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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.

Finger plethysmography is a well-known technique for the acquisition of arterial pulse waveforms in the field of cardiology. The technique involves the acquisition of the volumetric variation of the finger due to pulsatile flow of blood in ulnar artery, to obtain the arterial pulse waveform of the subject. Conventionally, finger plethysmography is carried out by pulse-oximetry method which evaluates the blood flow using the oxygen saturation levels in blood. Though this method is widely used, the data acquired from this method is not the actual pulse pressure experienced by the arterial walls. Therefore, in the present work, a novel, non-invasive Fiber Bragg Grating based arterial pulse acquisition device employing finger Plethysmographic technique is designed and developed. The developed Fiber Bragg Grating Plethysmographic Pulse Recorder (FBGPPR) can acquire the volumetric variations of the finger on a beat-to-beat basis, which represents the arterial pulse waveform. Further, Pulse Transit Time (PTT) evaluation is also illustrated employing FBGPPR and an electronic stethoscope wherein both the devices are triggered simultaneously. Furthermore, the acquired pulse waveforms are analyzed to obtain the accelerated pulse plethysmograph (APG) which is noteworthy to observe the minute inflections and vital features of the pulse waveform.

Pain is often mismanaged due to incorrect assessment of pain level. Currently, pain is evaluated with subjective methods only, such as pain questionnaires. It may lead to erroneous evaluation of pain level. For this reason, there is a need for objective pain evaluation. The aim of this study is to test different neural network architectures and different types of inputs derived from finger plethysmography to evaluate which type of network and input type is most suitable for objective pain detection. Photoplethysmogram signals were filtered, segmented into heartbeat pulses, and normalized in amplitude and duration. The fifty-three signal intensity and fifteen time-domain features were extracted from the pre-processed photoplethysmogram signal. Three different neural network architectures were employed with ten different types of input. Results showed that feature-based models performed better than signal-based models. All three neural networks architectures achieved a mean accuracy of 0.85 for feature-based models and 0.76 for signal-based models. Multi-layer perception neural network with 12-heartbeats averaged showed the best performance with an accuracy of 0.92. Feature-based approach and multi-layer perception neural network showed the highest accuracy, specificity, and sensitivity for pain recognition. Additional post-processing could increase model accuracy and may be used in future research.

Aging is associated with reductions in endothelial function, observations primarily reported using brachial artery ultrasound. There is growing interest in the use of peripheral artery tonometry (PAT) of microvessels in the fingertip to assess endothelial function because it is less technically demanding and has a high sensitivity and specificity for assessing coronary endothelial function. Moreover, similar to brachial artery flow-mediated dilation (FMD), PAT predicts cardiovascular disease outcomes. However, the relationship between PAT and FMD have yet to be examined in the context of aging. To address this question, reactive hyperemic index (RHI) using EndoPAT and FMD using brachial artery ultrasound were assessed after 5 min of forearm ischemia in 20 younger (18–40 yr old; 29 ± 4 yr) and 20 older (60–75 yr old; 65 ± 4 yr) healthy adult men. Higher values of both FMD and RHI indicate better endothelial function. Endothelial function assessed via brachial artery FMD was lower in older (4.8 ± 2.1%), compared with younger (7.5 ± 1.6%) men (P < 0.001). In contrast, the RHI assessed via PAT was greater in older (2.2 ± 0.6), compared with younger (1.8 ± 0.5) men (P = 0.014). FMD and RHI were not correlated (r = –0.15; P = 0.35). We conclude that PAT may not be an appropriate measure to evaluate age-associated changes in endothelial function. NEW & NOTEWORTHY Microvessel endothelial function assessed via finger plethysmography may not reflect age-associated reductions in large artery endothelial function assessed via brachial artery flow-mediated dilation.

SummaryPurpose Blood pressure (BP) is commonly assessed by brachial oscillometry in clinical practice, whereas in physiological studies, finger plethysmography is often employed. This study assessed the limits of agreement between BP metrics obtained from each device. Methods In 96 participants, we simultaneously recorded BP by brachial oscillometry (BP+; Uscom, Sydney, NSW, Australia) and finger plethysmography (Finometer MIDI, MLE1054-V; Finapres Medical Systems B.V., Amsterdam, the Netherlands). Agreement between the two devices was assessed by correlation and Bland–Altman analysis. We assessed average BP differences between the two devices using the criteria of the Association for the Advancement of Medical Instruments (AAMI), which require systolic and diastolic BP differences to be within ≤5 ± 8 (mean ± SD). Results Bland–Altman analysis showed wide limits of agreement (±~17 mmHg or greater) between finger-derived brachial and oscillometric BP. Both systolic and mean BP exhibited positive proportional biases (both P

In recent years, video plethysmography (VPG) which is pulse wave derived from the skin video image has attracted attention as a non-contact heart rate measurement technique. In this study, we propose an extraction method of VPG which can be used for arterial pulse waveform analysis. The extraction algorithm is based on periodic component analysis. The value of the second derivative analysis of palm VPG derived by proposed method had correlation with that of finger plethysmography (PPG). This results indicate the possibility of the non-contact evaluation of peripheral vascular function by VPG.

