We would like to extend our gratitude to the Link&#246;ping staff of The Swedish Defense Agency (FOI) and the Center for disaster medicine and Traumatology (KMC) for their kind support.

The study described here followed the local ethic guidelines and was approved by the regional ethical review board in Link&#246;ping (permit number 2015/99-31).
1. Informed Consent and Screening
<ol>
	<li>Obtain informed consent from the subject.</li>
	<li>Screen according to inclusion/exclusion criteria. 
	NOTE: Inclusion criteria were: (i) Healthy adult &#62;18 years of age, (ii) Able to understand written and oral information, and (iii) Provides oral and written consent. Exclusion criteria were: (i) Unable or unwilling to provide informed consent, (ii) Ongoing skin conditions, (iii) Cardiovascular disease,&#160;(iv) Medication that can interfere with vascular function. Oral contraceptives are allowed. If the subject uses oral contraceptives this should be noted on the subject&#39;s protocol file,&#160;(v) Scar free and non-bruised skin of the forehead,&#160;(vi) No intake of caffeine or tobacco 2 h prior to the onset of the test, and&#160;(vii) No strenuous physical activity at least 2 h prior to onset of the test.</li>
</ol>
2. Acclimatization and Equipment Setup
<ol>
	<li>Let the test subject acclimatize for at least 20 min in a supine position prior to the onset of the test. 
	NOTE: Correct positioning of the subject and equipment is shown in supplemental figure 1.</li>
	<li>Set up the camera recording of the capillary refill tests using the designated software and digital camera (see Table of Materials).
	<ol>
		<li>Connect the USB cable to the camera and the computer and adjust camera settings to video mode.</li>
		<li>Turn on the camera and make sure that it connects to the computer.</li>
		<li>Start the remote-controlled camera software (see Table of Materials).</li>
		<li>Turn off ambient light and turn the computer screen away from the measurement area.</li>
	</ol>
	</li>
</ol>
3. Data Acquisition
<ol>
	<li>Click the &#34;life view&#34; (Sic) button and press &#34;Start&#34;.</li>
	<li>Switch between &#39;video&#39; mode and &#39;TiVi&#39; mode by clicking the radio buttons (this will not affect the recording, only the on-screen presentation). Ensure that a live video stream of the subject&#39;s forehead is visible on the display of the camera and on the computer screen.</li>
	<li>Adjust the camera to a height of approximately 15 cm directly above the subject&#39;s forehead.</li>
	<li>Make sure that the focus of the camera is set to &#34;AF&#34; (auto focus).</li>
	<li>Ask the subject to keep his/her head still for the duration of the test and to refrain from talking. Inform the subject that it is OK to keep his/her eyes closed during the test by saying: &#34;Please, place your head on this pillow and keep your head still for the duration of the test. Please, do not talk during the 20 seconds that the test will last. You may keep your eyes closed for the whole time if you find the light too bright&#34;.</li>
	<li>Do not move the camera while recording.</li>
	<li>In the &#34;life view&#34; window find and click &#34;HD record&#34; to start a continuous recording for 20 s. Note that the duration of the recording (seconds), can be seen on the camera display; the first 5 s of the recording is to acquire the normal capillary blood concentration of the forehead.</li>
	<li>At the end of the 5 s of baseline recording, apply a firm blanching pressure to the measurement area for 5 s. Use the index finger with a plastic teaspoon between the finger and the forehead for pressure equalization and temperature insulation.</li>
	<li>Release the pressure and quickly withdraw the examiner&#39;s finger and plastic teaspoon from the measurement area.</li>
	<li>Continue recording for another 10 s to capture the subsequent hyperemic response.</li>
	<li>Stop recording by clicking &#34;Stop&#34; in the &#34;life view&#34; window.</li>
	<li>Once the recording has stopped, a window will open for saving and naming the file (in .mov format); choose a folder and name for the video. Do not disconnect the camera from the computer while the video is downloading to the designated folder on the computer.</li>
</ol>
4. Data Analysis
<ol>
	<li>Proceed to performing image analysis and curve construction with a dedicated analysis software (see Table of Materials).</li>
	<li>Start the analysis software by double-clicking the desktop icon.</li>
	<li>Once the software has started, on the main screen, select &#34;Movie page.&#34;</li>
	<li>In the &#34;Movie page&#34; window, click &#34;Load movie.&#34;&#160;Wait for the software to upload and analyze the movie. This may take up to a couple of minutes depending on the size of the video file.</li>
	<li>Once the upload and analysis of the movie is finished, click &#34;Save as images&#34; and wait for the software to analyze the video. 
	NOTE: This will automatically create a new folder on the computer containing the video sequence divided into individual jpeg images.</li>
	<li>Once the division of the video into individual jpeg images is finished, find and select &#34;Crop images page&#34; in the main screen window.</li>
	<li>In the &#34;Crop images page&#34;, click &#34;First Photo&#34; and navigate to the folder that contains the jpeg photos from the video and select the first photo to be analyzed; the software will automatically select the following photos of that batch.</li>
	<li>Click the &#34;Edit&#34; menu and choose between circular or rectangular markers for the region of interest.</li>
	<li>In the &#34;Select Photos&#34; window, find the &#34;Actual photo&#34; box and type in the name of the first photo in the batch where the investigator&#39;s finger is fully retracted from the measurement area. To find this photo, look through the folder containing the individual photos from the video.</li>
	<li>Select a region of interest by clicking and holding the left mouse button and draw a circle or rectangle in the photo window that is within the borders of the blanched area. The selected region of interest is automatically applied to all photos of the batch.</li>
	<li>Click the &#34;File&#34; menu and choose &#34;Save ROI&#34; to save the location of the selected region of interest for future reference.</li>
	<li>Click the &#34;Curve tracker&#34; button and wait for the software to analyze the region of interest.</li>
	<li>Once the curve tracker window opens, the change in red blood cell concentration for the selected region of interest for the duration of the test is displayed as a curve. The on-screen presentation can be changed by clicking the different radio buttons. This will not affect the raw data.</li>
	<li>Click &#34;Export data&#34; and save the raw data transcript for further analysis.</li>
	<li>In the raw data transcript, navigate to the column named &#34;Mean intensity TiVi values.&#34;&#160;Generate three new columns next to this column for &#34;image number,&#34;&#160;&#34;total time,&#34;&#160;and &#34;capillary refill time&#34; starting at 1 s, 0 s, and 0 s and with an incrementation of 1 s, 0.02 s, and 0.02 s, respectively. 
	NOTE: &#34;Capillary refill time&#34; correlates to the time of the subsequent reaction to the release of the blanching pressure and starts at the mean value that represents the first photo where the investigator&#39;s finger is fully retracted from the measurement area.</li>
	<li>Delete the values between baseline and capillary refill time, as these only contain noise generated by the investigator&#39;s index finger and plastic teaspoon during the blanching maneuver.</li>
	<li>Calculate a mean value for the baseline measurement (first 5 s of the recording).</li>
	<li>Find the first value that equals or surpasses the calculated mean baseline value and note the time in the &#34;Capillary refill time&#34; column. This time point represents the &#34;time to return to baseline 1.&#34;</li>
	<li>Find the highest mean intensity value of the values generated after pressure release and note the time point in the &#34;Capillary refill time&#34; column. This time point represents the &#34;Time to peak.&#34;</li>
	<li>Find the second value that is less than or equal to the calculated mean value for the baseline measurement and note the time point in the &#34;Capillary refill time&#34; column. This time point represents the &#34;time to return to baseline 2.&#34;</li>
</ol>

