Effect of stress on blood pressure measured by Doppler ultrasonography and high definition oscillometry in a large population of working dogs

The stress induced by the indirect blood pressure measurement procedure may contribute to increase systolic blood pressure and sometimes lead to a false diagnosis of hypertension. Cortisol dosage has already been used as an indicator of stress state in dogs.

The purpose of this study was to compare, in a well standardized population of working dogs, the influence of stress on systolic blood pressure measured by two indirect blood pressure devices: Doppler ultrasonography and high definition oscillometry (HDO). This study is included in the lupa project, a large European collaboration aiming at the identification of genetic variants influencing blood pressure.

First, we tested the intra-day (5 measures) and inter-day (5 exams) repeatability of the two devices in 5 beagle dogs. The variation coefficients for systolic arterial pressure (SAP) measured by Doppler and HDO were lower than 10%.

Thereafter, we included 70 healthy Belgian Shepherds from Belgian police department and from Belgian army. All dogs were male, working dogs, between 2 and 6 years old. The SAP was always measured by the same trained operator, under the same standardized procedure, in a calm environment. The Doppler measurement was made at the beginning of the exam and the HDO measurement 20 minutes after the Doppler test. At the end of the exam, a blood sample was taken to measure cortisol level. At each measurement, stress level and difficulty to perform the exam were scored by a four levels scale.

The SAP measured by Doppler and HDO were highly correlated (R = 0.429, p < 0,001). Nevertheless, SAP measured by the Doppler device (159mmHg ± 3.374) was higher (p < 0,001.) than SAP measured by HDO (143mmHg ± 1.877). The SAP measured by the Doppler device was positively correlated to the stress level (R = 0.612, p < 0,001), the difficulty of measurement (R = 0.394, p < 0.01) and blood cortisol concentration (R = 0.336, p < 0.02) while only a weak correlation was observed between SAP measured by HDO and the stress level (R = 0,262, p = 0,045).

These results suggest that the SAP value measured by a Doppler device is more importantly influenced by the stress level than the SAP value measured by HDO. Therefore, in nervous dogs such as working Belgian Shepherds, the HDO method seems more suitable than the Doppler method.