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Hultman M, Richter F, Larsson M, Strömberg T, Iredahl F, Fredriksson I. Robust analysis of microcirculatory flowmotion during post-occlusive reactive hyperemia. Microvasc Res 2024; 155:104715. [PMID: 39004173 DOI: 10.1016/j.mvr.2024.104715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2024] [Revised: 07/01/2024] [Accepted: 07/11/2024] [Indexed: 07/16/2024]
Abstract
BACKGROUND Flowmotion analysis of the microcirculatory blood flow is a method to extract information about the vessel regulatory function. It has previously shown promise when applied to measurements during a post-occlusive reactive hyperemia. However, the reperfusion peak and the following monotonic decline introduces false low frequencies that should not be interpreted as rhythmic vasomotion effect. AIM To develop and validate a robust method for flowmotion analysis of post-occlusive reactive hyperemia signals. METHOD The occlusion-induced reperfusion response contains a typical rapid increase followed by a monotonic decline to baseline. A mathematical model is proposed to detrend this transient part of the signal to enable further flowmotion analysis. The model is validated in 96 measurements on healthy volunteers. RESULTS Applying the proposed model corrects the flowmotion signal without adding any substantial new false flowmotion components. CONCLUSION Future studies should use the proposed method or equivalent when analyzing flowmotion during post-occlusive reactive hyperemia to ensure valid results.
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Affiliation(s)
- Martin Hultman
- Department of Biomedical Engineering, Linköping University, Sweden; Perimed AB, Datavägen 9A, Järfälla, Stockholm, Sweden.
| | - Freya Richter
- Primary Health Care Center, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
| | - Marcus Larsson
- Department of Biomedical Engineering, Linköping University, Sweden
| | - Tomas Strömberg
- Department of Biomedical Engineering, Linköping University, Sweden
| | - Fredrik Iredahl
- Primary Health Care Center, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
| | - Ingemar Fredriksson
- Department of Biomedical Engineering, Linköping University, Sweden; Perimed AB, Datavägen 9A, Järfälla, Stockholm, Sweden
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Huang SJY, Wang X, Halvorson BD, Bao Y, Frisbee SJ, Frisbee JC, Goldman D. Laser Doppler Fluximetry in Cutaneous Vasculature: Methods for Data Analyses. J Vasc Res 2024; 61:197-211. [PMID: 38749406 DOI: 10.1159/000538718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 03/27/2024] [Indexed: 08/09/2024] Open
Abstract
INTRODUCTION Acquisition of a deeper understanding of microvascular function across physiological and pathological conditions can be complicated by poor accessibility of the vascular networks and the necessary sophistication or intrusiveness of the equipment needed to acquire meaningful data. Laser Doppler fluximetry (LDF) provides a mechanism wherein investigators can readily acquire large amounts of data with minor inconvenience for the subject. However, beyond fairly basic analyses of erythrocyte perfusion (fluximetry) data within the cutaneous microcirculation (i.e., perfusion at rest and following imposed challenges), a deeper understanding of microvascular perfusion requires a more sophisticated approach that can be challenging for many investigators. METHODS This manuscript provides investigators with clear guidance for data acquisition from human subjects for full analysis of fluximetry data, including levels of perfusion, single- and multiscale Lempel-Ziv complexity (LZC) and sample entropy (SampEn), and wavelet-based analyses for the major physiological components of the signal. Representative data and responses are presented from a recruited cohort of healthy volunteers, and computer codes for full data analysis (MATLAB) are provided to facilitate efforts by interested investigators. CONCLUSION It is anticipated that these materials can reduce the challenge to investigators integrating these approaches into their research programs and facilitate translational research in cardiovascular science.
