Laser Doppler Flowmetry Index Research Articles

Using Arterial Pulse and Laser Doppler Analyses to Discriminate between the Cardiovascular Effects of Different Running Levels.

Running can induce advantageous cardiovascular effects such as improved arterial stiffness and blood-supply perfusion. However, the differences between the vascular and blood-flow perfusion conditions under different levels of endurance-running performance remains unclear. The present study aimed to assess the vascular and blood-flow perfusion conditions among 3 groups (44 male volunteers) according to the time taken to run 3 km: Level 1, Level 2, and Level 3. The radial blood pressure waveform (BPW), finger photoplethygraphy (PPG), and skin-surface laser-Doppler flowmetry (LDF) signals of the subjects were measured. Frequency-domain analysis was applied to BPW and PPG signals; time- and frequency-domain analyses were applied to LDF signals. Pulse waveform and LDF indices differed significantly among the three groups. These could be used to evaluate the advantageous cardiovascular effects provided by long-term endurance-running training, such as vessel relaxation (pulse waveform indices), improvement in blood supply perfusion (LDF indices), and changes in cardiovascular regulation activities (pulse and LDF variability indices). Using the relative changes in pulse-effect indices, we achieved almost perfect discrimination between Level 3 and Level 2 (AUC = 0.878). Furthermore, the present pulse waveform analysis could also be used to discriminate between the Level-1 and Level-2 groups. The present findings contribute to the development of a noninvasive, easy-to-use, and objective evaluation technique for the cardiovascular benefits of prolonged endurance-running training.

Features of laser Doppler flowmetry in patients with bacterial and viral (covid-19) community-acquired pneumonia

Introduction. As a result of the coronavirus infection (COVID-19) pandemic, almost 74.9 thousand people died of pneumonia in Russia in 2021. Community-acquired pneumonia (CAP) is accompanied by a systemic re­sponse of the body to inflammation in the lung tissue and disorder of microhemocirculation. The method of laser Doppler flowmetry (LDF) allows assessing the general parameters of the microcirculatory bed and determining the state of various factors regulating the nutritive flow.Aim. To conduct a comparative analysis of LDF indices in patients with COVID-19- associated and bacterial CAP.Materials and methods. 140 patients were examined, 100 of them with non-severe CAP (main group), and 40 patients with extrapulmonary pathology (comparison group). The main group included 44 people with bacterial CAP and 56 people with COVID-19-associated CAP. Bacteriological studies of sputum were performed; detection of SARS-CoV-2 RNA in swabs from the oropharynx and nasopharynx by PCR, LDF to assess the state of pe­ripheral blood flow was carried out.Results. In patients with COVID-19-associated CAP, compared with patients with bacterial CAP, a decrease in the microcirculation index by 1.26 times (p<0.0005), an increase in the coefficient of variation by 1.11 times (p<0.0005) was found.Conclusion. In patients with COVID-19-associated CAP, compared with patients with bacterial CAP, more significant pathological changes in Dopplerograms were detected, which may indicate more pronounced disorders in the microcirculatory bed in COVID-19-associated CAP caused by exposure to the SARS-COV- 2 virus. Perhaps the established fact can lead to adverse outcomes of the course of the disease.

Beat-to-beat and spectral analyses of the noninvasive radial pulse and laser-Doppler signals in patients with hypertension.

This study performed beat-to-beat and spectral analyses of 20-minute skin-surface laser-Doppler-flowmetry (LDF) and radial blood-pressure-waveform (BPW) signals in order to compare the blood-flow perfusion condition and regulatory mechanisms between essential-hypertension (EHT) patients and aged-matched control subjects. Beat-to-beat LDF analyses yielded the pulse width (PW), AC-to-DC ratio (AD), and their corresponding variability indices (coefficients of variation [CVs]). The relative energy contributions (RECs) of five characteristic frequency peaks (defined as FR1-FR5) were also calculated. Spectral BPW analysis obtained the amplitude proportion (Cn) and phase angle (Pn) of each harmonic component n. PW, AD, AD_CV, and REC of FR2 were significantly smaller in the EHT group than in the control group. Regarding BPW indices, C1, C2, C4, and C5 were significantly larger and P2-P8 were significantly smaller in EHT patients than in controls. The present results indicate that BPW and LDF indices can be used to evaluate the blood-flow perfusion efficiency and microcirculatory regulatory activities in EHT. Sex differences were found, with the effects being more prominent in female patients. These findings may be partly attributable to impairment of endothelial and neural regulatory functions. The present findings might aid the development of new noninvasive methods for reducing the risk of EHT-induced damage.

