Ten healthy adult horses, 5 males and 5 females, were included in the study.
Direct intra-abdominal pressures were measured through an intraperitoneal cannula and zeroed at the height midway between the height of the tuber ishii and point of the shoulder.
Indirect measurements of intra-abdominal pressure were performed by measuring intravesicular pressures through a transurethral catheter zeroed at the tuber ishii.
Direct pressure measurements obtained in the standing horse were subatmospheric (mean, −1.80 cm H2O; SD, 1.61 cm H2O; 95% CI, −2.80 to −0.80) and were shown to decrease as the horse`s weight increased (Pearson`s r=−0.67, P=0.04), with no effect of head position (P=0.15). ´
Mean baseline indirect pressure measurements (mean, −8.63 cm H2O; SD, 4.37 cm H2O; 95% CI, −13.05 to −4.21) were significantly different from the pressures measured directly from the abdomen (P<0.001).
Indirect pressure measurements were noted to increase with increasing volumes infused into the bladder, and were statistically different at a volume of 100 mL (P=0.004).
There was low to moderate correlation between direct and indirect pressure measurements of intra-abdominal pressure over a range of fluid volumes infused into the bladder (Pearson`s correlation range −0.38 to 0.58).
Conclusion: Pressures measured directly in the standing horse were subatmospheric, and increased as the horse`s weight increased.
Indirect pressures measured were altered by increasing volumes infused in the bladder.
There was no significant correlation between the 2 methods of intra-abdominal pressure measurement.
Source: Amelia S. Munsterman, R. Reid Hanson (2009): Comparison of direct and indirect methods of intra-abdominal pressure measurement in normal horses. In: Journal of Veterinary Emergency and Critical Care
Volume 19 Issue 6, Pages 545 - 553
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