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Affiliation(s)
- Sophie J Y Huang
- Departments of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Xuan Wang
- Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Brayden D Halvorson
- Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Yuki Bao
- Biomedical Engineering, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Stephanie J Frisbee
- Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Epidemiology and Biostatistics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Lawson Health Research Institute, London, Ontario, Canada
| | - Jefferson C Frisbee
- Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Daniel Goldman
- Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Biomedical Engineering, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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Kralj L, Potočnik N, Lenasi H. Evaluating transient phenomena by wavelet analysis: early recovery to exercise. Am J Physiol Heart Circ Physiol 2024; 326:H96-H102. [PMID: 37921668 PMCID: PMC11213473 DOI: 10.1152/ajpheart.00558.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 10/31/2023] [Accepted: 11/01/2023] [Indexed: 11/04/2023]
Abstract
Wavelet analysis (WA) provides superior time-frequency decomposition of complex signals than conventional spectral analysis tools. To illustrate its usefulness in assessing transient phenomena, we applied a custom-developed WA algorithm to laser-Doppler (LD) signals of the cutaneous microcirculation measured at glabrous (finger pulp) and nonglabrous (forearm) sites during early recovery after dynamic exercise. This phase, importantly contributing to the establishment of thermal homeostasis after exercise cessation, has not been adequately explored because of its complex, transient form. Using WA, we decomposed the LD signals measured during the baseline and early recovery into power spectra of characteristic frequency intervals corresponding to endothelial nitric oxide (NO)-dependent, neurogenic, myogenic, respiratory, and cardiac physiological influence. Assessment of relative power (RP), defined as the ratio between the median power in the frequency interval and the median power of the total spectrum, revealed that endothelial NO-dependent (5.87 early recovery; 1.53 baseline; P = 0.005; Wilcoxon signed-rank test) and respiratory (0.71 early recovery; 0.40 baseline; P = 0.001) components were significantly increased, and myogenic component (1.35 early recovery; 1.83 baseline; P = 0.02) significantly decreased during early recovery in the finger pulp. In the forearm, only the RP of the endothelial NO-dependent (1.90 early recovery; 0.94 baseline; P = 0.009) component was significantly increased. WA presents an irreplaceable tool for the assessment of transient phenomena. The relative contribution of the physiological mechanisms controlling the microcirculatory response in the early recovery phase appears to differ in glabrous and nonglabrous skin when compared with baseline; moreover, the endothelial NO-dependent influence seems to play an important role.NEW & NOTEWORTHY We address the applicability of wavelet analysis (WA) in evaluating transient phenomena on a model of early recovery to exercise, which is the only exercise-associated phase characterized by a distinct transient shape and as such cannot be assessed using conventional tools. Our WA-based algorithm provided a reliable spectral decomposition of laser-Doppler (LD) signals in early recovery, enabling us to speculate roughly on the mechanisms involved in the regulation of skin microcirculation in this phase.
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Affiliation(s)
- Lana Kralj
- Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Nejka Potočnik
- Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Helena Lenasi
- Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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Kralj L, Lenasi H. Wavelet analysis of laser Doppler microcirculatory signals: Current applications and limitations. Front Physiol 2023; 13:1076445. [PMID: 36741808 PMCID: PMC9895103 DOI: 10.3389/fphys.2022.1076445] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 12/28/2022] [Indexed: 01/21/2023] Open
Abstract
Laser Doppler flowmetry (LDF) has long been considered a gold standard for non-invasive assessment of skin microvascular function. Due to the laser Doppler (LD) microcirculatory signal's complex biological and physiological context, using spectral analysis is advisable to extract as many of the signal's properties as feasible. Spectral analysis can be performed using either a classical Fourier transform (FT) technique, which has the disadvantage of not being able to localize a signal in time, or wavelet analysis (WA), which provides both the time and frequency localization of the inspected signal. So far, WA of LD microcirculatory signals has revealed five characteristic frequency intervals, ranging from 0.005 to 2 Hz, each of which being related to a specific physiological influence modulating skin microcirculatory response, providing for a more thorough analysis of the signals measured in healthy and diseased individuals. Even though WA is a valuable tool for analyzing and evaluating LDF-measured microcirculatory signals, limitations remain, resulting in a lack of analytical standardization. As a more accurate assessment of human skin microcirculation may better enhance the prognosis of diseases marked by microvascular dysfunction, searching for improvements to the WA method is crucial from the clinical point of view. Accordingly, we have summarized and discussed WA application and its limitations when evaluating LD microcirculatory signals, and presented insight into possible future improvements. We adopted a novel strategy when presenting the findings of recent studies using WA by focusing on frequency intervals to contrast the findings of the various studies undertaken thus far and highlight their disparities.
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Affiliation(s)
- Lana Kralj
- Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Helena Lenasi
- Institute of Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia,*Correspondence: Helena Lenasi,
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Multiple blood flow surges during intermittent pneumatic compression: The origins and their implications. J Biomech 2022; 143:111264. [PMID: 36055052 DOI: 10.1016/j.jbiomech.2022.111264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 08/07/2022] [Accepted: 08/15/2022] [Indexed: 11/23/2022]
Abstract
Intermittent pneumatic compression (IPC) therapy has been used to enhance peripheral blood flow for prevention and rehabilitation of ischemic-related vascular diseases. A novel phenomenon has been reported that multiple blood flow surges appeared in the skin blood flow signal during each compression, but its mechanism has not been fully revealed. This study aimed to gain insights into the origins of these blood flow surges through experiment and biomechanical modeling methods. Foot skin blood flow (SBF) signals of 13 healthy adults (23.8 ± 0.5 yr old, 7 males) and air cuff pressure signals were recorded during IPC. Lumped parameter modeling and wavelet analysis were adopted to investigate the multiple blood flow surges (named as Peak1, Peak2 and Peak3). The results of the simulated Peak1 and Peak2 were in good agreements with the experiment results, suggesting that IPC could enhance foot SBF not only by deflation, but also by inflation. Statistical analysis demonstrated that high frequency compression with more frequent occurrence of Peak1 and Peak2 lead to significantly higher (Friedman test, p < 0.001) time-averaged SBF enhancement than the traditional mode. In addition, wavelet analysis showed that the major frequency component of the Peak3 (0.059 Hz) was within the range of the vascular myogenic activity, suggesting a vascular regulation process triggered by intravascular pressure changes. Our study provide new insights into the mechanism of how IPC enhance foot SBF.
