hospital, Adelaide, Australia.
Supported by National Health and Medical Research Council of Australia, Women’s and Children’s Hospital Research Foundation, Channel 7 Children’s Research Foundation of South Australia, and JH and JD Gunn Foundation. Dr Benninga’s involvement in this project was supported by the Ter Meulen Fund, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands, The Netherlands Organisation for Scientific Research and the Netherlands Digestive Diseases Foundation. Submitted for publication Dec 3, 1998; revision received Feb 19, 1999; accepted May 12, 1999. Taher I. Omari, BSc, PhD, Gastroenterology Unit, Women’s and Children’s Hospital, 72 King William Rd, North Adelaide, Australia 5006. Copyright © 1999 by Mosby, Inc. 0022-3476/99/$8.00 + 0 9/22/100094
522
Although Strobel’s formula (Esophageal length = 5 + 0.252 × Height) has been considered to be an appropriate methodology for pH catheter positioning in pediatric patients,1 the relationship between body length and esophageal length in infants younger than term age has not been determined. Despite this, some pH monitoring studies performed in premature in-
OMARI ET AL
THE JOURNAL OF PEDIATRICS VOLUME 135, NUMBER 4
Table. Regression equations for predicting the distance from nares to LES from PMA, body length, head circumference, and weight
Variable PMA (wk)
Body length (cm)
Head circumference (cm)
Weight (g)
Regression model Linear Logarithmic Polynomial (3rd order) Linear Logarithmic Polynomial (3rd order) Linear Logarithmic Polynomial (3rd order) Linear Logarithmic Polynomial (3rd order)
Regression equations y = –1.632 + 0.491x y = –44.224 + 16.827ln(x) y = –41.671 + 2.327x + 0.003x2 – 4.725E–4x3 y = –0.762 + 0.377x y = –44.127 + 15.853ln(x) y = –123.72 + 8545x – 0.178x2 + 0.001x3 y = –0.938 + 0.527x y = –38.877 + 15.819ln(x) y = –41.029 + 4.075x – 0.81x2 – 4.793E–4x3 y = 10.285 + 0.003x y = –20.216 + 4.73ln(x) y = 1.482 + 0.016x – 6.072e–6x2 + 8.361E–10x3
r 2 Value 0.571 0.595 0.656 0.725 0.754 0.802 0.722 0.751 0.789 0.725 0.826 0.848
The correlation between distance from nares to LES and every variable was statistically significant for all regression models used (P < .0001). For regression equations, y = distance from nares to LES in centimeters, x = variable tested. NB: Polynomial equations are truncated at an accuracy of 3 decimal places only.
fants have nevertheless applied Strobel’s formula to position esophageal pH probes.18,19,25 Over the last 5 years, our group has performed a large number of esophageal motility studies in premature babies during which the distance from the nares to the LES was manometrically determined. The aim of this study was to use these data to assess the accuracy of Strobel’s formula for pH probe positioning in the premature age group.
METHODS Between February 1994 and October 1998, 156 infants (74 boys and 82 girls) underwent esophageal motility studies as part of an ongoing medical research program for the evaluation of esophageal motility and mechanisms of gastroesophageal reflux in this age group. Esophageal motility was recorded by perfusion manometry in infants weighing between 610 and 3050 g (mean, 1998 ± 468 g) and ranging in postmenstrual age (gestation at birth + postnatal age) from 26 to 40 weeks (mean, 35 ± 2 weeks). The manometric approach used in this study has been previously described.26-28 In brief, studies were performed by using a pur-
pose-built silicone rubber micromanometric catheter (outer diameter, 2.0 mm), which had 9 recording lumina (0.35 mm inside diameter) arranged around a larger feeding channel. In addition, the catheter incorporated a 2-cm long sleeve sensor for accurate monitoring of the LES pressure.29,30 As part of the procedure to position the manometric assembly with the sleeve astride the LES, the location of the LES was determined manometrically with pullback of the perfused side hole at the top of the sleeve across the pressure inversion point of the LES. The distance from the nares to the LES was then recorded. This methodology is consistent with that used by Strobel et al.16 Body weight was measured by a research nurse at the time of manometric study with a daily calibrated balance. Body length and head circumference estimates were obtained by retrospective examination of the medical records; standard nursery practice was to take these measurements weekly with an accurate anthropometer. All study protocols used were approved by the ethics research committee of the Women’s and Children’s Hospital, Adelaide, South Australia, and written informed parental consent was obtained.
