Evaluation of gastric pressures as an indirect method for measurement of intraabdominal pressures in the horse

Objective – To develop an indirect method for measurement of intraabdominal pressures in the standing horse using measurement of gastric pressures as a less invasive technique, and to compare this method with direct intraabdominal pressures obtained from the peritoneal cavity. Design – Prospective, experimental study. Setting – University‐based equine research facility. Animals – Ten healthy adult horses, 7 geldings and 3 mares. Interventions – Gastric pressures were measured using a nasogastric tube with a U‐tube manometry technique, while intraperitoneal pressures were measured with a peritoneal cannula. Measurements of intraabdominal pressure were obtained by both methods, simultaneously, and were evaluated using 5 increasing volumes of fluid infused into the stomach (0, 400, 1,000, 2,000, and 3,000 mL). Bias and agreement between the 2 methods were determined using Bland‐Altman analysis and Lin's concordance correlation coefficients. Measurements and Main Results – Mean gastric pressure was 14.44±4.69 cm H₂O and ranged from 0 to 25.8 cm H₂O. Intraperitoneal pressure measurements were generally subatmospheric, and ranged from ?6.6 to 3.1 cm H₂O (mean±SD, ?1.59±2.09 cm H₂O). Measurements of intraperitoneal pressures were repeatable; however, intra‐ and interindividual variance was significantly larger for measurements of gastric pressures. The mean and relative bias for comparison between the 2 techniques was 15.9±5.3 cm H₂O and 244.3±199.2%, respectively. The Lin's concordance correlation coefficient between gastric and intraperitoneal pressures was ?0.003 but this was not statistically significant (P=0.75). Conclusions – There was no statistical concordance between measurements of intraabdominal pressure using gastric and intraperitoneal pressure measurement, indicating that gastric pressures cannot be substituted for intraperitoneal pressure measurement. Direct measurement of intraperitoneal pressures may be a more consistent method for comparison of intraabdominal pressures between horses, due to less variability within and between individuals.