Håvard Kalvøy

Guest researcher

Email havard.kalvoy@ous-hf.no

Phone +47 23 07 15 89

Username

Visiting address Rikshospitalet - Oslo University Hospital

Postal address OUS-Rikshospitalet Box 4950 Nydalen 0424 Oslo

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Academic Interests

Clinical and Biomedical Engineering, and Bioimpedance.

Higher education and employment history

Completed his M.Sc. degree at the Dept. of Physics, University of Oslo in 2003 (Development of equipment and methods for the characterization of single cells by measuring the complex electrical impedance -Norwegian), and has since worked as a researcher at the Dept. of Clinical and Biomedical engineering at Oslo University Hospital. Employee since 2006.

Phd in 2010 after defending his thesis Needle Guidance in Clinical Applications based on Electrical Impedance.

Kalvøy, Håvard; Hisdal, Jonny & Tronstad, Christian (2025). Toe digit pulsation measurement by impedance plethysmography in miniaturized devices: An early feasibility test. Journal of Electrical Bioimpedance. 16(1), p. 150–152. doi: 10.2478/joeb-2025-0020. Full text in Research Archive Show summary
This early feasibility test explores impedance plethysmography (IPG) for detecting toe pulse waves using a setup suited for miniaturized devices. Conventional tests often miss micro-circulatory impairment, which is critical for wound healing and limb survival. We designed a flexible 3D-printed clamp with Ag/AgCl electrodes positioned on the inner big toe to target the lateral plantar digital artery. 50 kHz impedance measurements were performed on a healthy volunteer using 3D-printed electrode clamp for a tetrapolar configuration. Custom designed flexible electrodes were tested with and without contact gel. Preliminary results suggest that IPG can capture distal pulsatile signals, motivating further exploration of the potential for early detection of peripheral vascular dysfunction.
Cunha, André; Schülke, Christin; Mesri, Alireza; Ruud, Simen Kristoffer; Aizenshtadt, Aleksandra & Ferrari, Giorgio [Show all 16 contributors for this article] (2024). Development of a Smart Wireless Multisensor Platform for an Optogenetic Brain Implant. Sensors. 24(2). doi: 10.3390/s24020575. Full text in Research Archive Show summary
Implantable cell replacement therapies promise to completely restore the function of neural structures, possibly changing how we currently perceive the onset of neurodegenerative diseases. One of the major clinical hurdles for the routine implementation of stem cell therapies is poor cell retention and survival, demanding the need to better understand these mechanisms while providing precise and scalable approaches to monitor these cell-based therapies in both pre-clinical and clinical scenarios. This poses significant multidisciplinary challenges regarding planning, defining the methodology and requirements, prototyping and different stages of testing. Aiming toward an optogenetic neural stem cell implant controlled by a smart wireless electronic frontend, we show how an iterative development methodology coupled with a modular design philosophy can mitigate some of these challenges. In this study, we present a miniaturized, wireless-controlled, modular multisensor platform with fully interfaced electronics featuring three different modules: an impedance analyzer, a potentiostat and an optical stimulator. We show the application of the platform for electrical impedance spectroscopy-based cell monitoring, optical stimulation to induce dopamine release from optogenetically modified neurons and a potentiostat for cyclic voltammetry and amperometric detection of dopamine release. The multisensor platform is designed to be used as an opto-electric headstage for future in vivo animal experiments.
Jerve, Fredrik Wilsbeck; Hjelme, Dag Roar; Kalvøy, Håvard; Allen, John & Tronstad, Christian (2024). Exploration of the Conditions for Occurrence of Photoplethysmographic Signal Inversion above the Dorsalis Pedis Artery. Sensors. 24(20). doi: 10.3390/s24206505. Full text in Research Archive
Krispel, Thomas; Badeli, Vahid; Jafarinia, Alireza; Reinbacher-Köstinger, Alice; Tronstad, Christian & Ranftl, Sascha [Show all 11 contributors for this article] (2024). arterioscope.sim: Enabling Simulations of Blood Flow and Its Impact on Bioimpedance Signals. Bioengineering. 11(12). doi: 10.3390/bioengineering11121273. Full text in Research Archive Show summary
