| 1. |
- Kvernebo, Anne Kari, et al.
(författare)
-
Quantification of ocular surface microcirculation by computer assisted video microscopy and diffuse reflectance spectroscopy
- 2020
-
Ingår i: Experimental Eye Research. - : ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD. - 0014-4835 .- 1096-0007. ; 201
-
Tidskriftsartikel (refereegranskat)abstract
- In piglets we tested the applicability of digital video microscopy and diffuse reflectance spectroscopy for non-invasive assessments of limbal and bulbar conjunctival microcirculation. A priori we postulated that the metabolic rate is higher in limbal as compared to bulbar conjunctiva, and that this difference is reflected in micro vascular structure or function between the two locations. Two study sites, Oslo University Hospital (OUH), Norway and Cleveland Clinic (CC), USA, used the same video microscopy and spectroscopy techniques to record limbal and bulbar microcirculation in sleeping piglets. Recordings were analyzed with custom-made software to quantify functional capillary density, capillary flow velocity and microvascular oxygen saturation in measuring volumes of approximately 0.1 mm(3). The functional capillary density was higher in limbus than in bulbar conjunctiva at both study sites (OUH: 18.1 +/- 2.9 versus 12.2 +/- 2.9 crossings per mm line, p < 0.01; CC: 11.3 +/- 3.0 versus 7.1 +/- 2.8 crossings per mm line, p < 0.01). Median categorial capillary blood flow velocity was higher in bulbar as compared with limbal recordings (CC: 3 (1-3) versus 1 (0-3), p < 0.01). Conjunctival microvascular oxygen saturation was 88 +/- 5.9% in OUH versus 94 +/- 7.5% in CC piglets. Non-invasive digital video microscopy and diffuse reflectance spectroscopy can be used to obtain data from conjunctival microcirculation in piglets. Limbal conjunctival microcirculation has a larger capacity for oxygen delivery as compared with bulbar conjunctiva.
|
|
| 2. |
- Namer, Barbara, et al.
(författare)
-
Specific changes in conduction velocity recovery cycles of single nociceptors in a patient with erythromelalgia with the I848T gain-of-function mutation of Na(v)1.7
- 2015
-
Ingår i: Pain. - : Ovid Technologies (Wolters Kluwer Health). - 0304-3959 .- 1872-6623. ; 156:9, s. 1637-1646
-
Tidskriftsartikel (refereegranskat)abstract
- Seven patients diagnosed with erythromelalgia (EM) were investigated by microneurography to record from unmyelinated nerve fibers in the peroneal nerve. Two patients had characterized variants of sodium channel Na(v)1.7 (I848T, I228M), whereas no mutations of coding regions of Na(v)s were found in 5 patients with EM. Irrespective of Na(v)1.7 mutations, more than 50% of the silent nociceptors in the patients with EM showed spontaneous activity. In the patient with mutation I848T, all nociceptors, but not sympathetic efferents, displayed enhanced early subnormal conduction in the velocity recovery cycles and the expected late subnormality was reversed to supranormal conduction. The larger hyperpolarizing shift of activation might explain the difference to the I228M mutation. Sympathetic fibers that lack Na(v)1.8 did not show supranormal conduction in the patient carrying the I848T mutation, confirming in human subjects that the presence of Na(v)1.8 crucially modulates conduction in cells expressing EM mutant channels. The characteristic pattern of changes in conduction velocity observed in the patient with the I848T gain-of function mutation in Na(v)1.7 could be explained by axonal depolarization and concomitant inactivation of Na(v)1.7. If this were true, activity-dependent hyperpolarization would reverse inactivation of Na(v)1.7 and account for the supranormal CV. This mechanism might explain normal pain thresholds under resting conditions.
|
|
| 3. |
- Wester, Torjus, et al.
(författare)
-
Skin microvascular morphology and hemodynamics during treatment with veno-arterial extra-corporeal membrane oxygenation
- 2014
-
Ingår i: Clinical hemorheology and microcirculation. - : IOS Press. - 1386-0291 .- 1875-8622. ; 56:2, s. 119-131
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: To explore the potentials of microcirculatory assessments for predicting outcome of patients treated with extra corporeal membrane oxygenation for cardiogenic shock. Methods: Eight patients with acute cardiogenic shock treated with ECMO and eight healthy controls were examined with skin vital microscopy and laser Doppler perfusion measurements. Results: Three patients died on ECMO (group 1). Five patients were successfully weaned off ECMO (group 2). Four patients were discharged from hospital and one died after successful weaning from bleeding complications. Patients surviving ECMO (group 2) had microcirculatory findings comparable with healthy controls. Patients in group 1 showed major skin microvascular pathology: pericapillary bleedings (n = 1), pericapillary dark haloes (n = 2) and capillary micro thrombi (n = 1). As compared with survivors they had lower functional capillary density (FCD) (n = 3), higher heterogeneity of functional capillary density (n = 3) and significantly reduced capillary mean flow-categorical velocity (n = 2). Laser Doppler measurements in group 1 had non-significant lower laser Doppler flux values as compared with survivors and controls. Conclusion: Skin microvascular pathology as detected with video microscopy (pericapillary bleedings or haloes, micro-thrombi/capillaries with “no flow”, low FCD with high spatial distribution heterogeneity or low mean flow-categorial velocity seems to be associated with poor prognosis.
|
|
| 4. |
- Asker, Claes, et al.