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Rizzoni D, Mengozzi A, Masi S, Agabiti Rosei C, De Ciuceis C, Virdis A. New Noninvasive Methods to Evaluate Microvascular Structure and Function. Hypertension 2022; 79:874-886. [PMID: 35114816 DOI: 10.1161/hypertensionaha.121.17954] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The structural and functional alterations of microvessels are detected because of physiological aging and in several cardiometabolic diseases, including hypertension, diabetes, and obesity. The small resistance arteries of these patients show an increase in the media or total wall thickness to internal lumen diameter ratio (MLR or WLR), often accompanied by endothelial dysfunction. For decades, micromyography has been considered as a gold standard method for evaluating microvascular structural alterations through the measurement of MLR or WLR of subcutaneous small vessels dissected from tissue biopsies. Micromyography is the most common and reliable method for assessing microcirculatory endothelial function ex vivo, while strain-gauge venous plethysmography is considered the reference technique for in vivo studies. Recently, several noninvasive methods have been proposed to extend the microvasculature evaluation to a broader range of patients and clinical settings. Scanning laser Doppler flowmetry and adaptive optics are increasingly used to estimate the WLR of retinal arterioles. Microvascular endothelial function may be evaluated in the retina by flicker light stimulus, in the finger by tonometric approaches, or in the cutaneous or sublingual tissues by laser Doppler flowmetry or intravital microscopy. The main limitation of these techniques is the lack of robust evidence on their prognostic value, which currently reduces their widespread use in daily clinical practice. Ongoing and future studies will overcome this issue, hopefully moving the noninvasive assessment of the microvascular function and structure from bench to bedside.
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Affiliation(s)
- Damiano Rizzoni
- Clinica Medica, Department of Clinical and Experimental Sciences, University of Brescia, Italy (D.R., C.A., C.D.C.).,Division of Medicine, Spedali Civili di Brescia, Montichiari (Brescia), Italy (D.R.)
| | - Alessandro Mengozzi
- Department of Clinical and Experimental Medicine, University of Pisa, Italy (A.M., S.M., A.V.).,Institute of Life Science, Sant'Anna School of Advanced Studies, Pisa, Italy (A.M.)
| | - Stefano Masi
- Department of Clinical and Experimental Medicine, University of Pisa, Italy (A.M., S.M., A.V.).,Institute of Cardiovascular Science, University College London, United Kingdom (S.M.)
| | - Claudia Agabiti Rosei
- Clinica Medica, Department of Clinical and Experimental Sciences, University of Brescia, Italy (D.R., C.A., C.D.C.)
| | - Carolina De Ciuceis
- Clinica Medica, Department of Clinical and Experimental Sciences, University of Brescia, Italy (D.R., C.A., C.D.C.)
| | - Agostino Virdis
- Department of Clinical and Experimental Medicine, University of Pisa, Italy (A.M., S.M., A.V.)