Objectives: Early detection of cardiovascular diseases and their pre-existing conditions, arteriosclerosis and atherosclerosis, is crucial to increasing a patient’s chance of survival. While imaging technologies and invasive procedures provide a reliable diagnosis, they carry high costs and risks for patients. This study aims to explore impedance plethysmography (IPG) as a non-invasive and affordable alternative for diagnosis. Methods: To address the current lack of large-scale, high-quality impedance data, we introduce arterioscope.sim, a simulation platform that models arterial blood flow and computes the electrical conductivity of blood. The platform simulates bioimpedance measurements on specific body segments using patient-specific parameters. The study investigates how introducing arterial diseases into the simulation affects the bioimpedance signals. Results: The simulation results demonstrate that introducing atherosclerosis and arteriosclerosis leads to significant changes in the computed signals compared to simulations of healthy arteries. Furthermore, simulation of a patient-specific healthy artery strongly correlates with measured signals from a healthy volunteer. Conclusions and significance: arterioscope.sim effectively simulates bioimpedance signals in healthy and diseased arteries and highlights the potential of using these signals for early diagnosis of arterial diseases, offering a non-invasive and cost-effective alternative to traditional diagnostic methods.
Tariverdi, Abbas; Côté-Allard, Ulysse Teller Masao; Mathiassen, Kim; Elle, Ole Jakob; Kalvøy, Håvard & Martinsen, Ørjan Grøttem [Show all 7 contributors for this article] (2023). Reinforcement Learning-Based Switching Controller for a Milliscale Robot in a Constrained Environment. IEEE Transactions on Automation Science and Engineering. ISSN 1545-5955. 21(2), p. 2000–2016. doi: 10.1109/TASE.2023.3259905. Full text in Research Archive
Tronstad, Christian; Amini, Maryam; Olesen, Eline; Qvigstad, Elisabeth; Pabst, Oliver & Martinsen, Tormod [Show all 11 contributors for this article] (2022). Diabetic foot assessment using skin impedance in a custom made sensor-sock. Journal of Electrical Bioimpedance. 13(1), p. 136–142. doi: 10.2478/joeb-2022-0019. Full text in Research Archive Show summary
Abstract Diabetic peripheral neuropathy (DPN) may lead to several changes in the skin, and some of these may influence the skin impedance spectrum. In the present study we have developed a prototype solution for skin impedance spectroscopy at selected skin sites (big toe pulp, heel and toe ball) that was tested in a pilot study on five patients with DPN and five healthy controls. At the big toe, most of the controls had markedly lower impedance than the DPN group, especially in the range of 1-100 kHz. The separation between the groups seems to be weaker at the heel and weakest at the toeball. The results may indicate that monitoring of the skin impedance spectrum may be a method for detection of skin changes associated with DPN, encouraging further studies with the big toe sensor in particular.
Tariverdi, Abbas; Mathiassen, Kim; Søyseth, Vegard; Kalvøy, Håvard; Elle, Ole Jakob & Tørresen, Jim [Show all 8 contributors for this article] (2022). Physics-Based Simulation and Control Framework for Steering a Magnetically-Actuated Guidewire. In Dilger, Lale Canan (Eds.), 2022 8th International Conference on Control, Decision and Information Technologies (CoDIT). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781665496070. doi: 10.1109/CoDIT55151.2022.9803963. Full text in Research Archive
Wiegerinck, Anouk; Thomsen, Andreas; Hisdal, Jonny; Kalvøy, Håvard & Tronstad, Christian (2021). Electrical impedance plethysmography versus tonometry to measure the pulse wave velocity in peripheral arteries in young healthy volunteers: a pilot study. Journal of Electrical Bioimpedance. 12(1), p. 169–177. doi: 10.2478/joeb-2021-0020. Full text in Research Archive Show summary
Abstract The leading cause of health loss and deaths worldwide are cardiovascular diseases. A predictor of cardiovascular diseases and events is the arterial stiffness. The pulse wave velocity (PWV) can be used to estimate arterial stiffness non-invasively. The tonometer is considered as the gold standard for measuring PWV. This approach requires manual probe fixation above the artery and depends on the skills of the operator. Electrical impedance plethysmography (IPG) is an interesting alternative using skin surface sensing electrodes, that is miniaturizable, cost-effective and allows measurement of deeper arteries. The aim of this pilot study was to explore if IPG can be a suitable technique to measure pulse wave velocity in legs as an alternative for the tonometer technique. The PWV was estimated by differences in the ECG-gated pulse arrival times (PAT) at the a. femoralis, a. popliteal, a. tibialis dorsalis and a. dorsalis pedis in nine healthy young adults using IPG and the SphygmoCor tonometer as a reference. The estimated PWV results from bioimpedance and the tonometer were fairly in agreement, and the beat-to-beat variability in PAT was similar. This pilot study indicates that the use of IPG may be a good alternative for estimating PWV in the legs.
