GB2368531A

GB2368531A - Anaesthesia breathing apparatus

Info

Publication number: GB2368531A
Application number: GB0026606A
Authority: GB
Inventors: Paul Fenton
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-10-31
Filing date: 2000-10-31
Publication date: 2002-05-08
Also published as: GB0026606D0; GB2368531A8

Abstract

An anaesthesia breathing system 1 is arranged as a circle system 3 with an inspiratory line 4 including a set of Oxford Inflating Bellows 9 and an expiratory line 5 including a patient ventilating valve 17 comprising an inflatable bladder 19. During controlled ventilation, positive pressure created by the Oxford Inflating Bellows causes the inflatable bladder to inflate and occlude gas flow and so inspiratory gas is provided to the patient rather than passing into the expiratory line.

Description

- 1 Anaesthesia breathing apparatus Description

The present invention relates to anaesthesia breathing apparatus in particular 5 although not exclusively to a circle-type of anaesthesia breathing apparatus.

Anaesthesia breathing apparatus is used to provide anaesthetic gas to a patient during a surgical procedure. One type of apparatus, known as a drawover system, is particularly suited for use in developing countries where bottles of compressed anaesthetic gas may not be available. The drawover system comprises an oxygen lo source which feeds oxygen to a drawover vaporiser where vapour from a volatile anaesthetic agent is added so as to produce an anaesthetic gas. The anaesthetic gas passes through a set of bellows or self inflating bag and is provided to the patient for inspiration. The anaesthetic gas may be drawn by negative pressure created by the patient's inspiratory effort during spontaneous breathing or fed under positive IS pressure by action of the bellows during controlled ventilation. The patient exhales and expired gas is vented into the atmosphere. An expiratory valve, located at or close to the patient to minimise line dead space, is used to ensure that the expired gas is not re-breathed.

Despite being of great utility, the drawover system has several disadvantages. One 20 disadvantage is that the expired gas is discharged into the atmosphere. Not only is this a waste since it contains a high concentration of oxygen and anaesthetic agent, but also the volatile agent is an environmental pollutant and a hazard to members of the theatre team operating on the patient. Another disadvantage is that the expiratory valve may jam and harm the patient. Furthermore, the expiratory valve is 25 located at or close to the patient, where it is difficult for an anaesthetist to see. Yet another disadvantage is that if controlled ventilation is used, not all the anaesthetic gas passes to the patient during inspiration. Some gas is forced under positive pressure through the expiratory valve.

The present invention seeks to provide an improved anaesthesia breathing 30 apparatus.

According tO a first aspect of the present invention, there is provided an anaesthesia breathing apparatus comprising an inspiratory line and an expiratory line, the expiratory line having a valve configured tO occlude gas flow therein in response to a positive pressure in the inspiratory line during inspiration.

s The valve may be configured tO permit gas flow in the expiratory line during expiration. The valve may comprise an inflatable bladder and may be housed in a tube. The valve may be located in the expiratory line far from a patient receiving inspiration using the inspiratory line. The positive pressure may appear in a portion .... ot 1nsplratory line.

to The inspiratory line and the expiratory line may be arranged in a circuit for ... reclrculatmg gas to a patient.

The apparatus may further comprise an oxygen concentrator and a vaporiser which may be configured to provide anaesthetic gas to the inspiratory line. The inspiratory line may include a set of bellows, for example a set of Oxford Inflating 75 Bellows and the valve may be configured to occlude gas flow in the expiratory line in response to a positive pressure in the set of bellows. The expiratory line may include a carbon dioxide absorber and a positive pressure relief valve, which may be non- adjustable. A breathing reservoir bag may be attached to the expiratory line.

The inspiratory line may include a negative pressure relief valve.

20 According to a second aspect of the present invention there is provided a ventilation valve comprising an inflatable bladder disposed within a tube. The valve may further comprise an annular bush, wherein the bladder is configured to urge against the bush when inflated so as to form a seal.

According to a third aspect of the present invention there is provided a method of 25 operating an anaesthetic breathing apparatus comprising an inspiratory line and an expiratory line, the method comprising providing inspiratory gas under positive pressure while occluding gas flow in the expiratory line by means of a valve operated by said positive pressure.