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Reynès C, Beaume JB, Latil-Plat F, Ennaifer H, Rocher L, Antoine-Jonville S, Benamo E, Knapp Y, Vinet A. Concomitant Peripheral Neuropathy and Type 2 Diabetes Impairs Postexercise Cutaneous Perfusion and Flowmotion. J Clin Endocrinol Metab 2021; 106:e3979-e3989. [PMID: 34111245 DOI: 10.1210/clinem/dgab414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Indexed: 12/18/2022]
Abstract
CONTEXT Type 2 diabetes and peripheral neuropathy exhibit microvascular dysfunction at rest. However, data regarding their microvascular perfusion during exercise remain scarce. OBJECTIVE This study investigated changes in microvascular perfusion during postexercise recovery in those with type 2 diabetes, with or without peripheral neuropathy, as well as in healthy controls and those with obesity. METHODS Skin blood perfusion was assessed in each group using laser Doppler flowmetry (LDF) and laser speckle contrast imaging before and immediately after a 6-minute walking test. LDF recordings underwent wavelet transformation to allow specific control mechanisms of blood perfusion to be studied (eg, endothelial nitric oxide-independent and -dependent, neurogenic, myogenic, respiratory, and cardiac mechanisms). RESULTS Skin blood perfusion increased after exercise in all groups (22.3 ± 28.1% with laser speckle contrast imaging and 22.1 ± 52.5% with LDF). Throughout postexercise recovery, the decrease was blunted in those with subclinical peripheral neuropathy and confirmed peripheral neuropathy when compared to the other 3 groups. After exercise, total spectral power increased in all groups. The relative contributions of each endothelial band was lower in those with confirmed peripheral neuropathy than in the healthy controls and those with obesity (nitric oxide-dependent function: 23.6 ± 8.9% vs 35.5 ± 5.8% and 29.3 ± 8.8%, respectively; nitric oxide-independent function: 49.1 ± 23.7% vs 53.3 ± 10.4% and 64.6 ± 11.4%, respectively). The neurogenic contribution decreased less in those with confirmed peripheral neuropathy and in those with type 2 diabetes alone, compared to those with subclinical peripheral neuropathy and those with obesity (-14.5 ± 9.9% and -12.2 ± 6.1% vs -26.5 ± 4.7% and -21.7 ± 9.4%, respectively). CONCLUSION Peripheral neuropathy, whatever the stage, altered the microvascular response to exercise via impaired endothelial and neurogenic mechanisms.
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Affiliation(s)
- Cécile Reynès
- Avignon Université, LAPEC EA4278, F-84000, Avignon, France
| | | | - Françoise Latil-Plat
- Service endocrinologie et maladies métaboliques, Centre hospitalier Henri Duffaut, F-84000, Avignon, France
| | - Houda Ennaifer
- Service endocrinologie et maladies métaboliques, Centre hospitalier Henri Duffaut, F-84000, Avignon, France
| | - Laure Rocher
- Service endocrinologie et maladies métaboliques, Centre hospitalier Henri Duffaut, F-84000, Avignon, France
| | | | - Eric Benamo
- Service endocrinologie et maladies métaboliques, Centre hospitalier Henri Duffaut, F-84000, Avignon, France
| | - Yannick Knapp
- Avignon Université, LAPEC EA4278, F-84000, Avignon, France
| | - Agnès Vinet
- Avignon Université, LAPEC EA4278, F-84000, Avignon, France
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Mechanisms of Venoarteriolar Reflex in Type 2 Diabetes with or without Peripheral Neuropathy. BIOLOGY 2021; 10:biology10040333. [PMID: 33920825 PMCID: PMC8071175 DOI: 10.3390/biology10040333] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 04/12/2021] [Indexed: 11/17/2022]
Abstract
Simple Summary Postural changes induce arteriolar vasoconstriction in response to an increase in venous pressure in the limbs known as the venoarteriolar reflex (VAR). Previous studies reported that skin blood perfusion is impaired during the VAR in persons with type 2 diabetes mellitus (T2DM) with or without peripheral neuropathy, compared to control subjects. The aim of this study is to investigate the underlying mechanisms of the VAR in T2DM, with and without peripheral neuropathy. This study provides evidence that confirmed neuropathy alters the VAR by an alteration of the neurogenic response to leg dependency. Abstract The aim of this study is to investigate the underlying mechanisms of the venoarteriolar reflex (VAR) in type 2 diabetes mellitus (T2DM), with and without peripheral neuropathy. Laser Doppler flowmetry (LDF) recordings were performed on the medial malleus and dorsal foot skin, before and during leg dependency in healthy controls, in persons with obesity, in those with T2DM, in those with T2DM and subclinical neuropathy, and in those with T2DM and confirmed neuropathy. LDF recordings were analyzed with the wavelet transform to evaluate the mechanisms controlling the flowmotion (i.e., endothelial nitric oxide-independent and -dependent, neurogenic, myogenic, respiratory and cardiac mechanisms). Skin blood perfusion decreased throughout leg dependency at both sites. The decrease was blunted in persons with confirmed neuropathy compared to those with T2DM alone and the controls. During leg dependency, total spectral power increased in all groups compared to rest. The relative contribution of the endothelial bands increased and of the myogenic band decreased, without differences between groups. Neurogenic contribution decreased in controls, in persons with obesity and in those with T2DM, whereas it increased in subclinical- and confirmed neuropathy. In conclusion, this study provides evidence that confirmed diabetic neuropathy alters the VAR through the neurogenic response to leg dependency.
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