AU2005201842A1 - Patient expired anaesthetic gas scavenging apparatus - Google Patents

Description

Regulation 3.2 Revised 2/98

AUSTRALIA

Patents Act, 1990

ORIGINAL

COMPLETE SPECIFICATION TO BE COMPLETED BY THE APPLICANT NAME OF APPLICANT: ACTUAL INVENTOR: ADDRESS FOR SERVICE: INVENTION TITLE: DETAILS OF ASSOCIATED APPLICATION NO(S) Add-Tech Medical Services Pty Limited ACN 003 299 572 Michael Adamsons Peter Maxwell Associates Level 6 Pitt Street SYDNEY NSW 2000 PATIENT EXPIRED ANAESTHETIC GAS SCAVENGING APPARATUS Nil The following statement is a full description of this invention including the best method of performing it known to us:m:\docs\20051014\077481 .doc The present invention relates to an apparatus used for scavenging anaesthetic gas expired by patients in a hospital or the like premises.

It is known that during inhalation anaesthesia of a patient undergoing an operation, some leakage of anaesthetic gas and pollution of the premises does occur, even though the anaesthetic gas machine that is used may be connected to a gas scavenging system. Supervising personnel operating in such an environment may be subject to adverse health effects arising from prolonged exposure to anaesthetic gases, such as increased risk of miscarriage in women, concentration and memory difficulties, and headache, nausea and tiredness. Anaesthetic gas can leak into the premises from anaesthetic gas machines due to technical defects, such as leaks in connectors, hoses, reservoir bags, and valves, or whilst being transferred from the anaesthetic gas machine to the patient, particularly through the mask during the induction of anaesthesia and at its end. Whilst measures can be taken by the medical staff to prevent such leakage during inhalation anaesthesia, escape of anaesthetic gas into the premises is more likely to occur when the gas is administered directly by the patient for pain relief (analgesia). This is especially so for pregnant women undergoing labour who are self administering nitrous oxide via a mask. In many cases, the mask is not connected to a gas scavenging system, and so the expired anaesthetic gas escapes into the premises where it may linger over time, to be exhausted ultimately by vents from the premises. The gas scavenging systems connected to anaesthetic gas machines cannot ordinarily be used in a labour ward, emergency area or recovery room, as they are a scarce resource for hospitals and are primarily dedicated to use in operating rooms.

Accordingly, there is a need for a stand alone, gas scavenging apparatus that can be connected to a mask used to administer anaesthetic gas 02/05/05 to a patient in circumstances where no other gas scavenging system is being used.

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It is a particularly preferred object of the invention to provide an apparatus that can be used to scavenge expired anaesthetic gas from both 0 5 spontaneous breathing patients, such as where a patient is breathing spontaneously in a recovery room following general anaesthesia, and demand Obreathing patients, such as where a patient requires analgesia for birthing contractions during labour and self administers anaesthetic gas via a mask or mouthpiece connected to an analgesia demand device.

According to the present invention, there is provided an anaesthetic gas scavenging apparatus, comprising:a body, a chamber defined within the body, an inlet port of the body in air flow communication with the chamber for receiving anaesthetic gas expired by a patient, an outlet port of the body in air flow communication with the chamber for exhausting anaesthetic gas from the chamber under vacuum applied through the outlet port, an inlet air flow passageway between the inlet port and a release port for releasing anaesthetic gas into the chamber, and valve means adapted to allow release of anaesthetic gas through the release port into the chamber, but prevent back flow of anaesthetic gas from the chamber through the inlet air flow passageway.

The apparatus may further include a plurality of ambient air entrainment apertures into the chamber.

02/05/05 Preferably, the valve means comprises a non-return flap valve adapted to open under the pressure of the patient's expired breath reaching the release port.

The chamber preferably comprises an inner sub-chamber and an outer sub-chamber, the release port being located within the inner sub-chamber.

It is preferred that the inner and outer sub-chambers are interconnected by at least one opening through a wall defining the inner chamber, the or each opening being located adjacent a floor of the inner chamber.

In a preferred form, the outlet port is in air flow communication with the outer sub-chamber through at least one outlet air flow passageway.

Preferably, there are a plurality of outlet air flow passageways, each having an entry vent port through a floor of the outer chamber.

It is preferred that the floor of the inner chamber and the floor of the outer chamber have a common level.

