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fstephenson17
12-14-2004, 01:07 AM
Dear BIOMCH-L subscribers:

I sent out a request for help regarding information for portable oxygen
consumption systems last week. The original post is as follows:

>We are currently looking for a new portable oxygen consumption
equipment for our gait lab. Our lab mainly serves children with
cerebral palsy. We had a Cosmed K2 in the
>past, but it is no longer functioning and it will not be possible to
have that equipment repaired. As a result, we are in the market for a
new set of equipment.

>We are wondering if the subscribers have any suggestions regarding any
portable oxygen consumption equipment. We are particularly interested
in the users' feedback on
>the equipment and the longevity of the equipment.

>The only information I got from searching the BIOMCH-L archives
regarding oxygen consumption/oxygen uptake/metabolic equipment is a
posting from Dr. Whittle in 1994.
>However, I am sure that the technology has improved since then.
Therefore, we would like to have more recent information on the
equipment.

>We will appreciate any suggestions and/or recommendations.

I would like to thank all who responded to my request. My special
thanks goes to Fabien Basset in Canada who forwarded me a similar
discussion on the sportscience list and a review on metabolic systems by
McFarlane. I would also like to thank George Havenith in the UK for
providing me with some information he received when he posted the same
question to the list a year ago.

>From the responses I received, there seems to be two major players on
the market: Cosmed and Cortex/Sensormedics. When I was talking to a
supplier last week, they said that the Sensormedics VmaxST (Cortex
Metamax 3B) is no longer available in Canada (I am not sure if that is
the case other countries as well). Apparently the parent company of
Sensormedics, Viasys, also manufactures the Jaeger Oxycon Mobile.
Viasys have stopped making the VmaxST units and concentrated their
efforts on the Oxycon Mobile instead. Unfortunately, the Oxycon Mobile
is a relatively new product so I did not receive any user feedback on
that particular system. Medical Graphics (Aerosport) also manufactures
a portable device called VO2000. A review on that system can be found
in the summary as well.

I recommend reading McFarlane's review published in 2001 titled
"Automatic Metabolic Gas Analysis Systems" in Sports Med; 31(12):
841-861 if you are interested in this topic.

Given the sensitive nature of equipment review, the following summary
will be anonymous and any statements that may identify the individuals
and/or their organizations have been removed. Some of the reviews are
paraphrased and some of the reviews are direct quotes. The reviews on
the sportscience list discussion are incorporated into the following
summary as well.

About the MedGraphics VO2000:
"It is a very affordable option but does not have the same capabilities
as the Cosmed unit. The VO2000 cannot do breath-by-breath. Instead it
averages measurements over a 10 or more second interval. We had some
persistent trouble with a CO2 sensor which was finally been remedied by
a replacement unit."

About Oxycon systems:
One reviewer commented they have heard very good things about Oxycon
units.

About Cosmed K4b2:
"We have a Cosmed K-4 unit in our lab that we have used quite
extensively. While it is reliable and relatively easy to use, it does
need regular maintenance."

"the Cosmed K4 seems to be prone to problems, we used one for a while
the other year and had a lot of trouble with calibration, and very high
VO2 values, so I would avoid that system."

"We get reliable data (sometimes) from the cosmed...My personal
experience for a technical point of view is that the equipment is poorly
manufactured. I have had to resolder wires on numerous occasions because
they were tacked onto the outside of the circuit board not soldered
through. Support also is woeful, possibly because they are dealing with
so many faulty machines."

"I've had experience of several COSMED units now...and they've all
suffered from a combination of unreliability and poor customer support.
I know several other owners of COSMED systems who have had similar
experiences."

About VmaxST/Metamax 3B:
"I have used it [VmaxST] for one study. It is fairly compact and can
work wirelessly. The oxygen sensor needs to be replaced every 6 months.
The battery life is about two hours, so I'd recommend two batteries.
I'm not sure how successful the harness would be on children, but I do
believe they come in different sizes. Weight should not be a problem
though, it's fairly light."

A group of users have used the VmaxST and they are happy with the unit.
They have not had a failure with that unit. They were also happy with
the training they have received. The only down side to the unit is that
the oxygen sensor needs to be replaced frequently

A group of users have a VmaxST but they have had problems with the CO2
cell and other parameters.