The method may further comprise permitting gas flow in the expiratory line during expiration. The providing the inspiratory gas under positive pressure may cause the occluding of the expiratory line. The providing of the inspiratory gas under positive pressure may comprise compressing a volume of gas.

s Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of a first embodiment of an anaesthesia breathing apparatus; Figure 2 is a perspective view of the anaesthesia breathing apparatus as shown in to Figure 1; Figure 3 is a plan view of a portion of the anaesthesia breathing apparatus shown in Figure 1; Figure 4 is an exploded view of a patient ventilating valve used in the anaesthesia breathing apparatus shown in Figure 1; 5 Figure 5 is a schematic diagram of a second embodiment of an anaesthesia breathing apparatus according to the present invention; Figure 6 is a schematic diagram of a third embodiment of an anaesthesia breathing apparatus according to the present invention; Figure 7 is a perspective view of the anaesthesia breathing apparatus shown in 20 Figure 6; Figure 8 is a plan view of part of the apparatus shown in Figure 6; and Figure 9 is a front view of the apparatus shown in Figure 6.

Referring to Figures 1, 2 and 3, a first embodiment of an anaesthesia breathing apparatus 1 for administering anaesthesia to a patient 2 is arranged as a circle system 2S having a gas circuit 3 comprising an inspiratory line 4 and an expiratory line 5. The apparatus 1 indudes an oxygen concentrator 6 and a continuous flow vaporiser 7, such as an Ohmeda FLUOTEC,,Ivaporiser, and is connected to the inspiratory line 4 of the gas circuit 3 by a fresh gas flow (FGF) inlet 8.

The inspiratory line 4 includes a set of Oxford Inflating Bellows (OIB) 9 having 30 bellows 10 connected to a chamber 11 disposed between unidirectional inlet and

- 4 outlet valves 12, 13. The OIB 9 is connected to an inspiratory tube 14 for providing inspiratory gas to the patient 2 through a Y-shaped mouthpiece tube 15.

The OIB 9 can be used to monitor respiration and to provide positive pressure . ventilation. 5 The expiratory line 5 comprises an expiratory tube 16 which is connected to the mouthpiece 15 and receives expiratory gas from the patient 2. The expiratory line 5 comprises a patient ventilating valve 17 having an elongate tube 18, which houses an inflatable bladder 19 and an annular bush 20. The tube 18, bladder 19 and bush 20 are configured so that when the bladder 19 is inflated a gas seal is formed. The to bladder 19 is connected to the chamber 11 of the OIB 9 by an inflating/deflating line 21. T)he expiratory line also comprises a one-way valve 22, similar to an "Ambu,\ valve, which includes a flap 23 and aperture 24. The one-way valve 22 is arranged to prevent re-breathing of the expiratory gas. The expiratory line 5 further comprises a CO2 absorber 25 which scrubs expiratory gas of CO2. A breathing Is reservoir bag 26, for example having a 2-litre capacity, is attached the expiratory line 5 downstream of the absorber 25 and is configured to receive CO2free expiratory gas before it is recycled. It will be appreciated that breathing reservoir bag 26 may be placed upstream of the absorber 25. The expiratory line 5 is also provided with a positive pressure relief valve 27 which is non-adjustable. Unlike prior art circle

20 systems, there is no need to close off the positive pressure relief valve 27 during controlled ventilation due to the patient ventilating valve 17. Here, the reservoir bag 26 need not be necessarily filled.

The inspiratory line 4 is provided with a negative pressure relief valve 28. The negative pressure relief valve 28 allows gas to enter the circuit 3 should the fresh gas 25 flow fail. In this example, the negative pressure relief valve 28 is connected to a back-up fresh flow supply comprising an alternative oxygen source 29 and a drawover vaporiser 30. Alternatively, instead of a back-up fresh flow supply, the negative pressure relief valve 28 may be configured to allow room air into the circuit 3. It will be appreciated that the negative pressure relief valve 28 may be replaced 30 with a manual switch.

- 5 The OIB inlet and outlet valves 12, 13 and the one-way valve 22 control the direction of flow around the circuit 3.

Referring to Figures 2 and 3, the OIB 9 is integrated into an anaesthetist's table 31.

