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Interpreting tcpo2 curves and results


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A short guide to interpreting tcpO2 data.

Published in: Health & Medicine
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Interpreting tcpo2 curves and results

  1. 1. Interpreting Curves and Results PeriFlux 6000 | tcpO2 made intelligent
  2. 2. 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 Perimed’s 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.
  3. 3. • Calibration • tcpO2 Site Selection • Electrode Maintenance • Interpreting Curves and Results
  4. 4. 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
  5. 5. 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…
  6. 6. 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
  7. 7. Typical Data
  8. 8. 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.
  9. 9. 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.
  10. 10. 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.
  11. 11. 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.
  12. 12. 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.
  13. 13. 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?
  14. 14. 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!
  15. 15. 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
  16. 16. 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
  17. 17. 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
  18. 18. 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)
  19. 19. 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.
  20. 20. 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
  21. 21. 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?
  22. 22. 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.
  23. 23. 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)
  24. 24. 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
  25. 25. 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
  26. 26. 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 Diabetic Foot ESVS (European Society for Vascular Surgery) CLI Guideline Committee 2011 ACC/AHA 2005 Guidelines for the Management of Patients With Peripheral Arterial Disease: Executive Summary, Update 2011 ACC/AHA (American Collage of Cardiology/American Heart Association) 2005, 2011 Transcutaneous Oximetry in Clinical Practice: Consensus statements from an expert panel based on evidence Fife CE, Smart DE, Sheffield PJ, Hopf HW, Hawkins G, Clarke D 2009 Comprehensive Foot Examination and Risk Assessment ADA (American Diabetes Association ) 2008 Inter-Society consensus for the Management of Peripheral Arterial Disease TASC II 2007
  27. 27. Thank You! PeriFlux 6000 | tcpO2 made intelligent