[How to express results of 24-hour gastric pH measurement? Choice of a mode of expression in 27 healthy subjects].

Twenty-four hour intragastric acidity was studied in 27 healthy subjects (mean age = 29 yrs) by continuous recording in standardized conditions. Data obtained were expressed according to several analytical methods as used extensively elsewhere. In our study, there was a wide discrepancy in results from one subject to another. The use of median values of pH was more appropriate than mean values to express half-hour acidity levels for 24 hours. The median value of H+ concentration is recommended as well. The median value of pH varied from 1 to 4.8 with a slight rise during the second half of the night. During the postprandial period, increase of pH values was prolonged over 2 h 30 in 50 p. 100 of subjects. Profile of pH allowed to demonstrate the distribution of pH value without excluding the extreme values. Both periodicity of pH measurement (30 or 60 min) and parameters used to quantify acidity (percentage of time or pH value at or below threshold values) did not modify results. As measured over a 24 hours period, the percentage of time (mean +/- SEM) at or below pH 1.5 and 3.5 was 54 +/- 3 p. 100 and 85 +/- 2 p. 100, respectively. Daytime and night-time profiles were similar. Mean 24 h H+ concentration (mean +/- SEM) was 47 +/- 35 mmol/l, with, once again, similarity between day and night-time values. The mean 24 h pH values underestimated true acidity with respect to median values.(ABSTRACT TRUNCATED AT 250 WORDS)