Respiratory connector for respiratory gas analysis

An improved respiratory connector for use with a respiratory analyzer is provided. The respiratory connector includes a housing configured to be supported in contact with the subject, a flow pathway within the housing for passing the inhaled and exhaled gases therethrough and a connector port extending from the housing for connecting the respiratory connector to the respiratory analyzer. The respiratory connector also includes a usage indicating means within the housing for indicating usage of the respiratory connector to the subject. The respiratory analyzer includes a flow pathway operable to receive and pass inhaled and exhaled gases. A first end of the flow pathway is in fluid communication with the respiratory connector and a second end is in fluid communication with a source and sink for respiratory gases. A flow meter generates electrical signals as a function of the instantaneous flow volume of inhaled and exhaled gases passing through the flow pathway. A component gas concentration sensor generates electrical signals as a function of the instantaneous fraction of a predetermined component gas in the inhaled and/or exhaled gases as the gases pass through the flow pathway. A computation unit receives the electrical signals from the flow meter and the component gas concentration sensor and calculates at least one respiratory parameter for the subject as the subject breathes through the calorimeter.