<ol><li>Strehlow, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Early+identification+of+shock+in+critically+ill+patients%5BTitle%5D)+AND+%22Emerg+Med+Clin+North+Am%22%5BJournal%5D)">Early identification of shock in critically ill patients.</a> Emerg Med Clin North Am. 28 (1), 57-66 (2010).</li>
<li>Advanced Life Support, G. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aAdvanced+Life+Support%2C+G+%22Acute+Medical+Emergencies%22">Acute Medical Emergencies</a>. , Wiley-Blackwell. 67-84 (2010).</li>
<li>Brasel, K. J., Guse, C., Gentilello, L. M., Nirula, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Heart+rate%3A+is+it+truly+a+vital+sign%3F%5BTitle%5D)+AND+%22J+Trauma%22%5BJournal%5D)">Heart rate: is it truly a vital sign?</a> J Trauma. 62 (4), 812-817 (2007).</li>
<li>De Backer, D., Ortiz, J. A., Salgado, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Coupling+microcirculation+to+systemic+hemodynamics%5BTitle%5D)+AND+%22Curr+Opin+Crit+Care%22%5BJournal%5D)">Coupling microcirculation to systemic hemodynamics.</a> Curr Opin Crit Care. 16 (3), 250-254 (2010).</li>
<li>Mrgan, M., Rytter, D., Brabrand, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Capillary+refill+time+is+a+predictor+of+short-term+mortality+for+adult+patients+admitted+to+a+medical+department%3A+an+observational+cohort+study%5BTitle%5D)+AND+%22Emerg+Med+J%22%5BJournal%5D)">Capillary refill time is a predictor of short-term mortality for adult patients admitted to a medical department: an observational cohort study.</a> Emerg Med J. 31 (12), 954-958 (2014).</li>
<li>Advanced Life Support, G. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aAdvanced+Life+Support%2C+G+%22Acute+Medical+Emergencies%22">Acute Medical Emergencies</a>. , Wiley-Blackwell. 55-65 (2010).</li>
<li>Lewin, J., Maconochie, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Capillary+refill+time+in+adults%5BTitle%5D)+AND+%22Emerg+Med+J%22%5BJournal%5D)">Capillary refill time in adults.</a> Emerg Med J. 25 (6), 325-326 (2008).</li>
<li>Lobos, A. T., Menon, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+multidisciplinary+survey+on+capillary+refill+time%3A+Inconsistent+performance+and+interpretation+of+a+common+clinical+test%5BTitle%5D)+AND+%22Pediatr+Crit+Care+Med%22%5BJournal%5D)">A multidisciplinary survey on capillary refill time: Inconsistent performance and interpretation of a common clinical test.</a> Pediatr Crit Care Med. 9 (4), 386-391 (2008).</li>
<li>Otieno, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Are+bedside+features+of+shock+reproducible+between+different+observers%3F%5BTitle%5D)+AND+%22Arch+Dis+Child%22%5BJournal%5D)">Are bedside features of shock reproducible between different observers?</a> Arch Dis Child. 89 (10), 977-979 (2004).</li>
<li>Raju, N. V., Maisels, M. J., Kring, E., Schwarz-Warner, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Capillary+refill+time+in+the+hands+and+feet+of+normal+newborn+infants%5BTitle%5D)+AND+%22Clin+Pediatr+%28Phila%29%22%5BJournal%5D)">Capillary refill time in the hands and feet of normal newborn infants.</a> Clin Pediatr (Phila). 38 (3), 139-144 (1999).</li>
<li>Klupp, N. L., Keenan, A. M. <a target="_blank" href="http://www.sciencedirect.com/science/article/pii/S0958259206000940">An evaluation of the reliability and validity of capillary refill time test.</a> The Foot. 17, 15-20 (2007).</li>
<li>Gorelick, M. H., Shaw, K. N., Baker, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effect+of+ambient+temperature+on+capillary+refill+in+healthy+children%5BTitle%5D)+AND+%22Pediatrics%22%5BJournal%5D)">Effect of ambient temperature on capillary refill in healthy children.</a> Pediatrics. 92 (5), 699-702 (1993).</li>
<li>Schriger, D. L., Baraff, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Defining+normal+capillary+refill%3A+variation+with+age%2C+sex%2C+and+temperature%5BTitle%5D)+AND+%22Ann+Emerg+Med%22%5BJournal%5D)">Defining normal capillary refill: variation with age, sex, and temperature.</a> Ann Emerg Med. 17 (9), 932-935 (1988).</li>
<li>Pandey, A., John, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Capillary+refill+time.+Is+it+time+to+fill+the+gaps%3F%5BTitle%5D)+AND+%22Med+J+Armed+Forces+India%22%5BJournal%5D)">Capillary refill time. Is it time to fill the gaps?</a> Med J Armed Forces India. 69 (1), 97-98 (2013).</li>