Statistical Analysis Associations between different variables were assessed by linear, logarithmic, and polynomial regression models with the data analysis program Statview 4.1 (Abacus Concepts Inc, Berkeley, Calif). A P value of <.05 was considered to indicate statistical significance of correlation.
RESULTS The relationships between distance from nares to LES and PMA, body length, body weight, and head circumference are shown in the Table. All variables correlated significantly with distance from nares to LES, regardless of the model used for regression analyses. However, in all cases a better curve fit was achieved by using the non-linear regression models. Of the variables tested, weight was the most predictive of distance from nares to LES (polynomial r 2 = 0.848); body length and head circumference were similar to each other but less predictive than weight (polynomial r 2 = 0.802 and 0.789, respectively); and PMA was the least predictive of the variables (polynomial r 2 = 0.656). A comparison of the relationship between distance from nares to LES and 523
OMARI ET AL
THE JOURNAL OF PEDIATRICS OCTOBER 1999
Fig 1. Individual data from 156 premature infants showing relationship between distance from nares to LES and body length. Included is the linear relationship predicted by using Strobel’s formula (dotted line).
was the least predictive variable. On the basis of these data and because of the inherent difficulties associated with deriving values from complex polynomial formulas, our group now routinely uses either of the predictive graphs (Fig 2) for the purposes of positioning esophageal pH probes in preterm infants. Our data show that existing formulas for estimation of LES position are inaccurate in premature infants. The use of these formulas for the purposes of positioning of pH probes will result in the sensor being positioned too close to the LES, with the possibility that clinically misleading data will be obtained. We would like to acknowledge the help and assistance of the many people who have worked in our unit during the period over which these data were compiled: Mrs Ros Lontis, Mrs Louise Goodchild, Mr Antonie Snel, Ms Wendy Goldsworthy, Dr Robert Fraser, Dr Kasu Miki, Dr Hisa Kawahara, Dr Chellam Kirubakaran, and Mr Malcolm Bakewell.
A
B
Fig 2. Predictive graphs for estimation of distance from nares to LES in premature infants by using weight (A) or body length (B). Graphs are based on the line of best fit with a 3rd-order polynomial regression model.
body length with the theoretical values generated by Strobel’s formula (Fig 1) indicates that the measured values agreed with Strobel’s model in premature infants with body lengths over 40 cm but deviated substantially from Strobel’s model in infants shorter than 40 cm. No discernible differences in these relationships were observed between boys and girls.
DISCUSSION This study has examined the relationship between the distance from nares to LES and variables of age and size in a population of premature infants. These data indicate that Strobel’s formula and other similar predictive formulas, which have been derived 524
in older infants and children, overestimate the distance from nares to LES in premature infants. In this study Strobel’s formula accurately predicted the distance from nares to LES of premature infants with body lengths over 40 cm, but not shorter infants. In shorter (smaller, younger) infants, the relationships between distance from nares to LES and all variables examined were non-linear because of the higher relative growth rate of very preterm infants compared with older infants. It would also seem, from other studies, that Strobel’s formula is less useful in children over 100 cm long1 and/or over 2 years of age.17 Of the variables examined, body weight was most predictive of distance from nares to LES, followed by body length and head circumference. PMA
REFERENCES 1. The Working Group of the European Society of Pediatric Gastroenterology and Nutrition. A standardized protocol for methodology of esophageal pH monitoring and interpretation of the data for the diagnosis of gastroesophageal reflux. J Pediatr Gastroenterol Nutr 1992;14:467-71. 2. Davidson G. Usefulness of oesophageal pH monitoring. Aust J Paediatr 1985;21:243-4. 3. Sondheimer J. Continuous monitoring of distal esophageal pH: a diagnostic test for gastroesophageal reflux in infants. J Pediatr 1980;96:804-7. 4. Newell S, Booth I, Morgan M, Durbin G, McNeish A. Gastro-oesophageal reflux in preterm infants. Arch Dis Child 1989;64:780-6. 5. Gustafsson P, Tibbling L. 24-hour oesophageal two-level pH monitoring in healthy children and adolescents. Scand J Gastroenterol 1988;23:91-4. 6. Spencer J. Prolonged pH recording in the study of gastroesophageal reflux. Br J Surg 1969;56:912-4. 7. Kalloor G, Deshpande A, Collis J. Observation on oesophageal length. Thorax 1976;31:284-8. 8. Jolley S, Johnson D, Herbst J, Pena A, Garnier C. An assessment of gas-
OMARI ET AL
THE JOURNAL OF PEDIATRICS VOLUME 135, NUMBER 4
9.
