Pressure support ventilatory assist system

• US 6,305,372 B1
• Filed: 06/24/1999
• Issued: 10/23/2001
• Est. Priority Date: 04/07/1995
• Status: Expired due to Term

• Current Assignee: RIC INVESTMENTS LLC (Koninklijke Philips N.V.)
• Original Assignee: John L. Servidio
• Inventors: Servidio, John L.
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US09/339,426
• Time in Patent Office: 852 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23
• US Class Current: 128/204.21
• 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 device for providing pressurized breathable fluid to a patient comprising:

a pressurized breathable fluid source for providing a fluid;

a conduit for placing said pressurized breathable fluid source in fluid communication with said patient;

a valve disposed between said pressurized breathable fluid source and said patient for varying a pressure of said fluid within said conduit, said valve including a valve housing defining a valve interior, said valve housing carrying at least one inlet port communicating said fluid from said pressurized breathable fluid source to said valve interior;

a piston slidably carried within said valve housing, said piston including a piston inlet port, said piston having a first position wherein said piston inlet port communicates with said housing inlet port enabling fluid from said pressurized breathable fluid source to enter into said conduit, and said piston having a second position wherein said piston inlet port is offset from said housing inlet port preventing fluid from entering said conduit; and

a force generator for moving said valve from said first position to said second position for controlling a pressure of said fluid within said conduit.

2. A pressure support ventilatory assist device including a patient interface for a patient comprising:

a pressurized breathable fluid source for presenting fluid to said patient;

a conduit for placing said pressurized breathable fluid source in fluid communication with said patient;

a bi-directional valve disposed within said conduit between said pressurized breathable fluid source and said patient interface for varying a pressure of said fluid within said conduit, said bidirectional valve moving to a first position to communicate fluid from said pressurized breathable fluid source to a patient for maintaining a predetermined fluid pressure within said conduit and said bidirectional valve also moving to a second position to communicate fluid from said conduit to ambient environment for maintaining a predetermined fluid pressure within said conduit; and

a variable valve actuator capable of providing varying forces to said bidirectional valve for regulating a pressure of said fluid within said conduit.

3. The pressure support ventilatory assist device of claim 2, wherein said force of said variable valve actuator relationally corresponds with a desired pressure of fluid within said conduit during both inhalation and exhalation of said patient.

4. The device of claim 3, including a microprocessor for controlling said variable valve actuator.

5. The device of claim 4, wherein said microprocessor utilizes predetermined pressure selections for controlling said variable valve actuator whereby said variable valve actuator regulates said valve to allow pressure to increase in said conduit to a predetermined pressure selection by producing a first force corresponding with a first predetermined pressure selection and regulates said valve to allow pressure to decrease in said conduit to a second predetermined pressure selection by producing a second force corresponding with said predetermined pressure.

6. The device of claim 4, wherein said microprocessor utilizes a rate of movement of said valve for controlling said variable valve actuator.

7. A method for providing a predetermined fluid pressure to a patient utilizing a pressure support ventilatory assist device, said device including a pressurized breathable fluid source for providing fluid, said method comprising:

positioning a valve between said pressurized breathable fluid source and said patient for controlling a pressure of said fluid presented to said patient;

determining a desired inhalation pressure of fluid for said patient;

manipulating a valve actuator to position said valve in a first position for providing fluid at a desired inhalation pressure;

determining a desired pressure within said conduit upon exhalation of said individual; and

manipulating said valve actuator to position said valve in a second position for venting said fluid into ambient environment until a desired exhalation pressure is achieved within said conduit.

8. A pressure support ventilatory assist system for providing breathable fluid to a patient at an inhalation pressure during patient inhalation and maintaining an exhalation pressure present in an airway of a patient during exhalation of a breathable fluid by such a patient, said system comprising:

a pressurized breathable fluid source for providing a fluid;

a conduit for placing said pressurized breathable fluid source in fluid communication with said patient; and

a pressure controller for controlling a rise in pressure within said conduit from said exhalation pressure to said inhalation pressure to correspond with a desired pressure rise profile.

9. The system of claim 8, wherein said pressure controller includes:

a microprocessor for generating a pressure rate form profile for determining a predetermined pressure at a predetermined time pertaining to a desired rise in pressure from said exhalation pressure to said inhalation pressure;

a valve disposed between said conduit and said pressurized breathable fluid source producing a force to correspond with a predetermined pressure of said pressure wave form profile for varying a pressure of fluid from said pressurized breathable fluid source to said patient; and

a valve actuator for controlling a position of said valve to control a rise of pressure within said conduit.

10. The system of claim 8, wherein said controller controls said rise in pressure such that a predetermined pressure is present in said conduit at a predetermined time during said rise in pressure from said exhalation pressure to said inhalation pressure.

11. A method for detecting inspiration in a pressure support ventilatory environment, said method comprising:

determining the amount of fluid delivered to a patient during inspiration;

determining the end of inspiration;

at the end of inspiration generating a predicted expiratory flow model based upon the inspired volume of fluid;

monitoring actual flow;

comparing said actual flow to said expiratory flow model and correcting said actual flow to correspond with said expiratory flow model; and

defining the start of inspiration when said corrected actual flow is greater than or equal to a predetermined threshold value.

12. The method of claim 11 wherein said method for detecting inspiration is repeated for every subsequent breath.

13. The method of claim 11 wherein correction of said actual flow to correspond with said expiratory flow model produces a leak flow parameter, said leak flow parameter determined at the start of inspiration.

14. The method of claim 13 wherein the measured flow-of fluid during inspiration is corrected utilizing said leak flow parameter for determining the amount of fluid inspired during inspiration.