<li>Strozik, K. S., Pieper, C. H., Roller, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Capillary+refilling+time+in+newborn+babies%3A+normal+values%5BTitle%5D)+AND+%22Arch+Dis+Child+Fetal+Neonatal+Ed%22%5BJournal%5D)">Capillary refilling time in newborn babies: normal values.</a> Arch Dis Child Fetal Neonatal Ed. 76 (3), F193-F196 (1997).</li>
<li>Doherty, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Sub-epidermal+imaging+using+polarized+light+spectroscopy+for+assessment+of+skin+microcirculation%5BTitle%5D)+AND+%22Skin+Res+Technol%22%5BJournal%5D)">Sub-epidermal imaging using polarized light spectroscopy for assessment of skin microcirculation.</a> Skin Res Technol. 13 (4), 472-484 (2007).</li>
<li>Noguchi, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effect+of+caffeine+contained+in+a+cup+of+coffee+on+microvascular+function+in+healthy+subjects%5BTitle%5D)+AND+%22J+Pharmacol+Sci%22%5BJournal%5D)">Effect of caffeine contained in a cup of coffee on microvascular function in healthy subjects.</a> J Pharmacol Sci. 127 (2), 217-222 (2015).</li>
<li>Reus, W. F., Robson, M. C., Zachary, L., Heggers, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Acute+effects+of+tobacco+smoking+on+blood+flow+in+the+cutaneous+micro-circulation%5BTitle%5D)+AND+%22Br+J+Plast+Surg%22%5BJournal%5D)">Acute effects of tobacco smoking on blood flow in the cutaneous micro-circulation.</a> Br J Plast Surg. 37 (2), 213-215 (1984).</li>
<li>Lenasi, H., Strucl, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effect+of+regular+physical+training+on+cutaneous+microvascular+reactivity%5BTitle%5D)+AND+%22Med+Sci+Sports+Exerc%22%5BJournal%5D)">Effect of regular physical training on cutaneous microvascular reactivity.</a> Med Sci Sports Exerc. 36 (4), 606-612 (2004).</li>
<li>Anderson, B., Kelly, A. M., Kerr, D., Clooney, M., Jolley, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Impact+of+patient+and+environmental+factors+on+capillary+refill+time+in+adults%5BTitle%5D)+AND+%22Am+J+Emerg+Med%22%5BJournal%5D)">Impact of patient and environmental factors on capillary refill time in adults.</a> Am J Emerg Med. 26 (1), 62-65 (2008).</li>
<li>John, R. T., Henricson, J., Nilsson, G. E., Wilhelms, D., Anderson, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Reflectance+spectroscopy%3A+to+shed+new+light+on+the+capillary+refill+test%5BTitle%5D)+AND+%22J+Biophotonics%22%5BJournal%5D)">Reflectance spectroscopy: to shed new light on the capillary refill test.</a> J Biophotonics. , (2017).</li>
<li>Blaxter, L. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+automated+quasi-continuous+capillary+refill+timing+device%5BTitle%5D)+AND+%22Physiological+measurement%22%5BJournal%5D)">An automated quasi-continuous capillary refill timing device.</a> Physiological measurement. 37, 83-99 (2016).</li>
<li>Bordoley, A., Irwin, R., Kalyani, V., MacDonald, C., Standish, D. <a target="_blank" href="https://debut.devpost.com/submissions/8131-d1git-automated-temperature-calibrated-measurement-of-capillary-refill-time">D1GIT: Automated, temperature-calibrated measurement of capillary refill time</a>. , (2012).</li>
<li>Kviesis-Kipge, E., Curkste, E., Spigulis, J., Eihvalde, L. <a target="_blank" href="https://www.spiedigitallibrary.org/conference-proceedings-of-spie/7715/1/Real-time-analysis-of-skin-capillary-refill-processes-using-blue/10.1117/12.854263.short?SSO=1">Real-time analysis of skin capillary-refill processes using blue LED.</a> Proc. of SPIE. 771523, (2010).</li>
<li>Shavit, I., Brant, R., Nijssen-Jordan, C., Galbraith, R., Johnson, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+novel+imaging+technique+to+measure+capillary-refill+time%3A+improving+diagnostic+accuracy+for+dehydration+in+young+children+with+gastroenteritis%5BTitle%5D)+AND+%22Pediatrics%22%5BJournal%5D)">A novel imaging technique to measure capillary-refill time: improving diagnostic accuracy for dehydration in young children with gastroenteritis.</a> Pediatrics. 118 (6), 2402-2408 (2006).</li>
<li>Cohen, J., et al. <a target="_blank" href="https://www.hindawi.com/journals/isrn/2013/578316/">Monitor to Measure Dermal Blood Flow in Critically Ill Patients: Study.</a> International Scholarly Research Notices. 578316, e578316(2013).</li>
</ol>