10.
11.
12.
13.
14.
15.
troesophageal reflux in children by extended pH monitoring of the distal esophagus. Surgery 1978;84:16-24. Friesen C, Hayes R, Hodge C, Roberts C. Comparison of methods of assessing 24-hour intraesophageal pH recordings in children. J Pediatr Gastroenterol Nutr 1992;14:252-5. Vandenplas Y, Derde M, Piepsz A. Evaluation of reflux episodes during simultaneous esophageal pH monitoring and gastroesophageal reflux scintigraphy in children. J Pediatr Gastroenterol Nutr 1992;14:256-60. Owen W. The role of the oesophageal laboratory. Gastroenterol Pract 1988; Feb/Mar:20-6. Donald I, Ford G, Wilkinson S. Is 24h ambulatory oesophageal pH monitoring useful in a district hospital? Lancet 1987;10:89-92. Marples M, Mughal M, Bancewicz J. Can an esophageal pH electrode be accurately positioned without manometry? In: Siewert J, Holscher A, editors. Diseases of the esophagus. Berlin: Springer-Verlag; 1987. p. 789-91. Kantrowitz P, Corson J, Fleischli D, Skinner D. Measurement of gastroesophageal reflux. Gastroenterology 1969;56:666-74. Rokkas T, Anggianisah A, Dorrington L, Owen W, Sladen G. Accurate positioning of the pH probe in the oesophagus without manometry. Ital J Gastroenterol 1987;19:176-8.
16. Strobel C, Byrne W, Ament M, Euler A. Correlation of esophageal lengths in children with height: application to the Tuttle test without prior esophageal manometry. J Pediatr 1979;94:81-4. 17. Staiano A, Clouse R. Value of subject height in predicting lower esophageal sphincter location. Am J Dis Child 1991;145:1424-7. 18. Sutphen J, Dillard V. Effects of maturation and gastric acidity on gastroesophageal reflux in infants. Am J Dis Child 1986;140:1062-4. 19. Blumenthal I, Lealman G. Effect of posture on gastro-oesophageal reflux in the newborn. Arch Dis Child 1982; 57:555-6. 20. Tobin J, McCloud P, Cameron D. Posture and gastro-oesophageal reflux: a case for left lateral positioning. Arch Dis Child 1997;76:254-8. 21. Heacock H, Jeffery H, Baker J, Page M. Influence of breast versus formula milk on physiological gastroesophageal reflux in healthy, newborn infants. J Pediatr Gastroenterol Nutr 1992;14: 41-6. 22. Jeffery H, Page M. Developmental maturation of gastro-oesophageal reflux in preterm infants. Acta Paediatr 1995;84:245-50. 23. Barabino A, Constantini M, Ciccone M, Pesce F, Parodi B, Gatti R. Reliability of short-term esophageal pH monitoring versus 24-hour study. J Pediatr Gastroenterol Nutr 1995;21:87-90.
24. Rode H, Stunden R, Millar A, Cywes S. Esophageal pH assessment of gastroesophageal reflux in 18 patients and the effect of two prokinetic agents: cisapride and metoclopramide. J Pediatr Surg 1987;22:931-4. 25. Ng S-Y, Quak S-H. Gastroesophageal reflux in preterm infants: norms for extended distal esophageal pH monitoring. J Pediatr Gastroenterol Nutr 1998;27:411-4. 26. Omari T, Miki K, Fraser R, Davidson G, Haslam R, Goldsworthy W, et al. Esophageal body and lower esophageal sphincter function in healthy premature infants. Gastroenterology 1995; 109:1757-64. 27. Omari T, Miki K, Davidson G, Fraser R, Haslam R, Goldsworthy W, et al. Characterisation of lower oesophageal sphincter relaxation in healthy preterm infants. Gut 1997;40:370-5. 28. Omari T, Barnett C, Snel A, Goldsworthy W, Haslam R, Davidson G, et al. Mechanisms of gastroesophageal reflux in healthy premature infants. J Pediatr 1998;133:650-4. 29. Dent J. A new technique for continuous sphincter pressure measurement. Gastroenterology 1976;71:263-7. 30. Omari T, Bakewell M, Fraser R, Davidson G, Dent J. Intraluminal micromanometry: an evaluation of the dynamic performance of micro-extrusions and sleeve sensors. Neurogastroenterol Motil 1996;8:241-5.
