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- Bergkvist, Max, et al.
(författare)
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Assessment of microcirculation of the skin using Tissue Viability Imaging: A promising technique for detecting venous stasis in the skin
- 2015
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Ingår i: Microvascular Research. - : Elsevier. - 0026-2862 .- 1095-9319. ; 101, s. 20-25
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Tidskriftsartikel (refereegranskat)abstract
- Background: : Venous occlusion in the skin is difficult to detect by existing measurement techniques. Our aim was to find out whether Tissue Viability Imaging (TiVi) was better at detecting venous occlusion by comparing it with results of laser Doppler flowmetry (LDF) during graded arterial and venous stasis in human forearm skin. Methods: : Arterial and venous occlusions were simulated in 10 healthy volunteers by inflating a blood pressure cuff around the upper right arm. Changes in the concentration of red blood cells (RBC) were measured using TiVi, while skin perfusion and concentration of moving red blood cells (CMBC) were measured using static indices of LDF during exsanguination and subsequent arterial occlusion, postocclusive reactive hyperaemia, and graded increasing and decreasing venous stasis. Results: : During arterial occlusion there was a significant reduction in the mean concentration of RBC from baseline, as well as in perfusion and CMBC (p less than 0.008). Venous occlusion resulted in a significant 28% increase in the concentration of RBC (p = 0.002), but no significant change in perfusion (mean change -14%) while CMBC decreased significantly by 24% (p = 0.02). With stepwise increasing occlusion pressures there was a significant rise in the TiVi index and reduction in perfusion (p = 0.008), while the reverse was seen when venous flow was gradually restored. Conclusion: : The concentration of RBC measured with TiVi changes rapidly and consistently during both total and partial arterial and venous occlusions, while the changes in perfusion, measured by LDF, were less consistent This suggests that TiVi could be a more useful, non-invasive clinical monitoring tool for detecting venous stasis in the skin than LDF.
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- Bergkvist, Max, 1976-, et al.
(författare)
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Vascular Occlusion in a Porcine Flap Model : Effects on Blood Cell Concentration and Oxygenation.
- 2017
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Ingår i: Plastic and Reconstructive Surgery - Global Open. - : Wolters Kluwer. - 2169-7574. ; 5:11
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Tidskriftsartikel (refereegranskat)abstract
- Background: Venous congestion in skin flaps is difficult to detect. This study evaluated the ability of tissue viability imaging (TiVi) to measure changes in the concentration of red blood cells (CRBC), oxygenation, and heterogeneity during vascular provocations in a porcine fasciocutaneous flap model.Methods: In 5 pigs, cranial gluteal artery perforator flaps were raised (8 flaps in 5 pigs). The arterial and venous blood flow was monitored with ultrasonic flow probes. CRBC, tissue oxygenation, and heterogeneity in the skin were monitored with TiVi during baseline, 50% and 100% venous occlusion, recovery, 100% arterial occlusion and final recovery, thereby simulating venous and arterial occlusion of a free fasciocutaneous flap. A laser Doppler probe was used as a reference for microvascular perfusion in the flap.Results: During partial and complete venous occlusion, increases in CRBC were seen in different regions of the flap. They were more pronounced in the distal part. During complete arterial occlusion, CRBC decreased in all but the most distal parts of the flap. There were also increases in tissue oxygenation and heterogeneity during venous occlusion.Conclusions: TiVi measures regional changes in CRBC in the skin of the flap during arterial and venous occlusion, as well as an increase in oxygenated hemoglobin during venous occlusion that may be the result of reduced metabolism and impaired delivery of oxygen to the tissue. TiVi may provide a promising method for measuring flap viability because it is hand-held, easy to-use, and provides spatial information on venous congestion.
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- Bergram, Martin, et al.
(författare)
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Low awareness of non-alcoholic fatty liver disease in patients with type 2 diabetes in Swedish Primary Health Care
- 2022
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Ingår i: Scandinavian Journal of Gastroenterology. - : Taylor & Francis Ltd. - 0036-5521 .- 1502-7708. ; 57:1, s. 60-69
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Tidskriftsartikel (refereegranskat)abstract
- Objectives Non-alcoholic fatty liver disease (NAFLD) is more common in patients with type 2 diabetes mellitus (T2DM) compared to individuals without. Recent guidelines recommend screening for NAFLD in patients with T2DM. Our aim was to investigate the prevalence of NAFLD in patients with T2DM in a Swedish primary health care setting, how they are cared for and assess the risk of biochemical signs of advanced fibrosis. Material and methods In this cohort study, patients with T2DM from five primary health care centers were included. Medical records were retrospectively reviewed and living habits, medical history, results of diagnostic imaging and anthropometric and biochemical features were noted in a standardized form. The risk of steatosis and advanced fibrosis was assessed using commonly used algorithms (FLI, HSI, NAFLD-LFS, NAFLD ridge score, FIB-4 and NFS). Results In total 350 patients were included. Diagnostic imaging had been performed in 132 patients and of these, 34 (26%) had steatosis, which was not noted in the medical records in 16 (47%) patients. One patient with steatosis had been referred to a hepatologist. Of assessable patients, 71-97% had a high to intermediate risk of steatosis and 29-65% had an intermediate to high risk of advanced fibrosis according to the algorithms used. Conclusion This study indicates a high prevalence of NAFLD among T2DM patients in Swedish primary care. Patients with known NAFLD were followed up to a very low extent. Using fibrosis algorithms in primary health care would result in many patients needing further assessment in secondary care.
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- Fredriksson, Ingemar, 1980-, et al.
