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Pressures to breakdown skin

Discussion in 'Diabetic Foot & Wound Management' started by Orthican, Jan 15, 2015.

  1. Orthican

    Orthican Active Member


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    Good day all,

    I am in need of the great minds here to help with obtaining some information if I may ask.


    I have information that indicates normal skin will breakdown with 25 mmhg applied over a 1cm2 area for 15 min. Please correct that if it is wrong.

    My question is thus:

    If we have a "normal" value then do we have any values we can use on those with unhealthy tissue. For instance those with vascular complications and diabetes with history of wounds. The reason for asking is that here in Alberta we need to be valid with our outcomes. (as it should be of course)

    However, when I apply in shoe pressure measurement all I can really say is that I have "reduced" the pressure in the area of concern. But what can I compare to? All I have is a presumed value for "normal". these individuals do not always have "normal" skin as you all know. I presume that the values for breakdown on vascularly impaired with diabetes would be less than the normal but can find little info on that specific a parameter.

    Thoughts?

    Thanks for any input.
     
  2. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    I am pretty sure there are a couple of studies on this. I think Cavanagh was one of them ... from what I recall it was extremely variable. Some ulcerated at low thresholds and some at high
     
  3. Petcu Daniel

    Petcu Daniel Well-Known Member

  4. efuller

    efuller MVP

    There was a paper, I believe it was by Nigg, or maybe Cavanagh, that showed that pressure measurement was dependent on sensor size. What the study did was look at pressures at a single sensel and then look at the pressure value from four adjacent sensels. As I recall sometimes in the larger area the pressure would increase and sometimes it would decrease relative to the smaller sensors. So, the pressure value is dependent upon the equipment that you use. So, you can't have a standardized value of pressure at which you would expect skin to ulcerate.

    Just be happy that your intervention reduced the pressure. The real indicator for a successful intervention is the ulcer goes away and does not return and not the value on your machine. As they say in radiology, don't treat the x-ray.

    Eric
     
  5. wdd

    wdd Well-Known Member

    It seems as if there are two components to this problem.

    The first one, identified by Eric seems to berelated to the size and number of 'sensels' and the second one is associated to knowing how 'healthy' the skin and subcutaneous tissues are.

    I would think that both problems can be solved.

    By standardising the number and size of the 'sensels' you could standardise the results. Of course the measured pressures wouldn't be absolute but if everyone was using the same steps they would be comparable and could be used as a measure of relative pressure.

    The relative health of the tissues, which is likely to be a major factor in probability of ulceration, would seem to be covered by the concept of 'tissue vitality' which I think can now be measured non-invasively. That way you would have a measure of tisue health independent of any diagnosis of pathology. Although it would be interesting to see how the tissue vitality varied with different pathologies.

    With these two factor you could make a pretty good stab as computing the risk of ulceration.

    Bill
     
  6. vbnmurthy

    vbnmurthy Welcome New Poster

    Hello,
    I have been working on this subject for over two decades. You may like to read this recent publication.
    "Biomechanical Properties of the Foot Sole in Diabetic Mellitus Patients: A Preliminary Study to Understand Ulcer Formation
    V. B. Narayanamurthy (Division of Biomedical Engineering, Department of Applied Mechanics, Indian Institute of Technology, Madras, India), Richa Poddar (Department of Physiotherapy, Sundaram Medical Foundation, Chennai, India) and R. Periyasamy (Department of Biomedical Engineering, National Institute of Technology Raipur, Raipur, India)
    Volume 3, Issue 1. Copyright © 2014. 17 pages." International journal of biomedical and clinical engineering.

    Ulcer formation is an interplay of atleast these simple measurable parameters. I have developed an index which takes into account th pressure, hardness of the foot sole, loss of sensation and also the hardness of the footwear the patent is wearing.

    Dr V B NarayanaMurthy


    Please find the link as requested.
    http://www.igi-global.com/article/b...oot-sole-in-diabetic-mellitus-patients/115881
     
    Last edited: Jan 17, 2015
  7. Would it be possible to post a .pdf file/ link to the full text of your paper here please?
     
