Process for the automatic control of a respirator

• US 9,238,114 B2
• Filed: 07/29/2011
• Issued: 01/19/2016
• Est. Priority Date: 12/20/2010
• Status: Active Grant

• Current Assignee: Dragerwerk AG & Company KGaA (FPS Vermögensverwaltung GmbH)
• Original Assignee: Drager Medical GmbH (FPS Vermögensverwaltung GmbH)
• Inventors: Eger, Marcus, Hansmann, Hans-Ullrich, Glaw, Tobias, Sattler, Frank, Handzsuj, Thomas
• Primary Examiner(s): Dixon, Annette
• Assistant Examiner(s): Han, Mark K
• Application Number:
  US13/194,200
• Publication Number:
  US 20120152251A1
• Time in Patent Office: 1,635 Days
• Field of Search: 128/200.24, 12820418-20423, 12820426-20428, 12820513-20519, 12820523-20525, 12820714-20717, 128/898, 600/529, 600534-536
• US Class Current: 1/1
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/0003 Accessories therefor, e.g. sensors, vibrators, negative pressure
• 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 2016/0015 inhalation detectors
• CPC Class Codes: A61M 2205/33 Controlling, regulating or measuring
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/40 Respiratory characteristics

Abstract

A process for automatic control of a respirator changes between two phases of respiration by checking a detected respiratory breathing activity signal for a threshold criterion. If the threshold criterion is met, a changeover is made.

Claims

1. A process for automatic control of a respirator to change over alternately between inspiration and expiration phases of respiration, the process comprising the steps of:

checking a detected respiratory breathing activity signal, with a control unit, in a phase of respiration for a threshold criterion for changing over into a next phase of respiration and if the threshold criterion is met, a changeover is made from one phase of respiration into the other;

using, in an expiration phase, an inspiration dynamic threshold curve u_insp,thresh(t) for changing over into an inspiration phase, which inspiration dynamic threshold curve u_insp,thresh(t) is held, after a beginning of a present expiration phase, at high values until an end of a selected inspiratory refractory period t_i1 in order to prevent a changeover into inspiration, and then is lowered monotonically, dropping to an inspiratory threshold target value at an expected point in time of a phase duration maximum t_i2 of a present expiration phase and is then changed over into the inspiration phase when the breathing activity signal exceeds the inspiration dynamic threshold curve u_insp,thresh(t);

using, in an inspiration phase, an expiration dynamic threshold curve u_exp,thresh(t) for changing over into an expiration phase, which expiration dynamic threshold curve u_exp,thresh(t) is held, after a beginning of a present inspiration phase, at low values until an end of a selected expiratory refractory period t_e1 in order to prevent a changeover into expiration, and then is raised monotonically, increasing to an expiratory threshold target value at an expected point in time of a phase duration maximum t_e2 of the present inspiration phase and is then changed over into the expiration phase when the breathing activity signal drops below the expiration dynamic threshold curve u_exp,thresh(t);

storing a phase duration of inspiration and expiration phases or breath duration comprising inspiration and expiration phases;

deriving expected points in time of the phase duration maximum t_i2 and the phase duration maximum t_e2 from distributions of phase durations in relation to a beginning of a respective phase of respiration or from a distribution of the breath durations in relation to a beginning of the previous phase of respiration; and

controlling the respirator with said control unit based on the above process steps such that the respirator controls the delivery of breathing gas to a patient.

2. A process in accordance with claim 1, wherein an expected phase duration maximum t_i2 and phase duration maximum t_e2 are derived from the distributions of phase durations of the inspiration and expiration phases or distribution of breath durations as a P-quantile of these distributions, whereby parameters P_i2 and P_e2 are determined for the quantiles beforehand, and parameter values P_i2 and P_e2 are at least 0.8.

3. A process in accordance with claim 1, wherein an expected phase duration maximum t_i2 and phase duration maximum t_e2 are derived from the distributions of phase durations of the inspiration and expiration phases or distribution of breath durations under the assumption that the distributions follow a Gaussian distribution, and the expected phase duration maximum t_i2 are fixed above the mean value by a number of standard deviations, which correspond to a preset probability that a phase duration maximum lies before a fixed phase endpoint, whereby the preset probability is at least 0.8.

4. A process in accordance with claim 1, wherein points in time of an end of inspiratory and expiratory refractory periods t_i1 and t_e1 and expected points in time of the phase duration maximum t_i2 and phase duration maximum t_e2 are related to a point in time of changeover into a present phase of respiration.

5. A process in accordance with claim 1, wherein a pattern of the breathing activity signal is stored over at least a duration of a half phase of respiration and a beginning of a present phase of respiration is determined by examining a breathing activity signal pattern within a period about a point in time of the changeover into a present phase of respiration, and points in time of an end of the inspiratory refractory period t_i1 and the expiratory refractory period t_e1 and the expected points in time of the phase duration maximum t_i2 and phase duration maximum t_e2 are related to the determined point in time of the beginning of the present phase of respiration.

