BS ISO 18835:2015

This standard BS ISO 18835:2015 Inhalational anaesthesia systems. Draw-over anaesthetic systems is classified in these ICS categories:

• 11.040.10 Anaesthetic, respiratory and reanimation equipment

It is understood, that at the time of writing this International Standard, flammable anaesthetic agents, such as diethyl ether, are still being used in certain countries where draw-over anaesthetic systems are in use.

The use of monitoring is highly recommended and is the subject of the World Health Organization (WHO) guidelines, but was not considered essential with this intrinsically safe system of delivering inhalational anaesthesia. The unreliable supply of electricity and lack of resources for the continuous supply of consumables also render most monitors unsustainable.

ISO 8835-7:2011, 5 c) mandates that a means for the manual ventilation of the patient shall be included and refers to operator-powered resuscitators and inflating bellows. Operator-powered resuscitators are covered by ISO 10651-4. However, as bellows-type manual ventilators do not have a standard, they have been included in this International Standard.

A.4.4 Components for use with flammable anaesthetic agents

An example of a flammable anaesthetic agent in use is diethyl ether. Examples of non-flammable anaesthetic agents are halothane and isoflurane. ISO 80601-2-13:2011, Annex B, provides details on the methods of test to determine the flammability of anaesthetic agents.

A.5.2.2 Draw-over vaporizer — Accuracy of output

Draw-over vaporizers are designed and calibrated to operate at or slightly below atmospheric pressure.

The calibration might not be valid when the draw-over vaporizer is pressurized, for example, when used as a “push over” vaporizer.

A.5.3 Draw-over vaporizer — Ports and connectors

A sequential system of cones and sockets has been adopted as all the major components of this draw-over anaesthetic system are flow-direction-sensitive. Such a system does not overcome the hazard of omitting a major component or of assembling components in the wrong order, but in view of the small number of components employed, this risk is considered acceptable.

A.6.3.3 Breathing system — exhaust port

A 30 mm cone is specified at the exhaust port to facilitate connection to an anaesthetic gas scavenging system (AGSS) complying with ISO 80601-2-13. It is not anticipated that a sophisticated AGSS will be a high priority, but simple steps such as attaching a hose to lead waste gases to floor level can substantially reduce levels of pollution at the breathing level of theatre staff.

It is important that the instructions for use draw attention to the potential hazards in using non-anaesthetic proof gas (APG) category equipment with flammable agents [see 10 d) 7)].

A.7.1.2 reservoir — Instructions for positioning of the supplementary oxygen inlet

The positioning of the supplementary oxygen inlet connector is crucial. It should be as close as possible to the outlet of the reservoir where the reservoir connects to the inlet of the draw-over vaporizer. If placed elsewhere, there will be an inefficient use of oxygen and the possibility of a build-up of pressure and alteration of vaporizer output.

A.8.1 Bellows-type manual ventilator — Construction

The draw-over anaesthetic system comprises, in its most basic form, a draw-over vaporizer and a breathing system. The breathing system mandates a draw-over valve system, which in itself, mandates that the patient must be able to inhale and exhale during both spontaneous and positive pressure ventilation. If a bellows-type manual ventilator is then introduced, these requirements still apply, and as written, will ensure that the patient can inhale and exhale while receiving positive pressure ventilation.