A method of determining a respiratory parameter for a subject using an indirect
calorimeter is provided. The indirect calorimeter includes a respiratory connector
for passing inhaled and exhaled gases, a flow pathway operable to receive and pass
inhaled and exhaled gases having a flow tube within the flow pathway through which
the inhaled and exhaled gases pass, a flow meter for determining an instantaneous
flow volume of the inhaled and exhaled gases, a component gas concentration sensor
for determining an instantaneous fraction of a predetermined component gas and
a computation unit having a processor and a memory. The method includes the steps
of initializing the indirect calorimeter and the subject breathing into the respiratory
connector if the indirect calorimeter is initialized, sensing the flow volume of
the inhaled and exhaled gases passing through the flow pathway using the flow meter
and transmitting a signal representing the sensed flow volume to the computation
unit. The method also includes the steps of sensing a concentration of a predetermined
component gas as the inhaled and exhaled gases pass through the flow pathway using
the component gas sensor, and transmitting a signal representing the sensed concentration
of the predetermined component gas to the computation unit. The method further
includes the steps of calculating at least one respiratory parameter for the subject
as the subject breathes through the calorimeter using the sensed flow volume and
the sensed concentration of the predetermined component gas, and providing the
subject with the at least one respiratory parameter.
