Laser speckle contrast imaging of forehead cutaneous blood flow during carotid endarterectomy as a potential non-invasive method for surrogate monitoring of cerebral perfusion

ABSTRACT Objective: to evaluate the effects of increasing pressures on the cutaneous blood flow in the skin of pigs. Methods: we conducted an experimental study in pigs submitted to subcutaneous magnetic implants (n=30). After healing, were applied external magnets with varying magnetic forces to the skin, generating compression. We evaluated the cutaneous circulation of the skin under compression by the Laser Speckle Contrast Imaging (LSCI) technique. We measured the depth of the implants by ultrasonography, and applied computational simulations to the calculation of the different pressure values, considering the different distances between implants and external magnets. Results: nineteen implants presented complications. The remaining 11 were submitted to different magnetic compression forces and perfusion analysis. Two linear regression models showed an inverse correlation between exerted pressure and cutaneous perfusion, with significant variation, mainly in the initial pressure increases, of up to 20mmHg. Conclusion: The main reduction in cutaneous blood flow resulted from initial increases of up to 20 mmHg. The results suggest that tissue ischemia can occur even in low-pressure regimes, which could contribute to the appearance of skin lesions, particularly ulcers related to medical devices.

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Nephron blood flow dynamics measured by laser speckle contrast imaging

AJP Renal Physiology ◽

10.1152/ajprenal.00417.2010 ◽

2011 ◽

Vol 300 (2) ◽

pp. F319-F329 ◽

Cited By ~ 34

Author(s):

Niels-Henrik Holstein-Rathlou ◽

Olga V. Sosnovtseva ◽

Alexey N. Pavlov ◽

William A. Cupples ◽

Charlotte Mehlin Sorensen ◽

...

Keyword(s):

Blood Flow ◽

Signal Transmission ◽

Experimental Studies ◽

Flow Dynamics ◽

Laser Speckle ◽

Tubuloglomerular Feedback ◽

Contrast Imaging ◽

Laser Speckle Contrast Imaging ◽

Speckle Contrast ◽

Blood Flow Dynamics

Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50–100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization. Synchronization may take place among nephrons not immediately adjacent on the surface of the kidney.

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