No financial support from WheelsBridge AB was involved in the conduct of the study. The author JH is employed by the &#214;sterg&#246;tland County Council but has a royalty agreement with WheelsBridge AB. The senior author CDA has a full-time academic position but also limited involvement in WheelsBridge AB.

In order to get the best results with the system, variability caused by environmental factors must be controlled. All ambient light must be turned off. The camera must be positioned in vertical alignment with the measurement area. In order to ensure a constant measurement area, subjects should not move or talk during measurement. For the same reason, the camera is preferably mounted on a stand to avoid movement and to maintain a constant distance to the measurement area. Test subjects should avoid caffeine<sup class="xre...

Assessment and triage of the critically ill patient centers on the classical vital signs blood pressure (BP), heart rate (HR), respiratory rate (RR), oxygen saturation, and body temperature1. Changes in these parameters appear relatively late in the course of circulatory deterioration. For instance, in hemorrhage, a decrease in BP will not occur until blood loss becomes moderate to severe2, and HR increase can also be an insensitive and unspecific marker3.
The capillary refill test (CR test) may offer an earlier indication of incipient circulatory collapse, as the refill time is believed to change prior to the vital signs as well as clinical appearance of cold, clammy, and mottled skin1,4,5. The capillary refill test is typically performed by application and then release of a firm blanching pressure to the skin with timing (in seconds) of the return of blood to the blanched area. According to guidelines, refill should occur within 2 seconds after release of 5 seconds of firm pressure (e.g., by the physician&#39;s finger) in the normal healthy supine patient6. The rationale for the test is that a slower refill time would indicate poor skin perfusion, possible caused by one of a number of critical events such as sepsis, blood loss, acute heart failure, or hypothermia.
At present, there is no consensus on a state of the art method for performing the CR test6,7,8,9,10. Contentious issues include lack of standardization of the actual blanching maneuver and the dependence on subjective (i.e., naked eye) assessments of the refill endpoint7,9,11. Furthermore, there are indications that gender influences CR time12,13. The temperature, both ambient and skin, is known to affect the capillary refill time, but to what extent is not clear. Lastly, the use of different measurement sites, peripheral or central, is probably a further cause of variability in results with few studies in this area14,15.
In the present work, we used an optical bioengineering system to record the course of return of blood and the subsequent hyperemic response seen during the CR test. The system utilizes diffuse polarization spectroscopy to quantify and describe, in more detail than possible with the naked eye, the time and course of the capillary refill. The system comprises a standard digital camera, fitted with an external light ring with 92 white LEDs, and specially developed software. The lens and the two polarization filters, attached orthogonally in front of the LEDs, block light that has been directly reflected from the skin surface allowing only light that has become depolarized in the tissue to reach the camera. This generates a &#34;sub-epidermal&#34; image of the tissue to a depth of approximately 0.5 mm. The image is divided into its color planes and the red and green content for every pixel is calculated, generating a value which corresponds to the tissue concentration of red blood cells16. In video mode, the temporal resolution of the system is 0.02 s.

