TRACHEA PRESSURE DETERMINATION METHOD AND DEVICE

• US 20100312132A1
• Filed: 06/03/2009
• Published: 12/09/2010
• Est. Priority Date: 06/03/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Li, Youzhi, Wood, Lockett E., Hayman, Sarah
• Granted Patent: US 8,603,003 B2
• Time in Patent Office: Days
• US Class Current: 600/529
• CPC Class Codes: A61B 5/036 by means introduced into body tracts A61B5/032 and A61B5/035 take precedence
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/085 Measuring impedance of respiratory organs or lung elasticity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0057 Pumps therefor
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/0434 Cuffs
• CPC Class Codes: A61M 16/044 External cuff pressure control or supply, e.g. synchronisation with respiration
• CPC Class Codes: A61M 16/0459 one cuff behind another
• CPC Class Codes: A61M 16/0816 Joints or connectors
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2205/70 with testing or calibration facilities

Abstract

According to various embodiments, methods and systems for determining pressure in the lungs may employ intracuff pressure measurements. The intracuff pressure measurements may calibrated or adjusted based on a set of calibration coefficients or a set of calibration curves, which may reflect patient parameters and cuff/tube geometry factors. The resulting calibration may be used to determine a more accurate estimate of lung pressure, which in turn may be used to control a ventilator and provide breathing assistance to a patient. Also provided are tracheal tubes with couplers or other memory devices for storing calibration information. Such tubes may allow calibration at the level of an individual tracheal tube to account for changes in tube geometry and individual patient factors.

Claims

1. A method for determining trachea pressure comprising:

receiving information related to a reference inflation pressure of an inflated cuff of a tracheal tube disposed in the trachea of a subject;

receiving information related to a monitored pressure of the inflated cuff;

determining a relationship between the monitored pressure and a trachea pressure in the patient based at least in part on the reference inflation pressure and the monitored pressure; and

determining the trachea pressure based upon the relationship.

2. The method of claim 1, wherein the relationship comprises a calibration factor representative of a physical characteristic of the inflated cuff.

3. The method of claim 1, wherein the relationship comprises a calibration factor representative of a physical characteristic of the tracheal tube.

4. The method of claim 3, wherein the relationship defines a ratio between the cuff pressure and the trachea pressure.

5. The method of claim 4, wherein the relationship ratio is determined by selecting a point on a calibration curve representative of the reference cuff pressure.

6. The method of claim 4, wherein the trachea pressure is determined by multiplying a sensed cuff pressure by the ratio and subtracting the reference cuff inflation value to the resulting product.

7. The method of claim 1, accessing stored parameters in a memory circuit defining the relationship.

8. The method of claim 7, wherein the memory circuit is included in a ventilator or monitor coupled to the tracheal tube.

9. The method of claim 8, wherein the memory circuit is included in a circuit coupled to the tracheal tube.

10. The method of claim 8, wherein the memory circuit is included in a component of a cable assembly coupled to the tracheal tube.

11. The method of claim 1, wherein the cuff pressure is monitored by a sensor disposed in the cuff or by a proximally located sensor in fluid communication with the cuff.

12. A method for determining trachea pressure comprising:

determining a monitored cuff pressure in an inflated cuff of a tracheal tube disposed in the trachea of a subject;

selecting a relationship from a plurality of relationships between the monitored cuff pressure and the trachea pressure; and

determining the trachea pressure based upon the selected relationship.

13. The method of claim 12, wherein the selected relationship is a function of monitored cuff pressure, and wherein the method comprises monitoring the current cuff pressure during respiration of the subject, and determining the trachea pressure based upon the relationship and the current cuff pressure.

14. The method of claim 13, wherein the trachea pressure is determined by multiplying a sensed cuff pressure by a ratio of the lung pressure to the cuff pressure determined by the selected relationship.

15. The method of claim 14, wherein the lung pressure is determined by subtracting the reference cuff pressure from the product of the sensed cuff pressure and the ratio.

16. The method of claim 12, wherein the lung pressure is determined by an algorithm that implements an equation generally of the from:

P_T=rP_Cs−

P_Co,

wherein P_T is the trachea pressure, P_Cs is a cuff pressure monitored during respiration of the subject, P_Co is a reference cuff pressure, and r is a ratio of lung pressure to sensed cuff pressure.

17. The method of claim 16, wherein the reference cuff pressure is the initial inflation pressure of the cuff or the lowest pressure seen in the breathing cycle after ventilation has begun.

18. The method of claim 16, wherein the ratio is a non-constant value.

19. The method of claim 18, wherein the ratio varies with monitored cuff pressure, and wherein the method includes monitoring current cuff pressure during respiration of the subject and determining the ratio based upon the monitored cuff pressure.

20. The method of claim 18, wherein the ratio is a function of a relationship between the tracheal tube and the trachea of the subject.

21. A system for determining trachea pressure comprising:

a tracheal tube comprising a conduit configured to be inserted into the trachea of a subject, an inflatable cuff surrounding the conduit and configured to contact the trachea of the subject, a pressure transducer associated with the cuff and an information element associated with the tracheal tube; and

a processor configured to determine a cuff pressure once the cuff is inflated based upon a signal from the transducer and information from the information element, and to determine lung pressure based upon a relationship between the cuff pressure and the lung pressure.

22. The system of claim 21, wherein the information element comprises a memory circuit storing a plurality of relationships, and wherein the processor is configured to determine the lung pressure based upon a selected one of the relationships.

23. A tracheal tube comprising:

a conduit configured to be inserted into the trachea of a subject;

a first inflatable cuff disposed on the conduit and configured to contact the trachea of the subject;

a second inflatable cuff disposed on the conduit, wherein the second inflatable cuff is configured to be smaller than a tracheal diameter at a widest point when the second inflatable cuff is inflated; and

a pressure transducer associated with the second inflatable cuff.

24. The tracheal tube of claim 23, comprising a memoir circuit storing data representative of a relationship between a pressure in the second inflated cuff and a trachea pressure.

25. The tracheal tube of claim 24, wherein the memory circuit is associated with a connection or cable on the tracheal tube.

26. The tracheal tube of claim 24, wherein the pressure transducer is disposed in the cuff.

27. The tracheal tube of claim 24, wherein the pressure transducer is located outside the cuff and is in fluid communication with the cuff.