A novel placement method of a calibration-free pH capsule for continuous wireless measurement of intragastric pH in horses

Abstract

Background: Current methods to measure intragastric pH in horses have limitations. A wireless capsule has been designed for continuous esophageal pH monitoring in humans.

Objectives: To (1) determine the feasibility and describe the methodology of measuring intragastric pH wirelessly in horses; and (2) determine attachment duration of the capsules.

Animals: Eleven healthy adult horses.

Methods: Capsules were attached to squamous and glandular gastric mucosa under gastroscopic guidance, using suture loops and 1 to 4 hemostasis clips. pH was continuously recorded using a wireless recorder in both fed and fasted states. Gastroscopy was performed daily to assess capsule attachment and any mucosal damage. Data were analyzed using commercially available software. Values are reported as median (interquartile range).

Results: Capsules were successfully placed and data obtained in squamous (n = 11) and glandular (n = 7) regions. The overall duration of squamous capsule attachment was 27 hours (15-32); 1 clip (n = 4) was 15 hours (11-20), 2 clips (n = 2) was 20 hours (16-23), 3 clips (n = 4) was 32 hours (30-32), and 4 clips (n = 1) was 33 hours. The overall duration of glandular capsule attachment was 10 hours (8-21); 1 clip (n = 2) was 11 hours (10-13), 2 clips (n = 2) was 19 hours (14-23), 3 clips (n = 2) was 7 hours (7-8), and 4 clips (n = 1) was 158 hours. There was no substantial damage to the gastric mucosa as a consequence of attachment.

Conclusions and clinical importance: This novel technique enables the wireless measurement of intragastric pH in horses at known locations under fed and fasted conditions, providing a viable alternative for continuous monitoring in both research and clinical scenarios.

Keywords: EGGD; EGUS; ESGD; equine; gastric; ulcers.

FIGURE 1

Calibration‐free pH capsule attached to the hemostasis clip via the suture loops and orthodontic elastic.

FIGURE 2

Gastroscopic images showing a capsule attached to the glandular mucosa ventral to the margo plicatus with 1 (A) and 4 (B) hemostasis clips.

FIGURE 3

Gastroscopic images showing a capsule attached to the squamous mucosa dorsal to the margo plicatus with 1 (A) and 4 (B) hemostasis clips.

FIGURE 4

Example of a graph of pH over time for squamous (top) and glandular (bottom) capsules generated by the software. Time (24‐hour clock) is on the x‐axis and pH is on the y‐axis. pH <4 is highlighted by red shading. The sharp vertical lines that extend beyond the y‐axis represent artifacts because of temporary transmission failure.

FIGURE 5

Duration of attachment of capsules with 1 hemostasis clip and 3 hemostasis clips at squamous and glandular locations (A), mean pH throughout duration of attachment at squamous and glandular locations (B) and the percentage of time the pH was less than 4 (%tpH < 4) at squamous and glandular locations (C). The median is marked by the central horizontal line, the box spans the interquartile range, and the whiskers span the upper and lower limits. Outliers are indicated by circles.

FIGURE 6

Median (individual) hourly pH at squamous and glandular locations over the first 24 hours after attachment for all capsules with ≥24 hours attachment and pH data (n = 8). Data are shown as mean ± SD. Feed was reintroduced between hours 1 and 2 (black arrow). Feed was withheld overnight from 8 pm and gastroscopy was performed at 8 am the following day, corresponding to periods starting at hours 8‐11 and ending at hours 20‐23.

FIGURE 7

Gastroscopic images showing superficial erosions on the squamous mucosa (A) and hyperemia of the glandular mucosa (B; black arrows) after detachment of the hemostasis clips.