'Universal' leak test?
(Maintenance and repair)
Pressure leak detectors (Usage)
|Publication:||Name: Anaesthesia and Intensive Care Publisher: Australian Society of Anaesthetists Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2008 Australian Society of Anaesthetists ISSN: 0310-057X|
|Issue:||Date: Nov, 2008 Source Volume: 36 Source Issue: 6|
|Topic:||Event Code: 260 General services|
|Product:||Product Code: 3841710 Anesthesia Apparatus; 3823411 Pressure & Vacuum Leak Detectors NAICS Code: 339112 Surgical and Medical Instrument Manufacturing; 334513 Instruments and Related Products Manufacturing for Measuring, Displaying, and Controlling Industrial Process Variables SIC Code: 3841 Surgical and medical instruments; 3823 Process control instruments|
|Geographic:||Geographic Scope: United Kingdom Geographic Code: 4EUUK United Kingdom|
A negative pressure test has been considered a
'universal' test for checking leaks in the low pressure
systems of anaesthesia machines because it was thought that it could be
used in all the machines, irrespective of their make or design (1).
However, this may no longer be the case. Recently, when checking a
Cavendish machine (Cavendish 680 M, Medical Industrial Equipment Ltd,
UK) the leak test was positive (the bulb inflated immediately). In
response, the machine was replaced with another similar Cavendish
machine and a report was sent to the technician in charge to organise a
repair of the fault. Unexpectedly, the 'universal' leak test
was positive also in this second machine. It then became apparent that
both machines had recently undergone servicing.
The service engineer (accredited by the company for servicing purposes) explained that during the recent service, he had altered the machine by introducing a change in the "ratio valve" of the minimum ratio system. This ratio valve, the purpose of which is to ensure a minimum ratio of 25% [O.sub.2]. in anaesthesia gases (2), is vented to the atmosphere as soon as the master control switch is turned off, hence making the negative pressure leak test positive (false positive). This was in accordance with the recent changes introduced in the service manual of the anaesthesia machine provided by the manufacturer.
The manufacturer's current recommendation to check for leaks is to turn the machine's pneumatic switch on and with the basal flow of oxygen (150 ml/min), to observe the manometer pressure. This should rise to more than 100 mm of Hg. Anything less suggests a significant leak. This information has now been circulated to our staff.
We have also recently purchased a new Penlon anaesthesia machine (Penlon Prima SP), which recommends the same leak test as the Cavendish Machine (3).
With newer machines of different makes and designs, it may be difficult to remember the various leak tests. In the past, the 'universal' negative pressure leak test could always be used. However, this example indicates that the test may no longer be 'universal'.
A. G. BHAGwAT
New Delhi, India
(1.) Dorsch JA, Dorsch SE. Equipment checking and Maintanance. In Understanding Anesthesia Equipment, 4th ed. Philadelphia, Pennsylvaia: Lippincott Williams & Wilkins 2002. p. 946-947.
(2.) Cavendish 460 M/680 M. Anesthesia Machine Operator's Manual, 4th ed. Medical Industrial Equipment Ltd, United Kingdom; p.14.
(3.) Penlon Prima SP Anesthesia machine range user manual. Penlon Ltd, United Kingdom 2004; p. 37.
|Gale Copyright:||Copyright 2008 Gale, Cengage Learning. All rights reserved.|