[Power spectrum of experimental gas embolism in dogs and a new device for its detection]

We studied the power spectrum of precordial Doppler sounds during experimental CO2 and air embolism and developed a new device for detection (intravascular gas detector) and examined its usefulness in experimental CO2 and air embolism in dogs and in a patient during laparoscopic surgery. We did digital tape recordings during CO2 and air embolism in seven anesthetized mongrel dogs (7-16 kg body) to generate power spectrum of the heart sound on a dynamic signal analyzer. The power spectrum of "mill-wheel murmur" was found to be 10-30 dB higher than the baseline heart sound in the range of 200 and 2500 Hz. The intravascular gas detector was designed to set off alarm sounds whenever the difference of energy between the Doppler sounds low-pass filtered at 250 Hz and the Doppler sounds high-pass filtered at 250 Hz was increased. The alarm was activated immediately during experimental CO2 and air embolism and also during laparoscopic appendectomy. The alarm sounds during the appendectomy coincided with gas bubbles detected by a transesophageal echocardiography. By use of this detector, CO2 and air embolism can be easily detected and the anesthesiologist does not need to pay continuous attention to Doppler sounds by diverting his or her concentration on the patient.