Jet pump adaptor for ventilation system

An adaptor for fluidly coupling a flow generator to a ventilation mask in a respiratory assistance system, the adaptor comprising:

• a base element which is fluidly connectible to the ventilation mask, the base element having:
• a connector which defines an interior;
• a tubular wall which protrudes into the interior of the connector and at least partially defines a throat, the tubular wall having a distal end which fluidly communicates with the interior of the connector and a proximal end which is opposite the distal end, the proximal end defining an opening;
• at least one entrainment port in open fluid communication with ambient air, the at least one entrainment port being at least partially defined by an aperture in the tubular wall between the distal end and the proximal end;
• and
• a nozzle element connectable to the base element and fluidly connectible to a main gas delivery tube in fluid communication with the flow generator, the nozzle element including a jet nozzle having a distal tip and at least partially defining a gas delivery lumen;
• wherein when the nozzle element is connected to the base element with the jet nozzle advanced through the opening, a gas-tight coupling is formed between the jet nozzle and the proximal end of the tubular wall defining the opening and the distal tip of the jet nozzle is positioned within the tubular wall at a distance from the distal end of the tubular wall to fluidly communicate gas into the throat, such that when gas is flowed through the gas delivery lumen, out the jet nozzle, and into the throat, ambient air is entrained through the at least one entrainment port;
• and
• wherein the connection of the nozzle element to the base element is selectively variable between at least two connected configurations so as to permit the distance from the distal tip of the jet nozzle to the distal end of the tubular wall to be varied by transitioning the connection of the nozzle element to the base element to one of the connected configurations.