A New Alarm Device for Air Embolism during Neurosurgery in the Sitting Position

Abstract

The high sensitivity of Doppler ultrasound for monitoring venous air embolism was confirmed by injecting various amounts of air into the jugular veins of dogs in the upright position. The frequency distribution of the Doppler sound changed by air embolism was analyzed on the sonogram and was compared with polygraphic recordings of pathophysiological data from animals and clinical cases. An electronic alarm circuit triggered by the intensity and duration of the Doppler output of a particular frequency range characteristic for air embolism was designed and tested with animals and clinical data. This device detects variations in Doppler output from preoperative levels, thereby relieving the anesthesiologist and surgical team from the need of monitoring the Doppler sound throughout surgery.