Tronstad, Christian; Martinsen, Tormod; Olsen, Morten; Rosseland, Leiv Arne; Pettersen, Fred-Johan & Martinsen, Ørjan Grøttem [Show all 8 contributors for this article] (2020). Splitting one ventilator for multiple patients - a technical assessment. arXiv.org. ISSN 2331-8422. Full text in Research Archive
Amini, Maryam; Niemi, Essi Maria; Hisdal, Jonny; Kalvøy, Håvard; Tronstad, Christian & Scholz, Hanne [Show all 8 contributors for this article] (2020). Monitoring the quality of frozen-thawed venous segments using bioimpedance spectroscopy. Physiological Measurement. ISSN 0967-3334. 41(4). doi: 10.1088/1361-6579/ab85b7. Full text in Research Archive Show summary
Objective: Storage at temperatures as low as −80 °C and below (cryopreservation) is considered a method for long-term preservation of cells and tissues, and especially blood vessel segments, which are to be used for clinical operations such as transplantation. However, the freezing and thawing processes themselves can induce injuries to the cells and tissue by damaging the structure and consequently functionality of the cryopreserved tissue. In addition, the level of damage is dependent on the rate of cooling and warming used during the freezing-thawing process. Current methods for monitoring the viability and integrity of cells and tissues after going through the freezing-thawing cycle are usually invasive and destructive to the cells and tissues. Therefore, employing monitoring methods which are not destructive to the cryopreserved tissues, such as bioimpedance measurement techniques, is necessary. In this study we aimed to design a bioimpedance measurement setup to detect changes in venous segments after freezing-thawing cycles in a noninvasive manner. Approach: A bioimpedance spectroscopy measurement technique with a two-electrode setup was employed to monitor ovine jugular vein segments after each cycle during a process of seven freezing-thawing cycles. Main results: The results demonstrated changes in the impedance spectra of the measured venous segments after each freezing-thawing cycle. Significance: This indicates that bioimpedance spectroscopy has the potential to be developed into a novel method for non-invasive and non-destructive monitoring of the viability of complex tissue after cryopreservation.
Amini, Maryam; Kalvøy, Håvard & Martinsen, Ørjan Grøttem (2020). Finite element simulation of the impedance response of a vascular segment as a function of changes in electrode configuration. Journal of Electrical Bioimpedance. 11(1), p. 112–131. doi: 10.2478/JOEB-2020-0017. Full text in Research Archive Show summary
Abstract Monitoring a biological tissue as a three dimensional (3D) model is of high importance. Both the measurement technique and the measuring electrode play substantial roles in providing accurate 3D measurements. Bioimpedance spectroscopy has proven to be a noninvasive method providing the possibility of monitoring a 3D construct in a real time manner. On the other hand, advances in electrode fabrication has made it possible to use flexible electrodes with different configurations, which makes 3D measurements possible. However, designing an experimental measurement set-up for monitoring a 3D construct can be costly and time consuming and would require many tissue models. Finite element modeling methods provide a simple alternative for studying the performance of the electrode and the measurement set-up before starting with the experimental measurements. Therefore, in this study we employed the COMSOL Multiphysics finite element modeling method for simulating the effects of changing the electrode configuration on the impedance spectroscopy measurements of a venous segment. For this purpose, the simulations were performed for models with different electrode configurations. The simulation results provided us with the possibility of finding the optimal electrode configuration including the geometry, number and dimensions of the electrodes, which can be later employed in the experimental measurement set-up.
Cunha, Andrè Bastos da; Schuelke, Christin; Heiskanen, Arto; Asif, Afia; Hassan, Yasmin M. & Keller, Stephan S. [Show all 10 contributors for this article] (2020). Bioimpedance Measurements on Human Neural Stem Cells as a Benchmark for the Development of Smart Mobile Biomedical Applications. International Federation for Medical and Biological Engineering Proceedings. ISSN 1680-0737. 72, p. 38–47. doi: 10.1007/978-981-13-3498-6_6. Full text in Research Archive Show summary
