GB2540024A

GB2540024A - Ventilator systems and controls

Info

Publication number: GB2540024A
Application number: GB1608301.6A
Authority: GB
Inventors: Lucio Belisario Anthony; James Leslie Bennett Paul; James Burchell Robert; Qassim Mohammad Khasawneh Mohammad; Charles Oliver Mark
Original assignee: Smiths Medical International Ltd
Current assignee: Smiths Medical International Ltd
Priority date: 2015-06-11
Filing date: 2016-05-10
Publication date: 2017-01-04
Also published as: GB201608301D0

Abstract

A ventilator system comprises a conventional ventilator 1 and a control unit 2 connected with the outlet of the ventilator 10 between the ventilator and a breathing circuit 3. An inspiratory gas path 22 through the control unit connects with the ventilator outlet at one end and at its opposite end with an inspiratory limb 301 of the breathing circuit. An expiratory gas path 34 has its inlet 35 connected with an expiratory limb 302 of the breathing circuit and its outlet 37 opens to atmosphere. An adjustable flow restrictor 31, 41 is provided in the inspiratory path and/or expiratory path and is controlled (via control means 31) by the control unit. In one embodiment the control means receives signals from sensors 32, 33, 39, 40 (e.g. pressure or flow rate sensors) in the gas paths and from a manual flow rate control knob 43 and an expiratory pressure control knob 44; controlling the flow restrictors in response to these signals.

Description

VENTILATOR SYSTEMS AND CONTROLS

This invention relates to ventilator systems of the kind including a source of breathing gas capable of providing a supply of breathing gas at a regulated pressure suitable for supply to a patient.

Portable gas-powered, pneumatic ventilators are widely used in both emergency and transport situations. The ventilators can be rugged and simple to operate, which makes them especially suitable for use outside hospitals and by less qualified people. Such ventilators are usually powered by compressed oxygen, firom a cylinder via a regulator. Spontaneously breathing patients with certain respiratory ailments or diseases such as asthma or chronic obstructive pulmonary disease (COPD) can benefit from various therapies, such as, continuous positive airway pressure (CPAP) or bi-level positive pressure therapy. Patients suffering from acute respiratory distress (ARD) or respiratory failure my benefit fi*om positive end expiratory pressure (PEEP). These features can be achieved using a demand valve or an entrainment device connected to the ventilator but rely on the gas being maintained at a certain elevated pressure above atmosphere continuously during the expiratory period. This can result in pressure levels that cause discomfort to the patient or excessive physical effort during the entire inspiratory or expiratory cycle. Some existing ventilators are either not capable of providing these features or can only do so at inflexible levels.

It is an object of the present invention to provide alternative ventilator systems and controls.

According to one aspect of the present invention there is provided a ventilator system of the above-specified kind, characterised in that the system also includes a control unit having a first inlet adapted for connection to an outlet of the source of breathing gas, an inspiratory gas path extending within the control unit and connected at one end with the IBrst inlet of the control unit, that the opposite end of the inspiratory gas path is arranged for connection externally with an inspiratory limb of a breathing circuit extending to a patient interface, that the control unit includes a second inlet arranged for connection externally with an expiratory limb of the breathing circuit, an expiratory gas path extending within the control unit and coimected at one end with the second inlet, that the opposite end of the expiratory gas path is connected with a gas outlet on the control unit, that the control unit further includes an adjustable flow restrictor in one or both of the inspiratory gas path and the expiratory gas path, and that the control unit includes control means arranged to adjust the or each flow restrictor.

The control unit preferably includes an adjustable flow restrictor in both the inspiratory and expiratory gas path. The inspiratory gas path may connect with a side path that opens to atmosphere via a pressure relief valve. The control means preferably includes a processor and the or each flow restrictor is preferably an electronically-controlled restrictor controlled by signals from the control means. The system preferably includes a pressure sensor located in the inspiratory gas path and connected with the control means. The system preferably includes a flow sensor located in the inspiratory gas path and connected with the control means. The system preferably includes a pressure sensor located in the expiratory gas path and connected with the control means. The system preferably includes a flow sensor located in the expiratory gas path and connected with the control means. The control unit may include a first manual control arranged to select a flow rate of gas at an outlet of the control unit. The control unit may include a second manual control arranged to set an expiratory pressure for the patient. The source of breathing gas may be ventilator apparatus arranged to provide a cyclical supply of breathing gas at its outlet at a ventilation frequency.

According to another aspect of the present invention, there is provided a control unit for a ventilator system according to the above one aspect of the present invention. A ventilator system and control unit, both according to the present invention, will now be described, by way of example, with reference to the accompanying drawing, which shows the system schematically.

The system comprises a conventional source of regulated breathing gas such as provided by ventilator apparatus unit 1. The system also includes a control unit or modulator 2 connected between an outlet 10 of the ventilator unit 1 and a breathing circuit 3 extending to a patient interface 4, such as the mask shown or, for example, a tracheal tube. The modulator 2 is arranged to modify the pressure and, or alternatively, the flow of gas supplied to and firom the patient by the ventilator unit 1 in a manner described in greater detail below. The term “ventilator” is used herein to include ^)paratus for mechanical ventilation of patients who are not breathing spontaneously or those who need help with breathing and includes apparatus for providing respiratory therapy to a patient.

