Comparison of Doppler, oscillometric, auricular and carotid arterial blood pressure measurements in isoflurane anesthetized New Zealand white rabbits

Objective To assess agreement between carotid arterial pressure and auricular arterial, thoracic limb Doppler or thoracic limb oscillometric blood pressure measurements. Study design Prospective experimental study. Animals Six adult New Zealand white rabbits. Methods Rabbits were anesthetized with isoflurane in oxygen at 1, 1.5 and 2 MAC on two separate occasions. Catheters in the auricular and the contralateral external carotid artery were connected to calibrated pressure transducers via non-compliant tubing. Inflatable cuffs of width equal to approximately 40% of the limb circumference were placed above the carpus on both thoracic limbs with a Doppler transducer placed distal to the cuff on one. Systolic (SAP) and mean (MAP) arterial blood pressure measurements were obtained at each dose, on each occasion. Agreement between measurement techniques was evaluated by repeated measures Bland Altman analysis with carotid pressure as the reference. Variation in bias over the measurement range was evaluated by regression analysis. Results Carotid MAP and SAP ranged from 20 to 65mmHg and 37 to 103mmHg respectively. Bias and 95% limits of agreement for auricular and oscillometric MAP were 7 (0-14) and -5 (-21-11) mmHg, respectively, and for auricular, oscillometric and Doppler SAP were 23 (8-37), -2 (-24-20) and 13 (-14-39) mmHg, respectively. Bias varied significantly over the measurement range (p<0.001) for all three SAP techniques but not for MAP measurements. Conclusions and clinical relevance Limits of agreement for all measurements were large but less so for MAP than SAP. Variation in bias with SAP should be considered when using these measurements clinically.