The table 31 has first, second and third ports 32a, 32b, 32c for receiving the patient 5 ventilating valve 17, the expiratory tube 16 and the inspiratory tube 15 respectively.

The first and second ports are connected together by a first portion of the expiratory line 5a. The first port 32a also has a co-axial inner port 21a which forms part of the inflating/deflating line 21 connected to the OIB chamber 11. The third gas port 32c is connected to the OIB outlet valve 13.

lo A first end of the patient ventilating valve tube 18a is configured to connect to the first port 32a. The first end 18a has a co-axial inner tube 33 which is arranged to connect to the co-axial inner port 21a. The co-axial inner tube 33 is inserted into a neck 19a of the inflatable bladder 19. The co-axial inner tube 33 is fixed inside the tube 18 by a frame 34.

15 The annular bush 20 and the one-way valve 22 are inserted into a second end of the patient ventilating valve tube lab. The first end of the patient ventilating tube 18a is connected to the first gas port 32a and a second portion of the expiratory line 5b comprising a removable '- shaped pipe is used to connect the second end of the tube 18b to an inlet 25a of the CO2 absorber 25. An outlet (not shown) of the CO2 20 absorber 25 is attached to another gas port (not shown) on the table which is connected to a third portion of the expiratory line 5c which completes the expiratory line 5 to the fresh gas inlet 8.

Referring to Figure 4, the tube 18 of the patient ventilating valve 17 is made from clear plastics material, such as polythene, and is 10 cm long with an inner diameter 25 of 2 cm. The inflatable bladder 19 is made from rubber and when inflated is generally elongate. The neck portion 19a of the bladder is tom long and has a diameter of 0.4cm. A 2cm-long tapered portion 19b connects the neck 19a to a main portion 19c which is 5 cm long and has an inflated diameter of 2cm.

- 6 Referring again to Figure 1, operation of the anaesthesia breathing apparatus 1 will now be described.

Air is sucked into the oxygen concentrator 6 where nitrogen is removed so as to produce a supply of oxygen gas. Oxygen is driven into the vaporiser 7 where 5 vapour from a volatile anaesthetic agent is added so as to produce a flow of fresh anaesthetic gas, also called a fresh gas flow (PGF). In this example, the anaesthetic agent is halothane. It will be appreciated that other anaesthetic agents may also be used such as ether. The fresh gas is fed through the fresh gas inlet 8 into the inspiratory line 4 of the gas circuit 3 at a rate of about 2 litres per minute where it is lo mixed with re-cycled expiratory gas to produce inspiratory gas. The fresh gas flow rate is lower than the patient's minute volume which is about 5-8 litres per minute.

If the patient 2 is breathing spontaneously, when they inhale, negative pressure created by the patient's inspiratory effort draws inspiratory gas through the inlet and outlet valves 12, 13 of the OIB 9, which are open in this situation, into the 15 inspiratory tube 14 and into the patient's lungs. The one-way valve 22 prevents the patient 2 re-breathing expiratory gas from their previous breath remaining in the expiratory tube 16. The bladder 19 is deflated since the pressure in the bladder 19 is not greater than the pressure in the tube 18 due to a lack of positive pressure in the OIB chamber 11. When the patient 2 exhales, the one-way valve 22 allows gas 20 to flow through expiratory line 5. The outlet valve 13 prevents the patient 2 exhaling expiratory gas into the inspiratory line 4. Positive pressure in the expiratory line 5 created by the patient's expiratory effort keeps the bladder 19 deflated and so prevents jamming of the patient ventilating valve 17. Expiratory gas is forced under positive pressure through the patient ventilating and one- way valves 25 17, 22, through the CO2 absorber 25 and into the breathing reservoir bag 26. When the patient 2 draws another breath, CO2-*ee expiratory gas is drawn from bag 26 and is mixed with fresh gas from the vaporiser 7 to produce further inspiratory gas and the breathing cycle begins again.

