Abstract: This invention provides a headgear for a mask assembly including straps for positioning on the head and means to minimise deviation from an optimal mask assembly setting when engaging or disengaging the mask assembly from operative use. Preferably, the disengaging means is a variable-length strap incorporating at least one length delimiter, which may be a hub in the strap or an alternative means which employ friction to remain in place. The strap surfaces may be modified to provide the delimiting means. The strap may incorporate a second delimiting means in moveable engagement with the strap. Preferably, one engagement means is in fixed engagement with the strap. One delimiting means may be a thickened strap portion. However, other means for delimiting the effective strap length may be used.

Abstract: The present invention provides methods and apparatuses for gas delivery, in particular, a mask including at least one porous barrier defining at least two chambers in gaseous communication. The porous barrier may include a plurality of pores, which define a tapered shape. The mask may include a pliable nasal cushion. The invention provides a method for providing pressurised gas to a subject by supplying gas from a pressurised source to a mask, transmitting the gas into a first chamber at a first pressure, transmitting the gas into a second chamber at a second pressure through a plurality of pores, and transmitting the gas from the second chamber through a mask exit.