Ramirez M P, Sigaloff K C, Kubatina L V, Donahue M A, Venkatesh A K, Albert M S
Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
NMR Biomed. 2000 Jun;13(4):253-64. doi: 10.1002/1099-1492(200006)13:4<253::aid-nbm636>3.0.co;2-9.
The physiological effects of various hyperpolarized helium and xenon MRI-compatible breathing protocols were investigated in 17 Sprague-Dawley rats, by continuous monitoring of blood oxygen saturation, heart rate, EKG, temperature and endotracheal pressure. The protocols included alternating breaths of pure noble gas and oxygen, continuous breaths of pure noble gas, breath-holds of pure noble gas for varying durations, and helium breath-holds preceded by two helium rinses. Alternate-breath protocols up to 128 breaths caused a decrease in oxygen saturation level of less than 5% for either helium or xenon, whereas 16 continuous-breaths caused a 31.5% +/- 2.3% decrease in oxygen saturation for helium and a 30.7% +/- 1. 3% decrease for xenon. Breath-hold protocols up to 25 s did not cause the oxygen saturation to fall below 90% for either of the noble gases. Oxygen saturation values below 90% are considered pathological. At 30 s of breath-hold, the blood oxygen saturation dropped precipitously to 82% +/- 0.6% for helium, and to 76.5% +/- 7. 4% for xenon. Breath-holds longer than 10 s preceded by pre-rinses caused oxygen saturation to drop below 90%. These findings demonstrate the need for standardized noble gas inhalation procedures that have been carefully tested, and for continuous physiological monitoring to ensure the safety of the subject. We find short breath-hold and alternate-breath protocols to be safe procedures for use in hyperpolarized noble gas MRI experiments.
通过持续监测17只Sprague-Dawley大鼠的血氧饱和度、心率、心电图、体温和气管内压力，研究了各种超极化氦气和氙气MRI兼容呼吸方案的生理效应。这些方案包括纯惰性气体和氧气交替呼吸、纯惰性气体持续呼吸、不同时长的纯惰性气体屏气，以及在两次氦气冲洗后进行氦气屏气。对于氦气或氙气，多达128次的交替呼吸方案导致血氧饱和度水平下降不到5%，而16次持续呼吸导致氦气的血氧饱和度下降31.5%±2.3%，氙气下降30.7%±1.3%。长达25秒的屏气方案不会使任何一种惰性气体的血氧饱和度降至90%以下。血氧饱和度值低于90%被认为是病理性的。在屏气30秒时，氦气的血氧饱和度急剧降至82%±0.6%，氙气降至76.5%±7.4%。在预冲洗后进行超过10秒的屏气会导致血氧饱和度降至90%以下。这些发现表明需要经过仔细测试的标准化惰性气体吸入程序，以及持续的生理监测以确保受试者的安全。我们发现短屏气和交替呼吸方案是用于超极化惰性气体MRI实验的安全程序。
