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Thread: PPO2 difference inspired/exhaled

  1. #1

    PPO2 difference inspired/exhaled

    Hi Guys..i´ve read a ray manual..take a look of this: the oxygen sensor is located in the exhalation side so there is a difference between the ppo2 inspired and the ppo2 exhaled (reading by gauge)--they assume a constant 4.5% drop independent of pressure (aka depth)..my question:..is that correct?..i think isn´t

    below the info (from the manual )..

    thanks


    When using the Dräger OXYgauge this will be connect to
    the exhalation side of the breathing loop. This means it
    will always measure 4,5 Vol. % less Oxygen the actually
    are in the loop. The readings of the OXYgauge have to
    be corrected according to the following table:
    78
    Handling and Use
    Diving the DrägerRay
    Warning!
    It is important to use an alternative gas supply
    when using a dry suit. Filling the suit from the
    Nitrox-Supply is not admissible due to the risk of an
    Oxygen Burn.
    Diving depth
    (MSV/ feet)
    Differenz to add on
    the PPO2 reading
    (bar)
    0 / 0 /0,045
    10 / 33/ 0,090
    22 / 72/ 0,144
    Last edited by nostromo; 29th July 2011 at 14:06.

  2. #2
    RBW Member anarchista is an unknown quantity at this point anarchista's Avatar
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    Re: PPO2 difference inspired/exhaled

    Quote Originally Posted by nostromo  View Original Post
    Hi Guys..i´ve read a ray manual..take a look of this: the oxygen sensor is located in the exhalation side so there is a difference between the ppo2 inspired and the ppo2 exhaled (reading by gauge)--they assume a constant 4.5% drop independent of pressure (aka depth)..my question:..is that correct?..i think isn´t

    below the info (from the manual )..
    On the surface this is true.
    The meter measures the ppO2, at greater depths due to reduced metabolism ppO2 is less for the same work done.
    It's the basics.

    rc greet

  3. #3

    Re: PPO2 difference inspired/exhaled

    Quote Originally Posted by anarchista  View Original Post
    On the surface this is true.
    The meter measures the ppO2, at greater depths due to reduced metabolism ppO2 is less for the same work done.
    It's the basics.

    rc greet
    Yes that´s correct ( i mean the 4.5% plus at surface) ..but what´s about below the surface?....in that case the manufacturer assumes a linear relationship between this drop and depth...BUT metabolism remains quite similar despite your depth as you well know( depends on exersion mostly) .....the problem is quite basic but i do not understand why draeger consider this flawed data... i think they thought it would be simpler for user to consider it that way.. i don´t know...

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    RBW Member anarchista is an unknown quantity at this point anarchista's Avatar
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    Re: PPO2 difference inspired/exhaled

    Quote Originally Posted by nostromo  View Original Post
    Yes that´s correct ( i mean the 4.5% plus at surface) ..but what´s about below the surface?....in that case the manufacturer assumes a linear relationship between this drop and depth...BUT metabolism remains quite similar despite your depth as you well know( depends on exersion mostly) .....the problem is quite basic but i do not understand why draeger consider this flawed data... i think they thought it would be simpler for user to consider it that way.. i don´t know...
    It is not linear.
    However the detector measures the partial pressure of oxygen, this measure takes into account the changes and automatically gives the oxygen pressure, if done well on the surface of the calibration.

    rc greet

  5. #5

    Re: PPO2 difference inspired/exhaled

    Quote Originally Posted by anarchista  View Original Post
    It is not linear.
    However the detector measures the partial pressure of oxygen, this measure takes into account the changes and automatically gives the oxygen pressure, if done well on the surface of the calibration.

    rc greet
    Thanks for your answer but i think you did not understand what i´m trying to ask..my fault...i will try again...

    because breathing, o2 drop between inspiration and exhalation..until here ok

    important to know the ppo2 for inspiration ( to avoid hypoxia..MOD is given by % o2 into the tank)...to do that (remember the o2 cell is located in the exhalation counterlung in this model) you need to know how much the ppo2 drop is because breathing

    4.5% drop is OK for surface as you said but is not correct for the deep (inspiration and exhalation ppo2 are much closer in deeper water)...

    my question is: ..why did dräger gives the data shown below (from manual) which is not correct?..obviously that way to do the things are easier to the diver. and easier to teach and apply....anywway close to the surface where the gauge readings are better and accurate using these values, is exactly where are more relevant..

  6. #6
    RBW Member anarchista is an unknown quantity at this point anarchista's Avatar
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    Re: PPO2 difference inspired/exhaled

    Quote Originally Posted by nostromo  View Original Post
    my question is: ..why did dräger gives the data shown below (from manual) which is not correct?..obviously that way to do the things are easier to the diver. and easier to teach and apply....anywway close to the surface where the gauge readings are better and accurate using these values, is exactly where are more relevant..
    Read at the bottom is the correct course as a function of depth. This is not fixed exactly as it should be.
    "Oxygen Burn.
    Diving depth
    (MSV/ feet)
    Differenz to add on
    the PPO2 reading
    (bar)
    0 / 0 /0,045
    10 / 33/ 0,090
    22 / 72/ 0,144"
    http://www.rebreatherworld.com/showthread.php?t=28918
    The Swedes have tested this concept Ke to 450m (Interspiro). Draeger is sitting in the construction of CMF. They have done a successful SCR constant ppO2. Canadians have done such a structure.

    rc greet
    Last edited by anarchista; 31st July 2011 at 07:24.

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    Re: PPO2 difference inspired/exhaled

    Quote Originally Posted by nostromo  View Original Post
    because breathing, o2 drop between inspiration and exhalation..until here ok

    important to know the ppo2 for inspiration ( to avoid hypoxia..MOD is given by % o2 into the tank)...to do that (remember the o2 cell is located in the exhalation counterlung in this model) you need to know how much the ppo2 drop is because breathing

    4.5% drop is OK for surface as you said but is not correct for the deep (inspiration and exhalation ppo2 are much closer in deeper water)...

    my question is: ..why did dräger gives the data shown below (from manual) which is not correct?..obviously that way to do the things are easier to the diver. and easier to teach and apply....anywway close to the surface where the gauge readings are better and accurate using these values, is exactly where are more relevant..
    We are entering a CMF SCR theory. Can achieve higher levels of oxygen consumption of the respiratory factor. This can be accomplished in a precise SCR. So SCR CMR wnich is very constant fraction of oxygen and accurate mechanisms counting of ventilation.

    CMF SCR is simple, but least accurate in the basic form. Therefore, we must have more and smaller dosage of oxygen consumption levels than in the SCR. CMR.

    f(h)=Po / (Po + rgh) is a function of scaling
    Po -atmospheric pressure, r-water density, g-acceleration gravity, h-depth.

    rc greet

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