PREHOSPITAL BLOOD PRESSURES - INACCURACIES CAUSED BY AMBULANCE NOISE

Blood pressure measurements in a moving ambulance can be difficult to obtain. Sirens, engine noise, and road noise can all interfere with th e accurate detection of a patient's blood pressure. This study was und ertaken to determine the influence of ambulance noise and vibration on auscultated blood pressures. A model was developed that used dynamic pressures to simulate systolic Korotkoff sounds. Forty-nine emergency personnel were asked to obtain blood pressures using the model in both a quiet environment and in a moving ambulance. A total of 485 blood p ressure measurements were obtained. Systolic pressures were randomized to two settings: 76 mm Hg and 138 mm Hg. Stationary readings were com pared with moving readings using analysis of variance for repeated mea sures. Systolic blood pressure measurements obtained in the quiet envi ronment averaged 133 +/- 5 mm Hg at the high setting, and 45 +/- 6 mm Hg at the low setting. Systolic blood pressure measurements obtained i n a moving ambulance averaged 86 +/- 7 mm Hg at the high setting, and 41 +/- 7 mm Hg at the low setting. The average differences between qui et and moving measurements were 47 mm Hg at the ''high'' setting (P < .01) and 4 mm Hg at the ''low'' setting (P > .01). At physiological le vels, blood pressures obtained in moving ambulances differ significant ly from those obtained in a quiet environment, which may be caused by road noise and ambulance motion.