Over the past 30 years, stem cell technologies matured from an attractive option to investigate neurodegenerative diseases to a possible paradigm shift in their treatment through the development of cell-based regenerative medicine (CRM). Implantable cell replacement therapies promise to completely restore function of neural structures possibly changing how we currently perceive the onset of these conditions. One of the major clinical hurdles facing the routine implementation of stem cell therapy is the limited and inconsistent benefit observed thus far. While unclear, numerous pre-clinical and a handful of clinical cell fate imaging studies point to poor cell retention and survival. Coupling the need to better understand these mechanisms while providing scalable approaches to monitor these treatments in both pre-clinical and clinical scenarios, we show a proof of concept bioimpedance electronic platform for the Agile development of smart and mobile biomedical applications like neural implants or highly portable monitoring devices.
Amini, Maryam; Hisdal, Jonny; Rosales, Antonio; Kalvøy, Håvard & Martinsen, Ørjan Grøttem (2020). Evaluating the Effects of Cold Storage on Vascular Grafts Using Bioimpedance Measurement Techniques. International Federation for Medical and Biological Engineering Proceedings. ISSN 1680-0737. p. 127–132. doi: 10.1007/978-981-13-3498-6_19. Full text in Research Archive
Martinsen, Tormod; Pettersen, Fred-Johan; Kalvøy, Håvard; Tronstad, Christian; Kvarstein, Gunnvald & Bakken, André [Show all 10 contributors for this article] (2019). Electrosurgery and temperature increase in tissue with a passive metal implant. Frontiers in Surgery. 6:8, p. 1–8. doi: 10.3389/fsurg.2019.00008. Full text in Research Archive Show summary
Importance: During monopolar electrosurgery in patients, current paths can be influenced by metal implants, which can cause unintentional tissue heating in proximity to implants. Guidelines concerning electrosurgery and active implants such as pacemakers or implantable cardioverter defibrillators have been published, but most describe interference between electrosurgery and the active implant rather than the risk of unintended tissue heating. Tissue heating in proximity to implants during electrosurgery may cause an increased risk of patient injury. Objective: To determine the temperature of tissue close to metal implants during electrosurgery in an in-vitro model. Design, Setting, and Participants: Thirty tissue samples (15 with a metal implant placed in center, 15 controls without implant) were placed in an in vitro measurement chamber. Electrosurgery was applied at 5–60 W with the active electrode at three defined distances from the implant while temperatures at four defined distances from the implant were measured using fiber-optic sensors. Main Outcomes and Measures: Tissue temperature increase at the four tissue sites was determined for all power levels and each of the electrode-to-implant distances. Based on a linear mixed effects model analysis, the primary outcomes were the difference in temperature increase between implant and control tissue, and the estimated temperature increase per watt per minute. Results: Tissues with an implant had higher temperature increases than controls at all power levels after 1 min of applied electrosurgery (mean difference of 0.16°C at 5 W, 0.50°C at 15 W, 1.11°C at 30 W, and 2.22°C at 60 W, all with p < 0.001). Temperature increase close to the implant was estimated to be 0.088°C/W/min (95% CI: 0.078–0.099°C/W/min; p < 0.001). Temperature could increase to above 43°C after 1 min of 60 W. Active electrode position had no significant effect on temperature increases for tissues with implant (p = 0.6). Conclusions and Relevance: The temperature of tissue close to a metal implant increases with passing electrosurgery current. There is a significant risk of high tissue temperature when long activation times or high power levels are used.
Aria, Shafa; Elfarri, Yassine; Elvegård, Marius; Gottfridsson, Adam; Grønaas, Halvor & Harang, Sigve Smedsrud [Show all 25 contributors for this article] (2019). Measuring blood pulse wave velocity with bioimpedance in different age groups. Sensors. 19:850(4), p. 1–10. doi: 10.3390/s19040850. Full text in Research Archive Show summary
In this project, we have studied the use of electrical impedance cardiography as a possible method for measuring blood pulse wave velocity, and hence be an aid in the assessment of the degree of arteriosclerosis. Using two different four-electrode setups, we measured the timing of the systolic pulse at two locations, the upper arm and the thorax, and found that the pulse wave velocity was in general higher in older volunteers and furthermore that it was also more heart rate dependent for older subjects. We attribute this to the fact that the degree of arteriosclerosis typically increases with age and that stiffening of the arterial wall will make the arteries less able to comply with increased heart rate (and corresponding blood pressure), without leading to increased pulse wave velocity. In view of these findings, we conclude that impedance cardiography seems to be well suited and practical for pulse wave velocity measurements and possibly for the assessment of the degree of arteriosclerosis. However, further studies are needed for comparison between this approach and reference methods for pulse wave velocity and assessment of arteriosclerosis before any firm conclusions can be drawn.