<table><tbody><tr><td>TiVi701 Camera</td><td>WheelsBridge AB</td><td>TiVi701 Camera, version 1.5.1</td><td>Software</td></tr><tr><td>TiVi700</td><td>WheelsBridge AB</td><td>TiVi700 Analysis, version 1.2.9</td><td>Software</td></tr><tr><td>Canon EOS 700D</td><td>Canon U.S.A., inc.</td><td>Canon EOS 700D</td><td>Digital SLR Camera</td></tr><tr><td>Camera stand</td><td>Manfrotto</td><td>681B</td><td>Modified camera stand to hold the digital camera in position</td></tr><tr><td>Camera stand</td><td>Disa Denmark</td><td>9020B</td><td>Modified camera stand to hold the digital camera in position</td></tr></tbody></table>

diffuse reflectance spectroscopy: getting the capillary refill test under one's thumb

The capillary refill test was introduced in 1947 to help estimate circulatory status in critically ill patients. Guidelines commonly state that refill should occur within 2 s after releasing 5 s of firm pressure (e.g., by the physician&#39;s finger) in the normal healthy supine patient. A slower refill time indicates poor skin perfusion, which can be caused by conditions including sepsis, blood loss, hypoperfusion, and hypothermia. Since its introduction, the clinical usefulness of the test has been debated. Advocates point out its feasibility and simplicity and claim that it can indicate changes in vascular status earlier than changes in vital signs such as heart rate. Critics, on the other hand, stress that the lack of standardization in how the test is performed and the highly subjective nature of the naked eye assessment, as well as the test&#39;s susceptibility to ambient factors, markedly lowers the clinical value. The aim of the present work is to describe in detail the course of the refill event and to suggest potentially more objective and exact endpoint values for the capillary refill test using diffuse polarization spectroscopy.

Filming the course of the capillary refilling generates vast amounts of data not possible to obtain by naked eye assessment. We suggest here new endpoints to further improve the usability of the CR test as an early indicator of deterioration in circulatory status. We call these endpoints: "Baseline," "Blood Zero" (or "BZ"), "Time to Return to Baseline 1" (or "tRtB1"), "Time to Peak" or "Tpk." The "Baseline" value is derived by calculating a mean value of all the values obtained during t...

Watch this Scientific Journal Video about Diffuse Reflectance Spectroscopy: Getting the Capillary Refill Test Under One's Thumb at JoVE.com

Diffuse Reflectance Spectroscopy: Getting the Capillary Refill Test Under One's Thumb

This protocol describes how the use of diffuse polarization spectroscopy can improve the clinical usefulness of the capillary refill test. We suggest a more detailed analysis of the course of the capillary refill in healthy volunteers using diffuse reflectance spectroscopy videos and new informatic endpoints.

The capillary refill test was introduced in 1947 to help estimate circulatory status in critically ill patients. Guidelines commonly state that refill ...

diffuse-reflectance-spectroscopy-getting-capillary-refill-test-under

Research

Education

JoVE Core

JoVE Journal

Medical-Surgical Nursing

Neuroscience

Unit 1

An Overview of the Cardiovascular System: Anatomy, Physiology, Assessment, and Abnormalities

SCIENTISTS IN ACTION

9.1K Views.  Region Östergötland. Dit protocol wordt beschreven hoe het gebruik van diffuse polarisatie spectroscopie de klinische bruikbaarheid van de capillary refill test kunt verbeteren. Wij stellen voor een meer gedetailleerde analyse van het verloop van de capillary refill bij gezonde vrijwilligers met behulp van diffuse reflectie spectroscopie video's en nieuwe informatic eindpunten.

Video: Diffuse Reflectance Spectroscopy: Getting the Capillary Refill Test Under One's Thumb

Dual-mode Imaging of Cutaneous Tissue Oxygenation and Vascular Function

Accurate assessment of cutaneous tissue oxygenation and vascular function is important for appropriate detection, staging, and treatment of many health disorders such as chronic wounds. We report the development of a dual-mode imaging system for non-invasive and non-contact imaging of cutaneous tissue oxygenation and vascular function. The imaging system integrated an infrared camera, a CCD camera, a liquid crystal tunable filter and a high intensity fiber light source. A Labview interface was programmed for equipment control, synchronization, image acquisition, processing, and visualization. Multispectral images captured by the CCD camera were used to reconstruct the tissue oxygenation map. Dynamic thermographic images captured by the infrared camera were used to reconstruct the vascular function map. Cutaneous tissue oxygenation and vascular function images were co-registered through fiduciary markers. The performance characteristics of the dual-mode image system were tested in humans.

A dual-mode imaging system was developed for non-contact assessment of cutaneous tissue oxygenation and vascular function.

Accurate assessment of cutaneous tissue oxygenation and vascular function is important for appropriate detection, staging, and treatment of many health ...