BOUND VOLUMES AVAILABLE TO SUBSCRIBERS Bound volumes of the 1999 issues of The Journal of Pediatrics are available to subscribers (only) from the Publisher, at a cost of $100.00 for domestic, $125.19 for Canadian, and $117.00 for international subscribers, for Vol. 134 (January-June) and Vol. 135 (July-December), shipping charges included. Each bound volume contains subject and author indexes, and all advertising is removed. Copies are shipped within 60 days after publication of the last issue in the volume. The binding is durable buckram, with the Journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Mosby, Inc., Subscription Services, 11830 Westline Industrial Dr., St. Louis, MO 63146-3318, USA/800-4534351, or 314-453-4351. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular Journal subscription.
525
Lower esophageal sphincter position in premature infants cannot be correctly estimated with current formulas
Taher I. Omari, BSc, PhD, Marc A. Benninga, MD, PhD, Ross R. Haslam, MBBS, FRACP, Christopher P. Barnett, MBBS, FRACP, Geoff P. Davidson, MBBS, MD, FRACP, and John Dent, MBBChir, PhD, FRACP, FRCP Objectives: Strobel’s formula (Esophageal length = 5 + 0.252 × Height) is frequently used as a guide for determining the distance from the nares to the lower esophageal sphincter (LES) in term infants. The aim of this study was to examine this relationship in premature infants. Study design: The distance from nares to LES was manometrically determined in 156 premature infants (26-40 weeks’ postmenstrual age; body weights of 610-3050 g). The ability of body weight, height (body length), head circumference, and postmenstrual age to predict the manometrically determined LES position was evaluated with linear and non-linear regression analyses. Results: Body weight and body length were the most predictive of distance from nares to LES (r 2 = 0.848 and 0.802, respectively). These relationships were non-linear and, in the case of body length, deviated substantially from Strobel’s model. Conclusions: In premature neonates, a different formula is needed for prediction of the distance between nares and LES than that applied to term infants and children. (J Pediatr 1999;135:522-5)
Twenty-four–hour esophageal pH monitoring is used in the diagnosis of gastroesophageal reflux disease and to evaluate the effectiveness of anti-re-
flux therapy.1-3 The performance of reliable pH monitoring studies is critically dependent on accurate positioning of the pH sensor at a fixed distance
above the lower esophageal sphincter. Various methods, including manometry,4,5 fluoroscopy,6-10 endoscopy,11,12 and the identification of the gastroesophageal pH “step up”13-15 have been used to enable pH probe positioning. Of these, manometry and fluoroscopy are the most accurate. See related article, p. 517. Strobel et al16 and, more recently, Staiano and Clouse17 used manometric techniques to measure the distance from the nares to the proximal margin of the LES in human subjects of term age and older. Both studies described a highly significant linear correlation between body length and esophageal length and derived mathematical formulas, which are now used extensively to estimate the distance from the nares to the LES for the purposes of pH monitoring without performing manometry or fluoroscopy.18-24 LES PMA
Lower esophageal sphincter Postmenstrual age
From the Gastroenterology Unit and the Neonatal Medicine Unit, Women’s and Children’s Hospital, North Adelaide, Australia; and the Department of Gastrointestinal Medicine, Royal Adelaide Hospital, Adelaide, Australia.
