Oxygen Analysers

Should oxygen analysers become standard in all hospital areas where airway support is provided?

Anaesthetists have been using oxygen analysers for years to ensure adequate oxygen delivery to their patients. They’re particularly focussed on during the period of preoxygenation prior to induction of anaesthetic.

– Preoxygenation is the administration of oxygen to a patient prior to intubation to extend ‘the safe apnea time’.
– The primary mechanism is ‘denitrogenation’ of the lungs, however maximal preoxygenation is achieved when the alveolar, arterial, tissue, and venous compartments are all filled with oxygen.

(see here)

By far the best monitor we have of optimal preoxygenation is the oxygen analyser assessing the end tidal oxygen level. These monitors have been standard for airway management in anaesthetisia for many years (AAGBI, ANZCA). They’re also available for use outside theatre (GE, Masimo, Philips)

Oxygen analysers are extremely simple to use and cause no increased complexity on the front line. They provide a waveform, inspired and expired oxygen concentration (ETO2) from 0 to 100%. During preoxygenation the closer the ETO2 to 100% the better the preoxygenation – the DAS guidelines recommend aiming for an ETO2 of greater than 90% (see here).

There is no other monitor which provides real time assessment of preoxygenation adequacy. Pulse oximetry often provides no indication of preoxygenation – most individuals have an oxygen saturation close to 100% in room air – additional oxygen administration having no impact on this.

However oxygen analysers are rarely seen outside operating theatres. In effect this means that most preoxygenation performed outside theatre is performed without assessment – staff relying on inferences from trial data and the techniques used by those in positions of influence.

The issue with trial data is that it provides an artificial environment for assessment – where everything is performed perfectly. The ‘human factors’ have been removed and the trial subjects are often fit and well with guaranteed airways and minute ventilation.

Human Factors
– Pipeline mix ups (see here)
– Forgetting to connect to oxygen source
– Connecting to air instead of oxygen (see here)
– Inadequate O2 flow rate e.g. unrecognised empty oxygen cylinder
– Use of BVM without expiratory valve (see here)
– Poor technique of choice (see here)
– Unintended mask leak (e.g. using NC or PEEP valves – see here)
– Unrecognized airway obstruction
– Unrecognized impaired minute ventilation
– Insufficient length of time for pre-oxygenation

Often I hear the statement – ‘the staff in our department are highly trained’ – implying they don’t make the mistake of forgetting to connect the oxygen source, always preoxygenate for an adequate amount of time, have perfected their skills at assessing airway patency and adequate minute ventilation……

Unfortunately we are all human and all make mistakes. As an anaesthetist I want access to oxygen analysis in ED, ICU and all other areas of resuscitation. I am aware I am just as likely to make a mistake as anyone else. This is something the aviation industry learnt a long time ago – even the best trained and drilled individuals make mistakes.

Mistakes made by the most decorated and renowned pilot ‘the poster boy of the KLM fleet’ in Tenerife led to the worst disaster in aviation history (see here).

That we don’t already have oxygen analysers in areas of resuscitation allowed the death and severe brain damage of 2 newborn in Sydney last year (see here).

Should oxygen analysers be made standard (as they are in anaesthetic environments) in any other hospital area where airway support will be administered – emergency, intensive care, neonatal resuscitation trolleys and other arrest trolleys?

Some physicians highlight ETO2 may ‘over-read’ in the presence of a large shunt. This may be the case however given a shunt should be optimally managed this issue is of little clinical relevance in changing patient management.

Cost is often used as a barrier to change and a means to support the status quo – we have little doubt improved patient outcomes will lead to reduced overall costs when patients are provided with optimal care (see here). The payments made to the newborn who suffered from the pipeline error in Sydney last year, likely in the millions, will easily be less than providing oxygen analysers in all hospital areas of resuscitation.

We have a long way to travel in healthcare.

Perhaps those in positions of influence have yet to understand the value of oxygen monitoring. In particular they may have yet to appreciate the human in the room and how simulated studies exclude and so don’t take account for human mistakes in the real world of clinical practice.

We would be delighted to hear your thoughts. We are working with emergency physicians to trial oxygen analysers.

We would be particularly interested to hear what information would influence others to support oxygen analysers being made standard in resuscitation areas.

We would also like to hear from other manufacturers who supply equipment for combined capnography and oxygen analysis outside the  operating theatre.

We are trialling oxygen analysers for use outside operating theatres. We would be grateful for your feedback on this trial outline (see here).

Thank you.

 

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