SYSTEMS AND METHODS FOR COMPENSATING FOR PRESSURE DROP IN A BREATHING ASSISTANCE SYSTEM

• US 20090241952A1
• Filed: 03/24/2009
• Published: 10/01/2009
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Nadjafizadeh, Hossein, Mougel, Laurent, Nicolazzi, Pascal, Gentner, Julien, Grillier-Lanoir, Veronique
• Granted Patent: US 8,353,291 B2
• Time in Patent Office: Days
• US Class Current: 128/204.210
• CPC Class Codes: A61M 16/0009 with sub-atmospheric pressure, e.g. during expiration
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0063 Compressors
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 16/04 Tracheal tubes catheters in general A61M25/00
• CPC Class Codes: A61M 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0042 in the expiratory circuit
• CPC Class Codes: A61M 2016/102 Measuring a parameter of the content of the delivered gas
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: A61M 2205/505 Touch-screens; Virtual keyboard or keypads; Virtual buttons; Soft keys; Mouse touches
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2205/70 with testing or calibration facilities

Abstract

A breathing assistance system configured to determine pressure drop may include a gas delivery system configured to deliver gas toward a patient, one or more sensors configured to measure one or more parameters of gas delivered by the gas delivery system, a calibration module, and a pressure drop calculation module. The calibration module may be configured to perform one or more pressure drop calibration tests, each pressure drop calibration test measuring a pressure drop in gas flowing through a breathing assistance system apparatus at a particular flow rate; and based at least on the results of the one or more pressure drop calibration tests, generating a non-linear equation relating (a) pressure drop in gas flowing through the breathing assistance system apparatus with (b) flow rate of gas flowing through the breathing assistance system apparatus. The pressure drop calculation module may be configured to determine pressure drops in gas flowing through the breathing assistance system apparatus for various flow rates based at least on the non-linear equation.

Claims

1. A breathing assistance system configured to determine pressure drop, comprising:

a gas delivery system configured to deliver gas toward a patient;

one or more sensors configured to measure one or more parameters of gas delivered by the gas delivery system;

a calibration module configured to;

perform one or more pressure drop calibration tests, each pressure drop calibration test measuring a pressure drop in gas flowing through a breathing assistance system apparatus at a particular flow rate; and

based at least on the results of the one or more pressure drop calibration tests, generating a non-linear equation relating (a) pressure drop in gas flowing through the breathing assistance system apparatus with (b) flow rate of gas flowing through the breathing assistance system apparatus; and

a pressure drop calculation module configured to determine pressure drops in gas flowing through the breathing assistance system apparatus for various flow rates based at least on the non-linear equation.

2. A breathing assistance system according to claim 1, wherein generating a non-linear equation relating pressure drop with flow rate comprises calculating one or more coefficients for a non-linear equation relating pressure drop with flow rate.

3. A breathing assistance system according to claim 1, further comprising:

the calibration module being configured to calculate, based on the generated non-linear equation, coefficients for multiple linear equations defining multiple linear line segments corresponding to portions of a curve defined by the non-linear equation; and

memory configured to store the calculated coefficients; and

the pressure drop calculation module being configured to access the coefficients from the memory for determining pressure drops in gas flowing through the breathing assistance system apparatus for various flow rates.

4. A breathing assistance system according to claim 1, wherein the non-linear equation comprises a second degree polynomial equation.

5. A breathing assistance system according to claim 1, wherein:

the non-linear equation comprises a second degree polynomial equation in the form of;

Pressure Drop=A*(Flow Rate)̂

2+B*(Flow Rate); and

generating the non-linear equation based at least on the results of the one or more pressure drop calibration tests comprises determining the coefficients A and B for the second degree polynomial equation.

6. A breathing assistance system according to claim 1, wherein the pressure drop calculation module is configured to use the non-linear equation directly to calculate pressure drops in gas flowing through the breathing assistance system apparatus at various flow rates.

7. A breathing assistance system configured to determine pressure drop, comprising:

a gas delivery system configured to deliver gas toward a patient;

one or more sensors configured to measure one or more parameters of gas delivered by the gas delivery system; and

a pressure drop compensation system configured to;

perform multiple pressure drop calibration tests, each pressure drop calibration test measuring a pressure drop in gas flowing through a breathing assistance system apparatus at a particular flow rate;

calculate coefficients for multiple linear line segments based on the results of the multiple pressure drop calibration tests, the multiple linear line segments collectively approximating a non-linear relationship between (a) pressure drop in gas flowing through the breathing assistance system apparatus and (b) flow rate of gas flowing through the breathing assistance system apparatus; and

store the calculated coefficients for the multiple linear line segments such that the calculated coefficients may be accessed while providing breathing assistance to the patient to determine pressure drops in gas flowing through the breathing assistance system apparatus for various flow rates.

8. A breathing assistance system according to claim 7, wherein the pressure drop compensation system is configured to:

calculate first coefficients for first multiple linear line segments based on the results of first multiple pressure drop calibration tests for a first configuration of the breathing assistance system;

calculate second coefficients for second multiple linear line segments based on the results of second multiple pressure drop calibration tests for a second configuration of the breathing assistance system; and

store the first calculated coefficients and the second calculated coefficients such that, depending on the current configuration of the breathing assistance system, either the first calculated coefficients or the second calculated coefficients may be accessed while providing breathing assistance to the patient to determine pressure drops in gas flowing through the breathing assistance system apparatus for various flow rates.

9. A breathing assistance system configured to determine pressure drop, comprising:

a gas delivery system configured to deliver gas toward a patient;

one or more sensors configured to measure one or more parameters of gas delivered by the gas delivery system;

memory configured to store a look-up table of coefficients for linear equations representing multiple line segments, the line segments collectively approximating a non-linear relationship between (a) pressure drop in gas flowing through the breathing assistance system apparatus and (b) flow rate of gas flowing through the breathing assistance system apparatus; and

a pressure drop compensation system configured to;

receive a measured flow rate value for gas flowing through the breathing assistance system apparatus;

access from the stored look-up table one or more coefficients corresponding to a particular one of the multiple line segments that corresponds with the measured flow rate value; and

use the one or more accessed coefficients corresponding to the particular line segment to calculate a pressure drop corresponding with the measured flow rate value.

10. A breathing assistance system according to claim 9, wherein:

the look-up table of coefficients includes (a) a first table of coefficients for linear equations representing multiple line segments corresponding to a first configuration of the breathing assistance system, and (b) a second table of coefficients for linear equations representing multiple line segments corresponding to a second configuration of the breathing assistance system; and

the pressure drop compensation system is configured to;

determine whether the breathing assistance system is configured in the first or second configuration; and

access coefficients from the stored look-up table based on the determination of the breathing assistance system configuration.