Under controlled ventilation, an anaesthetist manually draws inspiratory gas into the 30 bellows 10. The bellows 10 are compressed and this forces inspiratory gas through

/ the outlet valve 13, into the inspiratory tube 14 and into the patient's lungs. The inlet valve 12 prevents inspiratory gas from being forced back up the inspiratory line 4 towards the gas inlet 8. The positive pressure in the chamber 11 inflates the bladder 19 via the inflating/deflating line 21 so that it abuts the annular bush 20 and 5 forms a gas seal. In this way, the inflated bladder 19 occludes gas flow in the expiratory line 5 and prevents inspiratory gas from bypassing the patient 2 and flowing directly into the expiratory line S. It will be appreciated that the inflated bladder 19 may additionally or alternatively fill the diameter of the tube 18 and form a gas seal in that way. During expiration, the anaesthetist ceases compressing the lo bellows 10 and the patient 2 exhales. The outlet valve 13 closes and prevents expiratory gas from flowing through the inspiratory line 4. The pressure in the expiratory tube 16 rises and the bladder 19 collapses as gas within it is discharged into the inflating/deflating line 21. Expiratory gas is forced through the patient ventilating and one-way valves 17, 22, through the CO2 absorber 25 and into the 15 breathing reservoir bag 26. When the bellows 10 expand again, CO2-free expiratory gas is drawn from bag 26 and is mixed with fresh gas from the vaporiser 7 to produce inspiratory gas and the controlled breathing cycle begins again.

Referring to Figure 5, a second embodiment of an anaesthesia breathing apparatus 1' is similar to the first embodiment except that a modified inflating deflating line 20 21' is configured to run through the inspiratory and expiratory tubes 14, 16.

Furthermore, in the second embodiment the OIB is not incorporated into the anaesthetist's table 31.

Referring to Figures 6, 7, 8 and 9, a third embodiment of an anaesthesia breathing apparatus 35 for administering anaesthesia to a patient 36 is arranged as a circle 25 system having a gas circuit 37 comprising an inspiratory line 38 and an expiratory line 39. The apparatus 40 includes an oxygen concentrator 41, a flow meter 42 and a continuous flow vaporiser 43, such as an Ohmeda Mark 3 FLUOTEC vaporiser, and is connected to a CO2 absorber 44.

The inspiratory line 38 includes a set of bellows 45 connected to a first portion of 30 the inspiratory line 38a which connects the CO2 absorber 44 to a uni-directional

valve 46 having a removable glass dome 47. An inspiratory tube 48 provides inspiratory gas to the patient 36 through a co-axial tube mouthpiece 49. The bellows 45 can be used to monitor respiration and to provide positive pressure ventilation. 5 The expiratory line 39 comprises an expiratory tube 50 which is connected to the mouthpiece 49 and receives expiratory gas *tom the patient 36. The expiratory line 39 comprises a water trap 51 followed by a removable patient ventilating valve 52 having an elongate tube 53, which houses an inflatable bladder 54 and an annular bush 55. The tube 53, bladder 54 and bush 55 are configured in a similar way to the to patient ventilating valve described in the first embodiment. The bladder 54 is connected to the first portion of the inspiratory line 38 by an inflating/deflating line 56. The expiratory line 39 is connected to the CO2 absorber 44 so as to complete the gas circuit 37. The CO2 absorber 44 includes an inlet one-way valve 57, which includes a flap 58 and aperture 59. The inlet one-way valve 57 is arranged to 5 prevent re-breathing of the expiratory gas. A breathing reservoir bag 60, for example having a two-litre capacity, is attached the CO2 absorber 44. The CO2 absorber 44 is also provided with a non- adjustable positive pressure relief valve 61.

A scavenger 62 is connected to the positive pressure relief valve 62 so as to collect any volatile agent before recycled expiratory air is vented. The CO2 absorber 44 20 includes an outlet one-way valve 65 having a flap and aperture construction. The outlet valve 65 prevents back flow into the CO2 absorber 44 and inflation of the bag 60 when the bellows 45 are compressed.

The inspiratory line 38 is provided with a changeover switch 63. In a first position, the switch 63 completes the gas circuit 37. In a second position, the switch allows 2S gas to enter the inspiratory line 38 from a back-up fresh flow supply including a drawover vaporiser 64, such as an Oxford Miniature Vaporiser. The back-up fresh flow supply is fitted with a one-way valve 66 to prevent back flow towards the drawover vaporiser 64 when the bellow 45 are compressed.

