Patient breathing apparatus comprises a hood having a front single-layer, transparent sheet and a rear two-layer section. An inflatable cuff extends around the lower end of the hood and is connected to a recirculating heliox gas supply unit. The cuff has perforations in its upper surface around the front part of the hood so that the gas supplied to inflate the cuff flows into the inside of the hood to provide at least a part of the breathing gas. The inner layer of the rear section is permeable so that the gas can flow from the inside of the hood into a space between the two layers and there to a gas outlet. A hose connects the gas outlet to an inlet of the gas supply for recirculation.