The ventilator 1 is a conventional gas-powered ventilator capable of providing a continuous mandatory ventilation (CMV) output, that is, an output with parameters set by the operator without any feedback from the patient. In general, the ventilator provides at its output a cyclical supply of breathing gas at regulated pressure and at a frequency appropriate for ventilating the patient. The invention could be used with other sources of breathing gas at a regulated pressure suitable for supply to a patient, such as, for example device capable of providing a CPAP output. These ventilators and sources of breathing gas are relatively simple, compact, portable, reliable and robust and are commonly used by paramedics such as in medical transport vehicles. One type of ventilator does not require any electrical supply and is powered exclusively by gas pressure, such as from an oxygen cylinder. Alternatively, the ventilator could be a simple electrical ventilator with a compressor that charges a gas pressure vessel. These ventilators are in common use and are relatively inexpensive but are not capable of reacting to the response of the patient so may cause discomfort to the patient or involve excessive physical effort by the patient. Another problem with such conventional ventilators is that they may continue delivering gas to the patient at a higher than necessary level as the patient recovers. This can be wasteful of the compressed gas used to drive frie ventilator, which may mean that it is not available for another patient. This is a particular problem in remote locations or in disaster situations Avith many injured people needing ventilation.

The control unit or modulator 2 is connected between the ventilator 1 and the patient in order to provide greater control of the gas output of the ventilator 1, such as in response to feedback from the patient. The modulator 2 has a housing 20 of rectangular section with an inlet 21 coimected to the outlet 10 of the ventilator 1. The inlet 21 could be connected directly with the outlet 10 as shown or it could be connected via a length of flexible tubing. The inlet 21 connects within the housing 20 to one end of an inspiratory gas conduit 22 forming a gas flow path via a one-way or non-return valve 23 that allows gas to flow from the inlet to the conduit but prevents flow in the opposite direction. The gas conduit 22 extends along the length of the housing 20 to its opposite side where it opens into a gas outlet 24 projecting on the outside of the housing via a second non-return valve 25. This valve 25 is arranged to allow gas to flow out from the conduit 22 into the outlet 24 but to prevent flow in the opposite direction. The inspiratory gas conduit 22 also connects with a short side branch 26 at a location close to the inlet 21 via a third non-return valve 27. The valve 27 allows gas to flow out from the conduit 22 into the branch 26 but to prevent flow in the opposite direction. The side branch 26 opens into a pressure relief valve 28 mounted on the outside of the housing 20. The pressure relief valve 28 is normally closed to prevent gas escaping from the modulator 2 but is set to open to vent gas if the pressure should rise above a level that is safe for the patient. The gas conduit 22 also includes an electronically-controlled, fast-acting variable restrictor 30 controlled by signals from a processor 31. The processor 31 is connected to receive input signals from a pressure sensor 32 and flow sensor 33 mounted in the gas conduit 22 downstream of the restrictor 30. The processor 31 has a display 131 visible externally of the housing 20.

The modulator 2 further includes an expiratory gas conduit 34 extending along the housing 20 between an inlet 35 adjacent the outlet 24 of the inspiratory gas conduit 22. The inlet 35 opens into the right-hand end of the expiratory gas conduit 34 via a fourth non-return valve 36 arranged to allow gas to flow into the conduit but to prevent gas flowing in the opposite direction. At its opposite end, the expiratory gas conduit 34 opens to atmosphere via a short outlet 37 and a fifth non-retum valve 38. The fifth non-return valve 38 is arranged to allow gas to flow out from the gas conduit 34 but to prevent flow in the opposite direction. The gas conduit 34 includes a pressure sensor 39 and a flow sensor 40 mounted in the conduit upstream of a second electronically-controlled, fast-acting variable restrictor 41. The sensors 39 and 40 provide inputs to the processor 31, which is connected to provide a control output to the restrictor 41.

The valves 23, 25, 36 and 38 could be electrically operated and synchronised together so that when the inspiratory valves 23 and 25 are open the other valves 36 and 38 are closed and vice versa.

The front panel of the housing 20 supports the display panel 131 and also two manual controls 43 and 44 in the form of rotary knobs the outputs of which are cormected to the processor 31. Other forms of manual control could be used. Knob 43 is adjusted by the user to select a desired flow rate of gas out of the outlet 24 to the patient. The processor 31 controls the state of the restrictor 30 in the inspiratory gas conduit 22 according to the setting of the flow control knob 43 and the outputs of the pressure and flow sensors 32 and 33 in the inspiratory conduit. The restrictor 30 is fully opened if the maximum flow rate is desired or is partially closed to achieve lower flow rates. The other knob 44 is used to set the expiratory pressure experienced by the patient. The pressure control knob 44 and the pressure and flow sensors 39 and 40 provide outputs to the processor 31, which controls operation of the restrictor 41 in the expiratory gas conduit 34 according to these inputs and the setting of the pressure control knob.

