Revised July 2012
ANESTHESIA GAS MACHINE> NEW GAS MACHINES>
NEW CAPABILITIES, NEW ISSUES> ADVANCED VENTILATION, INTEGRATED
MONITORING, LOW FLOWS, TRAINING, ELECTRONIC CHECKLIST
- Purchasing new gas machines
- Education and training (Advanced ventilation, Computer and
monitor integration, Low flows, Laryngeal mask airway and
mechanical ventilation, Electronic Checkout)
- Operating costs
- Installation of new machines
Purchasing new gas machines
What to consider when buying a new gas machine
How is anesthesia going to change in the next 15 years?
- No one knows - but there are some indications already from
patient population and demographics. The patient population will
be both younger, older, sicker and bigger than today. This puts
stress on the ventilation ability. Buy the best ventilator you
can with volume and pressure control.
- More spontaneous breathing. The LMA is revolutionizing
anesthesia practice. Buy a ventilator that allows pressure
limited volume ventilation - limit the pressure to 20 cm
H2O to protect the airway and have the familiarity
and ease of mechanical ventilation.
- Make sure that the pressure control is able to ventilate the
- Make sure that the system doesn't restrict your future
options. Make sure the machine you purchase will allow the
exporting of fresh gas values to any information system or
automated record-keeper. Make sure that whatever you buy can
support an electronic anesthesia record. The electronic medical record is being installed in many areas from medical offices to the operating room.
- With monitoring make sure that you are comfortable with the
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.
Even the new products from one manufacturer are substantially
different- look at the three different approaches to flowmeters
in the Aestiva (mechanical needle valves and glass
flowtubes), ADU (mechanical needle
valves, electronic display of flows backed up by common gas
outlet flowmeter), and Aisys (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 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 gas 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
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
- Emphasis on low flows to decrease usage of volatile
- Some machines permit use of loose carbon dioxide granules rather than single-use
Installation of new machines
A few pearls from folks who have "been there":
- Budget weekend training time. Don't skimp here- and make it
mandatory for all attendings, CRNA's, students, and residents.
Buy them lunch and arrange to get CEs or CMEs.
- Work closely with the manufacturer's installation team.
Invest some time in trying to foresee problems.
- Don't assume in a multi-building installation, that
everything that worked well in your new ambulatory center will
function indentically in your aging main OR.
- Check for suction adequacy. Open scavenger interfaces demand
a lot of suction.
- Make a plan for disposables early. Four days before
"go-live", we found that our former breathing circuits, which we
had "assumed" would fit, wouldn't.
- Involve in the planning those anesthetists who are most
familiar with obstetrics, pediatrics, ambulatory, and
cardiovascular. All these areas have special needs for
- Consider the pluses and minuses of integrated monitoring. The
gas machine will last 10-15 years. Will you get tired of an
integrated monitor before then, or wish you weren't locked into
one company's monitoring solution? On the other hand, integrated
monitors are compact, and there's a logic to the whole system
that is very comfortable, once the initial learning curve is
- Your temperature probe and transducer sales representatives
will be happy to get cabling for you that lets their disposable
sensors talk to anyone's monitor.