| 1. |
- Glasin, Joakim, et al.
(författare)
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Wireless vitals : Proof of concept for wireless patient monitoring in an emergency department setting
- 2019
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Ingår i: Journal of Biophotonics. - : Wiley-VCH Verlagsgesellschaft. - 1864-063X .- 1864-0648. ; 12:4
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Tidskriftsartikel (refereegranskat)abstract
- Vital sign assessment is a common task in emergency medicine, but resources for continuous monitoring are restricted, data is often recorded manually, and entangled wires cause frustration. Therefore, we designed a small, wireless photoplethysmographic device capable of continuously assessing pulse, respiratory frequency and oxygen saturation on the sternum and tested the performance and feasibility in an emergency department setting. Fifty (56.3 20.2 years), consenting emergency patients (29 male) were recruited. Heart rate, respiratory rate and oxygen saturation were recorded simultaneously using the device and standard monitoring equipment. Data was compared using Bland-Altman plotting (heart rate, respiratory rate) and mean difference (oxygen saturation). The bias for heart- and respiratory rate was 0.4 (limits of agreements -11.3, 12.2 and -6.1, 7.0). Mean difference for oxygen saturation was -0.21 +/- 2.35%. This may be the first wireless device to use photoplethysmography on the sternum for vital sign assessment. We noted good agreement with standard monitors, but lack of standardization in data processing between monitoring systems may limit the generalizability of these findings. Although further improvements are needed, the feasibility of this approach provides proof of concept for a new paradigm of large scale, wireless patient monitoring.
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| 2. |
- Henricson, Joakim, 1977-, et al.
(författare)
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Respiratory rate monitoring in healthy volunteers by central photoplethysmography compared to capnography
- 2022
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Ingår i: Journal of Biophotonics. - : Wiley-V C H Verlag GMBH. - 1864-063X .- 1864-0648. ; 15:4
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring of respiration is a central task in clinical medicine, crucial to patient safety. Despite the uncontroversial role of altered respiratory frequency as an important sign of impending or manifest deterioration, reliable measurement methods are mostly lacking outside of intensive care units and operating theaters. Photoplethysmography targeting the central blood circulation in the sternum could offer accurate and inexpensive monitoring of respiration. Changes in blood flow related to the different parts of the respiratory cycle are used to identify the respiratory pattern. The aim of this observational study was to compare photoplethysmography at the sternum to standard capnography in healthy volunteers. Bland Altman analysis showed good agreement (bias -0.21, SD 1.6, 95% limits of agreement -3.4 to 2.9) in respiratory rate values. Photoplethysmography provided high-quality measurements of respiratory rate comparable to capnographic measurements. This suggests that photoplethysmography may become a precise, cost-effective alternative for respiratory monitoring.
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| 3. |
- 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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| 4. |
- Bergkvist, Max, et al.
(författare)
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Assessment of oxygenation with polarized light spectroscopy enables new means for detecting vascular events in the skin
- 2020
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Ingår i: Microvascular Research. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0026-2862 .- 1095-9319. ; 130
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Impaired oxygenation in the skin may occur in disease states and after reconstructive surgery. We used tissue viability imaging (TiVi) to measure changes in oxygenation and deoxygenation of haemoglobin in an in vitro model and in the dermal microcirculation of healthy individuals. Materials and methods: Oxygenation was measured in human whole blood with different levels of oxygenation. In healthy subjects, changes in red blood cell concentration (C-RBC,(TiVi)), oxygenation (Delta C-OH,(TiVi)) and deoxygenation (Delta C-DOH,(TiVi)) of haemoglobin were measured during and after arterial and venous occlusion using TiVi and were compared with measurements from the enhanced perfusion and oxygen saturation system (EPOS). Results: During arterial occlusion, C-RBC,(TiVi) remained unchanged while Delta C-OH,(TiVi) decreased to -44.2 (10.4) AU (p = 0.04), as compared to baseline. After release, C-RBC,C-TiVi increased to 39.2 (18.8) AU (p < 0.001), Delta C-OH,C-TiVi increased to 38.5. During venous occlusion, C-RBC,C-TiVi increased to 28.9 (11.2) AU (p < 0.001), Delta C-OH,C-TiVi decreased to -52.2 (46.1) AU (p < 0.001) compared to baseline after 5 min of venous occlusion. There was a significant correlation between the TiVi Oxygen Mapper and EPOS, for arterial (r = 0.92, p < 0.001) and venous occlusion (r = 0.87, p < 0.001), respectively. Conclusion: This study shows that TiVi can measure trends in oxygenation and deoxygenation of haemoglobin during arterial and venous stasis in healthy individuals.
