Non-contact determination of arterial blood pressure alterations induced by blood loss using laser irradiation on the common carotid artery

Abstract

In order to avoid the secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, we have reported a method for non-contact monitoring of heart and respiratory rates, using microwave radar or laser irradiation. In large-scale disasters, it is important to be able to diagnose shock without touching patients. We evaluated a non-contact method of monitoring arterial blood pressure alterations of New Zealand rabbits induced by blood loss, using He-Ne laser reflection on the common carotid artery. PVR was significantly correlated with systolic blood pressure (r = 0.95, p < 0.01), where PV = peak voltage of reflected laser amplitude, and PVR = PV(present moment state)/PV(normal state). The following formula was derived using the least-squares linear fitting: SBP = 69.6 PVR + 8.2, in which SBP is the systolic blood pressure. Before blood withdrawal, the mean blood pressure, heart rate and haematocrit were 68 ± 3 mmHg, 154 ± 10 bpm and 40 ± 2%, respectively. After intervention, the mean blood pressure, heart rate and haematocrit were 38 ± 5 mmHg, 197 ± 25 bpm and 30 ± 2%, respectively. The proposed non-contact method appears promising for future clinical application in determining arterial blood pressure alterations. It is likely to be useful in reducing the risk of secondary exposure to toxic chemicals or infectious organisms in the case of large-scale disasters.