Supported by National Health and Medical Research Council of Australia, Women’s and Children’s Hospital Research Foundation, Channel 7 Children’s Research Foundation of South Australia, and JH and JD Gunn Foundation. Dr Benninga’s involvement in this project was supported by the Ter Meulen Fund, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands, The Netherlands Organisation for Scientific Research and the Netherlands Digestive Diseases Foundation. Submitted for publication Dec 3, 1998; revision received Feb 19, 1999; accepted May 12, 1999. Taher I. Omari, BSc, PhD, Gastroenterology Unit, Women’s and Children’s Hospital, 72 King William Rd, North Adelaide, Australia 5006. Copyright © 1999 by Mosby, Inc. 0022-3476/99/$8.00 + 0 9/22/100094
522
Although Strobel’s formula (Esophageal length = 5 + 0.252 × Height) has been considered to be an appropriate methodology for pH catheter positioning in pediatric patients,1 the relationship between body length and esophageal length in infants younger than term age has not been determined. Despite this, some pH monitoring studies performed in premature in-
OMARI ET AL
THE JOURNAL OF PEDIATRICS VOLUME 135, NUMBER 4
Table. Regression equations for predicting the distance from nares to LES from PMA, body length, head circumference, and weight
Variable PMA (wk)
Body length (cm)
Head circumference (cm)
Weight (g)
Regression model Linear Logarithmic Polynomial (3rd order) Linear Logarithmic Polynomial (3rd order) Linear Logarithmic Polynomial (3rd order) Linear Logarithmic Polynomial (3rd order)
Regression equations y = –1.632 + 0.491x y = –44.224 + 16.827ln(x) y = –41.671 + 2.327x + 0.003x2 – 4.725E–4x3 y = –0.762 + 0.377x y = –44.127 + 15.853ln(x) y = –123.72 + 8545x – 0.178x2 + 0.001x3 y = –0.938 + 0.527x y = –38.877 + 15.819ln(x) y = –41.029 + 4.075x – 0.81x2 – 4.793E–4x3 y = 10.285 + 0.003x y = –20.216 + 4.73ln(x) y = 1.482 + 0.016x – 6.072e–6x2 + 8.361E–10x3
r 2 Value 0.571 0.595 0.656 0.725 0.754 0.802 0.722 0.751 0.789 0.725 0.826 0.848
The correlation between distance from nares to LES and every variable was statistically significant for all regression models used (P < .0001). For regression equations, y = distance from nares to LES in centimeters, x = variable tested. NB: Polynomial equations are truncated at an accuracy of 3 decimal places only.
fants have nevertheless applied Strobel’s formula to position esophageal pH probes.18,19,25 Over the last 5 years, our group has performed a large number of esophageal motility studies in premature babies during which the distance from the nares to the LES was manometrically determined. The aim of this study was to use these data to assess the accuracy of Strobel’s formula for pH probe positioning in the premature age group.
METHODS Between February 1994 and October 1998, 156 infants (74 boys and 82 girls) underwent esophageal motility studies as part of an ongoing medical research program for the evaluation of esophageal motility and mechanisms of gastroesophageal reflux in this age group. Esophageal motility was recorded by perfusion manometry in infants weighing between 610 and 3050 g (mean, 1998 ± 468 g) and ranging in postmenstrual age (gestation at birth + postnatal age) from 26 to 40 weeks (mean, 35 ± 2 weeks). The manometric approach used in this study has been previously described.26-28 In brief, studies were performed by using a pur-
pose-built silicone rubber micromanometric catheter (outer diameter, 2.0 mm), which had 9 recording lumina (0.35 mm inside diameter) arranged around a larger feeding channel. In addition, the catheter incorporated a 2-cm long sleeve sensor for accurate monitoring of the LES pressure.29,30 As part of the procedure to position the manometric assembly with the sleeve astride the LES, the location of the LES was determined manometrically with pullback of the perfused side hole at the top of the sleeve across the pressure inversion point of the LES. The distance from the nares to the LES was then recorded. This methodology is consistent with that used by Strobel et al.16 Body weight was measured by a research nurse at the time of manometric study with a daily calibrated balance. Body length and head circumference estimates were obtained by retrospective examination of the medical records; standard nursery practice was to take these measurements weekly with an accurate anthropometer. All study protocols used were approved by the ethics research committee of the Women’s and Children’s Hospital, Adelaide, South Australia, and written informed parental consent was obtained.
Statistical Analysis Associations between different variables were assessed by linear, logarithmic, and polynomial regression models with the data analysis program Statview 4.1 (Abacus Concepts Inc, Berkeley, Calif). A P value of <.05 was considered to indicate statistical significance of correlation.
