Lung ventilator device

• US 5,107,830 A
• Filed: 03/30/1990
• Issued: 04/28/1992
• Est. Priority Date: 02/21/1987
• Status: Expired due to Term

• Current Assignee: University of Manitoba
• Original Assignee: University of Manitoba
• Inventors: Younes, Magdy
• Primary Examiner(s): Burr, Edgar S.
• Assistant Examiner(s): Lewis, Aaron J.
• Application Number:
  US07/501,757
• Time in Patent Office: 760 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23, 128/204.26
• US Class Current: 128/204.18
• 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 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/0072 Tidal volume piston pumps
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit

Abstract

Ventilation to a patient is provided in response to patient effort. The free flow of gas from a piston, or similar air source, in response to patient inhalation is detected, the instantaneous rate and volume of flow are measured and the measurements are used as control signals to a drive motor for the piston to move the piston to generate a pressure which is proportional to the sum of measured and suitably amplified rate and volume of flow signals. Since the command signal to the pressure generator only changes subsequent to, and not in advance of, a change in flow and volume, the ventilator is subservient to the patient and provides a proportional assist to patient ongoing breathing effort during inspiration (Proportional Assist Ventilation, PAV).

Claims

1. A method for providing breathing assistance in proportion to patient ongoing inspiratory effort, which comprises:

providing a free flow of gas from a gas delivery system to a patient in response to a pressure gradient generated by patient inspiratory effort,

determining the rate and volume of flow of said gas to said patient,

independently amplifying signals corresponding to said determined rate and volume of flow, and

providing a pressure assist to said gas in proportion to the sum of said determined and amplified rate and volume of flow.

2. The method of claim 1, wherein said pressure assist is determined by the equation:

space="preserve" listing-type="equation">P.sub.vent =K.sub.1 V+K.sub.2 V

where P_vent is the magnitude of the pressure assist, K₁ is a gain factor applied to a variable ongoing volume signal V and K₂ is a gain factor applied to a variable ongoing flow-signal V.

3. The method of claim 2 wherein non-linear functions are employed in place of K₁ and K₂.

4. The method of claim 1 wherein said pressure assist is determined by the equation:

space="preserve" listing-type="equation">P.sub.vent =A·

P.sub.mus

where P_vent is the magnitude of the pressure assist, A is an independent factor which determines the proportionally between the pressure assist and patient generated pressure, and P_mus is the estimated instantaneous patient generated pressure determined by the equation;

space="preserve" listing-type="equation">P.sub.mus =V·

E.sub.rs +V·

R.sub.rs -P.sub.vent

where V is the magnitude of the variable ongoing volume signal, V is the magnitude of the variable ongoing flow signal, E_rs is the elastance of the respiratory system of the patient and R_rs is the resistance against which the respiratory system of the patient is operating.

5. The method of claim 1 wherein said rate and volume of flow are determined by continuously sensing the movement of gas to the patient and generating an electrical signal corresponding in magnitude to each of the sensed rate and volume of gas, continuously separately amplifying each signal to a degree required to provide the pressure assist and providing a summed signal combining each of said amplified signals, and continuously applying said summed signal to said gas delivery system, thereby to provide said pressure assist.

6. The method of claim 5 wherein said movement of gas is sensed to generate an electrical signal corresponding to the rate of flow of gas through a tube connecting said gas delivery system to the patient, and said electrical signal is integrated to provide a further electrical signal corresponding to the volume of flow through said tube.

7. The method of claim 6 wherein said gas delivery system comprises bellows means and an electrical motor operatively connected to said bellows means to generate a pressure corresponding in magnitude to the magnitude of the summed signal applied to said electrical motor.

8. The method of claim 1 wherein said gas delivery system develops negative pressure to assist patient'"'"'s breathing through the application of negative pressure to a body surface of the patient.

9. The method of claim 1 when used in conjunction with a method of ventilatory assist employing a predetermined relationship of pressure, flow and/or volume versus time, including continuous positive airway pressure (CPAP), intermittent mandatory ventilation (IMV), pressure support ventilation (PSV), and airway pressure release ventilation (APRV).

10. Apparatus for delivering proportional assist ventilation to a patient, comprising:

means for delivering a free flow of gas to said patient in response to patient inhalatory effort,

means operatively connected to said gas delivery means for generating pressure in said free flow of gas in response to an electrical command signal,

detection means for detecting the instantaneous volume and rate of gas flow to said patient and for generating a separate electrical signal corresponding in magnitude to each of said detected values,

means for selectively applying amplification to each of said electrical signals, and

means for generating said electrical command signal to said pressure generating means in proportion to the sum of said amplified electrical signals corresponding in magnitude to said instantaneous rate and volume of flow.

11. The apparatus of claim 10 wherein said gas delivery means comprises bellows means and said gas pressure generating means comprises an electrical drive motor operatively connected to said bellows means.

12. The apparatus of claim 11 wherein said bellows means comprises a rolling seal piston.

13. The apparatus of claim 10, wherein said detection means comprises flow rate sensing means operatively connected to a pipe joining said bellows means to a patient for generating an electrical signal indicative of the instantaneous rate of flow of gas through said pipe and electrical circuit means for generating an electrical signal indicative of volume flow through said pipe from said electrical signal indicative of gas flow rate as said detected instantaneous value of flow volume.

14. The apparatus of claim 13, wherein said means for generating an electrical command signal comprises summing means for summing amplified electrical signals of said volume and gas flow rates, and including means for applying said command signal to said electrical motor means, thereby to provide a ventilatory assist to said patient corresponding to the magnitude of said summed signal.

15. The apparatus of claim 10 adapted to deliver ventilatory assist in the form of negative pressure intended for application to a body surface.

16. The apparatus of claim 10, including electrical circuit means to override said means for generating said electrical command signal to provide an alternative command signal corresponding to an operator predetermined relationship of pressure, flow and/or volume versus time, including continuous positive airway pressure (CPAP), intermittent mandatory ventilation (IMV), pressure support ventilation (PSV), and airway pressure release ventilation (APRV).