Medicine

Synthesis and Operation of Fluorescent-core Microcavities for Refractometric Sensing

This paper discusses fluorescent core microcavity-based sensors that can operate in a microfluidic analysis setup. These structures are based on the formation of a fluorescent quantum-dot (QD) coating on the channel surface of a conventional microcapillary. Silicon QDs are especially attractive for this application, owing in part to their negligible toxicity compared to the II-VI and II-VI compound QDs, which are legislatively controlled substances in many countries. While the ensemble emission spectrum is broad and featureless, an Si-QD film on the channel wall of a capillary features a set of sharp, narrow peaks in the fluorescence spectrum, corresponding to the electromagnetic resonances for light trapped within the film. The peak wavelength of these resonances is sensitive to the external medium, thus permitting the device to function as a refractometric sensor in which the QDs never come into physical contact with the analyte. The experimental methods associated with the fabrication of the fluorescent-core microcapillaries are discussed in detail, as well as the analysis methods. Finally, a comparison is made between these structures and the more widely investigated liquid-core optical ring resonators, in terms of microfluidic sensing capabilities.

Fluorescent-core microcavity sensors employ a high-index quantum-dot coating in the channel of silica microcapillaries. Changes in the refractive index of fluids pumped into the capillary channel cause shifts in the microcavity fluorescence spectrum that can be used to analyze the channel medium.

This paper discusses  fluorescent core microcavity-based sensors that can operate in a microfluidic  analysis setup. These structures are based on the ...

Engineering

Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers. A typical inkjet ink is a colloidal dispersion containing approximately ten components including solvent, the nano to micron scale particles which will comprise the printed layer, polymeric dispersants to stabilize the particles, and polymers to tune layer strength, surface tension and viscosity. To rationally and efficiently formulate such an ink, it is crucial to know how the components interact. Specifically, which polymers bond to the particle surfaces and how are they attached? Answering this question requires an experimental procedure that discriminates between polymer adsorbed on the particles and free polymer. Further, the method must provide details about how the functional groups of the polymer interact with the particle. In this protocol, we show how to employ centrifugation to separate particles with adsorbed polymer from the rest of the ink, prepare the separated samples for spectroscopic measurement, and use Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) for accurate determination of dispersant/particle bonding mechanisms. A significant advantage of this methodology is that it provides high level mechanistic detail using only simple, commonly available laboratory equipment. This makes crucial data available to almost any formulation laboratory. The method is most useful for inks composed of metal, ceramic, and metal oxide particles in the range of 100 nm or greater. Because of the density and particle size of these inks, they are readily separable with centrifugation. Further, the spectroscopic signatures of such particles are easy to distinguish from absorbed polymer. The primary limitation of this technique is that the spectroscopy is performed ex-situ on the separated and dried particles as opposed to the particles in dispersion. However, results from attenuated total reflectance spectra of the wet separated particles provide evidence for the validity of the DRIFTS measurement.

Formulation of stable, functional inks is critical to expanding the applications of additive manufacturing. In turn, knowledge of the mechanisms of dispersant/particle bonding is required for effective ink formulation. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) is presented as a simple, inexpensive way to gain insight into these mechanisms.

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers.  A typical inkjet ink is a colloidal ...

Chemistry

Non-invasive Assessment of Microvascular and Endothelial Function

The authors have utilized capillaroscopy and forearm blood flow techniques to investigate the role of microvascular dysfunction in pathogenesis of cardiovascular disease. Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. Percent capillary recruitment is assessed by dividing the increase in capillary density induced by postocclusive reactive hyperemia (postocclusive reactive hyperemia capillary density minus baseline capillary density), by the maximal capillary density (observed during passive venous occlusion). Percent perfused capillaries represents the proportion of all capillaries present that are perfused (functionally active), and is calculated by dividing postocclusive reactive hyperemia capillary density by the maximal capillary density. Both percent capillary recruitment and percent perfused capillaries reflect the number of functional capillaries. The forearm blood flow (FBF) technique provides accepted non-invasive measures of endothelial function: The ratio FBFmax/FBFbase is computed as an estimate of vasodilation, by dividing the mean of the four FBFmax values by the mean of the four FBFbase values. Forearm vascular resistance at maximal vasodilation (FVRmax) is calculated as the mean arterial pressure (MAP) divided by FBFmax. Both the capillaroscopy and forearm techniques are readily acceptable to patients and can be learned quickly.
The microvascular and endothelial function measures obtained using the methodologies described in this paper may have future utility in clinical patient cardiovascular risk-reduction strategies. As we have published reports demonstrating that microvascular and endothelial dysfunction are found in initial stages of hypertension including prehypertension, microvascular and endothelial function measures may eventually aid in early identification, risk-stratification and prevention of end-stage vascular pathology, with its potentially fatal consequences.

Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. The forearm blood flow technique provides accepted non-invasive measures of endothelial function.

The authors have utilized capillaroscopy and forearm blood flow techniques to investigate the role of microvascular dysfunction in pathogenesis of ...