In a preferred form, the inlet port is located in a top portion of the body, and the outlet port is located in a bottom portion of the body.

The top portion preferably comprises a head block through which a first part of the inlet air flow passageway is formed.

The bottom portion preferably comprises a base block through which the or each outlet air flow passageway is formed.

Preferably, the chamber is located between the head block and the base block.

It is preferred that a second part of the inlet air flow passageway comprises a pipe, connected at a top open end thereof to a bottom open end of the first part of the inlet air flow passageway, and having the release port at a bottom open end thereof to which is connected the valve means.

02/05/05 In a preferred form, the pipe is aligned substantially vertically within the C inner sub-chamber.

In order that the invention may be readily understood and put into cpractical effect, reference will now be made to the accompanying drawings, in 00 05 which:- Fig 1 is a side elevational view of a preferred anaesthetic gas Sscavenging apparatus of the invention, Fig 2 is a bottom perspective view of top and bottom portions of the apparatus of Fig 1, Fig 3 is a front perspective view of a bottom portion and the interior details of a lower portion of the chamber of the apparatus of Fig 1, Fig 4 is a front perspective view of the apparatus of Fig 1 showing the interior details of both the chamber and the top portion, Fig 5 is a side sectional view of a top portion and pipe with valve means of the apparatus of Fig 1, Fig 6 is a side sectional view of a bottom portion of the apparatus of Fig 1, and Fig 7 is a plan view of the bottom portion shown in Fig 6.

The anaesthetic gas scavenging apparatus shown in the drawings, and especially Fig 1, has a body 12 consisting of a head block 14 defining a top portion of the body, a base block 16 defining a bottom portion of the body, and a chamber 18 located therebetween.

There is an inlet port 20 located through a side wall of the head block 14 of the body. The inlet port 20 is in air flow communication with the chamber 18.

Anaesthetic gas expired by a patient is received through the inlet port There is an outlet port 22 defined by a vacuum hose connector 24 that extends from a side wall of the base block 16. The outlet port 22 is also in air 02/05/05 flow communication with the chamber 18. Under a vacuum applied through the outlet port 22, anaesthetic gas is exhausted from the chamber 18.

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The chamber 18 has a plurality of ambient air entrainment apertures 26 (Ni through one or more outer side walls thereof that allow ambient air to enter the 0 5 chamber 18 in response to negative pressure therein.

0 As shown in Fig 2, the head block 14 is secured to the chamber 18 by 0 locking devices 28, and the base block 16 is secured to the chamber 18 also by locking devices As also shown in Figs 4 and 5, there is an inlet air flow passageway between the inlet port 20 and a release port 32 for releasing anaesthetic gas into the chamber 18. The inlet air flow passageway comprises a first part formed as a tunnel 34 through the solid material of the head block, and a second part comprising a pipe 36. The pipe 36, which is aligned substantially vertically within the chamber 18, is connected at its top open end to a bottom open end of the tunnel 34. The release port 32 is defined by the bottom open end of the pipe 36, and a valve means is connected thereto for allowing release of anaesthetic gas through the release port 32 into the chamber 18, but preventing back flow of anaesthetic gas from the chamber 18 through the inlet air flow passageway. In the present embodiment, the valve means comprises a non-return flap valve 40 which is normally closed under ambient air pressure but can open under the minimal pressure of the patient's expired breath reaching the release port 32.

As also shown in Figs 6 and 7, the base block 16 is made of solid material through which are formed a plurality of outlet air flow passageways between the outlet port 22 and four entry vent ports 42 located through a top surface of the base block 16, which top surface also serves as a floor 44 of the chamber 18.

02/05/05 ISupported on a side surface of the base block 16 is a vacuum strength cindicator 46 that is operably connected to the vacuum line leading to the outlet port 22 to indicate the strength of the vacuum exhausting the anaesthetic gas Cfrom the chamber 18.

S 5 As shown in Figs 3 and 4, the chamber 18 has an inner sub-chamber or cturbulence chamber 48, and an outer sub-chamber or vacuum chamber OThe release port 32 is located within the turbulence chamber 48. The turbulence chamber 48 is defined within a cylindrical wall 52 extending from the floor 44 of the chamber 18 to a circular indent 54 (containing a rubber O-ring) formed in a bottom surface of the head block 14, which bottom surface also serves as a ceiling 56 of the chamber 18. There are a plurality of openings 58 through the wall 52 that are adjacent the floor 44 and interconnect the turbulence chamber 48 and vacuum chamber 50. The vacuum chamber 50 is defined between the cylindrical wall 52 and the external walls 60 which extend from the floor 44 to the ceiling 56 of the chamber 18.

