Detection of localized pulsatile motion in cutaneous microcirculation by speckle decorrelation optical coherence tomography angiography

SIGNIFICANCE

Pulsatility is a vital characteristic of the cardiovascular system. Characterization of the pulsatility pattern locally in the peripheral microvasculature is currently not readily available and would provide an additional source of information, which may prove important in understanding the pathophysiology of arterial stiffening, vascular ageing, and their linkage with cardiovascular disease development.

AIM

We aim to confirm the suitability of speckle decorrelation optical coherence tomography angiography (OCTA) under various noncontact/contact scanning protocols for the visualization of pulsatility patterns in vessel-free tissue and in the microvasculature of peripheral human skin.

RESULTS

Results from five healthy subjects show distinct pulsatile patterns both in vessel-free tissue with either noncontact or contact imaging and in individual microvessels with contact imaging. Respectively, these patterns are likely caused by the pulsatile pressure and pulsatile blood flow. The pulse rates show good agreement with those from pulse oximetry, confirming that the pulsatile signatures reflect pulsatile hemodynamics.

CONCLUSIONS

This study demonstrates the potential of speckle decorrelation OCTA for measuring localized peripheral cutaneous pulsatility and defines scanning protocols necessary to undertake such measurements. Noncontact imaging should be used for the study of pulsatility in vessel-free tissue and contact imaging with strong mechanical coupling in individual microvessels. Further studies of microcirculation based upon this method and protocols are warranted.

Aged garlic extract preserves cutaneous microcirculation in patients with increased risk for cardiovascular diseases: A double-blinded placebo-controlled study

Laser Doppler velocimetry estimates tissue perfusion providing a record of microvascular blood flow. Patients with heart disease or diabetes mellitus have impaired microvascular perfusion leading to impaired wound healing. Aged garlic extract (AGE) has a positive effect on vascular elasticity. This study aimed to assess the effect of long-term treatment with AGE on cutaneous tissue perfusion. A total of 122 patients with Framingham Risk Score ≥ 10 were randomised in a double-blinded manner to placebo or 2400 mg AGE daily for 1 year and monitored. Cutaneous microcirculation was measured at 0 and 12 months using laser Doppler velocimetry. A repeated measures analysis of variance (ANOVA) with a Greenhouse-Geisser correction determined that mean post-occlusive reactive hyperaemia differed significantly between time points. The mean percent change between the two time points 0 and 12 months was 102, 64 (174, 15)% change for AGE and 78, 62 (107, 92)% change for the placebo group (F[1, 120] = 5. 95, P < 0.016), 12 months of AGE increases the microcirculation in patients with an increased risk for cardiovascular events estimated using the Framingham risk score. Increased microcirculation could hypothetically facilitate wound healing.

Medical compression stockings reduce hypertension of nailfold capillaries at the toe of patients with chronic venous insufficiency1

In five patients who suffered from chronic venous insufficiency clinical stage C4 (n = 3) and C6 (n = 2) the capillary blood pressure was measured twice by means of invasive direct cannulation of nailfold capillaries of the toe. During one measurement course the patients wore below knee medical compression stockings (40 mmHg) during the other they did not have compression therapy. With the patient in supine position, the CP was investigated by the servo-nulling technique under resting conditions and under dynamic conditions: the calf-muscle/ankle joint venous pump was simulated by means of inflating a blood pressure cuff, which surrounded the mid lower leg, to 60 mmHg for 60 s.

RESULTS

The simulated calf-muscle contraction induced a steep increase of CP with 5.65 mmHg/s (Q1 5.27 mmHg/s, Q3 5.92 mmHg/s), which was significantly (p = 0.013) reduced by MCS to 2.47 mmHg/s (Q1 1.65 mmHg/s, Q3 3.0 mmHg/s). Time needed to reach the max. CP was 11.35 s, which was lengthened by MCS to 23.4 s (p = 0.134).

CONCLUSION

Compression therapy prevents capillary hypertension, the major hemodynamic reason for the development of advanced stages of chronic venous insufficiency which are defined by skin disease like hyperpigmentation, lipodermatosclerosis and ulcer.

Cardiac frequency and cutaneous microcirculation during and after exercising in the view of physical condition

INTRODUCTION

In the field of cardiovascular diseases an ergometer test is a common diagnostical method in which a change in microcirculation can be reached. In this paper cardiac frequency and cutaneous microcirculation during and after exercising will be compared with each other.

MATERIALS AND METHODS

The cutaneous microcirculation of  6 healthy volunteers (2 females, 4 males) is measured. As an instrument the PeriFlux 5000 combined with a Laser-Doppler-Flow(LDF)-Probe (Perimed Instruments) is used. The cardiac frequency (CF) is measured by the POLAR T31 sensor and as an ergometer the ERGO-FIT ® 457 is used.

