Method for compensating a pressure drop in a ventilator tube, ventilator and memory medium

• US 20050241640A1
• Filed: 05/19/2005
• Published: 11/03/2005
• Est. Priority Date: 11/19/2002
• Status: Active Grant

• Current Assignee: Vyaire Medical GmbH
• Original Assignee: Ewald Anger, Jurgen Reinstadtler, Martin Baecke
• Inventors: Baecke, Martin, Reinstadtler, Jurgen, Anger, Ewald
• Granted Patent: US 7,367,338 B2
• Time in Patent Office: Days
• US Class Current: 128/204.230
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient

Abstract

The present invention relates to a method of compensating the pressure drop in an ordinary ventilator tube. The method comprises the measurement of a first air flow at a first pressure on the apparatus'"'"' side of the ventilator tube and with the respiratory mask taken off. Moreover, a parameter is calculated in a function which provides the pressure drop in the ventilator tube in dependence on the air flow. The parameter for the air flow and pressure is calculated. Later, the air flow is calculated with the respiratory mask being put on. By means of the function a correction pressure is calculated from the air flow. Finally, a target pressure is set which results as a sum of the selected mask pressure and the correction pressure. The invention moreover relates to ventilator for performing the aforementioned method and to a memory medium for storing a corresponding program.

Claims

1. A method of compensating the pressure drop in a ventilator tube, comprising:

measuring a first air flow at a first pressure on the apparatus'"'"' side of a ventilator tube and with the respiratory mask taken off;

calculating a parameter in a function providing the pressure drop in said ventilator tube in dependence on the air flow, wherein the parameter for the first air flow and the first pressure is calculated;

measuring the air flow with the respiratory mask being put on;

calculating a correction pressure by means of the function for the measured air flow; and

setting a target pressure determined as sum of the selected mask pressure and the correction pressure.

2. The method according to claim 1, further comprising:

measuring a second air flow at a second pressure on the apparatus'"'"' side unequal to the first pressure and with the respiratory mask taken off;

calculating the first parameter and a second parameter of the function, wherein both parameters are calculated from the first and second air flow and the first and second pressure.

3. The method according to claim 1, further comprising:

setting a plurality of pressures on the apparatus'"'"' side of a ventilator tube with the respiratory mask taken off; and

measuring the air flow at each of the plurality of pressures.

4. The method according to claim 3, further comprising:

calculating a parameter of the function such that the pressures calculated from said measured air flows by said function optimally correspond to the set pressures.

5. The method according to claim 1, wherein after the calculation of the parameter or the parameters only the parameter(s) is/are stored, but not the pressures set with the respiratory mask taken off.

6. The method according to claim 3, wherein for each interval between two flows measured with the respiratory mask taken off the parameter for the function is calculated from the flows limiting the interval and the corresponding pressures and, when calculating the correction pressure, at first the interval between two pressures measured with the respiratory mask taken off is searched and used in the function of the parameters for the interval.

7. The method according to claim 3, wherein during the setting of the plurality of pressures the pressures increase monotonously and no further pressures are set, if the difference between a predefined target pressure and a measured actual pressure exceeds a predetermined value.

8. The method according to claim 6, wherein the parameter for a flow interval is calculated after both flows were measured at the interval boundaries and the corresponding pressures were set and before another pressure is set, wherein another pressure is set only if said parameter is within a predefined interval.

9. The method according to claim 1, wherein it is checked whether the calculated parameter is within a predefined range and, if this is not the case, a stored parameter value is used.

10. The method according to claim 1, wherein actual pressure values measured by a pressure sensor are used for calculating the parameter(s).

15. The ventilator according to claim 1, wherein it is checked whether the calculated parameter is within a predefined range and, if this is not the case, a stored parameter value is used.

11. A ventilator comprising:

a housing;

a fan within said housing;

a mask;

a ventilator tube, connecting said fan and said mask;

said flow sensor measuring a first air flow at a first pressure on the ventilator side of said ventilator tube while the respiratory mask taken being taken off;

a controller for calculating a parameter in a function providing the pressure drop in said ventilator tube in dependence on the air flow, wherein the parameter for the first air flow and the first pressure is calculated;

said flow sensor measuring the air flow while the respiratory mask being put on;

said controller calculating a correction pressure by means of the function for the measured air flow; and

said controller setting a target pressure determined as sum of the selected mask pressure and the correction pressure.

12. The ventilator according to claim 11, said flow sensor measuring a second air flow at a second pressure unequal to the first pressure and with the respiratory mask taken off;

said controller calculating the first parameter and a second parameter of the function;

both parameters being calculated from the first and second air flow and the first and second pressure.

13. The ventilator according to claim 11, wherein, during the setting of a plurality of pressures, the pressures increase monotonously and no further pressures are set, if the difference between a predefined target pressure and a measured actual pressure exceeds a predetermined value.

14. The ventilator according to claim 11, wherein the parameter for a flow interval is calculated after both flows at the interval boundaries were measured and the corresponding pressures were set and before another pressure is set, wherein another pressure is set only if said parameter is within a predefined interval.

16. A memory medium for use with a CPAP-apparatus storing commands, comprising a central processing unit for processing the commands stored in the memory medium, the CPAP-apparatus performing the following during the processing of the commands stored in the memory medium:

measuring a first air flow at a first pressure on the apparatus'"'"' side of a ventilator tube and with the respiratory mask taken off;

calculating a parameter in a function providing the pressure drop in said ventilator tube in dependence on the air flow, wherein the parameter for the first air flow and the first pressure is calculated;

measuring the air flow with the respiratory mask being put on;

calculating a correction pressure by means of the function for the measured air flow; and

setting a target pressure determined as sum of the selected mask pressure and the correction pressure.