interpreting tcpo2 curves and results

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  • Interpreting Curves and Results

    PeriFlux 6000 | tcpO2 made intelligent

  • Disclaimer

    The information contained in this document is intended to provide general

    information only. It is not intended to be, nor does it constitute, medical advice.

    Under no circumstances is the information contained in this document to be

    interpreted as a recommendation for a particular treatment for specific

    individuals. In all cases it is recommended that clinicians perform their own

    interpretations of data in conjunction with the clinical assessment of their patient.

    Due to Perimeds commitment to continuous improvement of our products, all

    specifications are subject to change without notice.

    All information and content in this document is protected by copyright. All rights

    are reserved. Users are prohibited from modifying, copying, distributing,

    transmitting, displaying, publishing, selling, licensing, creating derivative works,

    or using any information available in or through the document for commercial or

    public purposes. All responsibility for any liability, loss or risk, personal or

    otherwise, which is incurred as a consequence, directly or indirectly, of the use

    and application of any of the material in this document is specifically disclaimed.

  • Calibration

    tcpO2 Site Selection

    Electrode Maintenance

    Interpreting Curves and Results

  • Transcutaneous oxygen (tcpO2 / TCOM)

    Reference values

    50-70 mmHg Normal < 40 mmHg Impaired Wound Healing

    < 30 mmHg Critical Limb Ischemia

    Measures the local oxygen tension in the skin deriving from the local capillary (nutritive) blood perfusion.

    Predicts wound healing potential

    Helps define degree of small vessel disease

    Accurately determines amputation level

    Monitors efficacy of patients ongoing therapy

    Establishes candidacy for HBO treatment

  • Influencing Factors

    Impaired macrocirculation - Peripheral Arterial Disease

    Capillary impairment

    or

    Cardiopulmonary disease

    Edema

    High consumption of O2 (e.g. infection or inflammation)

    Hair

    Topical skin products, lotions, dirt, grease

    Bony prominences, sharply curved anatomy, calloused

    skin

  • Procedure Details

    Typical procedure:

    15 minute baseline

    5 minute leg elevation

    5 minute post-elevation

    10 minute oxygen challenge

    Above procedure can also be done without leg elevation (if large vessel disease has been ruled out).

    Provocations

  • Typical Data

  • Why Provocations?

    Leg Elevation Test

    Lift legs 30 with wedge.

    May be used to confirm macrovascular disease.

    Oxygen Challenge

    tcpO2 measurement during 100 % oxygen inhalation.

    Discriminates between vascular disease and barriers to diffusion such as edema and/or inflammation. Identifies candidates for HBO therapy.

  • Leg Elevation Test

    Lift legs 30

    Expect a drop of < 10 mmHg and/or < 20% (of baseline value).

    Values should revert to baseline after wedge (30) is removed.

    Other methods to confirm macrovascular disease include toe and ankle pressure.

  • O2 Challenge

    tcpO2 measurement during 100% oxygen inhalation

    Expect > 100 mmHg and/or > 100% increase from baseline.

    A tight fitting mask, e.g. an NRB mask at 15 l/min, is essential for a successful O2 challenge.

    IMPORTANT Patients with chronic obstructive

    pulmonary disease should NOT be

    subjected to an O2 challenge.

  • Example 1 - O2 Challenge

    Baseline

    tcpO2 = 10 mmHg

    O2 challenge

    tcpO2 = 105 mmHg

    Low tcpO2 values due to barrier to O2 diffusion.

    Confirmed by good response to O2.

    Wound healing potential exists. Candidate for HBO.

  • RIGHT

    LEFT

    tcpO2 baseline = 64 mmHg

    tcpO2 baseline = 43 mmHg

    Example 2 O2 Challenge

    Patient with wound on right foot.

    Low toe pressures on both sides (R = 16 mmHg, L = 18 mmHg)

    Is the right side tcpO2 value reliable or is it falsely high?

    tcpO2 curve shape slowly declining. No initial dip(compared with left).

    Toe pressure results indicate severe macrocirculatory problems (< 30 mmHg).

    An O2 challenge would have been useful!

    No response to O2 would have confirmed severe microcirculatory disturbance.

  • Example 3 O2 Challenge

    Similar curves for which an O2 challenge would have

    been beneficial for the interpretation!

    No initial dip. Slowly

    declining tcpO2.

    Leakage at end of

    measurement?

    Falsely high baseline

    value?

    True low value due to

    PAD or falsely low due

    to barrier to O2

    diffusion?

