Hypoxia ? Hypoxic?

I was wondering if someone could explain what these terms mean i often hear them but have no idea what they mean. I've heard them in Casualty before from doctors but i've always felt to ill to ask - can someone explain what it means?

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Not enough oxygen in very simple terms.

Bex

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cheers, so i am guessing that is how it is related to asthma. Is it comon during asthma attacks? what are symptoms?

Lauren/jayne xx

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I assume you have had sats( saturation moniter,usually a peg on finger) checked in a & e before? Well the numbers tell docs if u hypoxic, the usual guideline in our hospital is <90 % oxygen is given. The sysmptoms i have seen in my son are a not very flattering shade of blue lips and nails and confusion but I'm sure there are many other symptoms. Blood gases will also tell docs if u hypoxic. Some people can have lower sats and function perfectly well which ive seen many times at Rbh

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Hi Laurenjayne,

As Julie and Bex have said, hypoxia or being hypoxic is simply a way of describing not having enough oxygen in your blood. In asthma, this occurs because air is not getting into the lungs very effectively, so oxygen therefore cannot get from the lungs into the bloodstream. This usually only happens in a fairly severe asthma attack, although presumably you know that, as you would not be in A&E for a mild attack!

As Julie says, hypoxia is detected by low sats, measured via the peg on your finger, or by low blood oxygen levels, measured via those uncomfortable blood gas tests we all know and love! Symptoms would include headache, confusion, disorientation and drowsiness as well as the blue discolouration to the lips, face and fingernails that Julie mentioned. It is possible to be hypoxic without experiencing any of these symptoms, though. In extreme cases hypoxia can cause unconsciousness, seizures and heart problems, but this is *very* unlikely to occur in asthma provided that appropriate hospital treatment is sought early.

The treatment for hypoxia due to asthma is usually just the same as the treatment for asthma in general, with the addition of supplementary oxygen, which is usually given in a controlled amount of anything from 24% - 85% by a face mask, or occasionally via nasal cannulae, those small tubes that go up the nose.

If you suspect that you are hypoxic, you need to get yourself to hospital via 999 and an ambulance as soon as you can, because as I have said, it is a sign of a severe attack.

Hope this helps,

Em H

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Thanks for that EmilyH! A wonderfully detailed explanation!! I think i have heard it said when i've been in casualty but always been too ill to ask questions but i am nosy and like to know whats going on!!

xx

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Does the pulse oxy machine( Peg on finger) measure the same thing as a blood gas? Reason im asking is that on a few occassions my sats have been ok when monitered with peg. But then blood gas is taken and drs start to panic cos my oxygen is low. I know blood gases also measure carbon dioxide etc. But if my sats are ok shouldnt my blood gas O2 also be fine? The dr usually take a 2nd blood gas just to make sure its from an artery not a vein ,but the results are usually the same. Anybody know whats going on?

Sarah

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Hi Sarah,

The sats probe and the oxygen level on the blood gas essentially measure more or less the same thing. It's slightly complicated but I'll attempt to explain without it degenerating into gibberish! I'm not sure that I'll succeed, though, so do feel free to skip to the last paragraph if you want to!

*GIBBERISH COMING UP*

Oxygen is carried in the blood by the chemical haemoglobin, which is contained in red blood cells. When it is carrying oxygen, it is described as 'saturated' and is red in colour, as in arteries, which are bringing blood from the lungs via the heart to the rest of the body, which needs oxygen. When haemoglobin is not carrying oxygen, it is described as 'desaturated' and is blue/purple/blackish in colour, as in veins, which are carrying 'old' blood from the body tissues to the heart and lungs to pick up more oxygen again.

The finger probe measures the 'sats' or percentage of haemoglobin in the blood which is saturated with oxygen. It is essentially measuring arteries (well, actually the small blood vessels, capillaries, but the numbers are very much the same) and so, in normality, the sats should be high, usually between 96 - 100% and certainly not lower than 90%.

The blood gas, taken from an artery, measures the actual level of oxygen in the blood itself, not attached to haemoglobin, as well as the carbon dioxide levels, the pH (blood acidity) and several other important blood levels to do with the way the respiratory and metabolic systems are working. The actual level of oxygen in the blood (called the pO2 or PaO2) is related to the saturation, as in parts of the body where the blood oxygen level is low, the haemoglobin releases more oxygen, but the relationship is not a linear one - ie if you plot the two on a graph against each other, you don't get a straight line, but more a sort of flattened S shape.

The key thing about this is that the 'knuckle' of the S is about at the level of sats of roughly 90 - 92%. This means that if you have sats at that level, it is very difficult for doctors to predict what your actual blood oxygen level, and thus the amount of oxygen available to your body tissues, is going to be. So potentially it could be just a little low, but still perfectly safe; on the other hand, potentially the blood oxygen level could be rather more worryingly low. This is why doctors tend to get upset when the sats are around that figure - higher than that, and they can be pretty sure that the blood oxygen levels are adequate, but at that level, they just don't know. That is why they do a gas, to give a more accurate idea, as well as to get an idea of the carbon dioxide, pH, and all the other important numbers.

It gets even more complicated than that, because sats are also dependent on other factors such as the amount of haemoglobin that's there in the first place, ie whether you are anaemic or not. If your haemoglobin level is low, it will be relatively easier to saturate more of it - so your sats will be higher for the same blood oxygen level, although there will be no more oxygen available to your body tissues. There are other factors that can also alter the relationship between sats and blood oxygen - the position of the curve, in other words - so things can get really complicated.

*GIBBERISH OVER*

So, basically, yes, the two are roughly equivalent, but there can be a discrepancy between the two on some occasions - which is why, if there is any doubt, doctors prefer to resort to the unpleasant blood gas test we all know and hate! Plus, as we have also discussed, the blood gas will tell doctors the carbon dioxide level, which can be elevated in very severe asthma attacks.

Hmmmm, not at all sure I have avoided the gibberish trap, there - hope that makes some sort of sense anyway!

Take care anyway, everyone

Em H

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Thanks Emily H

Always wondered what they actually measured. Thanks for the explanations made great bedtime reading! Im anaemic so would that explain the differences between the two results? Sorry my brain not functioning at this time of night, will read through wot you wrote tomorrow when more with it!

All the best

Sarah

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Yes, Sarah, being anaemic would give you slightly higher sats for a given blood oxygen level, although you would usually have to be really fairly severely anaemic (ie Hb <5) to dramatically affect your sats.

Glad it seemed to make some sort of sense!

Em