Laser Doppler Skin Perfusion Pressure in the Assessment of Raynaud's Phenomenon

Microcirculatory response to cold stress test in the healthy hand

OBJECTIVE

Cold sensitivity of the fingers is common in several conditions. It has been linked to digital vasospasm, microvascular dysfunction, and neural mechanisms. This study aimed to investigate the normal digital microvascular response to a cold stress test in healthy individuals using Laser Speckle Contrast Imaging (LSCI).

METHODS

Twenty-six healthy individuals, mean age 31 (SD 9) years were included. Skin perfusion of digits II-V was measured using Laser Speckle Contrast Imaging before and after a standardized cold stress test. Changes in skin perfusion from baseline were analyzed between hands, digits, and sexes.

RESULTS

Skin perfusion was significantly (p < 0.0001) affected by cold provocation in both the cold exposed and the contralateral hands in all participants of the study. This effect was significantly different between the radial (digit II and III) and the ulnar (digit V) side of the hands (p < 0.001). There was a trend towards a larger decrease in perfusion in men (ns), and a faster recovery to baseline values in women (ns). A larger inter subject variability was seen in perfusion values in women.

CONCLUSIONS

The normal microvascular response to cold provocation may involve both centrally and regionally mediated processes. When exposing one hand to a cold stress test, the contralateral hand responds with simultaneous but smaller decreases in perfusion.

Light Emitting Diodes based Photoacoustic Imaging and Potential Clinical Applications

Using low cost and small size light emitting diodes (LED) as the alternative illumination source for photoacoustic (PA) imaging has many advantages, and can largely benefit the clinical translation of the emerging PA imaging technology. Here, we present our development of LED-based PA imaging integrated with B-mode ultrasound. To overcome the challenge of achieving sufficient signal-to-noise ratio by the LED light that is orders of magnitude weaker than lasers, extensive signal averaging over hundreds of pulses is performed. Facilitated by the fast response of the LED and the high-speed driving as well as the high pulse repetition rate up to 16 kHz, B-mode PA images superimposed on gray-scale ultrasound of a biological sample can be achieved in real-time with frame rate up to 500 Hz. The LED-based PA imaging could be a promising tool for several clinical applications, such as assessment of peripheral microvascular function and dynamic changes, diagnosis of inflammatory arthritis, and detection of head and neck cancer.

Postocclusive Hyperemia Measured with Laser Doppler Flowmetry and Transcutaneous Oxygen Tension in the Diagnosis of Primary Raynaud's Phenomenon: A Prospective, Controlled Study

The aim of this study was to measure the sensitivity and specificity of transcutaneous oxygen tension and postocclusive hyperemia testing using laser Doppler flowmetry in patients with primary Raynaud's phenomenon. One hundred patients and one hundred controls were included in the study. Baseline microvascular blood flow and then time to peak flow following occlusion were measured using laser Doppler flowmetry. Afterwards, the transcutaneous oxygen tension was recorded. The sensitivities of baseline microvascular blood flow, postocclusive time to peak flow, and transcutaneous oxygen tension were 79%, 79%, and 77%, respectively. The postocclusive time peak flow had a superior specificity of 90% and area under the curve of 0.92 as compared to 66% and 0.80 for baseline microvascular flow and 64% and 0.76 for transcutaneous oxygen tension. Time to postocclusive peak blood flow measured by laser Doppler flowmetry is a highly accurate test for differentiating patients with primary Raynaud's phenomenon from healthy controls.

Evaluation for hypoperfusion distal to arteriovenous vascular access using skin perfusion pressure in fingers

PURPOSE

The usefulness of skin perfusion pressure (SPP) measurement in the assessment of critical ischemia of the lower limb has previously been established. This study investigated whether finger SPP measurement is useful to evaluate hypoperfusion distal to arteriovenous vascular access in dialysis patients.

METHODS

Seventeen asymptomatic hemodialysis patients with upper extremity arteriovenous access and 17 non-dialysis control patients were prospectively examined. SPP in the thumb, the middle finger and the little finger of both hands was measured. The bilateral difference of the mean SPP of the three fingers was evaluated.