  8. The output from the sensel is also dependent upon the surface angulation and the stiffness of the surface that the sensel is sitting upon as we discussed here: http://www.ncbi.nlm.nih.gov/pubmed/21084541 Just to be clear, the intervention may not have reduced the pressure even if the technology tells you that it has, rather you may have merely changed the angle/ stiffness of the surface that the sensor was sitting upon. As Eric said, the real indicator is in your treatment outcome to the patient.
     
  9. vbnmurthy

    vbnmurthy Welcome New Poster

  10. vbnmurthy

    vbnmurthy Welcome New Poster

  11. Orthican

    Orthican Active Member

    Thankyou Eric

    Yes the size of the sensor is something I was aware could skew what I was seeing to what might be actually happening. As always I have relied on follow up and visual checks to see what is actually happening. In applying a numerical I am looking to do nothing more than be cosistent within what I am measuring with the same device every time. I am hoping in that way at least I can be consistent with my own measure on each pateint and use the visual and the measured to validate the outcome for the payer.
     
  12. Orthican

    Orthican Active Member

    I want to thank everyone that contributed thus far to this information. I have a few things to now read and will come back with any thoughts..

    As usual thankyou podiatry arena.
    Best source of minds and information on the subject virtually anywhere!!
     
  13. Petcu Daniel

    Petcu Daniel Well-Known Member

    Found this:

    The mechanism of soft tissue damage: It is all in the rub

    Sarah A Curran1
    J Martin Carlson2
    1Wales Centre for Podiatric Studies, Cardiff Metropolitan University, Cardiff, UK
    2Tamarack Habilitation Technologies, Blaine, MN 55449, USA
    Sarah A Curran, Wales Centre for Podiatric Studies, Cardiff Metropolitan University, Western Avenue, Cardiff CF5 2YB, UK. Email: sarah.curran@ispoint.org


    Abstract

    Understanding mechanisms of injury to the skin and soft tissue are an important feature in optimizing management strategies. As technology advances and innovative wound products evolve, the need for the awareness of such developments is key to enhancing knowledge and their clinical application. This article provides an overview of the role of repetitive loading of the skin and tissues and the influence of thickness and mobility of these structures. The role of friction and pressure strategies is also discussed along with a brief overview of new products.


    Clinical relevance Pressure and friction are important parameters in the management of wounds. Clinicians should be aware of these concepts and be cognizant of new technologies that are available for the reduction of these parameters.

    http://poi.sagepub.com/content/39/1/82?etoc
     
  14. Orthican

    Orthican Active Member

    So from what I can see what we can say for sure is that we know what the normal uncomplicated average adult tissue will do under a certain pressure over a certain area over a certain time.

    We cannot with any reliability truly predict ulceration nor can we say what pressures will cause ulceration in the diabetes/vascularly compromised individual other than rough estimates.
    We do know that "on average" the numerical values of pressure and shear of those with these complications that lead to skin breakdown will be less than normals. I believe we can say that.

    We cannot say that we have a set of values that predict breakdown for these individuals.
    We can say that with regular monitoring and follow up that adjustment to pressures and shear can be achieved thus reducing ulceration complication and lead to healing.
    We cannot say that the patient will achieve healing even with all this because of compliance to treatment protocols we set out. Sometimes I feel like I am banging my head against the wall with some of them but that is what it is.
     
  15. Petcu Daniel

    Petcu Daniel Well-Known Member

    Do you know any work regarding a different risk of ulceration between left and right feet ?

    Sincerely,

    Daniel
     
  16. Orthican

    Orthican Active Member

    Not offhand at the moment. But it does happen. Partial spinal chord lesions can set up a scenario like that. One side will have lost propriception and have differing paralytic effects depending on the case while contralateral side loses pain and temperature senses. A Brown Sequard lesion will do that.
     
  17. Petcu Daniel

    Petcu Daniel Well-Known Member

    Another interesting article: " Twelve steps per foot are recommended for valid and reliable in-shoe plantar pressure data in neuropathic diabetic patients wearing custom made footwear" , http://www.sciencedirect.com/science/article/pii/S0268003311001239
    One of the conclusions: " ...Moreover, left–right differences for the primary parameter, peak pressure, were small. Therefore, no specific conclusion should be drawn from the discrepancies between the left and right foot."

