The Anesthesia Gas Machine

Michael P. Dosch CRNA PhD, Darin Tharp CRNA MS
University of Detroit Mercy Graduate Program in Nurse Anesthesiology
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Revised Mar 2016


Purchasing new gas machines

What to consider when buying a new gas machine

How is anesthesia going to change in the next 15 years?

Education and training

An anesthetist who knew how to use an Excel could easily walk up to a Modulus or any of the Narkomeds and use them with very few problems, and essentially no training time or reading. However, the new machine features such as advanced ventilation modes, computer and monitor integration, and the electronic checklist are very different than anything that has gone before. New models are substantially different- look at the three different approaches to flowmeters in the Aestiva or Aespire (mechanical needle valves and glass flowtubes), Fabius/Apollo (mechanical needle valves, electronic display of flows backed up by common gas outlet flowmeter), and Aisys and Perseus (all electronic, digital display in which the inspired oxygen, carrier gas flow, and total fresh gas flow are set). Comfort with one make and model translates much less to other models than it used to.

Furthermore, anesthesia practice is changing. Spontaneous ventilation for longer than a few moments during general anesthesia was rare. Now because of the laryngeal mask airway it is much more common. Cost of the volatile agents is substantial enough that low flows are undergoing somewhat of a renaissance. When users at a total fresh gas flow of 1 L/min find inspired oxygen dropping slowly, or a 2-3% difference between dialed and end-tidal desflurane in the middle of a case, they may have trouble remembering that these are expected findings as fresh gas flow decreases.

Comfort with the monitoring technology can be an issue. I know that a little ball in a glass tube would drop unless oxygen is flowing- a physical fact that I can sense. You mean my trust must now repose in a green bar graph??

The new machines simply cannot be used safely without a personal and institutional commitment to time spent in training and reading.

Operating costs

With the new machines, operating costs may be higher. Carefully compare the cost of disposables per case (e.g. spirometry tubing, carbon dioxide granule canisters, breathing circuits). This can be mitigated by several tactics:

Installation of new machines

A few pearls from folks who have "been there":

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