The unidirectional valve 47 and the absorber inlet and outlet valves 57, 65 control 30 the direction of flow around the circuit 37.

Referring to Figures 7, 8 and 9, the bellows 45 are integrated into an anaesthetist's table 67. The table 67 has first and second ports 68a, 68b. The first port 68a receives the inspiratory tube 48 and the second port receives, via the water trap 51, the expiratory tube 52. In this example, the inspiratory tube 48 is co-axial with the 5 expiratory tube 50.

The third embodiment operates in a substantially similar fashion to the first and second embodiments.

The anaesthesia breathing apparatus hereinbefore described have several advantages over conventional continuous flow circles systems using oxygen and nitrous oxide lo gases. Oxygen is supplied from an oxygen concentrator and is available as long as the concentrator is powered with electricity. Therefore, the need for cylinders, pipelines, pressure regulators, gauges and similar pieces of equipment is reduced or removed. This provides significant savings in terms of both capital outlay and recurring costs. Furthermore, the apparatus may be used in regions of the world where compressed gases may not be available. Also, nitrous oxide, which is expensive and difficult to procure in bottled form in some regions of the world, is not used. Additionally, there is no need to adjust the positive pressure relief valve when switching from spontaneous breathing to controlled ventilation. Another advantage is that inflation of the lungs during controlled ventilation is more 20 convenient using bellows than a breathing bag.

The anaesthesia breathing apparatus also have several advant(age over conventional drawover systems using oxygen gas and air, a so-called "Ambu bag" or bellows and an inflating valve. Plenum vaporisers operate at low flow rates, for example 1 litre per minute and so less volatile agent can be used with a consequent reduction in 2S pollution. The patient inflating valve no longer needs to be located at or close to the patient. For example, it may be located in the expiratory line several tens of centimetres from the patient. Prior art expiratory valves are attached to the mask

covering, or tube inserted into, the patient's mouth. Furthermore, s cave) nging of expiratory gas is possible. Continuous flow vaporisers with Selectatec/lfittings may

- 10 be used which allows many, if not all, of the common anaesthetic agents to be used, including all-ethyl ether, halothane, isoflurane and sevoflurane.

The anaesthesia breathing apparatus include several improvements in safety. For example, the chances of delivering a hypoxic gas mixture is substantially reduced or 5 eliminated. As explained earlier, the inflating valve is configured not to jam. The likelihood of over- inflation of the lungs or pulmonary barotrauma is substantially reduced or eliminated.

The anaesthesia breathing apparatus hereinbefore described are particularly suited to being used in third-world countries.

to It will be appreciated that many modifications may be made to embodiments hereinbefore described. For example, other types of bellows may be used instead of Oxford Inflating Bellows. The bellows may be pneumatically powered. This system may be used with compressed anaesthetic gases. A drawover vaporiser may be used instead of a continuous fly ow) vaporiser. Conventional Jackson Rees T-piece or 5 drawover paediatric Ambu, bag and Pedivalve can be used for babies. The apparatus may include alarms to indicate electricity, oxygen or vaporiser failure. Tubes, pipes, ports and connections may be made of plastics material, rubber or metal and may connect together using standard fittings.

Claims

- 11 Claims

1. Anaesthesia breathing apparatus comprising an inspiratory line and an expiratory line, the expiratory line having a valve configured to occlude gas flow therein in response to a positive pressure in the Aspiratory line during inspiration.

5

2. Apparatus according to claim 1, wherein the valve is configured to permit gas flow in the expiratory line during expiration.

3. Apparatus according to claim 1 or 2, wherein the inspiratory line and the expiratory line are arranged in a circuit for recirculating gas to a patient.

4. Apparatus according to any preceding claim, further comprising an oxygen 10 concentrator.

5. Apparatus according to any preceding claim, further comprising a vaporiser.

6. Apparatus according to claim 5, wherein the vaporiser is configured to provide anaesthetic gas to the inspiratory line.

