GB2174607A

GB2174607A - Anaesthetic gas scavenging system

Info

Publication number: GB2174607A
Application number: GB08601603A
Authority: GB
Inventors: Dr J A Gil-Rodriquez
Original assignee: Automated Process & Control
Current assignee: Automated Process & Control
Priority date: 1985-01-23
Filing date: 1986-01-23
Publication date: 1986-11-12
Also published as: GB8501706D0; GB8601603D0; GB2174607B

Abstract

An open reservoir gas scavenging system 1 is provided with an open reservoir 8 in tubular form and an extractor tube 9 coupled to an air mover, the extractor tube being situated within the reservoir and emerging from its open end. There may further be provided a secondary reservoir 4 in the form of an expandable bag coupled to the system near the inlet to the open reservoir. <IMAGE>

Description

SPECIFICATION Anaesthetic gas scavenging system The invention relates to an anaesthetic gas scavenging system of the open reservoir kind.

In such a kind of system there is provided a reservoir for expired anaesthetic gases, the reservoir being coupled at one end (the inlet) to the gas extractor system which includes an air mover. At times of peak flow (patient expiration) the reservoir contains exhaust gases beyond the capacity of the system to extract.

Subsequently the gases are extracted from the reservoir by the air mover.

In an open reservoir system the other end of the reservoir is open to atmosphere. This should avoid undue pressure drop being experienced by the patient. It is found, however, that problems exist with known open-reservoir scavenging systems and an object of the invention is to provide an improved system.

According to one aspect of the invention an open-reservoir anaesthetic gas scavenging system is provided with an open reservoir in tubular form and an extractor tube coupled to an air mover, the extractor tube being situated within the reservoir and emerging from its open end. This arrangement makes it virtually impossible to block the open end of the reservoir inadvertently. The danger of such blocking is a disadvantage of existing open-reservoir systems.

According to another aspect of the invention an open reservoir anaesthetic gas scavenging system has a secondary reservoir in the form of an expandable bag coupled to the system near the inlet to the open reservoir.

Because of the presence of the open reservoir, there is not the usual danger of a closed- bag reservoir causing negative pressures. Nevertheless, additional reservoir capacity is provided, so alleviating the problem of risk of anaesthetic gases escaping from the open end of the open reservoir. The bag also provides an indication (bag collapsed) that the system is on.

The invention will further be described with reference to the accompanying drawings, of which: Figure 1 is a side elevation of an anaesthetic gas scavenging system in accordance with the invention; and Figure 2 is a schematic sectional view of the system, from the other side.

Referring to Figs. 1 and 2 the system comprises a safety block 1 which has a positive safety relief valve 2 and a negative safety relief valve 3. A peak reservoir bag 4 is coupled to the safety block at 6. Also coupled to the block 1 is a non-crushable flexible 22mm patient inlet tube 7 and a non-crushable 30mm tube 8. Tube 8 is open at the end 10 remote from the block and constitutes the open reservoir of the system.

An exhaust tube 9 is coupled to the block 1 and runs within the reservoir tube 8, emerging from the open end 10. This prevents the open end of the reservoir from becoming obstructed inadvertently. The exhaust tube is coupled to an air mover (vacuum system or suction pump). A "V" plate 11 is fixed to the block 1 to allow direct mounting on the anaesthetic machine (not shown).

In use, the patient's exhaled gases are passively collected from the output of a safety scavenging valve or ventilator of the anaesthetic machine and transferred through tube 7 to the main body of the safety block 1. From there they are actively removed through the suction tube 9 together with room air which enters tht reservoir tube 8 through its open end 10. This reservoir tube will momentarily store the patient's expiratory peaks when the volume of the gases voided by the patient into the system exceeds the volume of gases extracted (i.e. the suction flow rate of the system).

The bag 4 in the system acts not only as a secondary peak flows absorber but also as a "system on" indicator (bag collapsed). The primary peak flow reservoir is the tube 8 with the extract tube 9 within its lumen.

The system is designed to run within the following limits: Performance a) The system should capture a minimum steady flow rate of 30 litres per minute.

b) The system should capture a minimum peak flow rate of 130 litres per minute for 0.25 second in a 3 second period.

Patient Safety a) The system should not impose a resistance to expiration greater than 50 Pa at a continuous flow of 30 litres per minute or greater than 500 Pa at a continuous flow of 90 litres per minute.

b) In the event of an obstruction or fault in the AGSS, the maximum resistance to expiration should not exceed 1000 Pa at a continuous flow of 30 litres per minute.

In practice, a system of the kind shown in Figs. 1 and 2 has achieved the following results, at a scavenging flow rate of 60 litres per minute:~ steady state flow rate 55 litres taken by the system per minute peak flow rate taken by 160 litres the system per minute inlet pressure at 30 12 Pa litres per minute in Pa inlet pressure at 90 120 Pa litres per minute in Pa inlet suction pressure -5 Pa in Pa Safety valves Positive open at 1000 Pa Negative open at -5 Pa

Claims

1. An open reservoir anaesthetic gas scavenging system having an open reservoir in tubular form and an extractor tube coupled to an air mover, the extractor tube being situated within the reservoir and emerging from its open end.

2. An open reservoir anaesthetic gas scavenging system as claimed in claim 1 wherein there is a secondary reservoir in the form of an expandable bag coupled to the system near the inlet to the open reservoir.

3. An open reservoir anaesthetic gas scavenging system having a secondary reservoir in the form of an expandable bag coupled to the system near the inlet to the open reservoir.

4. An open reservoir anaesthetic gas scavenging system substantially as hereinbefore described with reference to the accompanying drawings.