RESULTS

The mean difference of SPP between the contralateral and the arteriovenous access sides among hemodialysis patients (33±2 5 mmHg) was significantly larger than the mean difference of SPP between the left and the right hands among control patients (1.0±6.0 mmHg, p<0.01).

CONCLUSIONS

This report shows the potential usefulness of SPP measurement to evaluate hypoperfusion distal to arteriovenous vascular access.

Comparison of instruments for investigation of microcirculatory blood flow and red blood cell concentration

The use of laser Doppler perfusion imaging (LDPI) and laser speckle perfusion imaging (LSPI) is well known in the noninvasive investigation of microcirculatory blood flow. This work compares the two techniques with the recently developed tissue viability (TiVi) imaging system, which is proposed as a useful tool to quantify red blood cell concentration in microcirculation. Three systems are evaluated with common skin tests such as the use of vasodilating and vasoconstricting drugs (methlynicotinate and clobetasol, respectively) and a reactive hyperaemia maneuver (using a sphygmomanometer). The devices investigated are the laser Doppler line scanner (LDLS), the laser speckle perfusion imager (FLPI)-both from Moor Instruments (Axminster, United Kingdom)-and the TiVi imaging system (WheelsBridge AB, Linkoping, Sweden). Both imaging and point scanning by the devices are used to quantify the provoked reactions. Perfusion images of vasodilatation and vasoconstriction are acquired with both LDLS and FLPI, while TiVi images are acquired with the TiVi imager. Time acquisitions of an averaged region of interest are acquired for temporal studies such as the reactive hyperaemia. In contrast to the change in perfusion over time with pressure, the TiVi imager shows a different response due its measurement of blood concentration rather than perfusion. The responses can be explained by physiological understanding. Although the three devices sample different compartments of tissue, and output essentially different variables, comparisons can be seen between the three systems. The LDLS system proves to be suited to measurement of perfusion in deeper vessels, while FLPI and TiVi showed sensitivity to more superficial nutritional supply. LDLS and FLPI are insensitive to the action of the vasoconstrictor, while TiVi shows the clear boundaries of the reaction. Assessment of the resolution, penetration depth, and acquisition rate of each instrument show complimentary features that should be taken into account when choosing a system for a particular clinical measurement.

Surgical result of critical limb ischemia due to tibial arterial occlusion in patients with systemic scleroderma

OBJECTIVE

To analyze the outcome after surgery for critical limb ischemia (CLI) due to tibial artery occlusion in patients with systemic scleroderma.

METHODS

The medical records of scleroderma patients with CLI due to tibial artery occlusion were reviewed with respect to demographic data and perioperative variables.

RESULTS

Eight patients were identified at The University of Tokyo Hospital from 1991 to 2007. The underlying collagen disease was progressive systemic scleroderma in 6 patients and CREST syndrome in 2 patients. The subjects were 1 man and 7 women with a mean age of 68 years. While hypercoagulability including positive anticardiolipin antibodies was found in only 1 patient, all patients were antinuclear antibody (ANA) positive and 6 of 8 patients had a high titer of centromere-type ANA. Five underwent pedal artery bypass and 1 underwent distal peroneal artery bypass, while 2 underwent primary limb amputation. Although 1 patient with bypass had early graft occlusion (with subsequent below-knee amputation), the other 5 patients with patent grafts quickly achieved pain relief and initial wound healing. However, four of the five patent grafts developed graft occlusion several months after surgery, with severe intimal thickening at the anastomosis. As a result, 2 of 6 patients with bypass (totally 4 of 8 patients) underwent limb loss and 1 patient developed persistent recurrent ulcer.

CONCLUSION

Bypass surgery in patients with scleroderma and CLI can be successful in achieving early pain relief and ischemic wound healing. However, the long-term effectiveness is limited with high rates of graft failure and limb loss.

Skin perfusion pressure in chronic venous disorders

OBJECTIVE

To examine whether a patient group with chronic venous disorders (CVDs) would show a different response to a pressure provocation test, such as skin perfusion pressure (SPP) of microcirculatory function.

DESIGN

A cuff inflation technique was applied to the gaiter area of the lower legs to induce complete occlusion of the microcirculation. The cuff was then released to measure the pressure at which perfusion resumed, and SPP was measured with a laser Doppler flowmeter (LDF). The measurements at reperfusion were taken of skin of the lower legs of individuals with CVD and compared with the lower-leg skin of control participants.

