Temperature compensation of a respiratory gas sensor

A mainstream gas monitoring system and method that includes a mainstream airway adapter, and a gas sensing assembly associated with the mainstream airway adapter to measure an analyte of a gas flow through the adapter. A gas sensing portion outputs a signal indicative of the analyte in a gas flow in the mainstream airway adapter. A processing portion receives the signal from the gas sensing portion and determines an amount of the analyte in the gas flow based on the signal from the gas sensing portion. The gas sensing portion is subject to temperature variations associated with variations in flow rate and direction of respiratory gases. Methods are described that utilize the measurement of instantaneous respiratory flow rate combined with estimates of gas temperature and composition to estimate the sensor cooling effects from which a flow based time varying compensation factor is derived.