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    Would measuring the pulse from your finger compared to your ear make any difference to the ECG and blood volume signal obtained?
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    (Original post by MickeyMaccy)
    Would measuring the pulse from your finger compared to your ear make any difference to the ECG and blood volume signal obtained?
    I'm not even sure what you're asking but I think the answer is no lol
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    (Original post by MickeyMaccy)
    Would measuring the pulse from your finger compared to your ear make any difference to the ECG and blood volume signal obtained?
    Not necessarily. However it does depend upon the resting HR of the individual themselves. So any ambulation and the ECG would automatically pick it up therefore results are automatically void and the ECG has to be carried out again.
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    (Original post by MickeyMaccy)
    Thanks for your reply. I'm wondering whether distance from the heart would have anything to do with it? If the finger is further away, would this have an effect on the signal obtained?
    It can play a factor depending on how rapid the HR is going. That is why patients are informed to keep still although its difficult the reading is required to be accurate to administer and falter out the treatment required to make the patient better.

    It can give an inaccurate reading as I have stated previously therefore having to repeat the ECG to gather accurate reading.
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    (Original post by MickeyMaccy)
    Ok. So would the pressure be lower at the finger than the ear and thus result in a weaker signal?
    Yes. This is because traction is easily sensored on the ECG machine therefore it not only voids the whole examination, the signals cannot be detected due to the ambulation of the patient itself.

    With the ear although it can seem tricky I have found that patients dont tend to have ambulation much when it comes to that specific area though this only taken into consideration when the results come out inaccurate a number of times. Although its an easier method of testing so that signal is not lost the reading here can also be misread at times.
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    An ECG is not a measurement of pressure or pulse, so I'm at a bit of a loss as to what you're both going on about here.

    OP, your question is vague and makes no sense. Are you asking about ECGs or about saturation probes and their waveforms?
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    (Original post by moonkatt)
    An ECG is not a measurement of pressure or pulse, so I'm at a bit of a loss as to what you're both going on about here.

    OP, your question is vague and makes no sense. Are you asking about ECGs or about saturation probes and their waveforms?
    I thought OP was talking about Electrocardiography. (ECG.)
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    (Original post by MiszshorTea786)
    I thought OP was talking about Electrocardiography. (ECG.)
    Part of their question goes on about blood volume, this isn't something an ECG would measure, which makes me think it's more about the pressure wave detected on saturation probes, which are routinely put on fingers or on ears.

    Generally, if we're struggling to get a decent reading from a finger probe we'll use an ear probe to measure pulse oximetry.
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    (Original post by MickeyMaccy)
    Essentially I'm trying to establish whether changing the position of a pulse plethysmograph from ear to finger would change the ECG obtained?
    No, because a pleth doesn't measure electrical activity in the heart.
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    (Original post by moonkatt)
    Part of their question goes on about blood volume, this isn't something an ECG would measure, which makes me think it's more about the pressure wave detected on saturation probes, which are routinely put on fingers or on ears.

    Generally, if we're struggling to get a decent reading from a finger probe we'll use an ear probe to measure pulse oximetry.
    Of course. Though the most adequate way to undertake an ECG is via an individuals finger.

    Yes, that can also be done via obs as well. ECG can be differed if an individual has slight traction whilst undertaking the reading.

    Im sorry, if I misguided the OP. That was not my intention.
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    (Original post by MiszshorTea786)
    Of course. Though the most adequate way to undertake an ECG is via an individuals finger.

    Yes, that can also be done via obs as well. ECG can be differed if an individual has slight traction whilst undertaking the reading.

    Im sorry, if I misguided the OP. That was not my intention.
    I've never seen an ecg measured from someone's finger. You can measure pulse oximetry from a finger, which will give you a pulse rate which is relatable to heart rate, but you record the electrical activity of the heart (i.e. an ecg) through using wires and electrodes on the chest.


    (Original post by MickeyMaccy)
    I'm getting a little confused myself. This is the question I'm tasked with:
    Attachment 727750
    That question is worded terribly. There would be a difference in the volume of the pulse, as the distance in relation to the heart has changed, but there would be no effect on ECG because a pleth does not record an ecg.
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    (Original post by MickeyMaccy)
    Thanks for your help. I've got a couple of questions:

    1. Surely the ECG is relatable to pulse oximetry as the R-R interval represents one cardiac cycle and can be used to determine heart rate?

    2. Why would the volume of the pulse change as the distance in relation to the heart changes? (finger and ear)
    It's relatable, but pulse oximetry is a measurement of pulse, not of electrical activity, just as an ECG will not give you a pulse but will give you a heart rate. You can have an ecg waveform that should sustain life but no pulse, as in PEA.

    You're nearer to the heart, the source of the pulse wave. Think about how much stronger your carotid pulse feels compared to your radial pulse.
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    I haven't a clue what a plethysmograph is, but surely moving it would not alter the temporal relationship between the heart sounds and ECG?