MAIN OUTCOME MEASURES

To establish whether a measurable difference in SPP exists between the group with CVD and the group without CVD, the means of 9 measurements taken were compared using the Student t test. The lowest value of the 9 measurements of minimum pressure (LMV) was used to estimate the pressure at which reperfusion occurred (SPP). The means of those estimates were then compared using the Student t test.

MAIN RESULTS

The mean LMV measured in the CVD group was slightly higher than that measured in the group without CVD. Although this could be considered a clinically significant result, it was not statistically different.

CONCLUSIONS

For this study, SPP was not significantly different for those with CVD compared with those without. These results suggest that SPP conducted with an LDF has little potential to detect "invisible" changes in the microcirculatory function of the skin affected by CVDs.

The relationship between local scalp skin temperature and cutaneous perfusion during scalp cooling

Cooling the scalp during administration of chemotherapy can prevent hair loss. It reduces both skin blood flow and hair follicle temperature, thus affecting drug supply and drug effect in the hair follicle. The extent to which these mechanisms contribute to the hair preservative effect of scalp cooling remains unknown. The purpose of this study was to establish a relationship between local scalp skin temperature and cutaneous blood flow during scalp cooling. We measured skin temperature and cutaneous perfusion during a cooling and re-warming experiment. Experiments on a single subject showed that the measurements were reproducible and that the response was identical for the two positions that were measured. Inter-subject variability was investigated on nine subjects. We found that for the first 10 degrees C of cooling, perfusion of the scalp skin decreases to below 40%. Perfusion can be further reduced to below 30% by a few degrees more cooling, but a plateau is reached after that. We found that a generally accepted relation in thermal physiology between temperature and perfusion (i.e. Q(10) relation) does not describe the data well, but we found an alternative relation that describes the average behavior significantly better.

A cold-response index for the assessment of Raynaud's phenomenon

BACKGROUND

Quantification of Raynaud's phenomenon (RP) is a prerequisite in the evaluation of novel therapeutic strategies. Fingertip rewarming in response to local cold provocation has been used in many studies but not been systematically validated. We have previously described the time elapsed before 63% of pre-cooling temperature is reached as a RP activity index.

OBJECTIVE

A comprehensive evaluation of fingertip rewarming in primary and scleroderma-associated RP.

METHODS

We defined a cold-response index (CRI) as the log transformation of the 63% rewarming time upon cold challenge.

RESULTS

The CRI shows high intra-individual reproducibility. The mean CRI values were (mean+/-S.D.): 2.4+/-0.3 in controls (n=53) versus 2.7+/-0.3 in RP (n=50, p<0.0001 versus controls), and 2.7+/-0.3 in scleroderma patients (n=46, p<0.0001). In addition, baseline fingertip temperature was also found to be significantly reduced both in primary as well as scleroderma-associated RP. Kinetic analysis of rewarming temperature curves demonstrates that the CRI is independent of individual rewarming patterns. Finally, the CRI decreases significantly upon a single low-level systemic hyperthermia treatment in scleroderma patients (2.68+/-0.28 before versus 2.45+/-0.33 after, p=0.0003), while the extent of cooling remained unchanged, thus demonstrating sensitivity to change.

CONCLUSION

Our results provide a solid basis for using the cold-response assay as an endpoint in addition to clinical activity scores in RP treatment trials.

Understanding, assessing and treating Raynaud's phenomenon

PURPOSE OF REVIEW

New insights in the pathophysiology and molecular mechanisms implicated in cutaneous vasomotor response to cooling are emerging from recent literature. These advances are introducing significant changes in the management of Raynaud's phenomenon. In this review, we outline how these new findings are leading to novel methods of assessment and new opportunities for specific targeted therapy.

