Changes of EKG and Arterial Blood Gas during PEEP by Venous Air Embolism in Rabbits

Kim, Joo Wan; Jun, Jong Hun; Shim, Jae Chul; Kim, Kyoung Hun; Lee, Dong Ho; Kim, Kyo Sang; Suh, Jung Kook; Yoo, Hee Koo; Seung, Ik Sang; Chon, Se Ung

Abstract

Positive end expiratory pressure (PEEP) has been used to prevent and treat venous air embolism in patients in the sitting position undergoing neurosurgical operations However, the safety of PEEP has recently been questioned, because of concern that PEEP might incresae right atrial pressure more than left atrial pressure, thereby predisposing patients with a probe-patent foramen ovale to paradoxical air embolism. But it is controversial and needs further evaluation. In a prior study in rabbits with various venous air volume, the authors found that suddenly decreased mean arterial pressure and arterial PO2 showed peaked P wave, arrhythmias, ST depression and premature ventricular contraction on the EKG. In the present study, the authors examined the effects of 0, 3 and 5 cmHO PEEP (PEEP0, PEEP3, and PEEP5,) in 30 rabbits positioned supine with intravenous 0.5 mg/kg of air injection. In a prior study, we found that 0.5 mg/kg of air injection has serious change but showed low mortality. The measurements were obtained by the precordial doppler ultrasound, end tidal PCO2, mean arterial pressure, arterial PCO2, arterial PO2, and EKG. The results were as follow; 1) Doppler ultrasound was the most sensitive device even with PEEP and end tidal PCO2 was higher with PEEP5 than with PEEP3 and PEEP0 after suddenly decreased by the air injection. In PEEP statistic singnificance was observed (p<0.05). 2) The mean arterial pressure was significantly decreased by the air injection in PEEP0 PEEP3 and PEEP5 but there were no significant differences in all groups. It seemed likely due to low PEEP. 3) In PaCO2, slightly higher PaCO2 was observed in PEEP5 than in PEEP3 and PEEP. No statistic significance was obaerved. In PaO2, significant decrease was observed in all group but in PEEP3 small decrease was observed. 4) The incidence of bradycardia and ST depression was less in PEEP3 and PEEP5 than in PEEP0. In PEEP5, PVC was appeared relatively short duration than other group due to the air lock phenomenon. It was suspeeted that air was more freely passed according to increased right ventricular pressure after air lock. Authors conclude that PEEP has a benefit effect for the prevention of venous air embolism but after the occurence there is little benefit in the treatment.