Performance of isolated rat hearts perfused with helium- or nitrogen-containing, gas-saturated solutions

Effects of helium on the isolated perfused rat heart were studied employing the Langendorff technique. The perfusate consisted of Krebs-Henseleit solution saturated with one of three gas mixtures: 1) 95% O2-5% CO2, 2) 50% O2-45% He-5% CO2, and 3) 50% o2-45% N2-5% CO2. Contractile indices measured revealed the performance of hearts with the helium mixture to be equivalent to those perfused with the 95% O2-5% CO2 mixture. Those perfused with the nitrogen gas mixture exhibited contractile activity lower than that in the other two groups. It was concluded that helium exerts a direct effect on the coronary vasculature of the isolated rat heart by reducing its resistance to flow. A greater oxygen delivery to hearts perfused with the He-saturated solution compared to the N2-perfused hearts may account for the difference in performance.