Pressure support ventilatory assist system

• US 5,598,838 A
• Filed: 04/07/1995
• Issued: 02/04/1997
• Est. Priority Date: 04/07/1995
• Status: Expired due to Term

• Current Assignee: Respironics Incorporated (Koninklijke Philips N.V.)
• Original Assignee: Healthdyne Technologies, Inc. (Koninklijke Philips N.V.)
• Inventors: Servidio, John L., Beverly, Bruce
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US08/419,640
• Time in Patent Office: 669 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23, 128/204.26, 128/205.23
• US Class Current: 128/204.23
• 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 16/204 used for inhalation control
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/3561 local, e.g. within room or hospital
• CPC Class Codes: A61M 2205/42 Reducing noise

Abstract

A pressure support ventilatory assist device is disclosed. Pressure is provided by a blower which is operated at the minimum speed necessary to achieve the desired inspiration pressure. Pressure regulation is achieved by means of a novel pressure regulator valve, rather than by modulating blower speed, thereby reducing perceptible noise. The flow sensor is removed from its conventional location between the regulator valve and the patient mask to a location upstream of the regulator valve to minimize resistance to patient expiration and to isolate the valve from possible fluids in the tubing. Since the flow sensor in this location cannot sense expiration flows, the device includes circuitry for generating a model of the expiratory waveform based upon the inspiratory waveform. Actual pressure is then modulated to conform to the model waveform.

Claims

1. A pressure support ventilatory assist device comprising:

a blower;

a patient mask;

a conduit for placing said blower in fluid communication with said patient mask;

a valve disposed in-line of said conduit between said blower and said patient mask;

a flow sensor disposed between said blower and said valve for measuring airflow within said conduit between said blower and said valve, said measured airflow corresponding to air inspired by a patient plus bias flow and leakage;

inspiration/expiration detection means operatively associated with said flow sensor for detecting the beginning and the end of a patient'"'"'s inspiration;

modeling means operative upon detection of an end of inspiration by said inspiration/expiration detection means for generating a predicted expiration waveform based upon said measured airflow;

comparator means for comparing actual airflow measured by said flow sensor to said predicted expiration waveform; and

valve control means for operating said valve to conform said actual airflow to said predicted expiration waveform.

2. The device of claim 1, further comprising means for computing bias flow and leakage based upon the corrections necessary to conform said actual airflow to said predicted expiration waveform.

3. The device of claim 2, further comprising means for subtracting said computed bias flow and leakage from subsequent breaths.

4. The device of claim 2, wherein said inspiration/expiration detection means identifies the onset of an inspiration when airflow measured by said flow sensor exceeds computed bias flow and leakage.

5. The device of claim 1, further comprising means responsive to a detected onset of patient inspiration for operating said valve to increase pressure in said conduit between said valve and said patient mask.

6. The device of claim 5, further comprising:

timing means for timing the interval between the beginning of an inspiration and the end of said inspiration, and

limit means responsive to said timed interval exceeding a predetermined time period for operating said valve to increase pressure in said conduit between said valve and said mask.