An airway adaptor that measures the concentration of at least one of a specific component and the flow rate of a supply gas and a return gas. The airway adapter may include a tube having a flow path in which the supply gas and the return gas passes. The tube may include a first end having a first aperture for guiding the supply gas into the flow path, and second end having a second aperture for guiding the return gas. Further, the airway adapter may include a measurement device operable to measure at least one of the supply gas and the return gas in the air flow path and a partial shielding disposed at the first aperture and structured to shield a portion of the air flow path. The supply gas may be a respiratory gas and the return gas may be inhaled or exhaled breath of a person.
