Inspiratory airway pressure system with admittance determining apparatus and method

• US 5,134,995 A
• Filed: 12/21/1990
• Issued: 08/04/1992
• Est. Priority Date: 05/19/1989
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Original Assignee: Puritan Bennett Corp. (Medtronic Plc)
• Inventors: Snook, James A., Gruenke, Roger A., Wyble, Marilyn S., Loethen, Steven W., Lasnier, Christopher D., Trimble, Russell L., Orlt, Jiri G.
• Primary Examiner(s): Burr, Edgar S.
• Assistant Examiner(s): Asher, Kimberly L.
• Application Number:
  US07/632,327
• Time in Patent Office: 592 Days
• Field of Search: 128/204.21, 128/204.18, 128/204.23, 128/207.18, 128/207.14, 128/719, 128/724, 128/670
• US Class Current: 128/204.23
• CPC Class Codes: A61F 5/56 Devices for preventing snoring by influencing the respiratory system by gas treatment A61M16/00
• 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 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• 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 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/0633 with forehead support
• CPC Class Codes: A61M 16/0683 Holding devices therefor
• CPC Class Codes: A61M 16/1055 bacterial
• CPC Class Codes: A61M 16/107 in the inspiratory path
• CPC Class Codes: A61M 16/204 used for inhalation control
• CPC Class Codes: A61M 16/205 used for exhalation control
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/054 with electrotherapy
• CPC Class Codes: A61M 2205/3561 local, e.g. within room or hospital
• CPC Class Codes: A61M 2210/0618 Nose

Abstract

An apparatus and method for facilitating the respiration of a patient are disclosed which are particularly useful in treating mixed and obstructive sleep apnea and certain cardiovascular conditions, among others, by increasing nasal air pressure delivered to the patient'"'"'s respiratory passages just prior to inhalation and by subsequently decreasing the pressure to ease exhalation effort. The preferred apparatus includes a patient-coupled gas delivery device for pressurizing the patient'"'"'s nasal passages at a controllable pressure, and a controller coupled with the delivery device having a pressure transducer for monitoring the nasal pressure and a microcontroller for selectively controlling the nasal pressure. In operation, the controller determines a point in the patient breathing cycle just prior to inhalation and initiates an increase in nasal pressure at that point in order to stimulate normal inhalation, and subsequently lowers the nasal pressure to ease exhalation efforts.

Claims

1. An apparatus for determining the airway patency of a patient exhibiting a breath cycle having inhalation and exhalation phases, said apparatus comprising:

means for supplying a breathable gas from a source thereof under a controllable pressure to at least a portion of the patient'"'"'s airway;

means for sensing patient respiration flow and pressure and for producing signals representative of substantially simultaneous flow and pressure;

signal processing means for receiving said signals and responsive thereto for determining the patient'"'"'s respiratory admittance from said substantially simultaneous flow and pressure; and

means for controlling said pressure in accordance with said admittance,

said signal processing means including means for determining said admittance as the dividend of flow divided by pressure.

2. The apparatus as set forth in claim 1, said breathable gas including ambient air.

3. The apparatus as set forth in claim 1, said sensing means including flow sensor means for sensing patient respiration flow and for producing signals representative thereof.

4. The apparatus as set forth in claim 3, said flow sensor means including a differential pressure flow sensor.

5. The apparatus as set forth in claim 1, said sensing means including pressure sensing means for sensing a pressure of breathable gas delivered to the patient.

6. The apparatus as set forth in claim 1, said signal processing means including

means for storing at least one admittance template composed of a plurality of admittances in memory,

means for storing a set of patient admittances, and

means for comparing said admittance set with said at least one stored admittance template.

7. The apparatus as set forth in claim 6, said storing means including a plurality of stored templates, said controlling means including means for determining which of said templates presents the closest match with said admittance set, said closest match being representative of patient airway patency.

8. the apparatus as set forth in claim 7, said controlling means including means for controlling said pressure in accordance with said closest match.

9. The apparatus as set forth in claim 7, said templates presenting normalized amplitudes and time bases, said controlling means including means for normalizing the amplitude and time base of said respiratory admittance in accordance with said stored templates.

10. The apparatus as set forth in claim 7, said controlling means including memory means for storing pressure change data in association with each of said templates, said controlling means including means for controlling said breathable gas pressure in accordance with pressure change data associated with said closest match.

11. The apparatus as set forth in claim 7, said controlling means including a microprocessor.

12. The apparatus as set forth in claim 1, said admittance being determined as a function of said flow and pressure during patient inhalation.

13. The apparatus as set forth in claim 1, said controlling means including a microprocessor.

14. The apparatus as set forth in claim 1, said signal processing means including means for using Fast Fourier Transforms for processing data representative of said flow and pressure.

15. A method of determining the airway patency of a patient, the patient exhibiting a breath cycle having inhalation and exhalation phases, said method comprising:

using sensing means for repeatedly sensing a plurality of substantially simultaneous patient respiration flows and pressures during a patient inhalation phase and for producing signals representative thereof;

using signal processing means for receiving said signals and responding thereto for determining a set of patient admittances from said flows and pressures and storing admittance data representative of said admittance set in a memory device, and using said signal processing means for determining said admittances as the dividend of flow divided by pressure;

comparing in said signal processing means said admittance data with predetermined admittance templates stored in said memory device; and

determining in said signal processing means the closest match of said admittance templates with said admittance data, said closest match being representative of patient airway patency during said phase.

16. The method as set forth in claim 15, said step of determining admittance data including the step of using Fast Fourier Transforms for processing data representative of said flow and pressure.

17. The method as set forth in claim 15 further including the steps of

supplying the patient with a breathable gas from a source thereof under a controllable pressure to at least a portion of the patient'"'"'s airway;

and

controlling said gas pressure in accordance with said patient airway patency.

18. The method as set forth in claim 15, further including the steps of

storing in a memory device a set of pressure change actions corresponding to said templates, and

executing an action corresponding to said template presenting the closest match to said admittance data.

19. An apparatus for determining the airway patency of a patient comprising:

means for repeatedly sensing a plurality of substantially simultaneous patient respiration flows and pressures and for producing signals representative thereof;

signal processing means for receiving said signals and responsive thereto for determining a set of respiratory admittances from said flows and pressure, said signal processing means including means for determining each of said admittances as the dividend of flow divided by pressure; and

memory means for storing a plurality of airway admittance templates representative of a plurality of predetermined airway admittances correlated with airway patency,

said signal processing means including means for determining which of said templates presents the closest matching admittance to said admittance set, the airway patency correlated with said matching admittance being representative of the patient'"'"'s airway patency.