RESULTS The relationships between distance from nares to LES and PMA, body length, body weight, and head circumference are shown in the Table. All variables correlated significantly with distance from nares to LES, regardless of the model used for regression analyses. However, in all cases a better curve fit was achieved by using the non-linear regression models. Of the variables tested, weight was the most predictive of distance from nares to LES (polynomial r 2 = 0.848); body length and head circumference were similar to each other but less predictive than weight (polynomial r 2 = 0.802 and 0.789, respectively); and PMA was the least predictive of the variables (polynomial r 2 = 0.656). A comparison of the relationship between distance from nares to LES and 523
OMARI ET AL
THE JOURNAL OF PEDIATRICS OCTOBER 1999
Fig 1. Individual data from 156 premature infants showing relationship between distance from nares to LES and body length. Included is the linear relationship predicted by using Strobel’s formula (dotted line).
was the least predictive variable. On the basis of these data and because of the inherent difficulties associated with deriving values from complex polynomial formulas, our group now routinely uses either of the predictive graphs (Fig 2) for the purposes of positioning esophageal pH probes in preterm infants. Our data show that existing formulas for estimation of LES position are inaccurate in premature infants. The use of these formulas for the purposes of positioning of pH probes will result in the sensor being positioned too close to the LES, with the possibility that clinically misleading data will be obtained. We would like to acknowledge the help and assistance of the many people who have worked in our unit during the period over which these data were compiled: Mrs Ros Lontis, Mrs Louise Goodchild, Mr Antonie Snel, Ms Wendy Goldsworthy, Dr Robert Fraser, Dr Kasu Miki, Dr Hisa Kawahara, Dr Chellam Kirubakaran, and Mr Malcolm Bakewell.
A
B
Fig 2. Predictive graphs for estimation of distance from nares to LES in premature infants by using weight (A) or body length (B). Graphs are based on the line of best fit with a 3rd-order polynomial regression model.
body length with the theoretical values generated by Strobel’s formula (Fig 1) indicates that the measured values agreed with Strobel’s model in premature infants with body lengths over 40 cm but deviated substantially from Strobel’s model in infants shorter than 40 cm. No discernible differences in these relationships were observed between boys and girls.
DISCUSSION This study has examined the relationship between the distance from nares to LES and variables of age and size in a population of premature infants. These data indicate that Strobel’s formula and other similar predictive formulas, which have been derived 524
in older infants and children, overestimate the distance from nares to LES in premature infants. In this study Strobel’s formula accurately predicted the distance from nares to LES of premature infants with body lengths over 40 cm, but not shorter infants. In shorter (smaller, younger) infants, the relationships between distance from nares to LES and all variables examined were non-linear because of the higher relative growth rate of very preterm infants compared with older infants. It would also seem, from other studies, that Strobel’s formula is less useful in children over 100 cm long1 and/or over 2 years of age.17 Of the variables examined, body weight was most predictive of distance from nares to LES, followed by body length and head circumference. PMA
REFERENCES 1. The Working Group of the European Society of Pediatric Gastroenterology and Nutrition. A standardized protocol for methodology of esophageal pH monitoring and interpretation of the data for the diagnosis of gastroesophageal reflux. J Pediatr Gastroenterol Nutr 1992;14:467-71. 2. Davidson G. Usefulness of oesophageal pH monitoring. Aust J Paediatr 1985;21:243-4. 3. Sondheimer J. Continuous monitoring of distal esophageal pH: a diagnostic test for gastroesophageal reflux in infants. J Pediatr 1980;96:804-7. 4. Newell S, Booth I, Morgan M, Durbin G, McNeish A. Gastro-oesophageal reflux in preterm infants. Arch Dis Child 1989;64:780-6. 5. Gustafsson P, Tibbling L. 24-hour oesophageal two-level pH monitoring in healthy children and adolescents. Scand J Gastroenterol 1988;23:91-4. 6. Spencer J. Prolonged pH recording in the study of gastroesophageal reflux. Br J Surg 1969;56:912-4. 7. Kalloor G, Deshpande A, Collis J. Observation on oesophageal length. Thorax 1976;31:284-8. 8. Jolley S, Johnson D, Herbst J, Pena A, Garnier C. An assessment of gas-
OMARI ET AL
THE JOURNAL OF PEDIATRICS VOLUME 135, NUMBER 4
9.
10.
11.
12.
13.
14.
