Department of Human Physiology, University of Oregon, Eugene, Oregon, USA.
J Appl Physiol (1985). 2011 Jan;110(1):35-45. doi: 10.1152/japplphysiol.00145.2010. Epub 2010 Sep 16.
Concern has been raised that altering the fraction of inspired O₂ (Fi(O₂)) could accelerate or decelerate microbubble dissolution time within the pulmonary vasculature and thereby invalidate the ability of saline contrast echocardiography to detect intrapulmonary arteriovenous shunt in subjects breathing either a low or a high Fi(O₂). The present study determined whether the gaseous component used for saline contrast echocardiography affects the detection of exercise-induced intrapulmonary arteriovenous shunt under varying Fi(O₂). Twelve healthy human subjects (6 men, 6 women) performed three 11-min bouts of cycle ergometer exercise at 60% peak O₂ consumption (Vo(2peak)) in normoxia, hypoxia (Fi(O₂) = 0.14), and hyperoxia (Fi(O₂) = 1.0). Five different gases were used to create saline contrast microbubbles by two separate methods and were injected intravenously in the following order at 2-min intervals: room air, 100% N₂, 100% O₂, 100% CO₂, and 100% He. Breathing hyperoxia prevented exercise-induced intrapulmonary arteriovenous shunt, whereas breathing hypoxia and normoxia resulted in a significant level of exercise-induced intrapulmonary arteriovenous shunt. During exercise, for any Fi(O₂) there was no significant difference in bubble score when the different microbubble gas compositions made with either method were used. The present results support our previous work using saline contrast echocardiography and validate the use of room air as an acceptable gaseous component for use with saline contrast echocardiography to detect intrapulmonary arteriovenous shunt during exercise or at rest with subjects breathing any Fi(O₂). These results suggest that in vivo gas bubbles are less susceptible to changes in the ambient external environment than previously suspected.
人们担心改变吸入氧气的分数（Fi（O₂））可能会加速或延缓肺血管内微泡的溶解时间，从而使生理盐水对比超声心动图无法检测到在低或高 Fi（O₂）下呼吸的受试者中的肺内动静脉分流。本研究旨在确定用于生理盐水对比超声心动图的气体成分是否会影响在不同 Fi（O₂）下检测运动引起的肺内动静脉分流。12 名健康人类受试者（6 名男性，6 名女性）在正常氧合、低氧（Fi（O₂）= 0.14）和高氧（Fi（O₂）= 1.0）下分别以 60%峰值摄氧量（Vo（2peak））进行了三次 11 分钟的踏车运动。使用两种不同的方法，用五种不同的气体制造生理盐水对比微泡，并以 2 分钟的间隔顺序静脉内注射：空气、100%N₂、100%O₂、100%CO₂和 100%He。呼吸高氧可防止运动引起的肺内动静脉分流，而呼吸低氧和正常氧合会导致显著水平的运动引起的肺内动静脉分流。在运动过程中，对于任何 Fi（O₂），当使用任何方法制造的不同微泡气体组成时，气泡评分均无显着差异。本结果支持我们以前使用生理盐水对比超声心动图的工作，并验证了在运动或休息期间使用空气作为可接受的气体成分与生理盐水对比超声心动图一起使用，以检测任何 Fi（O₂）下呼吸的受试者中的肺内动静脉分流。这些结果表明，体内气体气泡对外界环境的变化比以前认为的要少受影响。
