Helium

Due to its lower density, helium achieves more effective flow of gas due to lowered resistance to gas flow within the airways and reduces the work of breathing by decreasing the pressure gradient needed to achieve a turbulent flow. Helium has a higher diffusion coefficient for carbon dioxide relative to oxygen thus promotes exhalation of trapped carbon dioxide. This reduces hypercapnia and normalizes pH. Helium increases the coronary collateral circulation and enhances the vasodilatory effects of inhaled nitric oxide on pulmonary vessels. It is suggested to possess neuroprotective properties. Cardioprotective effects against ischemia are mediated through early and late preconditioning by exposing the myocardial tissues to short ischemic episodes. Studies show that helium is associated with activation of pro-survival signalling kinases and inhibition of the opening of mitochondrial permeability transition pore (mPTP).