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

Article type: Research Article

Authors: van Campen, C. (Linda) M.C.^a | Verheugt, Freek W.A.^b | Rowe, Peter C.^c | Visser, Frans C.^a

Affiliations: [a] Stichting CardioZorg, Hoofddorp, The Netherlands | [b] Radboud UMC, Nijmegen, The Netherlands | [c] Department of Paediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA

Correspondence: [*] Corresponding author: Frans C. Visser, Stichting CardioZorg, Planetenweg 5, 2132 HN Hoofddorp, The Netherlands. Tel.: +31 653475995; Fax: +31 205241235; E-mail: fransvisser@stichtingcardiozorg.nl.

Abstract: BACKGROUND: Finger plethysmography derived stroke volumes are frequently measured during tilt table testing. There are two algorithms to determine stroke volumes: Modelflow and Nexfin CO Trek. Most tilt studies used Modelflow, while there are differences between the two algorithms. OBJECTIVE: To compare stroke volume indices by Nexfin CO Trek (SVINexfinCOTrek) with suprasternal Doppler derived SVI (SVIDoppler) in healthy controls (HC) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients during tilt testing. These patients may have a large SVI decrease during the tilt enabling a large range of SVI to be studied. METHODS: One hundred and fifty-four patients and 39 HC with a normal tilt test were included. Supine and end-tilt SVIDoppler and SVINexfinCOTrek were compared using the Bland-Altman analysis. Also, the effect of calibrating supine SVINexfinCOTrek to SVIDoppler was studied. RESULTS: Supine and end-tilt SVINexfinCOTrek were significantly higher than SVIDoppler: both P< 0.005. Bias, limits of agreement, and percent error (PE) were high with PE’s between 37 and 43%. The calibration procedure resulted in an acceptable variance with a PE of 29%. CONCLUSIONS: SVINexfinCOTrek overestimates stroke volumes compared to SVIDoppler, leading to high PE’s. Calibration reduced variance to an acceptable level, allowing SVINexfinCOTrek to be used for assessment of SVI changes during tilt testing.

Keywords: Stroke volume index, aortic VTI Doppler imaging, finger plethysmography, tilt table testing, chronic fatigue syndrome, myalgic encephalomyelitis

DOI: 10.3233/THC-202669

Journal: Technology and Health Care, vol. 29, no. 4, pp. 629-642, 2021