RECENT FINDINGS

New potential targets for treatment of Raynaud's phenomenon derive from experimental observations. Increased protein tyrosine kinase activity and tyrosine phosphorylation have been described in vascular smooth muscle cells in response to cooling and are linked to excessive alpha2-adrenergic response. Activation of Rho/Rho kinase pathway is triggered by increase of reactive oxygen species and up-regulates alpha2c-adrenergic receptors on the surface of vascular smooth muscle cells, thus determining an excessive vasoconstrictive response to cooling. This observation generated pilot trials testing rho-kinase inhibitors and alpha2c-adrenergic receptors antagonists in vasospastic conditions with encouraging results. Therapies already in use for pulmonary hypertension are also showing an effect in Raynaud's phenomenon. Studies evaluating anti-endothelin-1 (bosentan), phosphodiesterases inhibitors (sildenafil), and prostanoids (given for critical digital ischemia) in the treatment of Raynaud's phenomenon all determined improvement of symptoms and/or digital ischemic lesions. Novel techniques for better visualization and quantification of cutaneous microvascular defects are under development. The hope is that these new tools will allow earlier discrimination between primary and secondary Raynaud's phenomenon as well as a better way to predict outcome and response to therapy.

SUMMARY

Remarkable progress towards a rational approach to the management and treatment of Raynaud's phenomenon is emerging.

Infrared-monitored cold response in the assessment of Raynaud's phenomenon

BACKGROUND

Evaluation of treatments for Raynaud's phenomenon (RP) requires objective response parameters in addition to clinical activity scores. Thermographic monitoring of fingertip re-warming after cold challenge has been widely used but usually requires sophisticated equipment. We have previously shown that fingertip re-warming after cold challenge follows a first-order transient response curve that can be described by a single variable, designated tau.

OBJECTIVES

Here, we describe a novel device termed a duosensor, which records the tau value upon cold challenge in an automated manner.

METHODS

We determined tau values in healthy probands, patients with primary or secondary RP associated with autoimmune disease and patients with scleroderma-associated RP following cold challenge, to determine assay variability, sensitivity and specificity.

RESULTS

Duosensor-based thermography exhibited low intraindividual variability in healthy probands. As expected, tau values in RP patients were significantly increased compared with controls (8.08 +/- 3.65 min vs. 3.23 +/- 1.65 min). The duosensor-determined tau value yielded a specificity of 94.6% and predictive value of 95.3% for the presence of RP in a retrospective analysis of 139 patients. Furthermore, in a cohort of scleroderma patients with RP, patient self-assessment of RP severity correlated with tau values.

CONCLUSIONS

Taken together, the present data suggest that tau value determination provides a suitable outcome measure for clinical studies of novel RP treatments. As the duosensor is a simple stand-alone device requiring no supporting equipment and minimal personnel attention, it should allow RP activity monitoring even in clinical settings with minimal technical infrastructure.

Raynaud phenomenon and the vascular disease in scleroderma

PURPOSE OF REVIEW

Raynaud phenomenon is the earliest and most common clinical manifestations of scleroderma (systemic sclerosis). Therefore, Raynaud phenomenon offers the best window into the investigation of the early steps in the pathogenesis of systemic sclerosis. This review focuses on the differential diagnosis of Raynaud phenomenon, the transition of Raynaud phenomenon to systemic sclerosis, mechanisms and consequences of vascular injury and dysfunction in systemic sclerosis, and therapeutic options.

RECENT FINDINGS

Careful clinical evaluation using a simple definition of Raynaud phenomenon is the most reliable and reproducible method in the diagnosis. Although the assessment of vascular function by noninvasive methods is still not sensitive enough for the evaluation and follow-up of individual patients, it helps in the differential diagnosis and in population studies. Progressive deficiency in vasodilatory capacity of the vessels is proposed as a mechanism of Raynaud phenomenon, particularly in systemic sclerosis. In addition, decreased fibrinolysis and enhanced coagulation pathways undoubtedly contribute to vascular dysfunction. The mechanism of endothelial injury is still elusive, yet endothelial apoptosis mediated by antiendothelial antibodies is the most attractive hypothesis now. Therapies directed at the vascular disease continue to focus on the alleviation of vascular spasm. However, immunosuppressive therapy may influence the levels of vascular injury markers and thus may have an effect on the vascular disease itself.

SUMMARY

Continued progress in the investigation of the vascular aspects of scleroderma is described in this review. Immune involvement in the early stages of the disease and mechanism of vascular repair in advance cases are some of the highlights of last year's progress.