Evaluation of oscillometric and Doppler ultrasonic methods of indirect blood pressure estimation in conscious dogs

Abstract

To assess the accuracy and precision of indirect measurements of systemic arterial blood pressure (BP), results obtained with an oscillometric device (BPo) and a Doppler ultrasonic device (BPud) were compared with those obtained by direct radiotelemetry (BPrt) in 12 conscious beagles. The correlation between indirectly obtained and directly measured values for BP parameters ranged widely for the different indirect methods and sites of cuff placement, with R2 between 0.001 and 0.901. Both indirect methods underestimated all BP parameters, the degree of underestimation increasing at higher values for the BP. The highest correlation occurred when estimates were the average of 5 values consecutively obtained with the oscillometric device and cuff placement at the coccygeal artery (R2 = 0.854 for mean BPo, 0.886 for systolic BPo, and 0.901 for diastolic BPo; P < 0.0001 for all parameters) or with the ultrasonic Doppler device at the metatarsal arteries (R2 = 0.810 for systolic BPud; P < 0.0001). Multiple consecutively obtained values are advised, as this approach improves the reliability of indirect BP measurements. The strong correlation between directly measured values and estimates derived as the average of 5 consecutive indirectly obtained values indicates that the latter approach provides a useful estimate of BP in conscious dogs and is likely to be useful in monitoring disease progress and treatment in dogs with abnormal BP.

Figure 1

Simple linear regression relation (dotted line) and line of identity (dashed) for systolic arterial blood pressure (BP) values obtained in 12 conscious beagles by oscillometry (SBP_o) at the coccygeal artery site and by radiotelemetry (SBP_rt). Each data point corresponds to simultaneously obtained values for SBP_o and SBP_rt. There were 174 comparisons (R² = 0.786; P < 0.0001).

Figure 2

Simple linear regression relation (dotted line) and line of identity (dashed) for systolic arterial BP values obtained in 12 conscious beagles by Doppler ultrasonography (SBP_ud) at the metatarsal arteries site and by radiotelemetry (SBP_{r t}). Each data point corresponds to simultaneously obtained values for SBP_ud and SBP_rt. There were 270 comparisons (R² = 0.753; P < 0.0001).

Figure 3

Bland–Altman limits-of-agreement plots (36) for SBP_rt and SBP_o at the coccygeal site. Each data point corresponds to the difference between 1 pair of simultaneously obtained direct and indirect measurements. Also depicted are the mean overall difference (dotted line), the mean ± 1 standard deviation (s) (dashed line), the mean ± 2 s (solid line), and the simple linear regression relation between the differences and averages of the 2 methods (thick solid diagonal line).

Figure 4

Bland–Altman limits-of-agreement plots for SBP_{r t} and SBP_ud. Each data point corresponds to the difference between 1 pair of simultaneously obtained direct and indirect measurements. Also depicted are the mean overall difference (dotted line), the mean ± 1 s (dashed line), the mean ± 2 s (solid line), and the simple linear regression relation between the differences and averages of the 2 methods (thick solid diagonal line).