(författare)
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Vasomotion analysis of speed resolved perfusion, oxygen saturation, red blood cell tissue fraction, and vessel diameter : Novel microvascular perspectives
- 2022
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Ingår i: Skin research and technology. - : Wiley-Blackwell Publishing Inc.. - 0909-752X .- 1600-0846. ; 28:1, s. 142-152
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundVasomotion is the spontaneous oscillation in vascular tone in the microcirculation and is believed to be a physiological mechanism facilitating the transport of blood gases and nutrients to and from tissues. So far, Laser Doppler flowmetry has constituted the gold standard for in vivo vasomotion analysis.Materials and methodsWe applied vasomotion analysis to speed-resolved perfusion, oxygen saturation, red blood cell tissue (RBC) tissue fraction, and average vessel diameter from five healthy individuals at rest measured by the newly developed Periflux 6000 EPOS system over 10 minutes. Magnitude scalogram and the time-averaged wavelet spectra were divided into frequency intervals reflecting endothelial, neurogenic, myogenic, respiratory, and cardiac function.ResultsRecurrent high-intensity periods of the myogenic, neurogenic, and endothelial frequency intervals were found. The neurogenic activity was considerably more pronounced for the oxygen saturation, RBC tissue fraction, and vessel diameter signals, than for the perfusion signals. In a correlation analysis we found that changes in perfusion in the myogenic, neurogenic, and endothelial frequency intervals precede changes in the other signals. Furthermore, changes in average vessel diameter were in general negatively correlated to the other signals in the same frequency intervals, indicating the importance of capillary recruitment.ConclusionWe conclude that vasomotion can be observed in signals reflecting speed resolved perfusion, oxygen saturation, RBC tissue fraction, and vessel diameter. The new parameters enable new aspects of the microcirculation to be observed.
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- Hackethal, Johannes, et al.
(författare)
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Microvascular effects of microneedle application
- 2021
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Ingår i: Skin research and technology. - : WILEY. - 0909-752X .- 1600-0846. ; 27, s. 121-125
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Tidskriftsartikel (refereegranskat)abstract
- Background The efficiency of transdermal drug delivery may be increased by pretreating the skin with microneedles, but distinct effects of microneedles and the microneedle-enhanced delivery of vasoactive drugs on the skin microvasculature are still not well investigated. Materials and Methods In eight healthy human subjects, we measured the microvascular response to microneedle-induced microtraumas in the skin microvasculature using polarized light spectroscopy imaging (Tissue Viability imaging, TiVi). The microvascular response was assessed for up to 48 hours for three microneedle sizes (300 mu m, 500 mu m, and 750 mu m) and for different pressures and application times. Results In our results, microneedle application increased the local red blood cell (RBC) concentration for up to 24 hours dependent on the needle lengths, applied time, and force. Conclusion Optimization of microneedles size, pressure, and application time should be taken into account for future protocols for drug delivery and experimental provocations.
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| 9. |
- Henricson, Joakim, 1977-, et al.
(författare)
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In vivo dose-response analysis to acetylcholine : pharmacodynamic assessment by polarized reflectance spectroscopy
- 2022
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Ingår i: Scientific Reports. - London, United Kingdom : Nature Publishing Group. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Transdermal iontophoresis offers an in vivo alternative to the strain-gauge model for measurement of vascular function but is limited due to lack of technical solutions for outcome assessment. The aims of this study were to, after measurement by polarized reflectance spectroscopy (PRS), use pharmacodynamic dose-response analysis on responses to different concentrations of acetylcholine (ACh); and to examine the effect of three consecutively administered iontophoretic current pulses. The vascular responses in 15 healthy volunteers to iontophorised ACh (5 concentrations, range 0.0001% to 1%, three consecutive pulses of 0.02 mA for 10 min each) were recorded using PRS. Data were fitted to a four-parameter logistic dose response model and compared. Vascular responses were quantifiable by PRS. Similar pharmacodynamic dose response curves could be generated irrespectively of the ACh concentration. Linearly increasing maximum vasodilatory responses were registered with increasing concentration of ACh. A limited linear dose effect of the concentration of ACh was seen between pulses. Polarized reflectance spectroscopy is well suited for measuring vascular responses to iontophoretically administrated ACh. The results of this study support further development of iontophoresis as a method to study vascular function and pharmacological responses in vivo.
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| 10. |
- Henricson, Joakim, 1977-, et al.
(författare)
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Micropuncture closure following high density microarray patch application in healthy subjects
- 2022
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Ingår i: Skin research and technology. - : Wiley. - 0909-752X .- 1600-0846. ; 28:2, s. 305-310
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Tidskriftsartikel (refereegranskat)abstract
- Background The high-density microarray patch (HD-MAP) promises to be a robust vaccination platform with clear advantages for future global societal demands for health care management. The method of action has its base not only in efficient delivery of vaccine but also in the reliable induction of a local innate physical inflammatory response to adjuvant the vaccination process. The application process needs to induce levels of reactivity, which are acceptable to the vaccine, and from which the skin promptly recovers. Materials and methods 1 x 1 cm HD-MAP patches containing 5000, 250-mu m long microprojections were applied to the skin in 12 healthy volunteers. The return of skin barrier function was assessed by transepidermal water loss (TEWL) and reaction to topical histamine challenge. Results Skin barrier recovery by 48 h was confirmed for all HD-MAP sites by recovered resistance to the effects of topical histamine application. Conclusions Our previous observation, that the barrier disruption indicator TEWL returns to normal by 48 h, is supported by this papers demonstration of return of skin resistance to topical histamine challenge in twelve healthy subjects.
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