PeriFlux 6000 now supports Exercise TcpO2
by Jimmy Bakker (Global Product Manager)
The latest release of PSW ExM, version 5.6.2, compatible with PeriFlux 6000 system versions, adds support for Exercise TcpO2, also known as DROP (delta from resting oxygen pressure).
Before diving into this new functionality, we would like to acknowledge the work of Dr. Pierre Abraham, MD, PhD, at the University Hospital of Angers (CHU Angers) in France, and thank him for his contributions, collaboration, and patience.
In this post, I will outline what Exercise TcpO2 is, when clinicians use it, how to prep your patient, and how to interpret the curves generated by PeriFlux 6000.
According to Dr. Abraham,
“The value of the DROP parameter lies in its ability to objectively demonstrate ischemia during exercise, where many diagnostic uncertainties arise. It is encouraging to see this methodology implemented in a way that preserves its physiological relevance while making it practical for routine clinical use.”
Dr. Abraham, notes that Exercise TcpO2 is highly suitable in the following cases:
- For differentiating the diagnosis of exercise-induced lower back ischemia from neurogenic claudication (lumbar spinal stenosis).
- For specific interest in buttock claudication, where ultrasound and ABI are not optimal for these cases (as recommended by ESVS).
- As an alternative to ABI or Exercise ABI, especially when ABI and TBI are non–measurable (non-compressible calcified arteries, or arrhythmia).
- In the detection of exercise-induced hypoxemia (up to approx. 15% of my patients), which limits exercise capability.
- For evaluating the diffusion and severity of exercise-induced ischemia.
What is Exercise TcpO2 (DROP)
Exercise TcpO2 quantifies the change in lower-limb transcutaneous oxygen pressure between rest and exercise, after correcting for changes at a reference site. Let’s break it down. TcpO2 is a noninvasive estimate of oxygen availability in skin tissue and is commonly used to assess tissue viability and wound-healing potential.
During exercise, blood flow to the legs increases. In healthy individuals, TcpO2 remains largely stable because oxygen delivery tends to meet the increased metabolic demand. In the presence of arterial disease, however, blood flow increase may be restricted, reducing the microcirculation’s ability to deliver oxygen and causing a drop in TcpO2.
To isolate local ischemia from systemic effects, such as changes in systemic oxygen pressure, limb exercise TcpO2 measurements are corrected with a reference site. The chest is typically chosen because it is well perfused and generally unaffected by peripheral artery disease. At any point in time, Exercise TcpO2 (DROP) is calculated as:
DROP = ΔTcpO2 (limb) – ΔTcpO2 (chest)
To put that into numbers, if resting TcpO2 is 50mmHg at the limb and 70mmHg at the chest, respectively decreasing to 30mmHg and 65mmHg during exercise:
- Limb change 50 => 30 = -20 mmHg
- Chest change 70 => 65 = -5mmHg
- DROP: -20 – (-5) = -15mmHg.
Correcting the measurement ensures that the observed decrease in oxygen reflects local perfusion impairment rather than systemic physiological changes, improving diagnostic confidence.
DROP is acknowledged and used in clinical research and specialist practice, using cutoffs of ≤-15mmHg as an indication of significant arterial stenosis [1].
According to Dr. Abraham,
From my research, I have observed a DROP of:
- 0 to –5 mmHg indicates a normal/healthy response
- –5 to –15 mmHg is indicative of mild perfusion impairment
- –15 to –30 mmHg indicates moderate arterial impairment
- And < –30 mmHg is indicative of severe ischemia
By design, the average DROP over the resting period is zero, and is expected to return to zero at the end of the recovery period after exercise.
Differentiating vascular from neurogenic claudication
Exercise TcpO2 is typically used to help diagnose patients with exercise-induced pain in the hips, legs, buttocks, or lower back, and is particularly useful when resting ABI or toe pressures are inconclusive, normal, or borderline.
Pain onset after a predictable walking distance and relief with rest are symptomatic of peripheral artery disease (PAD) but also of lumbar spinal stenosis, and other conditions that mimic claudication. Without claudication, TcpO2 remains relatively stable during exercise because the pain is not caused by reduced blood flow but by other underlying issues, such as nerve compression. In other words, Exercise TcpO2 is suitable for identifying whether claudication is vascular or neurogenic.
Because the test reproduces the person’s symptoms under controlled conditions, it provides insight into perfusion during real physiological stress. When measured simultaneously at multiple body sites, such as the buttocks, thighs, and calves, Exercise TcpO2 can help localize ischemia to specific limb segments.
Patient preparation
With the patient standing on a treadmill, place the fixation rings bilaterally at the intended measurement sites, including one placed at chest level as the reference. Common sites include the buttocks (upper external quarter), thighs, and calves (lower third). Avoid concavities and tendinous structures.
