Systems, devices, and/or methods for measuring metabolic energy expenditure
Inventors
PARKER, JR., B. Eugene • Ehlmann, Kevin M. • Gressick, William T.
Assignees
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Publication Number
US-10271766-B1
Publication Date
2019-04-30
Expiration Date
Abstract
Certain exemplary embodiments can provide a system, machine, device, manufacture, circuit, composition of matter, and/or user interface adapted for and/or resulting from, and/or a method and/or machine-readable medium comprising machine-implementable instructions for, activities that can comprise and/or relate to, facilitating determination of the oxygen consumption, carbon dioxide production, respiratory exchange ratio, and/or energy expenditure of a mammal.
Core Innovation
The disclosed invention provides a Mobile Metabolic Measurement (M3) system for indirect calorimetry configured to facilitate determination of oxygen consumption, carbon dioxide production, respiratory exchange ratio (R), and/or energy expenditure. The system is flowmeter-free and uses exhaled gas sampling from a mammal via a mask or mouthpiece sampling flow tube that diverts only a small fraction of exhaled gas into a moisture-managing conduit. The conduit reduces the water vapor pressure of the exhaled gases before the gases enter a sealed mixing tank for homogeneous mixing of the sampled gases.
The mixing tank contains integrated sensors that measure volumetric oxygen fraction and volumetric carbon dioxide fraction of the mixture, together with relative humidity and temperature of the mixture. A barometric pressure sensor measures barometric pressure of the mixture, and the description emphasizes integration of the barometric pressure measurement with the oxygen sensor and integration of temperature and relative humidity measurements with the carbon dioxide sensor. The system also includes wireless telemetry for conveying sensor measurement data and battery power for operating the sensors and wireless transceiver, with one-way inlet and outlet or exhaust valve arrangements and port geometry to maintain substantially atmospheric pressure and reduce backflow or reversal.
A theoretical model of gas mixing in the mixing tank is described, including exponential gas mixing used to compute metabolic rates without dependence on sensor time constants. The disclosure also states measurement thresholds and steady state behavior and notes validation using a metabolic simulator.
Claims Coverage
The partial content includes two independent claims, a system claim and a method claim, that center on a flowmeter-free indirect calorimetry approach using a mixing tank and sensor suite to yield outputs for oxygen consumption, carbon dioxide production, respiratory exchange ratio, and/or energy expenditure. Across the independent claims, the inventive features include exhaled gas routing to a homogeneous mixing tank, moisture or water vapor pressure reduction within a conduit, sensor measurements of O2 and CO2 plus environmental variables, gas-tight tank construction and integrated sensor arrangements, and wireless transmission and computation that are substantially independent of sensor time constants while maintaining substantially atmospheric pressure in the tank.
Flowmeter-free indirect calorimetry using homogeneous mixing in a gas-tight mixing tank
A flowmeter-free indirect calorimetry system configured to facilitate determination of oxygen consumption, carbon dioxide production, respiratory exchange ratio, and/or energy expenditure using a mixing tank that contains a mixture comprising at least a portion of a group of exhaled-gas samples during a predetermined time period, where the tank is formed from non-conductive plastic, comprises a removable lid and a gasket to form a gas-tight seal, and is configured to promote homogeneous mixing.
Exhaled gas conduit reducing water vapor pressure
A conduit configured to convey exhaled gases from a flow tube toward the mixing tank and configured to reduce the water vapor pressure of the exhaled gases within the conduit to approximately a water vapor pressure in air outside the conduit.
Integrated sensor suite measuring O2, CO2, humidity, temperature, and barometric pressure
A plurality of sensors including an oxygen sensor measuring volumetric oxygen fraction of the mixture in the mixing tank, a self-calibrating carbon dioxide sensor measuring volumetric carbon dioxide fraction, a relative humidity sensor measuring relative humidity of the mixture, a temperature sensor measuring temperature of the mixture, and a barometric pressure sensor measuring barometric pressure of the mixture, with sensor integrations specified for barometric pressure with the oxygen sensor and temperature and relative humidity with the carbon dioxide sensor.
Wireless transmission with battery-powered sensing and substantially atmospheric pressure control
A wireless transceiver configured to convey sensor measurement data and a battery configured to power the sensors and/or wireless transceiver, together with one-way inlet valve preventing mixture from escaping via the conduit and tank inlet or outlet port geometry configured to maintain substantially atmospheric pressure and promote gas handling consistent with substantially atmospheric pressure throughout measurement.
Time-constant independent determination from volumetric O2 and CO2
A flowmeter-free indirect calorimetry method configured to facilitate determination of oxygen consumption, carbon dioxide production, respiratory exchange ratio, and/or energy expenditure by sampling exhaled gases toward a mixing tank, measuring volumetric oxygen and carbon dioxide fractions in the mixing tank, measuring relative humidity, temperature, and barometric pressure, wirelessly transmitting sensor measurement data, and determining the outputs based on the volumetric oxygen fraction and volumetric carbon dioxide fraction such that the determined outputs are substantially independent of a time constant of the oxygen sensor and a time constant of the carbon dioxide sensor while a pressure in the tank remains substantially atmospheric throughout the measuring activities.
Across the independent claims, the coverage centers on a flowmeter-free indirect calorimetry system and method that sample exhaled gases into a homogeneous mixing tank, reduce water vapor pressure via a conduit, measure volumetric oxygen and carbon dioxide fractions alongside humidity, temperature, and barometric pressure, and determine oxygen consumption, carbon dioxide production, respiratory exchange ratio, and/or energy expenditure using wireless transmission and determination that is substantially independent of oxygen and carbon dioxide sensor time constants while maintaining substantially atmospheric pressure.
Stated Advantages
Provides a flowmeter-free indirect calorimetry system configured to facilitate determination of oxygen consumption, carbon dioxide production, respiratory exchange ratio, and/or energy expenditure.
Conveys sample measurements with wireless transmission.
Enables determined oxygen consumption, carbon dioxide production, respiratory exchange ratio, and/or energy expenditure to be substantially independent of sensor time constants.
Maintains tank pressure at substantially atmospheric pressure throughout measuring activities.
Documented Applications
Indirect calorimetry on a mammal to determine oxygen consumption, carbon dioxide production, respiratory exchange ratio (R), and/or energy expenditure.
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