Tronstad, Christian; Høgetveit, Jan Olav; Elvebakk, Ole & Kalvøy, Håvard (2019). Age-related differences in the morphology of the impedance cardiography signal. Journal of Electrical Bioimpedance. 10(1), p. 139–145. doi: 10.2478/joeb-2019-0020. Full text in Research Archive Show summary
Impedance cardiography (ICG) is a non-invasive method of hemodynamic measurement, mostly known for estimation of stroke volume and cardiac output based on characteristic features of the signal. Compared with electrocardiography, the knowledge on the morphology of the ICG signal is scarce, especially with respect to age-dependent changes in ICG waveforms. Based on recordings from ten younger (20–29 years) and ten older (60–79) healthy human subjects after three different levels of physical activity, the typical interbeat ICG waveforms were derived based on ensemble averages. Comparison of these waveforms between the age groups indicates the following differences: a later initial upward deflection for the younger group, an additional hump in the waveform from many older subjects not presented in the younger group, and a more pronounced second wave in the younger group. The explanation for these differences is not clear, but may be related to arterial stiffness. Further studies are suggested to determine whether these morphological differences have clinical value.
Bjørhei, Andreas; Pedersen, Filip T.; Muhammad, Saeed; Tronstad, Christian; Kalvøy, Håvard & Wojniusz, Slawomir [Show all 8 contributors for this article] (2019). An investigation on bilateral asymmetry in electrodermal activity. Frontiers in Behavioral Neuroscience. 13(88). doi: 10.3389/fnbeh.2019.00088. Full text in Research Archive Show summary
The Multiple Arousal Theory (Picard et al., 2016) was proposed to explain retrospective observations of bilateral differences in electrodermal activities occurring in threat-related high-stake situations. The theory proposes different cortical and subcortical structures to be involved in the processing of various facets of emotional states. Systematic investigations of this effect are still scarce. This study tested the prediction of bilateral electrodermal effects in a controlled laboratory environment where electrodermal activity (EDA) was recorded bilaterally during normal activity and two stress-tasks in 25 healthy volunteers. A visual search stress task with a performance-related staircase algorithm was used, ensuring intersubjectively comparable stress levels across individuals. After completion of the task, a sense of ownership of an attractive price was created and loss aversion introduced to create a high-stake situation. Confirmation of the theory should satisfy the hypothesis of a bilateral difference in EDA between the dominant and non-dominant hand, which is larger during high-stake stressors than during low-stake stressors. The bilateral difference was quantified and compared statistically between the two stress-tasks, revealing no significant difference between them nor any significant difference between the stress tasks and the period of normal activity. Subgroup analysis of only the participants with maximum self-rating of their desire to win the price (n = 7) revealed neither any significant difference between the two tasks nor between the stress-tasks and the period of normal activity. Although the theory was not confirmed by this study, eight cases suggestive of bilateral difference within the recordings were identified and are presented. Because the study is limited in using one of several possible operationalizations of the phenomenon, it is not possible to draw a general conclusion on the theory. Nevertheless, the study might contribute to a better understanding and encourage systematic review and hypothesis development regarding this new theory. Possible explanations and suggestions for future pathways to systematically investigate the Multiple Arousal Theory are discussed.
Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre I.; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Gulseth, Hanne Løvdal [Show all 9 contributors for this article] (2019). A multiparameter model for non-invasive detection of hypoglycemia. Physiological Measurement. ISSN 0967-3334. 40(8), p. 1–14. doi: 10.1088/1361-6579/ab3676. Full text in Research Archive Show summary
