Heel skin hyperaemia: direct compression versus vascular occlusion

Assessing the impact of aging and blood pressure on dermal microvasculature by reactive hyperemia optical coherence tomography angiography

Visualization and quantification of the skin microvasculature are important for studying the health of the human microcirculation. We correlated structural and pathophysiological changes of the dermal capillary-level microvasculature with age and blood pressure by using the reactive hyperemia optical coherence tomography angiography (RH-OCT-A) technique and evaluated both conventional OCT-A and the RH-OCT-A method as non-invasive imaging alternatives to histopathology. This observational pilot study acquired OCT-A and RH-OCT-A images of the dermal microvasculature of 13 young and 12 old healthy Caucasian female subjects. Two skin biopsies were collected per subject for histological analysis. The dermal microvasculature in OCT-A, RH-OCT-A, and histological images were automatically quantified and significant indications of vessel rarefaction in both old subjects and subjects with high blood pressure were observed by RH-OCT-A and histopathology. We showed that an increase in dermal microvasculature perfusion in response to reactive hyperemia was significantly lower in high blood pressure subjects compared to normal blood pressure subjects (117% vs. 229%). These results demonstrate that RH-OCT-A imaging holds functional information of the microvasculature with respect to physiological factors such as age and blood pressure that may help to monitor early disease progression and assess overall vascular health. Additionally, our results suggest that RH-OCT-A images may serve as a non-invasive alternative to histopathology for vascular analysis.

Noninvasive imaging technologies for cutaneous wound assessment: A review

The ability to phenotype wounds for the purposes of assessing severity, healing potential and treatment is an important function of evidence-based medicine. A variety of optical technologies are currently in development for noninvasive wound assessment. To varying extents, these optical technologies have the potential to supplement traditional clinical wound evaluation and research, by providing detailed information regarding skin components imperceptible to visual inspection. These assessments are achieved through quantitative optical analysis of tissue characteristics including blood flow, collagen remodeling, hemoglobin content, inflammation, temperature, vascular structure, and water content. Technologies that have, to this date, been applied to wound assessment include: near infrared imaging, thermal imaging, optical coherence tomography, orthogonal polarization spectral imaging, fluorescence imaging, laser Doppler imaging, microscopy, spatial frequency domain imaging, photoacoustic detection, and spectral/hyperspectral imaging. We present a review of the technologies in use or development for these purposes with three aims: (1) providing basic explanations of imaging technology concepts, (2) reviewing the wound imaging literature, and (3) providing insight into areas for further application and exploration. Noninvasive imaging is a promising advancement in wound assessment and all technologies require further validation.

A quantitative analysis of microcirculation in sore-prone pressure areas on conventional and pressure relief hospital mattresses using laser Doppler flowmetry and tissue spectrophotometry

BACKGROUND

Pressure ulcers are associated with severe impairment for the patients and high economic load. With this study we wanted to gain more insight to the skin perfusion dynamics due to external loading. Furthermore, we evaluated the effect of different types of pressure relief mattresses.

METHODS

A total of 25 healthy volunteers were enrolled in the study. Perfusion dynamics of the sacral and the heel area were assessed using the O2C-device, which combines a laser light, to determine blood flow, and white light to determine the relative amount of hemoglobin. Three mattresses were evaluated compared to a hard surface: a standard hospital foam mattress bed, a visco-elastic foam mattress, and an air-fluidized bed.

RESULTS

In the heel area, only the air-fluidized bed was able to maintain the blood circulation (mean blood flow of 13.6 ± 6 versus 3.9 ± 3 AU and mean relative amount of hemoglobin of 44.0 ± 14 versus 32.7 ± 12 AU.) In the sacral area, all used mattresses revealed an improvement of blood circulation compared to the hard surface.

CONCLUSION

The results of this study form a more precise pattern of perfusion changes due to external loading on various pressure relief mattresses. This knowledge may reduce the incidence of pressure ulcers and may be an influencing factor in pressure relief mattress selection.

Effects of Support Surface Relief Pressures on Heel Skin Blood Flow in Persons with and without Diabetes Mellitus

OBJECTIVE

To investigate the effects of pressure relief magnitude on heel blood hyperemia in persons with and without diabetes mellitus.

DESIGN

Study participants (1 group of persons with diabetes and 1 group without diabetes) lay on a support surface for 70 minutes with 1 heel on an end cell of a support surface. Cell pressure was computer controlled to be 20 mm Hg during support and 5 or 0 mm Hg during relief. Heel skin blood perfusion was monitored by laser Doppler on the heel and foot dorsum. Heel hyperemia was determined as ratios of skin blood perfusion areas during hyperemia to preloading (AR) and peak hyperemia to mean skin blood perfusion during preload (QR).

SUBJECTS

13 persons with diabetes mellitus (6 females, 7 males; age 65.2 +/- 3.0 years) and no known diabetes-related complications, and 15 persons without diabetes mellitus (7 females, 8 males; age 54.7 +/- 3.1 years)

SETTING

University research center.

RESULTS

For the nondiabetes mellitus group, hyperemia was significantly greater with complete pressure-relief compared with partial relief (P < .001). In contrast, the diabetes mellitus group showed no significantly increased response to full relief, and the hyperemia achieved during full relief, measured by AR and QR, was significantly less than with the nondiabetes mellitus group.

CONCLUSIONS

These results suggest that a diabetes-related reduced microvascular vasodilatory capacity is not exceeded during partial pressure relief, but is exceeded during complete pressure relief. Accordingly, differences in hyperemic response would become unmasked only when maximum hyperemia could be established during complete heel off-loading. This would suggest that a diminished hyperemia during complete off-loading, as found in the present diabetes mellitus group, may be problematic if widely present in the diabetic (or possibly older) population, under conditions in which heel loading occurs for sustained intervals.