" - The build quality [of MetaMax 3B] is very poor (especially
considering this is designed to be used in the field). For example the
battery compartment has snapped off numerous times and has to be held on
with tape. The connectors into the machine are very delicate and have
snapped several times (including within the first hour of use!).
- The sports strap was an optional extra but is essential for any
exercise protocol. However despite being designed for sports use the
Velcro is insufficient to hold the unit in place and we have to use lots
of tape to stop it bouncing around and keep the wires out of the way.
- Poor reliability of the telemetry system which will only work under
'ideal' conditions and is temperamental.
- The oxygen sensor has been replaced 3 times and the volume sensor
also failed.
These points can be summarized by the fact we have returned the unit
for repairs 4 times and has been completely out action for as long as
it's been in action. We have now bought a power supply and extension
leads to use as a lab based online system as it dose not stand up to the
demands of being used in the field. I understand the 3B has now been
updated slightly and hopefully many of these problems will have been
addressed."

"We have been using their MetaMax I for a number of years. It is still
functioning although there were some small problems. They still provide
service and technical support. Latest models, e.g. MetaMax 3B, are
probably more suitable for your purpose."

"...on the whole I have been very happy with the MetaMax. I have mostly
been using it with the telemetry mode and monitoring participants on a
laptop. The Metasoft program is very clear, has a good display screen
(you can pick the parameters you want to see, it produces a real time
graph with the data on etc) and is pretty easy to use.
The only real problems we have had are with the telemetry device,
which hasn't always been reliable which can be frustrating, you can use
the main unit just as a data logger but then you cannot see the data
until you download it at the end of the test.
I have not really used the system outside so I am not 100% sure how
it would perform we have had issues of condensation build-up in the
volume turbine when used in cool environments (inside but at 15-16oC) if
this happens it interferes with the sensor detecting the turbine
rotation therefore missing data."

>From users that have used more than one system:
"We have never in over 4 years collected any data with it [Cosmed's
system]...The telemetry system gave bizarre data and
irregularly/spontaneously would work/not work. We purchased a new
Metamax and so far we have been happy and are using it in a study. No
problems to date."

"I have used it [Cosmed K4b2] extensively and found it to be reliable
and consistent. The software upgrades are easy to load and seem to add
something new each time. The capabilities of the unit are enormous,
particulalry for synchronising with other systems (treadmill, cycles and
12 lead ecg). The Oxygen analyser does need replacing once per year, and
other tubing should be changed and serviced regulalry. The straps on the
face mask harness are not brilliant but can be changed. The face mask
system however is good in my opinion.
I spent the last 12 months working in ... where a new Metamax system
had been purchased. I was keen to see this work as the system looked
neat and the software offered some differences to the cosmed. After3
months however I was not impressed with the continued breakdowns, the
system was more difficult to enter and operate than the cosmed and the
functionality I felt was not as good."

"we currently use a Cortex Metamax 3b Portable Gas Analyser but we are
currently bidding for a Cosmed k4b2 system to use instead as i've heard
better stories about it. We've used the cortex metamax for [a few]
years and it has some nice features such as a 1km telemetry range and
the data output is pretty comprehensive although the software is poorly
structured (but I believe it has been updated since we got ours), but
the quality of the system is very poor for the money involved, in
particular the outer casing and battery compartment. As well as the
annual servicing it is also away once or twice per year for repairs. We
have never stressed it highly either and it has never been used out of
the lab so if you are intending some heavy use with it then think twice
about the cortex (ours only gets used on a treadmill or cycle ergometer,
don't think i'd risk anything more intensive with it). The yoke is also
quite cumbersome and moves around a lot so if you are using it with
childen, particulary CP subjects, then it will probably be even more
obtrusive. Also, support and feedback are pretty much non-existant when
problems are encountered. In short, i personally wouldn't buy a Cortex
Metamax 3b again."

The bottom line:
It sounds like there is not a clear winner here. I believe one
respondent has a very good suggestion: "What may be just as important is
how good your local distributor is (and how local they are). These
things do need fixing every so often and you often want them sorted out
as quickly as possible." Therefore, I will find out where the local
distributors are located for these systems and go from there.

I hope this summary will be helpful to others.



Flora Stephenson, M.Sc., Certified Kinesiologist
Gait Lab Kinesiologist
Clinical and Technical Specialty Services
Thames Valley Children's Centre
779 Baseline Road East
London ON N6C 5Y6
Canada
http://www.tvcc.on.ca


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