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Video capillaroscopy clarifies mechanism of the photoplethysmographic waveform appearance.

ABSTRACT: Photoplethysmography (PPG) devices are widely used in clinical practice but the origin of PPG signal is still under debating. The classical theory assumes that the PPG waveform stems from variations of blood volume in pulsating arteries. In this research we analysed high-speed video recordings of capillaries in a fingernail bed. It was found that speed of erythrocytes in capillaries has pronounced modulation in time, which follows variations of instantaneous blood pressure in arteries. However, the mean speed significantly differs even for neighbour capillaries whereas change of the speed occurs in phase for the most of capillaries. Moreover, the light intensity remitted from the papillary dermis is also modulated at the heartbeat frequency displaying significant correlation with waveforms of the RBC speed. Obtained results can hardly be explained by the classical theory of PPG signal formation. Shallow penetrating visible light acquires modulation of erythrocytes density in the capillary bed without interacting with deeper situated pulsating arteries. Therefore, the capillary bed could serve as a distributed sensor for monitor the status of deep vessels. Better understanding of the photoplethysmography basis will result in a wider range of applications of this fast growing technology in both medical and research practice.

SUBMITTER: Volkov MV

PROVIDER: S-EPMC5643323 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Video capillaroscopy clarifies mechanism of the photoplethysmographic waveform appearance.

Volkov Mikhail V MV Margaryants Nikita B NB Potemkin Andrey V AV Volynsky Maxim A MA Gurov Igor P IP Mamontov Oleg V OV Kamshilin Alexei A AA

Scientific reports 20171016 1

Photoplethysmography (PPG) devices are widely used in clinical practice but the origin of PPG signal is still under debating. The classical theory assumes that the PPG waveform stems from variations of blood volume in pulsating arteries. In this research we analysed high-speed video recordings of capillaries in a fingernail bed. It was found that speed of erythrocytes in capillaries has pronounced modulation in time, which follows variations of instantaneous blood pressure in arteries. However, ...[more]

PMID: 29038533

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Project description:BackgroundAlthough pulmonary vascular bed has been the main subject of research for many years in pulmonary hypertension (PH), interest has recently started to divert towards the possibility of a co-existing peripheral microangiopathy. The aim of the current study was to investigate the presence of nailfold video-capillaroscopic (NVC) structural changes in patients with precapillary PH and to identify possible associations of NVC measurements with markers of disease severity.Methods? prospective case-control study was performed in 28 consecutive patients with precapillary PH [14 with idiopathic pulmonary arterial hypertension (IPAH) and 14 with chronic thromboembolic pulmonary hypertension (CTEPH)] and 30 healthy controls. NVC quantitative and qualitative parameters were evaluated using Optilia Digital Capillaroscope. To ensure inter-observer repeatability capillaroscopic images were reviewed by two independent investigators. For multiple comparisons among continuous variables, one-way ANOVA or the Kruskal-Wallis test were used. Differences between the groups were tested with post-hoc analysis with adjustment for multiple comparisons (Bonferroni test).ResultsBoth IPAH (71.4% were women, mean age 53.1?±?13.4 years) and CTEPH (64.3% women, mean age 60.9?±?14.4 years) groups presented reduced capillary density compared to healthy controls (8.4?±?1.2 loops/mm and 8.0?±?1.2 loops/mm vs. 9.7?±?0.81 loops/mm, p?<?0.001) and increased loop width (15.7?±?3.9 ?m and 15.8?±?1.9 ?m vs. 11.5?±?2.3 ?m, p?<?0.001). More than half of patients with IPAH presented microhaemorrhages on capillary nailfold, while increased shape abnormalities in capillary morphology and more capillary thrombi per linear mm were detected in patients with CTEPH compared to patients with IPAH and healthy controls. All PH patients presented a non-specific NVC pattern compared to controls (p?<?0.001).ConclusionThe findings of the study reveal a degree of significant peripheral microvascular alterations in patients with IPAH and CTEPH, suggesting a generalized impairment of peripheral microvasculature in pulmonary vascular disease.

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Video capillaroscopy clarifies mechanism of the photoplethysmographic waveform appearance.

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Video capillaroscopy clarifies mechanism of the photoplethysmographic waveform appearance.

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