Evaluation of changes in laser Doppler flowmetry indices in patients with a combined subtype of rosacea under the influence of a course of complex phototherapy

BACKGROUND: The development of new methods for the treatment of rosacea, as well as a combination of various methods of physiotherapy, is of scientific and practical interest. In this work, the assessment of changes in microcirculation indices under complex phototherapy has been carried out.
 AIMS: Тo assess changes in microcirculation indices in patients with a combination of rosacea subtypes according to laser Doppler flowmetry under a course of complex phototherapy.
 MATERIAL AND METHODS: In 20172020 a randomized controlled study of 130 patients with a combination of rosacea subtypes. All patients were divided into 4 groups. In each separate group, laser therapy and 1% metronidazole cream were used (group I); phototherapy and 1% metronidazole cream (group II); complex photolaser therapy and 1% metronidazole cream (group III); in the comparison group (group IV), patients show only 1% metronidazole cream. The treatment, the duration of which was 3 months, included 6 sessions with an interval of 2 weeks. The effectiveness of therapy was assessed according to the data of laser Doppler flowmetry, reflecting changes in the hemodynamics of the microvasculature in the affected skin areas.
 RESULTS: The developed complex method, including exposure to intense pulsed light (intense pulsed light, IPL) 5201100 nm in combination with submillisecond neodymium laser radiation 1064 nm (submilisecond Nd: YAG laser 1064 nm) and daily application of 1% metronidazole cream showed the most pronounced improvement in the state of microcirculation according to laser Doppler flowmetry in comparison with the rest groups. Against the background of the course of complex phototherapy for all patients with the combined subtype of rosacea, statistically significant changes were in the volume of blood flow, modulation coefficients, coefficient of variation. On the contrary, no statistically significant changes were found in the ranges corresponding to active regulatory factors endothelial, neurogenic, myogenic, and passive respiratory and cardiac, as well as in the T index.
 CONCLUSION: After the course of complex phototherapy in the group of patients with a combination of rosacea subtypes, there was a decrease in the severity of clinical manifestations of diseases, as well as an improvement in the main indicators of microcirculation according to laser Doppler flowmetry.

Characteristics of pulse-waveform and laser-Doppler indices in frozen-shoulder patients

This study tested the hypothesis that measuring and analyzing the arterial pulse waveform and the skin-surface blood flow makes it possible to noninvasively discriminate the different microcirculatory states of patients with frozen shoulder (FS). Radial blood pressure waveform (BPW), finger photoplethysmography (PPG), and skin-surface laser Doppler flowmetry (LDF) signals were measured noninvasively on the back of the hand in 25 FS and 18 control subjects. Beat-to-beat, spectral, and variability analyses were applied to the 3-minute-long recorded signals. Significant intergroup differences were found in the BPW, PPG, and LDF indices. For example, the amplitude indices of the predominant (lower-frequency) BPW components were significantly larger in FS subjects than controls. Some of the PPG phase-angle variability indices were significantly larger on the diseased side than on the contralateral side. The present results illustrate that LDF indices can be used to evaluate the blood-flow-perfusion responses and their regulation, and that pulse-waveform indices can help to evaluate changes in the arterial pulse-wave transmission condition and its regulation in FS. Moreover, the trends in the changes in certain spectral pulse-waveform indices were similar for the wrist BPW and finger PPG signals. These findings could facilitate the development of a rapid, inexpensive, and objective technique for evaluating the blood-flow responses induced by FS.

Complexity analysis of beat-to-beat skin-surface laser-Doppler signals in diabetic subjects

MotivationsThis study performed skin-surface laser-Doppler flowmetry (LDF) measurements with the aim of verifying if complexity analysis applied to the beat-to-beat LDF waveform index can be used to discriminate diabetic, prediabetic, and normoglycemic subjects. MethodsSixty-six subjects were assigned to three age-matched groups according to the results of oral glucose tolerance tests. Beat-to-beat analysis was performed on the pulsatile LDF waveform to obtain the pulse-to-mean ratio (AD) and pulse width (PW), and then approximate-entropy (ApEn) values for their 20-minute index sequences were calculated to evaluate the signal complexity. ResultsAD and PW did not differ significantly among the three study groups. ApEn values of AD and PW were significantly larger and marginally larger, respectively, in the diabetic group than in the prediabetic and normoglycemic groups. ConclusionThese results indicate the presence of significant differences in ApEn indexes among diabetic, prediabetic, and normoglycemic subjects. The presence of increased complexity in the LDF index sequence may be partly attributed to the adaptability of the microcirculatory regulatory activities or the impairment of the homeostasis mechanism of microcirculatory-blood-flow perfusion. The present findings may be pertinent to the early detection of the diabetes-induced impairment of this perfusion.

Connection between RR-interval length and the pulsatile microcirculatory flow

The present study used laser Doppler flowmetry (LDF) to investigate the connection between skin microcirculatory flow and the length of the RR interval (LRR). Local heating was performed on healthy volunteers to further elucidate its effect on LDF index. ECG and LDF signals were measured in 102 trials on seven volunteers. Each experiment involved a 5 min control and a 5 min heating-effect sequence. Each laser Doppler flux pulse was categorized into four groups according to its LRR compared with the 5 min average LRR. Synchronized averaging analysis was applied to the four groups of pulses to obtain their averaged waveforms, from which four flux parameters were calculated. The ac component of the flux increased significantly with increasing LRR, and the differences therein between the groups with LRR more than 4% smaller and more than 4% larger than the average LRR increased from 15.8% during the control period to 23.9% during the heating period. Understanding of the different flux responses between the control and local-heating experiments may aid the development of a new index, which helps to avoid LDF's main drawback of providing only qualitative measurement.