    Because when the heart pumps, all the blood moves in the body, if that makes sense. It's not like the heart pumps one specific bit of blood to the ear, then the finger.
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    (Original post by moonkatt)
    I've never seen an ecg measured from someone's finger. You can measure pulse oximetry from a finger, which will give you a pulse rate which is relatable to heart rate, but you record the electrical activity of the heart (i.e. an ecg) through using wires and electrodes on the chest.




    That question is worded terribly. There would be a difference in the volume of the pulse, as the distance in relation to the heart has changed, but there would be no effect on ECG because a pleth does not record an ecg.
    It does occur at times. I myself have undertaken ECG with patients finger but I get what you are saying. Normal procedures are to attach the electrical activity of the heart itself. Though this is only with the new machine though in an renowned cardiologist hospital.
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    (Original post by MickeyMaccy)
    Would measuring the pulse from your finger compared to your ear make any difference to the ECG and blood volume signal obtained?
    Hi,

    I have to go along with AortaStudyMore in saying, with due respect to OP, that the question is highly ambiguous and self-contradictory.

    Firstly, no electrode is placed on the ear to record an electrocardiogram, only electrodes to three of the limbs for the bipolar leads (I, II and III) and unipolar leads (aVR, aVL and aVF) plus six chest electrodes at specified locations on the anterior thorax (for leads V1-V6). So I am struggling to understand why you ask about replacing an ear electrode with a finger one.

    Secondly, unless there is some supercool advance in medical technology very recently, there is no instrument that measures/displays a patient's blood volume directly - yes, it is possible to use Fick's principle to work out cardiac output, and get an approximation of blood volume INDIRECTLY using a rather involved calculation - in any case, knowledge of blood volume has no role in clinical medicine, and certainly has no relationship to the electrocardiogram, except that a patient with severe hypovolaemia due to cardiogenic shock or massive haemorrhage will have greatly reduced cardiac output [following from Starling's Law due to reduced venous return to the heart), and will have reduced amplitude of all waves of the ECG (particularly the R wave).

    Hope this helps!
    M
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    Ah - now you are talking, young man, thank you!

    The answer is no - the plethysmograph would measure the blood volume at a local level, giving an indication of the balance between (in that direction) accumulation of blood in the part of the body concerned due to e.g. blocked venous drainage on the one hand e.g. by the use of a tournique, AND reduced supply of blood to the part due to any stenosis (narrowing) of arterial flow on the other hand [NOT a good idea since it could result in ischaemic [Greek is = not; haem = blood] damage].

    There will be no change in the temporal [i.e. time-related] correlation between your three variable signals because the minute change in blood flow dynamics introduced by the shift of a plethysmograph from one small part of the body [finger] to another small part [ear] can alter NEITHER the timing of the waves of the ECG [which are only occasionally altered by serious but relatively uncommon conditions such as heart block [refers to A:V [atrio-ventricular] block] NOR the timing of the heart sounds, which are generated by the closure of the valves within the heart [the second heart sound is split during inspiration into A2 and P2 [aortic component and pulmonary component] in normality, and its clinical features can be altered once again by e.g. A:V block], BUT NOT BY CHANGES IN BLOOD VOLUME OF PERIPHERAL ORGANS/TISSUES OF THE BODY.

    M [ex-medic]
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    Hi again young man,

    Once again, my knowledge of plethysmography is from an era when we used to perform the procedure "manually" and when we measured it using a physical electronic "pen" [rather like the pen of the old dot-matrix printers of the 90s lol) which you could see actually drawing the graph. In view of this (and please don't try to guess my age, because if you get it wrong, the whole of TSR community will run like hell haha), I am not conversant with the precise tech of the current digital plethysmographs; however, I would say there would be no significant effect due to distance from the heart being different, simply because you are not measuring any aspect of the force or volume of the remnant of the cardiac impulse at either the finger or the ear.

    You are only measuring the change in local volume (of the WHOLE finger OR ear then assuming that any changes are due to change in blood volume, at least in our traditional instruments) - I suppose because the pinna of the ear has a relatively rich blood supply so the signal at the ear might be a little stronger than the one for the finger, BUT SEVERAL OTHER FACTORS WOULD HAVE A POTENTIALLY GREATER EFFECT ON THE SIZE OF THE SIGNAL e.g. the tone of the sympathetic/parasympathetic outflow to the finger or ear, which itself is influenced by several complex mechanisms including any anxiety [it is conceivable that a young subject would be a bit upset if you are sticking all sorts of gadgets in various corners of their poor bodies lol) which would change the levels of NA (noradrenaline) in the blood, as well as the effect this tone has on the diameter of the medium-sized arterioles (the so called resistance vessels) which In turn would determine the level of blood flow to the finger or ear, etc, etc etc,

    Having said all this, it is opportune to say here that this point about signal strength is academic because the Q you originally posed was about the TEMPORAL RELATIONSHIP and NOT any AMPLITUDE BASED PARAMETER.

    I hope I have stimulated your brain enough for you to join Cambridge Uni in 2 hours time lol! (although they might request you to hold your horses till October!)

    M.
 
 
 
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