RESULTS

The mean initial LDF (97,7±57,3 PU) decreases at the beginning (64,5±21,7 PU), increases during theexercise, reaches its maximum (247,8±82,1 PU) after the end of the exercise and drops to lower values (256,4±69,5 PU)after a few minutes. Contrasting to the LDF the mean initial CF (86±22/min) increases at the beginning (97±9/min),furthermore during the whole exercise (103±9/min) and then falls after having finished the exercise (96±3/min).Furthermore, during regeneration, one can see the CF decreasing towards its initial value, while LDF reaches its maximum.

CONCLUSION

In further studies, realized with volunteers with well-known levels of physical condition, a directconnection between cutaneous microcirculation and physical condition might be found.

Camera-based photoplethysmography in critical care patients

BACKGROUND

Camera-based photoplethysmography (cbPPG) is an optical measurement technique that reveals pulsatile blood flow in cutaneous microcirculation from a distance. cbPPG has been shown to reflect pivotal haemodynamic events like cardiac ejection in healthy subjects. In addition, it provides valuable insight into intrinsic microcirculatory regulation as it yields dynamic, two-dimensional perfusion maps. In this study, we evaluate the feasibility of a clinical cbPPG application in critical care patients.

METHODS

A mobile camera set-up to record faces of patients at the bed site was constructed. Videos were made during the immediate recovery after cardiac surgery under standard critical care conditions and were processed offline. Major motion artefacts were detected using an optical flow technique and suitable facial regions were manually annotated. cbPPG signals were highpass filtered and Fourier spectra out of consecutive 10s signal segments calculated for heart rate detection. Signal-to-noise ratios (SNR) of the Fourier spectra were derived as a quality measure. Reference data of vital parameters were synchronously acquired from the bed site monitoring system.

RESULTS

Seventy patient videos of an average time of 28.6±2.8 min were analysed. Heart rate (HR) was detected within a±5 bpm range compared to reference in 83% of total recording time. Low SNR and HR detection failure were mostly, but not exclusively, attributed to non-physiological events like patient motion, interventions or sudden changes of illumination. SNR was reduced by low arterial blood pressure, whereas no impact of other perioperative or disease-related parameters was identified.

CONCLUSION

Cardiac ejection is detectable by cbPPG under pathophysiologic conditions of cardiovascular disease and perioperative medicine. cbPPG measurements can be seamlessly integrated into the clinical work flow of critical care patients.

Deteriorated function of cutaneous microcirculation in chronic congestive heart failure

Background

Chronic congestive heart failure is a complex condition that leads to dysfunction in the peripheral microcirculation. We have previously shown that vascular reactivity is reduced with increasing age. In this study, we examined a group of very old patients with severe chronic heart failure to test the hypothesis that vascular function is further compromised by a combination of heart failure and aging.

Methods

Cutaneous forearm blood flow was measured by laser Doppler flowmetry and compared among three groups: Group 1 (n = 20, mean ± SE: 85.5 ± 4 years), heart failure patients with New York Heart Association class IV (NYHA IV) and with a NT-proBNP level ≥ 5000 ng/L; Group 2 (n = 15, mean ± SE: 76.5 ± 2 years), heart failure patients with NYHA II and NT-proBNP ≤ 2000 ng/L, and Group 3 (n = 10, mean ± SE: 67.6 ± 3.0 years), healthy controls with no clinical signs of heart failure. The vasodilator response to the iontophoretic administration of acetylcholine (ACh), acting via an endothelial mechanism, and sodium nitroprusside (SNP), acting via a smooth muscle cell mechanism, were studied.

Results

All patients with heart failure had significantly reduced vascular reactivity independent of the mode of stimulation (ACh, SNP or heat) when compared to healthy controls. However, the responses did not differ between the two groups of heart failure patients.

Conclusions

Cutaneous vascular reactivity is reduced in heart failure patients and does not correlate with the severity of the condition or age of patients.

Cigarette smoking leads to reduced relaxant responses of the cutaneous microcirculation

Background

Smoking is a major risk factor for cardiovascular disease. The present study was undertaken to examine if cigarette smoking translates into reduced relaxant responses of the peripheral microcirculation.

Methods

The cutaneous forearm blood flow was measured by laser Doppler flowmetry. The vasodilator response to the iontophorectic administration of acetylcholine (ACh), acting via an endothelial mechanism, and sodium nitroprusside (SNP), and acting via a smooth muscle mechanism were studied. The study population consisted of 17 nonsmokers and 17 current smokers (mean age 64 ± 2 years, 13 females and 4 males) in each matched group.

Results

There was no difference between the groups in baseline characteristics or in basal flow. Smokers showed however significantly reduced responses to both ACh (mean ± SEM, from 973 ± 137% in nonsmokers to 651 ± 114% in smokers, p < 0.05) and SNP (from 575 ± 111% in nonsmokers to 355 ± 83% in smokers, p < 0.05). The response to the local heating (44 °C) was reduced in smokers (from 1188 ± 215% in nonsmokers to 714 ± 107% in smokers, p < 0.01). In addition, there was no difference between men and women within the groups.

Conclusions

The data show that cigarette smoking results in reduced peripheral microvascular responses to both endothelial and smooth muscle cell stimulation in healthy subjects, suggesting a generalized microvascular vasomotor function.