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| 5. |
- 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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| 6. |
- Droog Tesselaar, Erik, et al.
(författare)
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A protocol for iontophoresis of acetylcholine and sodium nitroprusside that minimises nonspecific vasodilatory effects
- 2004
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Ingår i: Microvascular research. - : Elsevier BV. - 0026-2862. ; 67:2, s. 197-202
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Tidskriftsartikel (refereegranskat)abstract
- Iontophoresis of vasoactive substances is a promising tool for studying pharmacological aspects of the (patho)physiology of the microvasculature. However, nonspecific microvascular responses are a common problem in most protocols used. We studied the effect of current density (mA/cm2), charge density (mC/cm2), drug concentration (mass %) and vehicle concentration (M) on the nonspecific vasodilatation during iontophoresis of sodium chloride, acetylcholine (ACh) and sodium nitroprusside (SNP). We found that nonspecific vasodilatation depended on current density and charge density in both anodal and cathodal iontophoresis. The responses to ACh and SNP were dependent on current density, charge density and drug concentration. We found that by limiting current density (<0.01 mA/cm2) and charge density (<7.8 mC/cm2) and with adjusted concentrations for drugs and vehicles, it is possible to prevent nonspecific effects during iontophoresis of ACh and SNP, while maximum drug effects (plateaus in the dose–response curves) are still obtained. These new findings are important for future iontophoresis studies in which vasoactive drugs are used to assess microvascular function because the presented approach has advantages compared to older techniques, which mainly have attempted to suppress or compensate for the nonspecific responses during iontophoresis by the use of local anaesthetics or the measurement of drug-minus-vehicle responses, both of which present well-known experimental shortcomings.
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| 7. |
- Farnebo, Simon, et al.
(författare)
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Hyperaemic changes in forearm skin perfusion and RBC concentration after increasing occlusion times
- 2010
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Ingår i: MICROVASCULAR RESEARCH. - : Elsevier Science B.V., Amsterdam. - 0026-2862. ; 80:3, s. 412-416
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Tidskriftsartikel (refereegranskat)abstract
- Tissue occlusion and the hyperaemic response upon reperfusion can be used as a tool to assess microvascular function in various vascular diseases. Currently, laser Doppler flowmetry (LDF) is applied most often to measure hyperaemic responses. In this study, we have applied tissue viability imaging (TiVi) and LDF to measure the change in red blood cell concentration and perfusion in the skin after occlusions of the forearm with increasing duration. We have found that there is a strong correlation between the changes in perfusion and red blood cell (RBC) concentration during post-occlusive hyperaemia (perfusion: r = 0.80; RBC concentration: r = 0.94). This correlation increases with longer occlusion durations (1, 5 and 10 min). Furthermore, for both perfusion and RBC concentration, the maximum responses (perfusion: r(2) = 0.59; RBC concentration: r(2) = 0.78) and the recovery times (perfusion: r(2) = 0.62; RBC concentration: r(2) = 0.91) increase linearly with the duration of the occlusion. Maximum responses and recovery times were more reproducible for RBC concentration (as measured with TiVi) than for perfusion (as measured with LDF). These results show that perfusion and RBC concentration are related during post-occlusive hyperaemia and that TiVi can be used as a tool in the assessment of hyperaemic responses that has advantages in terms of reproducibility, sensitivity and ease of use.