15.
troesophageal reflux in children by extended pH monitoring of the distal esophagus. Surgery 1978;84:16-24. Friesen C, Hayes R, Hodge C, Roberts C. Comparison of methods of assessing 24-hour intraesophageal pH recordings in children. J Pediatr Gastroenterol Nutr 1992;14:252-5. Vandenplas Y, Derde M, Piepsz A. Evaluation of reflux episodes during simultaneous esophageal pH monitoring and gastroesophageal reflux scintigraphy in children. J Pediatr Gastroenterol Nutr 1992;14:256-60. Owen W. The role of the oesophageal laboratory. Gastroenterol Pract 1988; Feb/Mar:20-6. Donald I, Ford G, Wilkinson S. Is 24h ambulatory oesophageal pH monitoring useful in a district hospital? Lancet 1987;10:89-92. Marples M, Mughal M, Bancewicz J. Can an esophageal pH electrode be accurately positioned without manometry? In: Siewert J, Holscher A, editors. Diseases of the esophagus. Berlin: Springer-Verlag; 1987. p. 789-91. Kantrowitz P, Corson J, Fleischli D, Skinner D. Measurement of gastroesophageal reflux. Gastroenterology 1969;56:666-74. Rokkas T, Anggianisah A, Dorrington L, Owen W, Sladen G. Accurate positioning of the pH probe in the oesophagus without manometry. Ital J Gastroenterol 1987;19:176-8.
16. Strobel C, Byrne W, Ament M, Euler A. Correlation of esophageal lengths in children with height: application to the Tuttle test without prior esophageal manometry. J Pediatr 1979;94:81-4. 17. Staiano A, Clouse R. Value of subject height in predicting lower esophageal sphincter location. Am J Dis Child 1991;145:1424-7. 18. Sutphen J, Dillard V. Effects of maturation and gastric acidity on gastroesophageal reflux in infants. Am J Dis Child 1986;140:1062-4. 19. Blumenthal I, Lealman G. Effect of posture on gastro-oesophageal reflux in the newborn. Arch Dis Child 1982; 57:555-6. 20. Tobin J, McCloud P, Cameron D. Posture and gastro-oesophageal reflux: a case for left lateral positioning. Arch Dis Child 1997;76:254-8. 21. Heacock H, Jeffery H, Baker J, Page M. Influence of breast versus formula milk on physiological gastroesophageal reflux in healthy, newborn infants. J Pediatr Gastroenterol Nutr 1992;14: 41-6. 22. Jeffery H, Page M. Developmental maturation of gastro-oesophageal reflux in preterm infants. Acta Paediatr 1995;84:245-50. 23. Barabino A, Constantini M, Ciccone M, Pesce F, Parodi B, Gatti R. Reliability of short-term esophageal pH monitoring versus 24-hour study. J Pediatr Gastroenterol Nutr 1995;21:87-90.
24. Rode H, Stunden R, Millar A, Cywes S. Esophageal pH assessment of gastroesophageal reflux in 18 patients and the effect of two prokinetic agents: cisapride and metoclopramide. J Pediatr Surg 1987;22:931-4. 25. Ng S-Y, Quak S-H. Gastroesophageal reflux in preterm infants: norms for extended distal esophageal pH monitoring. J Pediatr Gastroenterol Nutr 1998;27:411-4. 26. Omari T, Miki K, Fraser R, Davidson G, Haslam R, Goldsworthy W, et al. Esophageal body and lower esophageal sphincter function in healthy premature infants. Gastroenterology 1995; 109:1757-64. 27. Omari T, Miki K, Davidson G, Fraser R, Haslam R, Goldsworthy W, et al. Characterisation of lower oesophageal sphincter relaxation in healthy preterm infants. Gut 1997;40:370-5. 28. Omari T, Barnett C, Snel A, Goldsworthy W, Haslam R, Davidson G, et al. Mechanisms of gastroesophageal reflux in healthy premature infants. J Pediatr 1998;133:650-4. 29. Dent J. A new technique for continuous sphincter pressure measurement. Gastroenterology 1976;71:263-7. 30. Omari T, Bakewell M, Fraser R, Davidson G, Dent J. Intraluminal micromanometry: an evaluation of the dynamic performance of micro-extrusions and sleeve sensors. Neurogastroenterol Motil 1996;8:241-5.
BOUND VOLUMES AVAILABLE TO SUBSCRIBERS Bound volumes of the 1999 issues of The Journal of Pediatrics are available to subscribers (only) from the Publisher, at a cost of $100.00 for domestic, $125.19 for Canadian, and $117.00 for international subscribers, for Vol. 134 (January-June) and Vol. 135 (July-December), shipping charges included. Each bound volume contains subject and author indexes, and all advertising is removed. Copies are shipped within 60 days after publication of the last issue in the volume. The binding is durable buckram, with the Journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Mosby, Inc., Subscription Services, 11830 Westline Industrial Dr., St. Louis, MO 63146-3318, USA/800-4534351, or 314-453-4351. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular Journal subscription.
525