    On the other side, when the mean temperature difference in specific points on plantar surface is analyzed, a "difference between the left and the right foot was 2.65C in patients who needed immediate treatment" , http://online.liebertpub.com/doi/abs/10.1089/dia.2014.0052

    Daniel
     
  18. JFurmato

    JFurmato Welcome New Poster

    The amount of pressure needed to blanch skin in a horizontal subject is 3 N/cm2, or 30 kPa. This is equivalent to 225 mmHg. In the upright individual, the blanching pressure is 300 mmHg. Whatever the postural orientation, let's just refer to "blanching pressure". In the horizontal condition, a constant application of blanching pressure for four hours results in a decubitus ulcer.
    Blanching pressure exceeds the intralumenal (arterial) pressure. The externally applied pressure must compress the soft tissue surrounding the vessels supplying the skin and overcome the arterial pressure to occlude flow. Blanching pressure is a threshold value, however. It's seen under most locations in the weightbearing sole during quiet standing and in the Stance Phase of gait. However, it is not unusual to see peak plantar pressures at 20 times blanching pressure in some locations.
    When pressure at or above blanching is removed from the skin, the intraluminal pressure must perform sufficient work to reestablish flow. The compression of surrounding soft tissue is resolved through stress relaxation. If the externally applied pressure is 600 kPa, this level of compression must resolve before the vessel can reopen.
    Over an extended period of walking, blood flow may not have an opportunity to resume. The affected tissue is in a hypoxic state similar to having a tourniquet up for too long during surgery. Even under anesthesia, the patient begins to react to hypoxic pain. Under normal conditions, you complain about the pain, sit, maybe rub your feet and eventually resume your activity when you feel better.
    But if you can't feel the pain, you might not know when to stop walking or when it's safe to resume.
    I've shared this at several gait meetings in the US, World Congress of Podiatry meetings and it was the topic of my doctoral thesis in biomedical engineering. I'm working on manuscripts to have this published.
    Timing is an important consideration. The relaxation constants in the soft tissue and blood vessels, temporal sequencing of gait and pulsing in the cardiovascular system all play a part.
     
  19. Orthican

    Orthican Active Member

    That is a very good explanation thankyou.
    It makes me think about the relaxation demand to get flow of the vascular and if there is a connection there with forefoot ulceration and stiffness in the calf group that will increase pressure at the forefoot during late stance but with stiffness there is no relaxed state . There is a correlation I have noted with those with forefoot ulceration and stiffness in the calf group. I have always thought this to be a predominant cause but now it makes even more sense with the need to relax the tissues in order to allow flow of blood. I do understand that correlation does not imply causation.
     
  20. JFurmato

    JFurmato Welcome New Poster

    The stiffness in the calf muscle is a problem as far as developing plantar pressures in gait. However, tissue stiffness of greater concern may be in and around the small vessels. Glucose diffuses from areas of high concentration to low. Over time, glucose will cross link with protein, such as keratin, hemoglobin or collagen. This stiffens the protein. In the case of diabetes, or in a high sugar/carb diet, glucose diffuses with a higher gradient.

    The molecule knows nothing of diagnosis, it just diffuses and, if it sits around it undergoes an Amidori reaction. It not practically reversible, although amidoriase therapies are under investigation.

    None of this has to do with externally applied pressure: it happens throughout the body. Where we once considered pressures greater than 150 N/cm2 (1.5 MPa) pathological, subsequent research now suggests risk of ulceration is proportional to the amount of pressure or, more specifically, related to the integral of the Pressure-Time curve in an area.

    Stiffer material in and around the small vessels is like a garden hose. You can stop flow through a new flexible hose by stepping on it and when you step off--flow. An older stiffer hose might resist flexing and occluding at first. But if you work at it, stomping repeatedly, and stop the flow, it takes longer for flow to return after you take the load off.

    The stiff calf muscle helps provide a higher load, but, as I suggested earlier, any part of the sole bearing load in stance or standing is at risk.
     
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