interpreting tcpo2 curves and results

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 Perimed’s commitment to continuous improvement of our products, all

specifications are subject to change without notice.

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• 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:



tcpO2 during O2 challenge = 167 mmHg

Right foot:

Ankle Pressure = 146 mmHg

ABI = 1.22



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


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)


Example – Patient non-healing wound

tcpO2

< 30 mmHg

Minimal response to O2


No response to heat


Example – Patient with inflammation

tcpO2

< 30 mmHg

Responds to O2


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

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

Thank You!

PeriFlux 6000 | tcpO2 made intelligent

www.perimed-instruments.com

interpreting tcpo2 curves and results

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