7. Apparatus according to any preceding claim, wherein the inspiratory line 75 indudes a set of bellows.

8. Apparatus according to claim 7, wherein the set of bellows are a set of Oxford Inflating Bellows.

9. Apparatus according to claim 7 or 8, wherein the valve is configured to occlude gas flow in the expiratory line in response to a positive pressure in the set 20 of bellows.

10. Apparatus according to any preceding claim, wherein the expiratory line comprises a carbon dioxide absorber.

- 12

11. Apparatus according to any preceding claim wherein a breathing bag is attached to the expiratory line.

12. Apparatus according to any preceding claim, wherein the expiratory line includes a positive pressure relief valve.

s

13. Apparatus according to claim 12, wherein the positive pressure relief valve is non-adjustable.

14. Apparatus according to any preceding claim, wherein the inspiratory line includes a negative pressure relief valve.

15. Apparatus according to any preceding claim, wherein the valve comprises an to inflatable bladder.

16. Apparatus according to claim 15, wherein the inflatable bladder is housed in a tube.

17. Apparatus according to any preceding claim, wherein the positive pressure À À r....

appears m a portion or 1nsplratory lme.

Is

18. Apparatus according to any preceding claim, wherein the valve is located in the expiratory line substantially away from a patient receiving inspiration using the ... Aspiratory lme.

19. Anaesthesia breathing apparatus substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

20 20. Anaesthesia breathing apparatus substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.

21. Anaesthesia breathing apparatus substantially as hereinbefore described with reference to Figure 6 to 1O of the accompanying drawings.

- 13

22. A ventilation valve comprising an inflatable bladder disposed within a tube.

23. A valve according to claim 22, further comprising an annular bush, wherein the bladder is configured to urge against the bush when inflated so as to form a seal.

24. A valve substantially as hereinbefore described with reference to Figures 1 to 5 4 of the accompanying drawings.

25. A valve substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.

26. A valve substantially as hereinbefore described with reference to Figures 6 to 10 of the accompanying drawings.

26. A valve substantially as hereinbefore described with reference to Figure 6 to 10 of the accompanying drawings.

lo

27. A method of operating an anaesthetic breathing apparatus comprising an inspiratory line and an expiratory line, the method comprising providing inspiratory gas under positive pressure while occluding gas flow in the expiratory line by means of a valve operated by said positive pressure.

28. A method according to claim 27, further comprising permitting gas flow in 75 the expiratory line during expiration.

29. A method according to either claim 27 or 28, wherein the providing of the inspiratory gas under positive pressure causes the occluding of the expiratory line.

30. A method according to any one of claims 27 to 29, wherein the providing of the inspiratory gas under positive pressure comprises compressing a volume of gas.

20 31. A method of operating an anaesthetic breathing apparatus substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

- I Amendments to the claims have been filed as follows 1. Anaesthesia breathing apparatus comprising an inspiratory line and an expiratory line, the expiratory line having a valve configured to occlude gas flow therein in response to a positive pressure in the inspirator,v line during inspiration.

5 2. Apparatus according to claim 1, wherein the valve is configured to permit gas flow in the expiratory line during expiration.

5. Apparatus according to any preceding claim, further comprising a vaporiser.

7. Apparatus according to any preceding claim, wherein the inspiratory line 15 includes a set of bellows.

5 13. Apparatus according to claim 12, wherein the positive pressure relief valve is non-adjustable. 14. Apparatus according to any preceding claim, wherein the inspiratory line includes a negative pressure relief valve.

15. Apparatus according to any preceding claim, wherein the valve comprises an lo inflatable bladder.

17. Apparatus according to any preceding claim, wherein the positive pressure appears in a portion of inspiratory line.

75 18. Apparatus according to any preceding claim, wherein the valve is located in the expiratory line substantially away from a patient receiving inspiration using the inspiratory line.

20 20. Anaesthesia breathing apparatus substantially as hereinbefore described with reference to Figure S of the accompanying drawings.

21. Anaesthesia breathing apparatus substantially as hereinbefore described with reference to Figure 6 to 10 of the accompanying drawings.

Claims lo 22. A ventilation valve comprising an inflatable bladder and annular bush disposed within a tube.

23. A valve, according to claim 22, wherein the bladder is configured to urge against the bush thereby forming a seal which occludes Row in the tube.

24. A valve substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.