Indirect calorimeter for medical applications

• US 20010029340A1
• Filed: 02/01/2001
• Published: 10/11/2001
• Est. Priority Date: 02/02/2000
• Status: Active Grant

• Current Assignee: Microlife Medical Home Solutions Inc.
• Original Assignee: HealtheTech, Inc.
• Inventors: Mault, James R., Pearce, Edwin M. Jr.
• Granted Patent: US 6,629,934 B2
• Time in Patent Office: Days
• US Class Current: 600/532
• CPC Class Codes: A61B 2560/0295 adapted for recording user messages or annotations
• CPC Class Codes: A61B 2560/0456 Apparatus provided with a docking unit
• CPC Class Codes: A61B 2560/0462 Apparatus with built-in sensors
• CPC Class Codes: A61B 2560/0468 Built-in electrodes
• CPC Class Codes: A61B 2560/0475 Special features of memory means, e.g. removable memory cards
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/0833 Measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity
• CPC Class Codes: A61B 5/097 Devices for facilitating collection of breath or for directing breath into or through measuring devices
• CPC Class Codes: A61B 5/1112 Global tracking of patients, e.g. by using GPS
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/222 : combined with detection or measurement of physiological parameters, e.g. heart rate
• CPC Class Codes: A61B 5/339 : Displays specially adapted therefor
• CPC Class Codes: A61B 5/4866 : Evaluating metabolism A61B5/083 takes precedence
• CPC Class Codes: A61B 5/4872 : Body fat
• CPC Class Codes: A61B 5/6817 : Ear canal
• CPC Class Codes: A61B 5/6826 : Finger
• CPC Class Codes: A61B 5/6838 : Clamps or clips
• CPC Class Codes: A61B 5/6896 : Toys
• CPC Class Codes: A61B 5/742 : using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 7/00 : Instruments for auscultation
• CPC Class Codes: A61M 16/0051 : with alarm devices
• CPC Class Codes: A61M 16/024 : including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/08 : Bellows; Connecting tubes having means for taking samples G01N1/22; Water traps; Patient circuits
• CPC Class Codes: A61M 2016/0036 : in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2202/0275 : Nitric oxide [NO]
• CPC Class Codes: A61M 2205/3569 : sublocal, e.g. between console and disposable
• CPC Class Codes: A61M 2205/3584 : using modem, internet or bluetooth
• CPC Class Codes: A61M 2205/3592 : using telemetric means, e.g. radio or optical transmission
• CPC Class Codes: A61M 2205/52 : with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2209/086 : Docking stations
• CPC Class Codes: A61M 2230/43 : Composition of exhalation
• CPC Class Codes: A61M 2230/432 : partial CO2 pressure (P-CO2)
• CPC Class Codes: A61M 2230/435 : partial O2 pressure (P-O2)
• CPC Class Codes: G01F 1/662 : Constructional details
• CPC Class Codes: G01N 2291/02809 : Concentration of a compound, e.g. measured by a surface mass change
• CPC Class Codes: G01N 2291/02818 : Density, viscosity
• CPC Class Codes: G01N 2291/02836 : Flow rate, liquid level
• CPC Class Codes: G01N 29/024 : by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 33/497 : of gaseous biological material, e.g. breath

Abstract

An improved respiratory analyzer comprises a disposable flow module and non-disposable electronics module. An improved ventilator system comprises a supply of respiratory gases, a ventilator line for directing the respiratory gases to a patient, a flow module holder located in series with the ventilator line into which a flow module can be inserted, and an electronics module which connects to the flow module. In a preferred embodiment, the flow module and electronics module operate in combination to provide the functionality of an indirect calorimeter, so as to determine the metabolic rate of the patient. Feeding of an intubated patient can be controlled using determined patient metabolic rates. Other respiratory parameters can be determined by the system, such as peak flow, tidal volume, end-tidal concentrations, and respiratory quotient. The system provides a non-invasive method of cardiac output determination. A flow module can also be inserted into the mouth or internal respiratory tube of a person.

Claims

1. A ventilator system for a patient, the system comprising:

a supply of respiratory gases;

a conduit for directing the respiratory gases to the patient;

a flow module holder located within the conduit; and

a respiratory gas analyzer, the analyzer comprising;

a flow module, adapted to be placed within the flow module holder in the conduit, so that respiratory gases pass through a flow path of the flow module, the flow module containing a flow rate sensor, and

an electronics module, adapted to be connected to the flow module, and adapted to calculate volumes of gases flowing through the flow path.

2. The ventilator system of

claim 1

, wherein the supply of respiratory gas is a mechanical ventilator.