(författare)
-
Computer assisted evaluation of skin capillary density supports the hypothesis of microvascular shunting in erythromelalgia
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Erythromelalgia subjects often suffer from burning pain in distal parts of the extremities, aggravated by warmth and relieved by cooling. Affected skin is hyperemic and has an increased skin temperature. The shunting hypothesis for the pathogenesis of erythromelalgia, postulates maldistribution of skin microvascular blood flow with increased thermoregulatory flow through arteriovenous shunts and an inadequate nutritive perfusion with a corresponding tissue hypoxia. Our aim was to characterize recruitment and steal distribution changes in affected skin with the aid of an enhanced technique of computer-assisted analysis of capillary beds. This method was used to determine the capillary density before and after central body heating in 14 patients with erythromelalgia and 10 controls. Symptoms were induced in 8 patients and their skin temperature became higher (p<0.05) after central body heating, but the number of visible or active capillaries in the dorsal aspect of the foot decreased significantly, as compared to asymptomatic patients and controls. Since the increased temperature should, normally induce capillary recruitment, and other studies using laser Doppler techniques have shown an increase in global skin perfusion during EM attacks, we conclude that the reduced capillary density shown in this study, is compatible with the hypothesis of blood shunting through AV anastomoses, deep in the dermis.
|
|
| 5. |
- Bergkvist, Max, 1976-
(författare)
-
Studies on Polarised Light Spectroscopy
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis project focuses on measurements of dermal microcirculation during vascular provocations with polarised light spectroscopy. This is done with a non-invasive method commercially available as Tissue viability imaging (TiVi) which measures concentration and oxygenation of red blood cells in the papillary dermis. Three studies were done with human subjects and one with an animal model, to validate and compare the TiVi technique with laser Doppler flowmetry, which is an established method of measuring dermal microcirculation.The TiVi consists of a digital camera with polarisation filters in front of the flash and lens, with software for analysis of the picture. When taking a picture with the TiVi, the polarised light that is reflected on the skin surface is absorbed by the second filter over the lens (which is perpendicular to the first filter) but a portion of light penetrates the surface of the skin and is scattered when it is reflected on tissue components. This makes the light depolarised, passes the second filter, and produces a picture for analysis. The red blood cell (RBC) has a distinct absorption pattern that differs between red and green colour compared to melanin and other components of tissue. This difference is used by the software that calculates differences in each picture element and produces a measure of output which is proportional to the concentration of red blood cells. The oxygenation of RBC can also be calculated, as there is a difference in absorption depending on oxygen state.The first paper takes up possible sources of error such as ambient light, and the angle and distance of the camera. The main experiment was to investigate how the local heating reaction is detected with TiVi compared to LDF.In the second paper arterial and venous stasis are examined in healthy subjects with TiVi.The Third paper is an animal study where skin flaps were raised on pigs, and the vascular pedicle is isolated to enable control of inflow and outflow of blood.The measurements were made during partial venous, total venous, and total arterial occlusion. The TiVi recorded changes in the concentration of RBC, oxygenation and heterogeneity and the results were compared with those of laser Doppler flowmetry.In the fourth paper oxygenation and deoxygenation of RBC: s was studied. Studies were made on the forearms of healthy subjects who were exposed to arterial and venous occlusion. Simultaneous measurements were made with TiVi and Enhanced perfusion and oxygen saturation or EPOS, which is a new device that combines laser Doppler flowmetry and diffuse reflectance spectroscopy in one probe.With TiVi, one can measure RBC concentration and oxygenation in the area of an entire picture or in one or multiple user defined regions of interest (ROI). Methods such as laser Doppler flowmetry makes single point measurements, which is a potential source of error both because of the heterogeneity of the microcirculation, and that the circulation be insufficient in the margins of the investigated area. TiVi has been able to measure venous stasis more accurately than laser Doppler flowmetry, and venous stasis is the more common reason for flaps to fail.The TiVi is an accurate way to measure the concentration of RBC and trends in oxygenation of the dermal microcirculation. It has interesting possible applications for microvascular and dermatological research, monitoring of flaps, and diagnosis of peripheral vascular disease. Future clinical studies are needed as well as development of the user interface.
|
|
| 6. |
|
|
| 7. |
- Fredly, Siv, et al.
