Risberg J, Tyssebotn I
Undersea Biomed Res. 1986 Mar;13(1):77-90.
Previous studies on rats have demonstrated an increased myocardial blood flow (MBF) in spite of an unchanged cardiac output (CO), mean arterial pressure (MAP), and heart rate (HR) when rats were exposed to a 5 ATA ambient pressure (PN2 = 4.8 ATA, PO2 = 0.2 ATA). We have investigated the changes in CO and organ blood flow by the microsphere method on 9 awake, trained rats exposed to a 5 ATA ambient pressure with surface pressure of N2 (= 0.8 ATA) and O2 (= 0.2 ATA), increasing the ambient pressure with He. The chamber temperature was 30-31 degrees C. CO and organ blood flow were measured in control and after 15 min under pressure. No changes were observed in CO, HR, or MAP during the hyperbaric exposure, indicating unchanged external work of the heart when calculated as MAP X HR. The pulse pressure however increased significantly (P less than 0.05). MBF increased at the same time by 36% (P less than 0.01), equally distributed in the right and left ventricles (P less than 0.01). The fact that myocardial perfusion increases when ambient pressure is elevated, independent of atmospheric inert gas composition, invites the conclusion that this change is due to the ambient pressure itself and not to a specific effect of N2 or He as inert gas at 5 ATA. The blood flow to the adrenals increased by 77% (P less than 0.01), the liver by 105% (P less than 0.05), while the blood flow to the skeletal muscles decreased by 30% (P less than 0.05). The blood flow to the lungs, the paws, and the outer ear increased, most likely due to the high ambient temperature in the chamber. We may conclude that HR does not change in a normoxic hyperbaric atmosphere. High ambient pressure increases the pulse pressure, but the MAP and CO remain unchanged. These changes and the changes in organ blood flow need well-balanced neuronal or hormonal reflexes to distribute an unchanged CO under pressure. The exact explanation is not known.
先前对大鼠的研究表明，当大鼠暴露于5个绝对大气压的环境压力（PN2 = 4.8个绝对大气压，PO2 = 0.2个绝对大气压）时，尽管心输出量（CO）、平均动脉压（MAP）和心率（HR）未变，但心肌血流量（MBF）却增加了。我们采用微球法，对9只清醒、经过训练的大鼠进行了研究，这些大鼠暴露于5个绝对大气压的环境压力下，表面压力为N2（= 0.8个绝对大气压）和O2（= 0.2个绝对大气压），并用氦气增加环境压力。舱内温度为30 - 31摄氏度。在对照状态及加压15分钟后测量CO和器官血流量。在高压暴露期间，未观察到CO、HR或MAP的变化，这表明以MAP×HR计算时心脏的外部功未变。然而，脉压显著增加（P < 0.05）。与此同时，MBF增加了36%（P < 0.01），在左右心室中分布均匀（P < 0.01）。当环境压力升高时心肌灌注增加，且与大气惰性气体成分无关，这一事实使人得出结论，这种变化是由于环境压力本身，而非5个绝对大气压下作为惰性气体的N2或He的特定作用。肾上腺血流量增加了77%（P < 0.01），肝脏血流量增加了105%（P < 0.05），而骨骼肌血流量减少了30%（P < 0.05）。肺、爪子和外耳的血流量增加，很可能是由于舱内环境温度较高。我们可以得出结论，在常氧高压环境中HR不变。高环境压力会增加脉压，但MAP和CO保持不变。这些变化以及器官血流量的变化需要良好平衡的神经或激素反射，以便在压力下分配不变的CO。确切原因尚不清楚。