Multimodal Imaging and Spectroscopy Fiber-bundle Microendoscopy Platform for Non-invasive, In Vivo Tissue Analysis

Recent fiber-bundle microendoscopy techniques enable non-invasive analysis of in vivo tissue using either imaging techniques or a combination of spectroscopy techniques. Combining imaging and spectroscopy techniques into a single optical probe may provide a more complete analysis of tissue health. In this article, two dissimilar modalities are combined, high-resolution fluorescence microendoscopy imaging and diffuse reflectance spectroscopy, into a single optical probe. High-resolution fluorescence microendoscopy imaging is a technique used to visualize apical tissue micro-architecture and, although mostly a qualitative technique, has demonstrated effective real-time differentiation between neoplastic and non-neoplastic tissue. Diffuse reflectance spectroscopy is a technique which can extract tissue physiological parameters including local hemoglobin concentration, melanin concentration, and oxygen saturation. This article describes the specifications required to construct the fiber-optic probe, how to build the instrumentation, and then demonstrates the technique on in vivo human skin. This work revealed that tissue micro-architecture, specifically apical skin keratinocytes, can be co-registered with its associated physiological parameters. The instrumentation and fiber-bundle probe presented here can be optimized as either a handheld or endoscopically-compatible device for use in a variety of organ systems. Additional clinical research is needed to test the viability of this technique for different epithelial disease states.

Multimodal Imaging and Spectroscopy Fiber-bundle Microendoscopy Platform for Non-invasive, In Vivo Tissue Analysis

The assembly and use of a multimodal microendoscope is described which can co-register superficial tissue image data with tissue physiological parameters including hemoglobin concentration, melanin concentration, and oxygen saturation. This technique can be useful for evaluating tissue structure and perfusion, and can be optimized for individual needs of the investigator.

Recent fiber-bundle microendoscopy techniques enable non-invasive analysis of in vivo tissue using either imaging techniques or a combination of ...

Bioengineering

A Reproducible Computerized Method for Quantitation of Capillary Density using Nailfold Capillaroscopy

Capillaroscopy is a non-invasive, efficient, relatively inexpensive and easy to learn methodology for directly visualizing the microcirculation. The capillaroscopy technique can provide insight into a patient&#8217;s microvascular health, leading to a variety of potentially valuable dermatologic, ophthalmologic, rheumatologic and cardiovascular clinical applications. In addition, tumor growth may be dependent on angiogenesis, which can be quantitated by measuring microvessel density within the tumor. However, there is currently little to no standardization of techniques, and only one publication to date reports the reliability of a currently available, complex computer based algorithms for quantitating capillaroscopy data.1 This paper describes a new, simpler, reliable, standardized capillary counting algorithm for quantitating nailfold capillaroscopy data. A simple, reproducible computerized capillaroscopy algorithm such as this would facilitate more widespread use of the technique among researchers and clinicians. Many researchers currently analyze capillaroscopy images by hand, promoting user fatigue and subjectivity of the results. This paper describes a novel, easy-to-use automated image processing algorithm in addition to a reproducible, semi-automated counting algorithm. This algorithm enables analysis of images in minutes while reducing subjectivity; only a minimal amount of training time (in our experience, less than 1 hr) is needed to learn the technique.

Capillaroscopy is a non-invasive, efficient, relatively inexpensive and easy-to-learn methodology for directly visualizing capillaries in the microcirculation. However, only one publication to date describes the reliability of a complex software program available for quantitating capillaroscopy data. Here, we present a simple, reliable protocol for quantitating capillaries using a standardized algorithm.

Capillaroscopy is a non-invasive, efficient, relatively inexpensive and easy to learn methodology for directly visualizing the microcirculation. The ...

Agarose-based Tissue Mimicking Optical Phantoms for Diffuse Reflectance Spectroscopy

This protocol describes how to make agarose-based tissue-mimicking phantoms and demonstrates how to determine their optical properties using a conventional optical system with an integrating sphere. Measuring systems for the acquisition of the diffuse reflectance and total transmittance spectra are constructed with a broadband white light source, a light guide, an achromatic lens, an integrating sphere, a sample holder, an optical fiber probe, and a multi-channel spectrometer. An acrylic mold consisting of two rectangular acrylic pieces and a U-shaped acrylic piece is constructed to create an epidermal phantom and a dermal phantom with whole blood. The application of a sodium dithionite (Na2S2O4) solution to the dermal phantom enables the researcher to deoxygenate hemoglobin in red blood cells distributed in the dermal phantom. The inverse Monte Carlo simulation with the diffuse reflectance and total transmittance spectra measured by a spectrometer with an integrating sphere is performed to determine the absorption coefficient spectrum &#181;a(&#955;) and the reduced scattering coefficient spectrum &#181;s&#39;(&#955;) of each layer phantom. A two-layered phantom mimicking the diffuse reflectance of human skin tissue is also demonstrated by piling up the epidermal phantom on the dermal phantom.

Here, we demonstrate how agarose-based tissue-mimicking optical phantoms are made and how their optical properties are determined using a conventional optical system with an integrating sphere.

This protocol describes how to make agarose-based tissue-mimicking phantoms and demonstrates how to determine their optical properties using a ...