3. The ventilator system of

claim 1

, wherein the flow rate sensor comprises a pair of ultrasonic transducers operable so as to provide a signal correlated with flow rate through the flow path.

4. The ventilator system of

claim 1

, wherein the flow module further contains a gas component sensor, sensitive to a respiratory gas component, operable so as to provide a signal correlated with an instantaneous concentration of a respiratory gas component.

5. The system of

claim 1

, wherein the electronics module is adapted to calculate a metabolic rate of the patient.

6. A method of analyzing gases respired by a person connected to a mechanical ventilator, the gases passing through a conduit, the method comprising:

providing a holder within the conduit;

inserting a flow module into the holder, so that the gases respired by the person pass through the flow module; and

connecting an electronics module to the flow module, so that the flow module and electronics module in combination are operable to provide a flow measurement.

7. The method of

claim 6

, wherein the flow module and electronics module in combination are operable to provide metabolic rate measurement for the person.

8. A respiratory analyzer for analyzing gases breathed by a patient, the analyzer comprising:

a flow module, comprising;

a housing, adapted to be placed in a conduit for breathed gases, enclosing a flow path, so that the gases breathed by the patient form a gas flow through the flow path,

an in-line gas flow sensor within the flow path, and

a gas component sensor, exposed to the gas flow through the flow path, and

an electronics module;

comprising;

a housing, and

an electronic circuit within the housing, adapted to receive signals from the gas flow sensor and the gas component sensor of the flow module, and to provide a flow volume measurement; and

a communications link between the flow module and the electronics module.

9. The respiratory analyzer of

claim 8

, wherein the housing of the flow module is adapted to reversibly attach to the electronics module.

10. The respiratory analyzer of

claim 8

, wherein the gas component sensor is sensitive to oxygen, and the flow volume measurement is an oxygen volume flowing through the flow module.

11. A method of measuring the cardiac output of a patient, the method comprising:

providing a ventilator system, the system comprising an inhalation conduit, an exhalation conduit, a respiratory conduit, and a valve, the valve having a first condition in which the valve allows gases to pass from the inhalation conduit into the respiratory conduit, allows gases to pass from the respiratory conduit into the exhalation conduit, and prevents gases from entering the respiratory conduit from the exhalation conduit; and

the valve having a second condition in which the valve allows gases to pass from the exhalation conduit into the respiratory conduit so as to provide a period of partial rebreathing of exhaled carbon dioxide for the patient when the patient is connected to the ventilator system;

providing a flow module within the respiratory conduit;

providing an electronics module, operating in conjunction with the flow module so as to measure a flow of carbon dioxide through the flow module;

connecting the patient to the ventilator system with the valve in the first condition;

measuring an end tidal carbon dioxide concentration and a carbon dioxide production for the patient;

adjusting the valve to the second condition; and

measuring changes in the end tidal carbon dioxide concentration and the carbon dioxide production, due to the period of partial rebreathing by the patient, whereby cardiac output can be determined.

12. A system for providing intravenous feeding to a person connected to a ventilator, the method comprising:

a ventilator system, having a holder adapted to receive a flow module;

an indirect calorimeter, comprising a non-disposable electronics module and a disposable flow module, the flow module enclosing a flow path, the flow module being placed within the holder of the ventilator system so that gases respired by the person pass through the flow path;

an intravenous feeding unit, the unit comprising a source of intravenous food, a delivery tube for delivering the food to the patient, and a pump adapted to pump intravenous food from the source along the delivery tube at a controlled pump rate; and

a communications link between the indirect calorimeter and the infusion pump, so as to modify the controlled pump rate of food to the person according to data provided by the indirect calorimeter.

13. The system of

claim 12

, wherein the communications link is a cable.

14. The system of

claim 12

, wherein the communications link is a wireless communications link.

15. The system of

claim 12

, wherein the indirect calorimeter comprises a pair of ultrasonic transducers operable to determine respiratory flow volumes.

16. The system of

claim 12

, wherein the indirect calorimeter has a fluorescence oxygen sensor so as to determine oxygen concentrations of respired gases.

17. A respiratory analyzer for monitoring tracheal gas flow of a breathing subject, the analyzer comprising:

a flow module, adapted to fit within the trachea of the subject;

a pair of ultrasonic transducers located with the flow module;

a tube, connecting the flow module to a ventilator system;

an electronics module, located outside of the subject'"'"'s body, adapted to analyze data received from the flow module; and

a communications link, transmitting data from the flow module to the electronics module.

18. The analyzer of

claim 17

, wherein the communications link is a wire.

19. The analyzer of

claim 17

, wherein the communications link is a wireless link.