6. A process in accordance with claim 1, wherein points in time of the end of the inspiratory refractory period t_i1 and/or the expiratory refractory period t_e1 are each derived from distributions of the phase durations of the inspiration and expiration phases as a p-quantile of said distributions, whereby the p-quantile values used here p_i1 and p_e1 are selected beforehand and have values of less than 1.

7. A process in accordance with claim 1, wherein values of the breathing activity signal are stored at a plurality of points in time t_i^jε

[t_i1,t_im] and t_e^kε

[t_e1,t_em] (j=1, . . . m and k=1, . . . m), whereby t_im, and t_em correspond to the points in time of median values of distributions of the inspiratory and expiratory phase durations and are accumulated as amplitude distributions of the signal values of the breathing activity signal at said plurality of points in time, and the inspiratory and expiratory thresholds are fixed in the amplitude distributions, such that the probability of changeover according to the distribution function of the phase durations at points in time t_i^jε

[t_i1,t_im] and t_e^kε

[t_e1, t_em] follows the probability, with which the threshold criterion for changeover is met according to the amplitude distributions at the points in time t_i^j and t_e^k.

8. A process in accordance with claim 7, wherein the inspiratory threshold u_insp,thresh(t_i^j) is fixed such that the inspiratory threshold u_insp,thresh(t_i^j) forms a p-quantile with p=F₁(V(t_i^j) in the breathing activity signal distribution at the point in time t_i^j, whereby F₁(V(t_i^j)) is a predetermined function of the distribution function of phase durations, after which the inspiratory threshold is lowered, such that the inspiratory threshold reaches the inspiratory threshold target value at an expected phase duration maximum t_i2, and the expiratory threshold u_exp,thresh(t_e^k) is fixed such that the expiratory threshold u_exp,thresh(t_e^k) forms a p-quantile with p=F₂(V(t_e^k)) in the breathing activity signal distribution at point in time t_e^k, whereby F₂(V(t_e^k)) is a predetermined function of the distribution function of the phase durations, after which the expiratory threshold is raised, such that the expiratory threshold reaches the expiratory threshold target value at an expected phase duration maximum t_e2.

9. A process in accordance with claim 8, wherein F₁(V(t_i^j)=1−

V(t_i^j) and F₂(V(t_e^k)=V(t_e^k) is defined beforehand.

10. A process in accordance with claim 7, wherein assuming a Gaussian amplitude distribution, the inspiratory threshold is defined as μ

(t_i^j)+Q(V(t_i^j))*σ

(t_i^j), wherein μ

(t_i^j) is the mean value and σ

(t_i^j) is the standard deviation of the amplitude distribution at the point in time t_i^j and Q(V(t_i^j) is a factor with preselected dependence on the distribution function V(t_i^j), after which the inspiratory threshold is lowered, such that the inspiratory threshold reaches the inspiratory threshold target value at an expected phase duration maximum t_i2, and, assuming Gaussian amplitude distributions, the expiratory threshold is defined as μ

(t_e^k)+Q(V(t_e^k))*σ

(t_e^k), wherein μ

(t_e^k) is the mean value and σ

(t_e^k) is the standard deviation of the amplitude distribution at the point in time t_e^k and Q(V(t_e^k)) is a factor with preselected dependence on the distribution function V(t_e^k), after which the expiratory threshold is raised, such that the expiratory threshold reaches the expiratory threshold target value at an expected phase duration maximum t_e2.

11. A process in accordance with claim 7, wherein a curve of inspiratory and expiratory thresholds is interpolated between consecutive points in time t_i^j and t_e^k, respectively.

12. A process for control of a respirator to change over between inspiration and expiration phases of respiration, the process comprising the steps of:

receiving a respiratory breathing activity signal, with a control unit, during a phase of respiration;

changing over from a phase of respiration into another phase of respiration if a threshold criterion is met;

during each expiration phase, using a inspiration dynamic threshold curve u_insp,thresh(t) as the threshold criterion for changing over into an inspiration phase, the inspiration dynamic threshold curve u_insp,thresh(t) having high values until an end of a selected inspiratory refractory period t_i1 in order to prevent a changeover into inspiration, and then having lowered inspiratory threshold target values closer to an expected point in time of a phase duration maximum t_i2 of a present expiration phase;

during each inspiration phase, using a expiration dynamic threshold curve u_exp,thresh(t) as the threshold criterion for changing over into an expiration phase, the expiration dynamic threshold curve u_exp,thresh(t) having low values until an end of a selected expiratory refractory period t_e1 in order to prevent a changeover into expiration, and then having lowered expiratory threshold target values closer to an expected point in time of a phase duration maximum t_e2 of a present inspiration phase;

storing a phase duration of inspiration and expiration phases or breath duration comprising inspiration and expiration phases;

deriving expected points in time of the phase duration maximum t_i2 and phase duration maximum t_e2 from distributions of phase durations in relation to a beginning of a respective phase of respiration or from a distribution of the breath durations in relation to a beginning of the previous phase of respiration; and

controlling the respirator with said control unit based on the above process steps such that the respirator controls the delivery of breathing gas to a patient.

