Subject interface appliance and method for delivering a breathable substance to a subject while obtaining gas samples from the airway of the subject

A method of obtaining a sample of gas from the airway of a subject, the method comprising:

• engaging a first external orifice of the airway of a subject, wherein the first external orifice of the airway is engaged by a secondary interface of a subject interface appliance, the secondary interface comprising:
• a hollow prong having a first end and a second end, the hollow prong being inserted into the first external orifice of the airway of the subject such that the first end of the hollowing prong is positioned inside of the first external orifice to engage the first external orifice of the airway of the subject, and the second end of the hollow prong is positioned outside of the first external orifice, and
• a main conduit connected to the hollow prong at or near the second end to receive gas that has entered the first end of the hollow prong within the airway of the subject, the main conduit being configured to guide the received gas toward a sensor configured to generate an output signal conveying information related to one or more parameters of the received gas received by the secondary interface through the hollow prong;
• enclosing one or more external orifices of the airway of the subject, including the first external orifice of the airway, wherein the one or more external orifices of the airway of the subject are enclosed by a primary interface of the subject interface appliance, the primary interface including a mask barrier that encloses the one or more external orifices of the airway, wherein the mask barrier is shaped to form a delivery opening through which a breathable substance can be communicated to the one or more external orifices of the subject that are enclosed by the mask barrier;
• applying a resilient bias force to the secondary interface that maintains the engagement between the secondary interface and the first external orifice of the airway of the subject, wherein the resilient bias force is applied to the secondary interface by a resilient member extending from the primary interface to the secondary interface, the resilient member being configured to suspend and hold the secondary interface spatially apart from the mask barrier within the delivery opening of the primary interface at a default position near a plane defined by a seal portion with respect to the primary interface such that displacement of the secondary interface from the default position, in response to installation of the primary interface to enclose the one or more external orifices of the airway of the subject, results in the application of the resilient bias force by the resilient member on the secondary interface toward the default position, wherein the interface appliance is configured such that responsive to the primary interface being installed on a face of the subject, the resilient member resiliently biases the hollow prong to hold the hollow prong in place on the face of the subject with the first end of the hollow prong inside of the first external orifice of the airway of the subject;
• and
• adjusting the resilient bias force applied by the resilient member to customize the engaging between the secondary interface and the first external orifice of the airway of the subject.