Continuous 24 hour ambulatory monitoring of intragastric pH in man

Abstract

A system has been developed which permits continuous 24 hour ambulatory recording of intragastric pH under near-physiological conditions. The system utilises a Cecar combination pH electrode connected through a pre-amplifier to an Oxford Medical Systems Medilog 4-24 cassette recorder, and the pH recorded continuously on to tape. The data is replayed at high speed, digitised and then analysed. Sources of error included system drift, system noise and the effect of changes in electrode environment due to saliva, food, loss of fluid contact, temperature variations and electrode time constant. These were found to be small. In contrast, the major changes in pH detected reflect real changes at the electrode tip. These changes can be recorded by the system. Developments in electronics and improvements in both the size and quality of pH electrodes, over the past few decades, has enabled intragastric pH recordings to be made with greater ease. However, a large number of investigators still assess gastric acidity by infrequent, intermittent sampling of gastric secretion through a naso-gastric tube. This new ambulatory system is a significant improvement and its versatility allows studies in acid secretion physiology, pharmacology and pathophysiology.

Influence of Food, Posture and Gastric Alkaline Events on 24-Hour Gastric and Duodenal pH in Normals

“…Such events have also been reported by others [5,8,10,15]. Little et al [16] believe these epi sodes of intense gastric alkalinization are due to duode nogastric reflux, a view shared by many authors [1.5, 15.…”

“…Information on 24-hour gastric and duodenal pH pro files from intraluminal monitoring in health and disease is limited. In most studies, only small cohorts of asymp tomatic volunteers have been studied by this method with the exception of one group that has intensively studied 24-hour gastric pH in 20-25 healthy volunteers [5][6][7], For this reason, comparable, normal values of 24-hour gastric pH remain to be established [8][9][10][11], There are even fewer studies of duodenal pH profiles. Most studies reported are short-term and only recently has 24-hour pH monitoring in the duodenum been investigated [12][13][14].…”

24‐Hour intragastric pH measurement in the assessment of duodenogastric reflux

“…Saliva could track down the electrode from the mouth and accumulate at its tip giving an alkaline or neutral pH reading but the electrodes we have used are mounted 5 mm proximal to the tip of the catheter. Kapur and associates [19] have also shown that tracking of saliva down the electrode cable or catheter has a minimal effect on pH.…”