Tail-cuff blood pressure measurement without external preheating in awake rats

A new photoelectric sensor capable of detecting tail pulses even in unheated rats was tested for accuracy in indirect measurements of blood pressure. This sensor proved more sensitive than a Doppler ultrasonic flowmeter because it allowed detection not only of tail pulsations without preheating but also of peak oscillations usable for estimating mean arterial pressure. After blood pressures in anesthetized rats were elevated with norepinephrine or lowered with sodium nitroprusside, systolic pressures determined with the photoelectric sensor were almost identical with those recorded concurrently from femoral catheters (r = 0.939). Cuff pressure at peak oscillations in the tail correlated better with femoral mean pressure than with femoral diastolic pressure. However, similar comparisons in awake rats with chronically implanted carotid catheters showed that, although correlation between tail-cuff and carotid systolic pressures remained significant (r = 0.962), the correlation between peak tail oscillations and either mean or diastolic pressure was not. When systolic pressures were measured indirectly once a week for 7 weeks in unheated awake rats, normotensive rats could be easily distinguished from streptozotocin-diabetic and DOCA-salt hypertensive rats.