LETTER TO THE EDITOR

The Effect of Body Position on Lower Esophageal S p h i n c t e r P r e s s u r e

To the Editor: Lower esophageal sphincter (LES) pressure has been shown to correlate well with the presence of symptomatic gastroesophageal reflux-heartburn patients generally have a pressure less than 10 m m H g above intragastric pressure in the supine position (1). Patients with chronic reflux often note that their heartburn is more apparent when lying on the right or left side. Support for this clinical impression has recently been obtained from studies using a pH electrode placed in the lower esophagus. Pattrick has shown evidence of increased reflux in heartburn patients in the right decubitus position, but not in the left decubitus, or when sitting or standing (2). In addition, Skinner and Camp noted pH changes suggesting frequent reflux in normal subjects in the right decubitus position (3). Since the pressure at the LES forms the functional barrier against reflux, sphincter pressure levels relative to intragastric pressure in these body positions should be of interest. The effect of body position on LES pressure has not been recorded previously because the standard fluidfilled manometric system would measure artifactual pressure changes due to change in the position of the open catheter tip relative to the external transducers. The development of a catheter system with transducers in the catheter itself has made these measurements possible. We have studied LES pressure in 20 healthy subjects using an intraesophageal transducer assembly (Honeywell Inc--Model 31 Probe). The assembly consists of a flexible polyvinyl tube containing three small (5-mm diameter) pressure transducers spaced 5 cm apart, with the first transducer 5 cm from the distal end. Digestive Diseases, Vol. 18, No. 5 (May 1973)

This system allows direct measurement of pressures by intraluminal placement of the transducers. The transducers were passed through the nose into the stomach and allowed to equilibrate to body temperature. The LES pressure was recorded using intragastric pressure as a zero reference and determined for each position as the mean value obtained during a slow "pullthrough" of the three transducers from gastric fundus to esophagus. The transducers were replaced in the stomach before moving the patient to a new position. Thus LES pressure was studied in the following sequence; supine, right deeubitus, supine, left decubitus, supine, sitting. Nine values were obtained in the supine position and three for each other position for each of the 20 subjects.

20

9I- 15

IT"

E E UJ

4-

+

+

LEFT

SITTING

U,I

n,. a.

=,

o SUPINE

RIGHT

Fig 1. Mean resting lower esophageal sphincter (LES) pressure in 20 normal subjects in the supine, right decubitus, left decubitus, and sitting positions. Vertical lines indicate • SE of the mean. 441

The mean LES pressure in the supine position was 16.7 + 0.9 m m H g (SE) and was unchanged during the three pulls across the sphincter in this position. This pressure is comparable to basal supine LES pressure previously reported in normal subjects using an infused open-tipped catheter system (4). In all subjects a lower pressure was recorded in each of the other three positions studied (Figure 1). Mean LES pressure was 9.7 4- 0.7 m m H g in the right decubitus position and 10.4 :k 0.9 m m H g in the left decubitus position. In the sitting position mean LES pressure was 10.8 ~ 0.8 mmHg. The difference between mean supine pressure and that in each other position was highly significant (P < 0.001). There was no significant difference between mean LES pressures in right decubitus, left decubitus, and sitting positions. Mean gasteric fundic pressure did not change with change in body position. Our findings of a decreased LES pressure barrier in the right and left decubitus positions offer a possible explanation for increased gastroesophageal reflux in these positions. A1-

442

though pressure is also decreased in the sitting position, the lack of reflux symptoms in this position is probably due to the effect of gravity on the gastric pool. LCDRJoHN C. BABKA,MC USN GEORGE W. HAGER, M D CAPT DONALD O. CASTELL, MC USN

Gastrointestinal Branch Internal Medicine Service US Naval Hospital Philadelphia, Pennsylvania References

1. Winans CS, Harris LD: Quantitation of lower esophageal sphincter competence. Gastroenterology 52:773-778, 1967 2. Pattrick FG: Investigation of gastroesophageal reflux in various positions with a two lumen pH electrode. Gut 11:659-667, 1970 3. Skinner DB, Camp TF: Relation of esophageal reflux to lower esophageal sphincter pressures decreased by atropine. Gastroenterology 54:543551, 1968 4. Castell DO, Levine SM: Lower esophageal sphincter response to gastric alkalinization. Ann Intern Med 74: 223-227, 1971

Digestive Diseases, Vol. 18, No. 5 (May 1973)