E2 ModerateModerate confidencePEM ?Cross-SectionalPeer-reviewedMachine draft
Comparison of the finger plethysmography derived stroke volumes by Nexfin CO Trek and suprasternal aortic Doppler derived stroke volume measurements in adults with myalgic encephalomyelitis/chronic fatigue syndrome and in healthy controls.
van Campen, C Linda M C, Verheugt, Freek W A, Rowe, Peter C et al. · Technology and health care : official journal of the European Society for Engineering and Medicine · 2021 · DOI
Quick Summary
This study compared two different ways of measuring how much blood the heart pumps with each beat during a tilt table test (where patients lie down then are tilted upright). Researchers tested 154 ME/CFS patients and 39 healthy people using finger cuff measurements and ultrasound of the heart. They found that the finger cuff method gave higher readings than ultrasound, but after adjusting the finger cuff numbers to match ultrasound values, the device became reliable enough to track changes during tilt testing.
Why It Matters
ME/CFS patients often show exaggerated drops in stroke volume during tilt testing, a key diagnostic finding. This study validates that finger plethysmography can be used to reliably measure these stroke volume changes if properly calibrated, making this non-invasive method more practical for clinical and research settings where ultrasound expertise may be limited.
Observed Findings
- Nexfin CO Trek systematically overestimated stroke volume compared to Doppler ultrasound in both supine and end-tilt positions (p < 0.005)
- Percent error between methods ranged from 37-43% without calibration
- After calibrating supine Nexfin values to Doppler measurements, percent error decreased to 29%
- Both healthy controls and ME/CFS patients showed high initial error rates with uncalibrated measurements
Inferred Conclusions
- Nexfin CO Trek cannot be used interchangeably with Doppler ultrasound without adjustment due to algorithm-based differences
- A simple calibration procedure using supine baseline adjustment renders Nexfin CO Trek reliable for tracking relative stroke volume changes during tilt testing
- This calibration approach enables wider clinical use of finger plethysmography in ME/CFS diagnostics despite underlying measurement bias
Remaining Questions
- How does calibration accuracy vary across different age groups, body habitus categories, or disease severity levels in ME/CFS?
- Does the calibration remain stable over repeated testing sessions or does it require recalibration at each visit?
- How do these measurement methods compare in predicting orthostatic intolerance symptoms or long-term outcomes in ME/CFS patients?
What This Study Does Not Prove
This study does not establish that Nexfin CO Trek is accurate in isolation or suitable for all patient populations—accuracy was only validated after calibration to ultrasound. It also does not demonstrate whether stroke volume changes measured by these methods predict patient outcomes or treatment responses in ME/CFS.
Tags
Symptom:Orthostatic Intolerance
Biomarker:Blood Biomarker
Method Flag:Exploratory Only
Metadata
- DOI
- 10.3233/THC-202669
- PMID
- 33998565
- Review status
- Machine draft
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 8 April 2026