Noninvasive laser-based blood pressure measurement in rabbits

To obtain serial blood pressure measurements without trauma in rabbits, we developed a laser-based method which permits noninvasive determination of systolic and diastolic arterial blood pressure. The ease and accuracy of this method were evaluated over a range of blood pressures in five New Zealand White rabbits. Laser-based pressures from the central ear artery were compared with cannula-based pressures from the contralateral central ear artery. Pressures were measured before and during infusions of saline (control), nitroprusside, or epinephrine, and following induction of anesthesia. Noninvasive measurements correlated highly with direct measurements (systole: r = 0.89; diastole: r = 0.93). The difference between the non-invasive and direct pressure measurements during saline, nitroprusside, and epinephrine infusions, and following anesthesia, respectively, were (mean +/- SD, systole/diastole): 4.2 +/- 2.4 (P = NS)/9.3 +/- 1.4 (P less than .001), 4.1 +/- 1.6 (P less than .02)/3.2 +/- 1.1 (P less than .01), 0.6 +/- 2.4 (P = NS)/-3.0 +/- 2.7 (P = NS), and -5.1 +/- 2.9 (P = NS)/0.3 +/- 1.3 (P = NS). The noninvasive method did not result in observable agitation of the animals. To optimize results, visual inspection was required to assure that the instrument's diaphragm was not deformed or dried from previous use, and that the diaphragm was placed over the center of the arterial lumen. It was also necessary to dim room lights and to direct heating lights away from the ears to avoid degrading light signal quality. These results, albeit involving a small number of animals, indicate the potential utility of this method in the study of chronic pathophysiological processes requiring long-term repeated determination of systolic and diastolic blood pressure.