In use, a breathing circuit connector 62 is connected to the inlet port and a vacuum extraction hose is connected to the outlet port 22. A vacuum is created by applying suction at a continuous flow of, say, 50 LPM to exhaust gas from the chamber 18 through the outlet port 22 to the outside of the premises. A patient undergoing, say, demand breathing with an anaesthetic, self administered via a mask, expires anaesthetic gas which passes through the inlet port 20 and enters the turbulence chamber 48 via the non-return flap valve 40. The anaesthetic gas is heavier then air and flows to the bottom of the turbulence chamber 48, before passing through the openings 58 to the vacuum chamber 50 where it is exhausted through the entry vent ports 42 of the outlet air flow passageways under vacuum to the outlet port 22. The combined volume of the turbulence chamber 48 and vacuum chamber 50 is sufficiently 02/05/05 large to accommodate a patient undergoing rapid or peak demand breathing c-i and so prevents leakage of expired anaesthetic gas into the premises.

It will be apparent to persons skilled in the art that various modifications c-i may be made in details of design and construction of the anaesthetic gas scavenging apparatus described above without departing from the scope and c-i ambit of the invention.

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Claims (11)

1. An anaesthetic gas scavenging apparatus, comprising:- a body, a chamber defined within the body, an inlet port of the body in air flow communication with the chamber for receiving anaesthetic gas expired by a patient, an outlet port of the body in air flow communication with the chamber for exhausting anaesthetic gas from the chamber under vacuum applied through the outlet port, an inlet air flow passageway between the inlet port and a release port for releasing anaesthetic gas into the chamber, and valve means adapted to allow release of anaesthetic gas through the release port into the chamber, but prevent back flow of anaesthetic gas from the chamber through the inlet air flow passageway.

2. The apparatus of claim 1 and further including a plurality of ambient air entrainment apertures into the chamber.

3. The apparatus of claim 1 or claim 2 wherein the valve means comprises a non-return flap valve adapted to open under the pressure of the patient's expired breath reaching the release port. 02/05/05

4. The apparatus of any one of claims 1 to 3 wherein the chamber ccomprises an inner sub-chamber and an outer sub-chamber, the release port being located within the inner sub-chamber. 00 The apparatus of claim 4 wherein the inner and outer sub-chambers are (interconnected by at least one opening through a wall defining the inner 0 chamber, the or each opening being located adjacent a floor of the inner chamber.

6. The apparatus of claim 4 or claim 5 wherein the outlet port is in air flow communication with the outer sub-chamber through at least one outlet air flow passageway.

7. The apparatus of claim 6 wherein there are a plurality of outlet air flow passageways, each having an entry vent port through a floor of the outer chamber.

8. The apparatus of claim 7 wherein the floor of the inner chamber and the floor of the outer chamber have a common level.

9. The apparatus of any one of claims 1 to 8 wherein the inlet port is located in a top portion of the body, and the outlet port is located in a bottom portion of the body. The apparatus of claim 9 wherein the top portion comprises a head block through which a first part of the inlet air flow passageway is formed. 02/05/05 I

11. The apparatus of claim 9 or claim 10 wherein the bottom portion Ccomprises a base block through which the or each outlet air flow passageway is formed. oo 12. The apparatus of claim 11 wherein the chamber is located between the C head block and the base block.

13. The apparatus of claim 10 wherein a second part of the inlet air flow passageway comprises a pipe, connected at a top open end thereof to a bottom open end of the first part of the inlet air flow passageway, and having the release port at a bottom open end thereof to which is connected the valve means.

14. The apparatus of claim 13 wherein the pipe is aligned substantially vertically within the inner sub-chamber. An anaesthetic gas scavenging apparatus substantially as hereinbefore described with reference to the accompanying drawings. Dated this 2 day of May 2005 Add-Tech Medical Services Pty Limited Patent Attorneys for the Applicant PETER MAXWELL ASSOCIATES 02/05/05