Gas mixing control apparatus and method

A ventilator comprising:

• an air pathway configured to supply air to a mixing node;
• an oxygen pathway configured to supply oxygen to the mixing node, where the oxygen is mixed with air to obtain a mixed gas having a predetermined percentage of oxygen;
• a blower configured to pressurize the mixed gas during an inspiratory phase;
• a conduit configured to provide the pressurized mixed gas from the blower to an access port during the inspiratory phase, and to provide discharged gas from the access port to the air pathway during an expiratory phase;
• and
• a controller configured to delay supply of the oxygen gas from the oxygen pathway for a delay time in order to maintain the predetermined percentage of the oxygen in the mixed gas during a subsequent inspiratory phase.

A ventilator comprising:

• an air pathway configured to supply air to a mixing node;
• an oxygen pathway configured to supply oxygen to the mixing node, where the oxygen is mixed with air to obtain a mixed gas having a predetermined percentage of oxygen;
• a blower configured to pressurize the mixed gas during an inspiratory phase;
• a conduit configured to provide the pressurized mixed gas from the blower to an access port during the inspiratory phase, and to provide discharged gas from the access port to the air pathway during an expiratory phase;
• and
• a controller configured to delay supply of the oxygen gas from the oxygen pathway for a delay time in order to maintain the predetermined percentage of the oxygen in the mixed gas during a subsequent inspiratory phase, wherein the air pathway comprises an air flow sensor configured to determine a flow of the discharged gas received by the air pathway during the expiratory phase.

A method of controlling contents of a mixed gas provided to a patient by a single limb ventilator during an inspiratory phase, the mixed gas including a predetermined amount of extra oxygen mixed with air, the method comprising:

• measuring flow of a discharged gas through an air pathway during an expiratory phase with an air flow sensor, the discharged gas including at least a portion of the extra oxygen of the mixed gas;
• with a controller, calculating a volume of the discharged gas received by the air pathway during the expiratory phase based on the measured flow of discharged gas;
• with the controller, determining a delay time based on the calculated volume;
• and
• with a valve, stopping flow of oxygen from an oxygen pathway, separate from the air pathway, for the determined delay time in order to compensate for the portion of the extra oxygen in the discharged gas during a subsequent inspiratory phase.