Techniques for determining a volume of exhaled CO2 as a function of time using side-stream capnography, including obtaining flow dynamics measurements of a subject from a flow sensor； obtaining CO2 concentration measurements of the subject from a side-stream CO2 monitor； determining a duration of time (ΔTsl) for a sample of gas to flow from a reference point to the side-stream CO2 monitor； synchronizing in time the CO2 concentration measurement with the flow dynamics measurement, based on the determined ΔTsl； and determining a volume of CO2 exhaled as a function of time, based on the flow dynamics measurement and the synchronized CO2 concentration measurement.