(författare)
-
Noninvasive assessments of oxygen delivery from the microcirculation to skin in hypothermia-treated asphyxiated newborn infants
- 2016
-
Ingår i: Pediatric Research. - : Springer Science and Business Media LLC. - 0031-3998 .- 1530-0447. ; 76:6, s. 902-906
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Therapeutic hypothermia (TH) has become standard treatment for severe and moderate hypoxic-ischemic neonatal encephalopathy (HIE). Our group has developed an optically based, noninvasive concept of assessing the capacity for oxygen delivery from the microcirculation to the cells of a tissue under investigation. The hypothesis was that mechanisms of reduced oxygen delivery due to reduced metabolism in cooled asphyxiated neonates could be characterized with this concept.METHODS:The skin of 28 asphyxiated newborn infants was studied on days 1 and 3 during TH and on day 4 following rewarming with laser Doppler perfusion measurements (LDPM), computer-assisted video microscopy (CAVM), and diffuse reflectance spectroscopy (DRS). Twenty-five healthy neonates served as a control group.RESULTS:The LDPM decreased during cooling (P < 0.01). Functional capillary density was higher both during and following TH compared with control infants (P < 0.01). Capillary flow velocities were reduced during TH (P < 0.05). The heterogeneity of the flow velocities was larger in the HIE infants than in the control infants. Tissue oxygen extraction was higher during TH (P < 0.01).CONCLUSION:This study indicates that assessments of skin microvascular density, capillary flow velocity, and oxygen extraction can be used to characterize reduced oxygen delivery to cells during TH
|
|
| 8. |
|
|
| 9. |
- Fredly, Siv, et al.
(författare)
-
Skin microcirculation in healthy term newborn infants - assessment of morphology, perfusion and oxygenation
- 2015
-
Ingår i: Clinical hemorheology and microcirculation. - : IOS Press. - 1386-0291 .- 1875-8622. ; 59:4, s. 309-322
-
Tidskriftsartikel (refereegranskat)abstract
- Despite microcirculations fundamental role, assessments of its function are limited. We explored the applicability of Computer Assisted Video Microscope (CAVM), Laser Doppler Perfusion Measurements (LDPM) and Diffuse Reflectance Spectroscopy (DRS) to study skin microvascular morphology, perfusion and oxygen saturation in twenty-five healthy newborns day 1-3 of life. Results: Day 1-3 (mean (SD)): Microvascular density (CAVM; number of microvessels crossing a grid of lines/mm line, c/mm): Chest: 11.3 (1.5), 11.0 (1.7), 10.7 (1.6). Hand: 13.2 (2.0), 13.2 (1.9), 12.4 (1.6). Capillary density was significantly higher in the hand than in the chest each day (p less than 0.001). Perfusion (LDPM; arbitrary units): Chest: 109.1 (26.0), 101.4 (24.6), 100.8 (25.3). Hand: 58.9 (17.5), 54.3 (15.8), 46.9 (14.8). Perfusion was significantly higher in the chest than in the hand each day (p less than 0.01). Microvascular oxygen saturation (DRS; %): Chest: 88.1 (5.2), 87.8 (10.0), 86.7 (9.0). Hand: 79.9 (15.2), 82.7 (11.8), 82.2 (12.1) (p less than 0.05). Capillary flow velocities (CAVM) were similar in the chest and hand: 60-70% capillaries had "continuous high flow" and 30-40% "continuous low flow". Multimodal skin microvascular assessments with CAVM, LDPM and DRS are feasible with reproducible data in newborns. The hand has lower perfusion, higher capillary density and higher oxygen extraction than the chest.
|
|
| 10. |
- Karlsson, MG Daniel, 1974-
(författare)
-
Movement artifact reduction in laser Doppler blood flowmetry : myocardial perfusion applications
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Laser Doppler perfusion monitoring (LDPM) and imaging (LDPI) enable assessment of tissue microvascular perfusion. The techniques are based on the Doppler broadening of the optical spectrum occurring when coherent laser light is scattered by moving red blood cells (RBC). However, if tissue motion not related to moving RBCs is present, artifacts arise in the derived perfusion estimate. The aim of this thesis was to develop and evaluate methods to reduce tissue motion influence on the perfusion estimate in general and for the specific purpose of enabling myocardial perfusion monitoring in the beating heart.An LDPM system, based on digital signal processing, was developed for myocardial perfusion assessment. To achieve an accurate estimate of the local microvascular perfusion, the varying myocardial tissue motion during the cardiac cycle is taken into account. By means of ECG-triggering, periods of minimum myocardial tissue motion can be pinpointed. The system and proposed methods were successfully evaluated both in an animal model (3 calves) and during coronary artery bypass grafting (CABG) on 13 humans. Animal studies showed the importance of processing during minimum tissue motion, at late diastole and/or late systole, to reduce movement artifacts. The human evaluation confirmed earlier animal findings and revealed low flow situations in the intraoperative phase. Influence of mechanical ventilation on the myocardial blood flow was found. The results justify investigation postoperative of CABG, where myocardial perfusion monitoring may give a rapid response to potential ischemia.The influence of tissue motion on LDPI was studied in model measurements and on the skin. A relatively large tissue velocity, compared to microvascular flow velocities, was needed to significantly influence the perfusion signal. Movement artifact magnitude depended on the movement direction and the surface structure. An LDPI system utilizing a polarization technique that blocks specularly reflected light is proposed. The method was evaluated in a flow model and on the skin of 12 subjects and was found to significantly reduce influence from tissue motion. Finally, a theoretical explanation of the origin of LDPI movement artifacts is proposed. Reduction of movement artifacts makes measurements more reliable and increases the potential of LDPI as a clinical tool.
|
|