  • Leakage

    Unreliable data...

    Spikes in the curve are

    usually due to leakage.

    Leakage can also easily be

    verified by spraying oxygen

    around the fixed electrode!

  • Faulty setup?

    Expect an initial dip in the tcpO2 curve directly after

    the electrodes have been positioned in place.

    Curves with no initial dip.

    1. Re-position fixation ring to make sure that the site preparation is ok.

    2. If there is still no dip and the baseline is slowly declining, perform an

    O2 challenge to evaluate severe microcirculatory disturbance.

    Initial dip in tcpO2

  • Oscillations

    Regular variations...

    May be due to

    physiological reasons

    such as a respiratory

    problem causing

    varying oxygen

    delivery or, a cardiac

    output problem

    causing quick

    oscillations in the

    supplying arterial flow.

    CHEST

    CALF

    FOOT

  • Other Tips

    Contralateral reference and/or pulse oximeter

    rules out arterial hypoxemia due to e.g. pulmonary

    disease.

    A mean of several tcpO2 values

    is a better predictor of wound healing potential than

    single site values.

    To establish candidacy for HBOT (Hyperbaric Oxygen

    Therapy)

    expect in-chamber value: tcpO2 > 200 mmHg

  • Perform Additional Vascular Tests

    Add other pieces of information

    Toe pressure and ABI

    Pulse Volume Recording (PVR)

    Segmental pressures

    Tissue response to local heating (Heat-

    controlled laser Doppler)

    Skin Perfusion Pressure (SPP)

  • Toe Pressure - TBI

    Toe pressures/TBI are more reliable than ankle pressure in patients with calcified vessels (ABI > 1.40) 30 - 40 % of patients with diabetes show falsely high ABIs.

    ABI > 0.6 has low predictive value for healing in patients with calcified vessels.

    Requires sensitive technique Laser Doppler is sensitive at low pressures.

    Solution for cold ischemic feet built-in local heating.

  • Left foot:

    Toe Pressure = 70 mmHg

    Baseline tcpO2 = 10 mmHg

    tcpO2 during O2 challenge = 105 mmHg

    Combining Toe Pressure and tcpO2

    Example: Female with painful, discolored left foot.

    Falsely low tcpO2

    value on left foot

    due to barrier to

    O2 diffusion

    confirmed both by

    O2 challenge and

    toe pressure.

    Right foot:

    Toe Pressure = 68 mmHg

    Baseline tcpO2 = 57 mmHg

    tcpO2 during O2 challenge = 167 mmHg

  • Right foot:

    Ankle Pressure = 146 mmHg

    ABI = 1.22

    Toe Pressure = 42 mmHg

    Baseline tcpO2 = 43 mmHg

    Combining Toe Pressure and tcpO2

    Example: Male with painful left foot and amputated toes.

    Results from several

    tests will give a better

    overview of the limb

    circulation.

    Here : Patient with

    clear PAD but no CLI.

    Left foot:

    Ankle Pressure = incompressible arteries

    Toe Pressure = no toes

    Baseline tcpO2 = 42 mmHg

    Normal Ankle Pressure

    and ABI, is this really

    reliable or the beginning

    of media sclerosis and

    falsely elevated ABIs?

  • Tissue response to local heating

    Baseline Heat induced vasodilatation

    Spontaneous healing likely when

    Max perfusion during heat > 20 PU (> 100 PU if inflammation)

    and/or > 150 % increase from baseline during heat

    Measures the total local blood perfusion in the tissue -

    capillaries, arterioles, venules and shunts.

    Evaluates wound healing potential.

  • Combining laser Doppler and tcpO2

    tcpO2

    > 30 mmHg

    Responds to O2

    Tissue response to heat

    Responds well to heat

    Example Patient with wound healing potential (healer)

  • Combining laser Doppler and tcpO2

    Example Patient non-healing wound

    tcpO2

    < 30 mmHg

    Minimal response to O2

    Tissue response to heat

    No response to heat

  • Combining laser Doppler and tcpO2

    Example Patient with inflammation

    tcpO2

    < 30 mmHg

    Responds to O2

    Tissue response to heat

    High initial baseline

    Responds to heat

  • Guidelines and Consensus Documents

    Document Society/Association Published

    Practical guidelines on the management and

    prevention of the diabetic foot

    IWGDF International Working

    Group on the Diabetic Foot

    2007, 2012

    Guidelines for Critical Limb Ischemia and

    Diabe

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