The restrictors 30 and 41 could be controlled to vary the flow or pressure during a cycle or over the treatment period independently of the flow from the ventilator 1, such as a specified ramp up or profile of pressure or flow. The expiratory pressure could be set to provide a specified PEEP pressure that could be maintained constant or varied in a prescribed manner during a phase. The modulator 2 could be used to superimpose vibratory pulses of any desired frequency, amplitude, shape and duration on the output of the ventilator 1 and may vary over time or in response to changes in the measured flow and pressure. Additional features could be incorporated in the modulator 2, such as measurement and indication of the carbon dioxide or oxygen content of expired gases.

The outlet 24 of the modulator 2 connects with an inspiratory limb 301 of the breathing circuit 3. The inlet 35 connects with the expiratory limb 302 of the breathing circuit. At the patient end of the breathing circuit 3 two non-return valves 303 and 304 allow gas to flow out of the inspiratory limb 301 into the patient interface 4 and allow gas exhaled by the patient to flow into the expiratory limb 302 respectively. As shown, the two limbs 301 and 302 extend parallel to one another. In alternative arrangements the two limbs could extend coaxially, one within the other. Alternatively, the inspiratory and expiratory paths could be provided by a common tube with valves at opposite ends to direct the inspiratory and expiratory ventilation gases appropriately.

The modulator 2 gives the user greater control of ventilator parameters when connected to a conventional simple ventilator 1. A hospital with an existing ventilator intended for non-critical patients could readily upgrade the ventilator to provide additional control functions by simply connecting a modulator according to the present invention to the ventilator outlet. The invention can be used to increase patient comfort during breathing and improve clinical effectiveness both during patient therapy and mechanical ventilation. The invention can also be used to maintain improved control of ventilation and maximise the conservation of oxygen or oxygen enriched air.

Claims

1. A ventilator system including a source (1) of breathing gas capable of providing a supply of breathing gas at a regulated pressure suitable for supply to a patient, characterised in that the system also includes a control unit (2) having a first inlet (21) adapted for connection to an outlet (10) of the source (1) of breathing gas, an inspiratory gas path (22) extending within the control unit (2) and connected at one end with the first inlet (21) of the control unit, that the opposite end (24) of the inspiratory gas path (22) is arranged for connection externally with an inspiratory limb (301) of a breathing circuit (3) extending to a patient interface (4), that the control unit (2) includes a second inlet (35) arranged for connection externally with an expiratory limb (302) of the breathing circuit (3), an expiratoiy gas path (34) extending within the control unit (2) and connected at one end with the second inlet (35), that the opposite end of the expiratory gas path is connected with a gas outlet (37) on the control unit (2), that the control unit (2) fiirther includes an adjustable flow restrictor (30,41) in one or both of the inspiratory gas path (22) and the expiratory gas path (41), and that the control unit (2) includes control means (31) arranged to adjust the or each flow restrictor (30,41).

2. A system according to Claim 1, characterised in diat the control unit (2) includes an adjustable flow restrictor (30 and 41) in both the inspiratory and expiratory gas path (22 and 34).

3. A system according to Claim 1 or 2, characterised in that the inspiratory gas path (22) connects with a side path (26) that opens to atmosphere via a pressure relief valve (28).

4. A system according to any one of the preceding claims, characterised in that the control means includes a processor (31) and that the or each flow restrictor is an electronically-controlled restrictor (30,41) controlled by signals jfrom the control means (31).

5. A system according to any one of the preceding claims, characterised in that the system includes a pressure sensor (32) located in the inspiratory gas path (22) and connected with the control means (31).

6. A system according to any one of the preceding claims, characterised in that the system includes a flow sensor (33) located in the inspiratory gas path (22) and connected with the control means (31).

7. A system according to any one of the preceding claims, characterised in that the system includes a pressure sensor (39) located in the expiratory gas path (34) and connected with the control means (31).

8. A system according to any one of the preceding claims, characterised in that the system includes a flow sensor (40) located in the expiratory gas path (34) and connected with the control means (31).

9. A system according to any one of the preceding claims, characterised in that the control unit (2) includes a first manual control (43) arranged to select a flow rate of gas at an outlet (24) of the control unit.

10. A system according to any one of the preceding claims, characterised in that the control unit (2) includes a second manual control (44) arranged to set an expiratory pressure for the patient.

11. A ventilator system according to any one of the preceding claims, characterised in that the source of breathing gas (1) is ventilator apparatus arranged to provide a cyclical supply of breathing gas at its outlet (10) at a ventilation frequency.

12. A control unit (2) for a ventilator system according to any one of the preceding claims.

13. A ventilator system substantially as hereinbefore described with reference to the accompanying drawing.

14. A control unit for a ventilator system substantially as hereinbefore described with reference to the accompanying drawing.