Side-stream volumetric capnography
AssigneeCovidien LP
InventorsJoshua Lewis Coleman, Michal Ronen
Life of this patent
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Abstract
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.
Claims20
A method performed by a side-stream capnograph for determining a volume of exhaled carbon dioxide (CO2) as a function of time, the side-stream capnograph including a breath sampling tube and a monitor, the monitor including at least a CO2 sensor and a processor, the method comprising:
- receiving, by the monitor, a flow of exhaled breath from a subject via the breath sampling tube;
- determining, via the CO2 sensor, a plurality of CO2 concentration measurements based on the flow of exhaled breath in the breath sampling tube, wherein the plurality of CO2 concentration measurements corresponds to a waveform;
- identifying, via the processor, a notch or a peak in the waveform, wherein the notch or the peak results from a bolus of air being delivered to the flow of exhaled breath in the breath sampling tube;
- determining, via the processor, a shape distortion factor based on a deviation between the notch or the peak and an anticipated shape;
- transforming, via the processor, a shape of the waveform based on the shape distortion factor;
- synchronizing, via the processor, the transformed waveform with a flow dynamics measurement based on a duration of time;
- and
- determining, via the processor, a volume of exhaled CO2 as the function of time for the subject based on the flow dynamics measurement and the synchronized transformed waveform.
A system for determining a volume of exhaled carbon dioxide (CO2) as a function of time, the system comprising:
- a sampling tube configured to receive a gas sample from a subject;
- and
- a side-stream CO2 monitor coupled to the sampling tube, the side-stream CO2 monitor including at least a CO2 sensor and a processor, the side-stream CO2 monitor configured to determine the volume of exhaled CO2 as the function of time from the gas sample by:
- determining, by the CO2 sensor, a concentration of CO2 in the gas sample;
- determining, by the processor, a CO2 waveform based on the CO2 concentration;
- identifying a notch or a peak in the CO2 waveform resulting from a bolus of air;
- determining a shape distortion factor based on a deviation between the notch or the peak and an anticipated shape;
- transforming the CO2 waveform by applying the shape distortion factor;
- determining a duration of time for the gas sample to flow from a reference point of the sampling tube to the side-stream CO2 monitor, wherein the duration of time is determined from an on-start of inhalation until the notch or the peak in the transformed CO2 waveform;
- synchronizing the transformed CO2 waveform with a flow dynamics measurement based on the duration of time;
- and
- determining the volume of exhaled CO2 as the function of time based on the flow dynamics measurement and the synchronized transformed CO2 waveform.
A device for determining a volume of exhaled carbon dioxide (CO2) as a function of time for a subject, the device comprising:
- a side-stream CO2 monitor configured to measure CO2 concentration over time, wherein the side-stream CO2 monitor includes at least a CO2 sensor and a processor, and wherein the side-stream CO2 monitor is configured to:
- determine, by the CO2 sensor, a concentration of CO2 in a gas sample from the subject via a breath sampling line;
- determine, by the processor, a CO2 waveform based on the CO2 concentration of the gas sample;
- determine a shape distortion factor based on a deviation between a notch in the CO2 waveform and an anticipated shape;
- transform the CO2 waveform by applying the shape distortion factor;
- determine a duration of time for the gas sample to flow from a reference point of the breath sampling tube to the side-stream CO2 monitor, wherein the duration of time is determined from an on-start of inhalation until the notch in the transformed CO2 waveform, wherein the notch or the peak is caused by a bolus of air provided at the on-start of inhalation;
- synchronizing the transformed CO2 waveform with a flow dynamics measurement based on the duration of time;
- and
- determine the volume of exhaled CO2 as the function of time based on the flow dynamics measurement and the synchronized transformed CO2 waveform.
Dependencies are inferred from the claim text.