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Summary: Portable Oxygen Consumption Measurement Equipment

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  • Summary: Portable Oxygen Consumption Measurement Equipment

    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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