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| 8. |
- 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. |
- Haridass, Isha N., et al.
(författare)
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Cellular metabolism and pore lifetime of human skin following microprojection array mediation
- 2019
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Ingår i: Journal of Controlled Release. - : ELSEVIER SCIENCE BV. - 0168-3659 .- 1873-4995. ; 306, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- Skin-targeting microscale medical devices are becoming popular for therapeutic delivery and diagnosis. We used cryo-SEM, fluorescence lifetime imaging microscopy (FLIM), autofluorescence imaging microscopy and inflammatory response to study the puncturing and recovery of human skin ex vivo and in vivo after discretised puncturing by a microneedle array (Nanopatch (R)). Pores induced by the microprojections were found to close by similar to 25% in diameter within the first 30 min, and almost completely close by similar to 6 h. FLIM images of ex vivo viable epidermis showed a stable fluorescence lifetime for unpatched areas of similar to 1000 ps up to 24 h. Only the cells in the immediate puncture zones (in direct contact with projections) showed a reduction in the observed fluorescence lifetimes to between similar to 518-583 ps. The ratio of free-bound NAD(P)H (alpha 1/alpha 2) in unaffected areas of the viable epidermis was similar to 2.5-3.0, whereas the ratio at puncture holes was almost double at similar to 4.2-4.6. An exploratory pilot in vivo study also suggested similar closure rate with histamine administration to the forearms of human volunteers after Nanopatch (R) treatment, although a prolonged inflammation was observed with Tissue Viability Imaging. Overall, this work shows that the pores created by the microneedle-type medical device, Nanopatch (R), are transient, with the skin recovering rapidly within 1-2 days in the epidermis after application.
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| 10. |
- Henricson, Joakim, 1977-
(författare)
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Assessment of microvascular effects of vasoactive drugs : Methodological in vivo studies in humansbased on iontophoresis
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cardiovascular disease is the leading cause of death in western societies and endothelial dysfunction is one of the earliest signs seen in the development of such conditions. Thedevelopment of prognostic tools to aid in the prediction of micro- and macrovascular diseasebased on assessment of vascular reactivity is therefore of paramount importance.Transdermal iontophoresis offers a quick, non-invasive and relatively straightforward way todeliver vasoactive substances in order to provoke a vascular response in man. When combined with either laser Doppler flowmetry (LDF) or tissue viability imaging (TiVi) for quantification of these responses the methodology offers a potentially powerful tool forvascular investigations. The technique has, however, not been established in clinical practice yet and is mostly used in experimental settings. The lack of consensus in what data analysistechnique to use, uncertainty concerning the actual drug dose applied, and the difficulties associated with the assessment of responses to vasoconstrictors may have contributed to thisfact. The aim of this thesis is therefore to address these issues and thus facilitate the use and improve the applicability of transdermal iontophoresis for assessment of cutaneous microvascular function.More specifically, a non-linear dose-response model (Emax-model) that is commonly used in in vitro investigations of vascular function was applied to the iontophoresis data. The resultsshow that the Emax-model accurately describes the cutaneous vascular responses totransdermally iontophoresed acetylcholine (ACh) and, sodium nitroprusside (SNP). The Emaxmodelgenerates variables that can be used for quantitative statistical analysis of data andenables a more powerful analysis compared to the methods presently used. It is furtherdemonstrated that the maximal dose effect and vascular responses vary between differentprotocols with the same total iontophoretic charge but with different current strengths anddurations. This finding implies that the assumption that the local drug dose is linearlyproportional to the iontophoretic charge (used for estimation of delivered drug dose to themicrovascular bed) may be inaccurate in in vivo investigations and that there is need for amore refined model.It is also demonstrated that in a vasoconstrictive setting (iontophoresis of noradrenaline andphenylephrine) TiVi is the favourable technique for measuring vascular responses as it issensitive enough to generate data that can be fitted to the Emax-model even without predilatationof the vessels.
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