Pilmanis A A, Meissner F W, Olson R M
Armstrong Laboratory (AFMC), Crew Systems Directorate, Crew Technology Division, San Antonio, TX 78235-5104, USA.
Aviat Space Environ Med. 1996 Nov;67(11):1092-6.
Ultrasonic techniques have demonstrated venous gas emboli (VGE) during exposure to high altitude. VGE per se have not been considered clinically hazardous. Arterial gas emboli (AGE), however, are viewed with great concern. The crossing-over of venous gas to the arterial circulation has not previously been seen in human subjects at altitude. This transfer may occur via either intracardiac defects, pulmonary shunts, or the pulmonary microcirculation.
A non-invasive ultrasonic echo imaging Doppler system was used to monitor volunteer human subjects for gas emboli simultaneously in the right and left sides of the heart at simulated altitude in a chamber. Subjects found to have gas cross-over were evaluated for septal defects with either transthoracic or transesophageal echocardiography.
Previously unreported left ventricular gas emboli were observed with echo imaging in six subjects at altitude. In all six cases, at the time of AGE onset, the VGE scores were high from all monitored sites. Three subjects had no septal defect, another had a small sinus venosus defect, a third had a patent foramen ovale, and one was not available for evaluation. Five of the cases became symptomatic at the time of AGE onset.
Operational altitude exposures known to elicit high VGE counts in the majority of people should be avoided because of an increased risk of right-to-left gas cross-over and resulting potential for severe cerebral symptomatology.
超声技术已证实在暴露于高海拔环境时会出现静脉气体栓塞（VGE）。VGE本身在临床上未被视为具有危险性。然而，动脉气体栓塞（AGE）却备受关注。此前在高海拔的人体中尚未观察到静脉气体向动脉循环的交叉。这种转移可能通过心内缺损、肺分流或肺微循环发生。
使用无创超声回波成像多普勒系统，在模拟高海拔的舱室内同时监测志愿者心脏左右两侧的气体栓塞情况。对发现有气体交叉的受试者，用经胸或经食管超声心动图评估其间隔缺损情况。
在高海拔环境下，通过回波成像在6名受试者中观察到了此前未报告的左心室气体栓塞。在所有6例病例中，AGE发作时，所有监测部位的VGE评分都很高。3名受试者没有间隔缺损，另一名有小的静脉窦缺损，第三名有卵圆孔未闭，还有一名无法进行评估。其中5例在AGE发作时出现了症状。
由于从右向左气体交叉的风险增加以及由此导致严重脑症状的可能性，应避免已知会在大多数人身上引发高VGE计数的作业海拔暴露。
