Effect of limb and cuff positioning on measurement of arterial blood pressure with an oscillometry device (PetMAP) in anaesthetized cats

Arterial blood pressure (ABP) is often measured with oscillometry during anaesthesia. Changing the height of the measuring cuff with respect to the level of the heart is known to affect oscillometry accuracy in some species; however, this effect has not been investigated in cats. The objective of this study was to determine the effects of raising and lowering the measuring cuff from standard position (level of the heart) on ABP, measured with PetMAP, in anaesthetised cats. ABP readings were obtained from 29 cats with the cuff at standard position (baseline), and 5 cm above and below the heart. The end-tidal isoflurane concentrations were maintained constant during data acquisition. There were no differences between baseline values and those measured below the heart, while ABP measured above the heart was consistently lower than baseline for both the thoracic and pelvic limbs (P < 0.001), with absolute differences of 8.2 (2.5 – 14) mmHg and 6.5 (3.0 – 15.0) mmHg, respectively. Systolic ABP readings at the pelvic limb were consistently higher than those at the thoracic limb at standard position (112 ± 26 versus 103 ± 21 mmHg, p = 0.010), above (106 ± 22 versus 95 ± 20 mmHg, p = 0.003), and below the heart (116 ± 26 versus 107 ± 22 mmHg, p = 0.011). This study shows that raising the cuff by 5 cm above the heart, which may become necessary during procedural positioning, results in clinically significant underestimation of ABP measured with PetMAP.