Endothelial function has diagnostic, prognostic and therapeutic significance. A number of non-invasive techniques were introduced for its assessment, including flow-mediated dilation (FMD), finger plethysmography (RH-PAT) and digital thermal monitoring (DTM). All these methods can be performed simultaneously. In addition, various methods for measuring arterial wall stiffness are available such as: pulse wave analysis (PWA), pulse wave velocity (PWV), pulse contour analysis (PCA) and carotid wall distensibility coefficient (DC). Finally, carotid intima-media thickness (cIMT) and ankle brachial index (ABI) are used as surrogate read-outs of atherosclerosis. Here, we briefly describe the advantages, limitations and interrelationships of various methods used for the assessment of endothelial function, arterial stiffness, and present the concept of an integrated evaluation of vascular health based on multiple methods. This strategy may be useful to stratify cardiovascular risk and represents a step towards multiparametric assessment of endothelium for effective endothelium-guided therapy in patients with cardiovascular diseases.

Objective:Flow-mediated vasodilation (FMD) has become one of the most widely assessed parameter to analyze endothelial function. However, some techniques used to measure FMD have limitations. Recently, finger plethysmography (EndoPAT) failed to show any kind of reproducibility. A semi-automatic devi

In healthy subjects, variation in cardiovascular responses to sympathetic stimulation evoked by submaximal lower body negative pressure (LBNP) is considerable. This study addressed the question whether inter-subject variation in cardiovascular responses coincides with consistent and reproducible responses in an individual subject. In 10 healthy subjects (5 female, median age 22 years), continuous hemodynamic parameters (finger plethysmography; Nexfin, Edwards Lifesciences), and time-domain baroreflex sensitivity (BRS) were quantified during three consecutive 5-min runs of LBNP at −50 mmHg. The protocol was repeated after 1 week to establish intra-subject reproducibility. In response to LBNP, 5 subjects (3 females) showed a prominent increase in heart rate (HR; 54 ± 14%, p = 0.001) with no change in total peripheral resistance (TPR; p = 0.25) whereas the other 5 subjects (2 females) demonstrated a significant rise in TPR (7 ± 3%, p = 0.017) with a moderate increase in HR (21 ± 9%, p = 0.004). These different reflex responses coincided with differences in resting BRS (22 ± 8 vs. 11 ± 3 ms/mmHg, p = 0.049) and resting HR (57 ± 8 vs. 71 ± 12 bpm, p = 0.047) and were highly reproducible over time. In conclusion, we found distinct cardiovascular response patterns to sympathetic stimulation by LBNP in young healthy individuals. These patterns of preferential autonomic blood pressure control appeared related to resting cardiac BRS and HR and were consistent over time.

