GB2178325A

GB2178325A - Medical gas scavenging device

Info

Publication number: GB2178325A
Application number: GB08519277A
Authority: GB
Inventors: Clifford Graham Kersey
Original assignee: BOC Group Ltd
Current assignee: BOC Group Ltd
Priority date: 1985-07-31
Filing date: 1985-07-31
Publication date: 1987-02-11
Also published as: GB8519277D0; GB2178325B

Abstract

A medical gas scavenging device includes a chamber 4 and a tube extending into the chamber 4 for the passage thereinto of a patient's waste gases. The end 8 of the tube 6 within the chamber 4 is located immediately adjacent a resilient diaphragm 10. When the patient exhales, waste gases pass through the tube 6 and move the diaphragm 10 away from the end 8 of the tube 6 and spill over into the chamber 4 where they are subjected to a vacuum effect which sucks them from the chamber 4 via outlet 16 to atmosphere. At all other times the diaphragm 10 seals the end 8 of the tube 6. <IMAGE>

Description

SPECIFICATION Medical gas scavenging device The present invention relates to medical gas scavenging devices.

A known method of anaesthetising patients undergoing surgery is to administer conventional nitrous oxide/oxygen inhalant with anaesthetic vapours by way of a mask or intubation. These methods usually employ an inlet through which the anaesthetic is supplied and an outlet through which the exhaled waste gases are vented.

The exhaled gases usually include a significant portion of still effective anaesthetic which must be vented away from the surgeon and other attendants otherwise there is a risk that they may themselves become partially anaesthetised.

Further to this, there is a growing concern over the effects which may occur from long term exposure to even trace concentrations of nitrous oxide and the various other anaesthetic agents commonly admixed with the basic nitrous oxide/ oxygen mixture. It is therefore considered important to prevent, as far as possible, the pollution of the atmosphere in surgeries and operating theatres by gases exhaled by the anaesthetised patient.

Scavenging devices are known which use a vacuum source to scavenge gases exhaled by the patient and deliver said gases to atmosphere well away from the operating theatre. However, in such known devices the vacuum source can be effective in sucking away not only the patient's waste gases but also a proportion of the anaesthetic gas being delivered to the patient before the patient has inhaled the anaesthetic gas. This is potentially dangerous since the patient may not become fully anaesthetised. Furthermore, it is wasteful of the anaesthetic gas being delivered to the patient.

It is an aim of the present invention to provide a medical gas scavenging device in which the vacuum effect on the anaesthetic gases being supplied to a patient prior to inhalation by said patient is reduced to an acceptable minimum of 0.5 litres per minute or lower at maximum vacuum application.

According to the present invention, a medical gas scavenging device comprises a chamber, a tube extending into the chamber for the passage thereinto of a patient's waste gases, an end of the tube within the chamber being located immediately adjacent a resilient diaphragm such that other than when the patient is exhaling, the diaphragm will seal the end of the tube, an inlet into the chamber for ambient atmosphere and an outlet for communication with a vacuum source.

Preferably, the resilient diaphragm is located at one end of the chamber and the inlet for ambient air comprises a plurality of spaced perforations arranged the periphery of the diaphragm.

An embodiment of the invention will now be described, by way of example, reference being made to the Figures of the accompanying diagrammatic drawings in which:~ Figure 1 is a cross-section through a medical gas scavenging device; and Figure 2 is a plan view of a diaphragm forming part of the gas scavenging device of Figure 1.

As shown a medical gas scavenging device 1 includes a block 2 in which is formed a chamber 4. A tube 6 extends into the chamber 4 and at its lower (as shown) end is in communication with a patient's waste gases by means for example of a mask (not shown). The end 8 of the tube within the chamber 4 is located immediately adjacent a resilient diaphragm 10 of silicon rubber which is formed with a a plurality of peripheral perforations 12,12'.

In effect, diaphragm 10 defines one side of the chamber 4 and is anchored to the block 2 by means of screws 14.

The end 8 of the tube 6 is enlarged relative to the remainder of the tube 6 so that, as will be explained, for a small movement of the diaphragm away from the end 8 a large annular area will be available for the exit of a patient's waste gases.

An outlet port 16 extends from the chamber4for communication with a vacuum source (not shown).

In use, when the patient is inhaling, the vacuum source creates a relatively low pressure in the chamber 4 so that ambient atmosphere is drawn through the perforations 12, 12' in the diaphragm 10 and into chamber 4 and then out towards the vacuum source via outlet 16. In effect, the perforations 12, 12' act as an inlet into the chamber 4 for ambient atmosphere. At this time, the diaphragm 10 is held against the end 8 of the tube 6 by a combination of the air flow through the perforations 12, 12' and the sub-atmospheric pressure on the underside of the diaphragm 10.

Thus, no fresh anaesthetic gas being administered to the patient can flow through the tube 6 and into the chamber 4.

When the patient exhales, the pressure of waste gases in the tube 6 is such that the diaphragm 10 is pushed away from the end 8 of the tube 6 allowing the waste gases to spill over into chamber 4, which they leave via outlet 16 and proceed towards the vacuum source and eventually to atmosphere.

When expiration ceases the diaphragm 10 will again seal the end 8 of the tube 6.

A particular advantage of the above described embodiment is that having the tube 6 effectively sealed off by the diaphragm 10 during inhalation by the patient there can be virtually no loss through the tube 6 of fresh anaesthetic gases due to the action of the vacuum source.

For the avoidance of doubt although in the above described embodiment reference has been made to anaesthetic gases, the device could equally be used for analgesics and for the scavenging of other respirable but non-anaesthetic or analgesic gases for example pure oxygen.

The particular configuration of the perforations 12, 12' will depend on the material from which the diaphragm is made. In the present embodiment the diaphragm 10 is made from silicone rubber having a thickness of 0.4 mm. The outer peripheral perforations 12 are 24 in number and have a diameter of 5 mm and the inner ring of perforations 12' are 8 in number and have a diameter of 2.5 mm.

The number and size of the perforations 12, 12' in the diaphragm 10 is selected not only to keep the resistance of waste gas flow through the tube 6 low but at the same time still afford adequate sealing at low vacuum disposal flow rates.

By placing the perforations around the periphery of the diaphragm 10 it has been found at lower flow rates there was far less tendency for the diaphragm 10 to "crinkle" and as a result break the seal to the tube 6.

Claims

1. A medical gas scavenging device comprising a chamber, a tube extending into the chamber for the passage thereinto of a patients waste gases, an end of the tube within the chamber being located immediately adjacent a resilient diaphragm such that other than when the patient is exhaling, the diaphragm will seal the end of the tube, an inlet into the chamber for ambient atmosphere and an outlet for communication with a vacuum source.

2. A device as claimed in claim 1, in which the resilient diaphragm is located at one end of the chamber and the inlet for ambient air comprises a plurality of spaced perforations arranged around the periphery of the diaphragm.

3. A device as claimed in claim 1 or 2, in which the end ofthetube immediately adjacentthe resilient diaphragm is enlarged so that for a small movement of the diaphragm away from said end a large annular area will be available for the exit of the patient's waste gases.

4. A medical gas scavenging device constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the Figures of the accompanying drawing.