Understanding Oxyhemoglobin dissociation curve

  1. 0
    Hi I am a student nurse and reviewing my uni work as I have upcoming exams and I would love to get good marks and hope to achieve that.

    I am having problems understanding 'Oxyhemoglobin dissociation curve'. I know there is information on the Critcare Education website however I was hoping someone could just explain it clearly and simply without me saying Well what does it mean?

    Thank You and i hope to hear from you soon
  2. 5 Comments so far...

  3. 1
    This is the non-technical way that I understand it.

    At high oxygen saturations, the hemoglobin more easily "lets go" of the oxygen molecules in order to deliver them to the body's cells.

    At lower oxygen saturations, the hemoglobin holds the oxygen molecules more tightly due to the overall chemical composition of the blood.

    The more vertical part of the dissociation curve shows you that there's not much change in dissociation at lower saturations. The more horizontal part of the curve shows you that at higher saturations, it's relatively easy for oxygen to dissociate.

    good luck!

    peace,
    kori
    TrudyA likes this.
  4. 1
    hi
    basically it comes back to the sturcture of hameoglobin. it is a protein with four heme groups (all containing an iron molecule), each heme group can bind one molecule of oxygen. it has two different states, one is a tense state (T)...in this state it holds onto its oxygen molecules really tight and doesnt want to let them go. when Hb gets to the capillaries in the lungs it is exposed to lots and lots of oxygen molecules. the Hb takes up an oxygen molecule and this causes the Hb to switch to the relaxed (R) state. in the R state it is happy to take up more oxygen molecules as it has a higher affinity for oxygen.

    when it gets to tissues it finds an area of low oxygen...this causes one oxygen molecule to hop off...because one hopped off, others go with it...the one oxygen molecule leaving causes the Hb to shift to T state, it has a lower affinity for oxygen thus all of them leave...

    in the Hb-O2 curve there is a plateau portion bw the oxygen pressure of 60 and 100 mmHg...in this part of the curve a rise in oxygen content in the blood provides only a small increase in the extent to which Hb is bound to oxygen molecules.
    this gives us a nice sfatey margin. normally we walk around at approx 98% oxygen saturation (98 mmHg)...this number refers to the amount of dissolved oxygen in the blood...in our blood oxygen exists in two ways, dissolved and bound to HB...so between 60-100% oxygen saturation there is very little effect on Hb bound oxygen. that means if your o2 sat falls temporarily (you are at higher altitude for instance) you have some space BEFORE you start to get lower oxygen delivery to tissues. the oxygen delivery to tissues depends on the % of Hb bound to oxygen.
    when oxygen saturation drops under 60 mm Hg this tiggers the chemoreceptors in the medulla and stimulates the ventilation control bit of the brain. the bit of the curve (the steep bit) under 60 mmHG oxygen shows that as dissolved oxygen drops the % bound to Hb drops DRAMATICALLY...at which point you're in trouble

    the application of the Hb-O2 curve is that it can be shifted left or right

    eg. low ph (ie. acidic environment), high temp and high carbon dioxide shift the curve right. this is the environment that would be present in excercising muscles, lots of acid due to lactic acid production, lots of carbon dioxide from glycolosis and the citric acid cycle and lots of heat...therefore in excercising muscle Hb is more likeley to give up its oxygen

    eg2. in carbon monoxide poisening, the carbon monoxide molecules bind to Hb in the place of oxygen and cause the Hb to have a higher affinity for oxygen, ie. it holds onto what it does have much harder. thus carbon monoxide poiseining shifts the curve to the left and at a given oxygen content LESS oxygen will be given up to tissues then normal

    i dont know if that helped or made it worse...hope it helped

    elle
    TrudyA likes this.
  5. 1
    The only way I remember it is

    Left= Low

    I believe that after 89% the curve falls way down=Bad
    TrudyA likes this.
  6. 0
    Quote from SN_2B_RN
    Hi I am a student nurse and reviewing my uni work as I have upcoming exams and I would love to get good marks and hope to achieve that.

    I am having problems understanding 'Oxyhemoglobin dissociation curve'. I know there is information on the Critcare Education website however I was hoping someone could just explain it clearly and simply without me saying Well what does it mean?

    Thank You and i hope to hear from you soon

    o2 sat goes up
    with these conditions:
    Right
    Low o2sat l * o2 sat lowers with
    Left l * * these:
    aLkalosis l * * acidosis
    Low temp l * * fever
    Low co2 l * * high co2
    Low 23dpg l
    l________________________ (the pulse ox looks
    o2 tension bad, but the o2
    is being
    (the pulse ox looks good, but no o2 readily Released)
    is being released to the cells) hb hoLding on to o2
  7. 0
    Quote from SN_2B_RN
    Hi I am a student nurse and reviewing my uni work as I have upcoming exams and I would love to get good marks and hope to achieve that.

    I am having problems understanding 'Oxyhemoglobin dissociation curve'. I know there is information on the Critcare Education website however I was hoping someone could just explain it clearly and simply without me saying Well what does it mean?

    Thank You and i hope to hear from you soon
    http://www.ventworld.com/resources/oxydisso/dissoc.html


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