Accessory detection in capnography modules

A respiratory gas flow coupling, comprising:

• a device connector of a respiratory gas analyzer having a male nipple, the male nipple having a first longitudinal axis and a side-oriented leak path through a wall of the male nipple, the side-oriented leak path being oriented substantially orthogonal to the first longitudinal axis and comprising a passage having a first open end in fluid communication with a lumen of the male nipple and a second open end in fluid communication with ambient air;
• and
• a patient accessory connector of a patient accessory having a female receptacle adapted to connect with the male nipple of the device connector, the female receptacle having a second longitudinal axis that is substantially parallel with the first longitudinal axis;
• wherein the patient accessory is configured to be connected with the respiratory gas analyzer via the patient accessory connector of the patient accessory and the device connector of the respiratory gas analyzer;
• wherein the female receptacle of the patient accessory connector seals the side-oriented leak path of the male nipple of the device connector when the patient accessory connector is connected with the device connector;
• and
• wherein the side-oriented leak path is disposed at a position along the male nipple such that a shorter female receptacle of an incompatible patient accessory connector which is shorter than the female receptacle of the patient accessory connector does not seal the side-oriented leak path when the incompatible patient accessory connector with the shorter female receptacle is connected with the device connector.

A respiratory gas analysis method comprising:

• connecting a patient accessory with a respiratory gas analyzer using a patient accessory connector of the patient accessory and a device connector of the respiratory gas analyzer, the device connector having a first longitudinal axis and a female receptacle including a side-oriented leak path comprising a passage passing through a wall of the female receptacle, the passage having a first open end in fluid communication with a lumen of the female receptacle and a second open end in fluid communication with ambient air, the patient accessory connector having a second longitudinal axis that is parallel to the first longitudinal axis and having a male nipple adapted to connect with the female receptacle of the device connector, the side-oriented leak path being oriented substantially orthogonal to the first and second longitudinal axes, wherein the male nipple of the patient accessory connector seals the side-oriented leak path of the female receptacle of the device connector when the patient accessory connector is connected with the device connector, and wherein the side-oriented leak path is disposed at a position along the female receptacle such that a shorter male nipple of an incompatible patient accessory connector which is shorter than the male nipple of the patient accessory connector does not seal the side-oriented leak path when the incompatible patient accessory connector with the shorter male nipple is connected with the device connector;
• operating a pump to draw air flow from the patient accessory into the respiratory gas analyzer via the connected patient accessory connector and device connector;
• detecting whether the patient accessory is connected with the respiratory gas analyzer based on measurement of the air flow by detecting whether ambient air is flowing through the passage into the lumen of the female receptacle;
• and
• using the respiratory gas analyzer, performing respiratory gas analysis on the drawn air flow conditional upon the patient accessory being detected as connected with the respiratory gas analyzer.