13. A process in accordance with claim 12, wherein an expected phase duration maximum t_i2 and phase duration maximum t_e2 are derived from the distributions of phase durations of the inspiration and expiration phases or distribution of breath durations as a P-quantile of these distributions, whereby parameters P_i2 and P_e2 are determined for the quantiles beforehand, and the parameter values P_i2 and P_e2 are at least 0.8.

14. A process in accordance with claim 12, wherein an expected phase duration maximum t_i2 and phase duration maximum t_e2 are derived from the distributions of phase durations of the inspiration and expiration phases or distribution of breath durations under the assumption that the distributions follow a Gaussian distribution, and the expected phase duration maximum t_i2 are fixed above a mean value by a number of standard deviations, which correspond to a preset probability that a phase duration maximum lies before a fixed phase endpoint, whereby the preset probability is at least 0.8.

15. A process in accordance with claim 12, wherein points in time of an end of inspiratory and expiratory refractory periods t_i1 and t_e1 and expected points in time of the phase duration maximum t_i2 and phase duration maximum t_e2 are related to a point in time of changeover into a present phase of respiration.

16. A process in accordance with claim 12, wherein a pattern of the breathing activity signal is stored over at least a duration of a half phase of respiration and a beginning of a present phase of respiration is determined by examining the breathing activity signal pattern within a period about a point in time of the changeover into a present phase of respiration, and points in time of an end of the inspiratory refractory period t_i1 and the expiratory refractory period t_e1 and the expected points in time of the phase duration maximum t_i2 and phase duration maximum t_e2 care related to the determined point in time of the beginning of the present phase of respiration.

17. A process in accordance with claim 12, wherein points in time of the end of the inspiratory refractory period t_i1 and/or the expiratory refractory period t_e1 are each derived from distributions of the phase durations of the inspiration and expiration phases as a p-quantile of said distributions, whereby the p-quantile values used p_i1 and p_e1 are selected beforehand and have values of less than 1.

18. A process in accordance with claim 12, wherein values of the breathing activity signal are stored at a plurality of points in time t_i^jε

[t_i1,t_im] and t_e^kε

[t_e1, t_em] (j=1, . . . m and k=1, . . . m), whereby t_im and t_em correspond to the points in time of median values of distributions of the inspiratory and expiratory phase durations and are accumulated as amplitude distributions of the signal values of the breathing activity signal at this plurality of points in time, and the inspiratory and expiratory thresholds are fixed in the amplitude distributions, such that the probability of changeover according to the distribution function of the phase durations at points in time t_i^jε

[t_i1,t_im] and t_e^kε

[t_e1,t_em] follows the probability, with which the threshold criterion for changeover is met according to the amplitude distributions at the points in time t_i^j and t_e^k.

19. A process in accordance with claim 18, wherein the inspiratory threshold u_insp,thresh(t_i^j) is fixed such that the inspiratory threshold u_insp,thresh(t_i^j) forms a p-quantile with p=F₁(V(t_i^j) in the breathing activity signal distribution at the point in time t_i^j, whereby F₁(V(t_i^j) is a predetermined function of the distribution function of phase durations, after which the inspiratory threshold is lowered, such that the inspiratory threshold reaches the inspiratory threshold target value at an expected phase duration maximum t_i2, and the expiratory threshold u_exp,thresh(t_e^k) is fixed such that the expiratory threshold u_exp,thresh(t_e^k) forms a p-quantile with p=F₂(V(t_e^k)) in the breathing activity signal distribution at point in time t_e^k, whereby F₂(V(t_e^k)) is a predetermined function of the distribution function of the phase durations, after which the expiratory threshold is raised, such that the expiratory threshold reaches the expiratory threshold target value at an expected phase duration maximum t_e2.

20. A process in accordance with claim 18, wherein assuming a Gaussian amplitude distribution, the inspiratory threshold is defined as μ

(t_i^j)+Q(V(t_i^j)*σ

(t_i^j), wherein μ

(t_i^j) is a mean value and σ

(t_i^j) is the standard deviation of the amplitude distribution at the point in time t_i^j and Q(V(t_i^j) is a factor with preselected dependence on the distribution function V(t_i^j), after which the inspiratory threshold is lowered, such that the inspiratory threshold reaches the inspiratory threshold target value at an expected phase duration maximum t_i2, and, assuming Gaussian amplitude distributions, the expiratory threshold is defined as μ

(t_e^k)+Q(V(t_e^k))*σ

(t_e^k), wherein μ

(t_e^k) is the mean value and σ

(t_e^k) is the standard deviation of the amplitude distribution at the point in time t_e^k and Q(V(t_e^k)) is a factor with preselected dependence on the distribution function V(t_e^k), after which the expiratory threshold is raised, such that the expiratory threshold reaches the expiratory threshold target value at an expected phase duration maximum t_e2.