Simultaneous Evaluation of Cerebral Hemodynamics and Light Scattering Properties of the In Vivo Rat Brain Using Multispectral Diffuse Reflectance Imaging

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional multispectral diffuse reflectance imaging system. This system is constructed from a broadband white light source, a motorized filter wheel with a set of narrowband interference filters, a light guide, a collecting lens, a video zoom lens, and a monochromatic charged-coupled device (CCD) camera. An ellipsoidal cranial window is made in the skull bone of a rat under isoflurane anesthesia to capture in vivo multispectral diffuse reflectance images of the cortical surface. Regulation of the fraction of inspired oxygen using a gas mixture device enables the induction of different respiratory states such as normoxia, hyperoxia, and anoxia. A Monte Carlo simulation-based multiple regression analysis for the measured multispectral diffuse reflectance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) is then performed to visualize the two-dimensional maps of hemodynamics and the light scattering properties of the in vivo rat brain.

Simultaneous Evaluation of Cerebral Hemodynamics and Light Scattering Properties of the In Vivo Rat Brain Using Multispectral Diffuse Reflectance Imaging

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional multispectral diffuse reflectance imaging system.

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional ...

Real-Time Monitoring of Neurocritical Patients with Diffuse Optical Spectroscopies

Neurophysiological monitoring is an important goal in the treatment of neurocritical patients, as it may prevent secondary damage and directly impact morbidity and mortality rates. However, there is currently a lack of suitable non-invasive, real-time technologies for continuous monitoring of cerebral physiology at the bedside. Diffuse optical techniques have been proposed as a potential tool for bedside measurements of cerebral blood flow and cerebral oxygenation in case of neurocritical patients. Diffuse optical spectroscopies have been previously explored to monitor patients in several clinical scenarios ranging from neonatal monitoring to cerebrovascular interventions in adults. However, the feasibility of the technique to aid clinicians by providing real-time information at the bedside remains largely unaddressed. Here, we report the translation of a diffuse optical system for continuous real-time monitoring of cerebral blood flow, cerebral oxygenation, and cerebral oxygen metabolism during intensive care. The real-time feature of the instrument could enable treatment strategies based on patient-specific cerebral physiology rather than relying on surrogate metrics, such as arterial blood pressure. By providing real-time information on the cerebral circulation at different time scales with relatively cheap and portable instrumentation, this approach may be especially useful in low-budget hospitals, in remote areas and for&#160;monitoring in open fields (e.g., defense and sports).

Presented here is a protocol for non-invasively monitoring cerebral hemodynamics of neurocritical patients in real-time and at the bedside using diffuse optics. Specifically, the proposed protocol uses a hybrid diffuse optical systems to detect and display real-time information on cerebral oxygenation, cerebral blood flow and cerebral metabolism.

Neurophysiological monitoring is an important goal in the treatment of neurocritical patients, as it may prevent secondary damage and directly impact ...

Non-Invasive Monitoring of Microvascular Oxygenation and Reactive Hyperemia using Hybrid, Near-Infrared Diffuse Optical Spectroscopy for Critical Care

The detection of levels of impairment in microvascular oxygen consumption and reactive hyperemia is vital in critical care. However, there are no practical means for a robust and quantitative evaluation. This paper describes a protocol to evaluate these impairments using a hybrid near-infrared diffuse optical device. The device contains modules for near-infrared time-resolved and diffuse correlation spectroscopies and pulse-oximetry. These modules allow the non-invasive, continuous, and real-time measurement of the absolute, microvascular blood/tissue oxygen saturation (StO2) and the blood flow index (BFI) along with the peripheral arterial oxygen saturation (SpO2). This device uses an integrated, computer-controlled tourniquet system to execute a standardized protocol with optical data acquisition from the brachioradialis muscle. The standardized vascular occlusion test (VOT) takes care of the variations in the occlusion duration and pressure reported in the literature, while the automation minimizes inter-operator differences. The protocol we describe focuses on a 3-min occlusion period but the details described in this paper can readily be adapted to other durations and cuff pressures, as well as other muscles. The inclusion of an extended baseline and post-occlusion recovery period measurement allows the quantification of the baseline values for all the parameters and the blood/tissue deoxygenation rate that corresponds to the metabolic rate of oxygen consumption. Once the cuff is released, we characterize the tissue reoxygenation rate, magnitude, and duration of the hyperemic response in BFI and StO2. These latter parameters correspond to the quantification of the reactive hyperemia, which provides information about the endothelial function. Furthermore, the above-mentioned measurements of the absolute concentration of oxygenated and deoxygenated hemoglobin, BFI, the derived metabolic rate of oxygen consumption, StO2, and SpO2 provide a yet-to-be-explored rich data set that can exhibit disease severity, personalized therapeutics, and management interventions.

We describe a protocol to non-invasively and continuously measure absolute microvascular blood flow index and blood oxygen saturation using a multi-modal device based on near-infrared diffuse optics. We then evaluate the metabolic rate of oxygen consumption and reactive hyperemia utilizing a vascular occlusion test.

Diffuse Reflectance Spectroscopy: Getting the Capillary Refill Test Under One's Thumb

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