Although the fixation rings are self-adhesive, using a split-gauze dressing helps prevent probe movement during exercise. Add a few drops of contact liquid to the ring, then lock the electrode into place. With PeriFlux 6000, electrodes are color-coded, simplifying placement and ensuring correct channel assignment.
Key preparation points:
- Skin at the measurement site should be clean.
- Electrodes must be secure.
- Ensure your patient is comfortable and understands the procedure.
Measurement with PeriFlux 6000
Once you’ve prepped the patient, PeriFlux 6000 guides you through the exam, starting with a resting period, followed by the exercise period, and finally a recovery period. Corrected DROP values for each measurement site are displayed clearly throughout the test.
Interpreting curves
This example is intended to illustrate typical perfusion patterns in a controlled,
simulated scenario and does not represent clinical outcomes (see interpretation in the text below)
This fictitious example demonstrates exercise-induced ischemia with a left-sided predominance. The most pronounced oxygen desaturation occurs in the left calf (black curve) and left thigh (gray) with negative DROP values and delayed recovery, indicating perfusion limitation during exercise. The left buttock (orange) also shows a decrease.
On the right side, the calf (green) and thigh (yellow) exhibit relatively moderate decreases with rapid recovery — consistent with preserved perfusion, while the right buttock (blue) remains largely stable. Overall, resting perfusion is adequate, but exercise points toward segmental ischemia predominantly in the left lower limb.
To conclude…
Exercise TcpO2 adds a valuable functional dimension to vascular assessment, helping clinicians to:
- Differentiate vascular claudication from neurogenic claudication
- Confirm or exclude ischemia. With a particular interest in buttock ischemia
- Measure when ABI, Exercise ABI, or TBI are inconclusive due to non-compressible calcified arteries or arrhythmia.
- Quantify the severity of ischemia and hypoxemia during exertion.
- Reveal systemic hypoxemia as a worsening factor of muscle ischemia
Compatibility
Exercise TcpO2 is available for the following PeriFlux 6000 systems with TcpO2 running PSW ExM 5.6.2:
- PeriFlux 6000 TcpO2 System.
- PeriFlux 6000 Combined System.
- PeriFlux 6000 Pressure System — TcpO2 update is required to run Exercise TcpO2.
To run Exercise TcpO2, you need a minimum of two TcpO2 channels: one reference measurement and one site measurement. However, with more channels, you can measure bilaterally and across multiple levels simultaneously. I hope you found this post insightful.
For more information: Contact your local sales office or distributor
References
[1] SS08. Exercise Transcutaneous Oxygen Pressure Measurement Is a Reliable Method of Evaluation of Internal Iliac Artery Flow Compromise Sen, Indrani et al. Journal of Vascular Surgery, Volume 67, Issue 6, e87 – e88. DOI: 10.1016/j.jvs.2018.03.086
Additional papers
Clinical application of transcutaneous oxygen pressure measurements during exercise.
Abraham, P., Gu, Y., Guo, L., Kroeger, K., Ouedraogo, N., Wennberg, P., & Henni, S. (2018). Clinical application of transcutaneous oxygen pressure measurements during exercise. Atherosclerosis, 276, 117–123. https://doi.org/10.1016/j.atherosclerosis.2018.07.023
Abraham, P., Ramondou, P., Hersant, J., Sempore, W. Y., Feuilloy, M., & Henni, S. (2021). Investigation of arterial claudication with transcutaneous oxygen pressure at exercise: Interests and limits. Trends in cardiovascular medicine, 31(4), 218–223. https://doi.org/10.1016/j.tcm.2020.03.003
Exercise oximetry in clinical practice: A single-centre perspective on procedure and techniques.
Lecoq, S., Hersant, J., Feuilloy, M., Ouedraogo, N., Houle, M., & Abraham, P. (2025). Exercise oximetry in clinical practice: A single-centre perspective on procedure and techniques. Experimental physiology, 110(12), 1810–1818. https://doi.org/10.1113/EP092711
Abraham, P., Colas-Ribas, C., Signolet, I., Ammi, M., Feuilloy, M., Picquet, J., & Henni, S. (2018). Transcutaneous Exercise Oximetry for Patients With Claudication - A Retrospective Review of Approximately 5,000 Consecutive Tests Over 15 Years. Circulation journal : official journal of the Japanese Circulation Society, 82(4), 1161–1167. https://doi.org/10.1253/circj.CJ-17-0948
Global Product Manager
I’ve been with Perimed for over 10 years, and in my role as Global Product Manager, I get to work with amazing people who use our instruments to improve outcomes and find novel therapies for some of the world’s most prevalent diseases. I have a Master’s degree in applied physics and a Ph.D. in applied optics.
Disclaimer
The views expressed in this blog post are those of the author and do not necessarily represent the official position of Perimed. The content is provided for informational purposes only and is not intended to constitute clinical claims or medical advice. Clinical decisions should always be based on professional judgment and applicable clinical guidelines.