Das obstruktive Schlafapnoesyndrom ist eine in der westlichen Welt häufige Erkrankung, die mit einem erhöhten Risiko für kardiovaskuläre Erkrankungen einhergeht. Es wird davon ausgegangen, dass durch Hypoxie, Sympathikuserhöhung und thorakalem Scherstress eine endotheliale Dysfunktion verursacht wird. Dennoch ist nicht abschließend geklärt, ob die obstruktive Schlafapnoe alleine für diese Tatsache verantwortlich sein kann oder ob ein Zusammenhang aufgrund der häufigen Komorbiditäten (arterielle Hypertonie, Diabetes mellitus oder Adipositas) lediglich so erscheinen mag. In dieser Arbeit wurde versucht, mit einer nicht-invasiven Methode die Auswirkungen des obstruktiven Schlafapnoesyndroms auf das vaskuläre Endothel zu beurteilen. Dabei wurde darauf geachtet, dass die Studienteilnehmer neben einer obstruktiven Schlafapnoe keine weiteren Erkrankungen hatten, um mögliche Fehlerquellen ausschließen. Es wurden zwei Gruppen untersucht, wobei die ausschließlich männlichen Teilnehmer zwischen 18 und 65 Jahren sein sollten und keine kardiovaskulären Nebenerkrankungen haben durften. Die OSA-Gruppe mit 38 Teilnehmern sollte einen AHI von >5/h haben (AHI: 24,00/h ± 22,4/h), die Kontrollgruppe mit 34 Teilnehmern sollte einen AHI von ≤5/h (AHI: 2,1/h ± 1,4/h). Bei jeweils gleichen Untersuchungsbedingungen erfolgte eine abendliche Messung der Endothelfunktion und der Gefäßsteifigkeit mittels Fingerplethysmographie (EndoPAT™ 2000, Itamar). Im Anschluss wurde eine mindestens 6-stündige kardiorespiratorische Polysomnographie durchgeführt, um unmittelbar nach Wecken des Probanden eine zweite EndoPAT™-Messung durchzuführen. Es herrschten stets gleiche Bedingungen für beide Gruppen, die Messmethode wurde standardisiert für jeden Probanden genau gleich durchgeführt. Mittels der EndoPAT™-Messung wurde der RHI als Parameter für die endotheliale Funktion gemessen, der Augmentationsindex wurde als Parameter für die Gefäßsteifigkeit gemessen. Die Berechnung der jeweiligen Werte erfolgte durch die geräteeigene Software (Itamar). Die Ergebnisse der Polysomnographie wurden durch medizinisch technische Assistenten nach den Richtlinien der DGSM ausgewertet und dokumentiert. Ziel der Studie war es erstens aufzuzeigen, dass Patienten mit Schlafapnoe eine schlechtere endotheliale Funktion und eine höhere Gefäßsteifigkeit haben und zweitens, dass sich diese Eigenschaften während der Nacht durch die nächtlichen Hypoxiephasen beim Patienten mit Schlafapnoe negativ auswirkt. In beiden Punkten konnten in der vorliegenden Studie keine signifikanten Unterschiede aufgezeigt werden, wenngleich Tendenzen erkennbar sind, welche die Primär- und Sekundärhypothesen stützen. Wie bereits in verschiedenen anderen Arbeiten beobachtet, zeigt sich auch in unserem Kollektiv eine Korrelation zwischen Alter und Gefäßsteifigkeit. In unserer Studie konnte ein veränderter Gefäßstatus bei Patienten mit moderater obstruktiver Schlafapnoe nicht endgültig dargestellt werden. Abschließend ist für künftige Studien zu diesem Thema ein erweitertes Kollektiv zu empfehlen. Zudem sollten die Einschlusskriterien vor allem beim Lebensalter enger gefasst werden, um eine mögliche Fehlerquelle zu eliminieren., Obstructive sleep apnea (OSA) is a very common sleep disorder in the western civilization, which carries an increased risk of developing cardiovascular diseases. It is assumed, that hypoxia, sympathetic stress levels and thoracic shear stress may contribute to the development of endothelial dysfunction. Since patients suffering from obstructive sleep apnea, commonly also suffer from other comorbidities, particularly arterial hypertension, diabetes mellitus and obesity, there is not absolute certainty, that a sleep disorder alone is responsible for a loss of endothelial function. The aim of this study was to measure the consequences of obstructive sleep apnea on the vascular endothelium with a non-invasive method. We examined two groups of male patients between the ages of 18 and 65 who did not suffer from any cardiovascular diseases. To reduce any bias, we tried to exclude patients with any comorbidities. We included 38 patients with a median apnea hypopnea index (AHI) of 22,0 ± 22,4/h in the OSA-group (AHI≥5/h), and in the control-group (AHI≤5/h) 34 patients with a median AHI of 2,1 ± 1,4/h. In similar surroundings and under similar conditions we then performed the first EndoPAT™2000 measurement, followed by a polysomnography for at least 6 hours and another EndoPAT™2000 measurement. By measuring the reactive hyperaemic index (RHI) we received a parameter for evaluating the endothelial function. The arterial stiffness was assessed by measuring the augmentation index (AI). The RHI and AI were calculated through the use of the EndoPAT™2000-software, while the polysomnography was analyzed by experienced medical staff according to the DGSM-guidelines. The primary objective of the study was to show, that patients with obstructive sleep apnea have an impaired arterial stiffness and endothelial function. Another aim was to show, that the both functions decline during the night. Despite not finding significant differences, we did however see encouraging tendencies to prove our theories. Similar to the results of other studies we could show a correlation between age and arterial stiffness. For further studies we suggest a bigger collective of a more similar background regarding age and medical history. Moreover, the OSA-group should consist of patients suffering from severe OSA.