Objective: Severe hypoglycemia is the most serious acute complication for people with type 1 diabetes (T1D). Approximately 25% of people with T1D have impaired ability to recognize impending hypoglycemia, and nocturnal episodes are feared. Approach: We have investigated the use of non-invasive sensors for detection of hypoglycemia based on a mathematical model which combines several sensor measurements to identify physiological responses to hypoglycemia. Data from randomized single-blinded euglycemic and hypoglycemic glucose clamps in 20 participants with T1D and impaired awareness of hypoglycemia was used in the analyses. Main results: Using a sensor combination of sudomotor activity at three skin sites, ECG-derived heart rate and heart rate corrected QT interval, near-infrared and bioimpedance spectroscopy; physiological responses associated with hypoglycemia could be identified with an F1 score accuracy up to 88%. Significance: We present a novel model for identification of non-invasively measurable physiological responses related to hypoglycemia, showing potential for detection of moderate hypoglycemia using a wearable sensor system
Tronstad, Christian; Elvebakk, Ole; Staal, Odd Martin; Kalvøy, Håvard; Høgetveit, Jan Olav & Jenssen, Trond Geir [Show all 8 contributors for this article] (2019). Non-invasive prediction of blood glucose trends during hypoglycemia. Analytica Chimica Acta. ISSN 0003-2670. 1052, p. 37–48. doi: 10.1016/j.aca.2018.12.009. Full text in Research Archive
Martinsen, Ørjan Grøttem; Kalvøy, Håvard; Bari, Dindar S. & Tronstad, Christian (2019). A circuit for simultaneous measurements of skin electrical conductance, susceptance, and potential. Journal of Electrical Bioimpedance. 10, p. 110–112. doi: 10.2478/joeb-2019-0016. Full text in Research Archive Show summary
A circuit is presented that enables measurement of skin electrical conductance, susceptance, and potential simultaneously beneath the same monopolar electrode. Example measurements are shown to confirm the function of the circuit. The measurements are also in accordance with earlier findings that changes in skin conductance and potential do not always correspond and hence contain unique information.
Anso, Juan; Balmer, Thomas W; Jegge, Yves; Kalvøy, Håvard; Bell, Brett J & Dur, Cilgia [Show all 16 contributors for this article] (2018). Electrical impedance to assess facial nerve proximity during robotic cochlear implantation. IEEE Transactions on Biomedical Engineering. ISSN 0018-9294. 66(1), p. 237–245. doi: 10.1109/TBME.2018.2830303. Full text in Research Archive
Strand-Amundsen, Runar James; Tronstad, Christian; Kalvøy, Håvard; Ruud, Tom Erik; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem [Show all 7 contributors for this article] (2018). Small intestinal ischemia and reperfusion - Bioimpedance measurements. Physiological Measurement. ISSN 0967-3334. 39(2). doi: 10.1088/1361-6579/aaa576. Full text in Research Archive Show summary
Objective: Trans-intestinal bioimpedance measurements have previously been used to investigate changes in electrical parameters during 6h of ischemia in the small intestine. Knowledge is lacking regarding the time course of trans-intestinal bioimpedance parameters during reperfusion. As reperfusion is an important part in the clinical treatment of intestinal ischemia, we need to know how it affects the bioimpedance measurements. Approach: We performed bioimpedance measurements, using a two-electrode setup on selected segments of the jejunum in 15 pigs. A controlled voltage signal was applied while measuring the resulting current. In each pig, five or six 30 cm segments of the jejunum were made ischemic by clamping the mesenteric arteries and veins creating segments with ischemia from 1–16h duration. Reperfusion was initiated at selected time intervals of ischemia, and measured for 5–15h afterwards. Main results: The tan δ parameter (loss tangent) was different (p < 0.016) comparing ischemic and control tissue for the duration of the experiment (16h). Comparing the control tissue 30 cm from the ischemic area with the control tissue 60 cm from the ischemic tissue, we found that the mean tan δ amplitude in the frequency range (3900–6300 Hz) was significantly higher (p < 0.036) in the proximal control after 10h of experiment duration. After reperfusion, the time development of tanδm (loss tangent maximum over a frequency range) amplitude and frequency overlapped and periodically increased above the tanδm in the ischemic intestine. Dependent on the ischemic duration pre-reperfusion, the initial increase in tan δ stabilizes or increases drastically over time, compared to the tan δ amplitude of the ischemic tissue. Significance: As during ischemia, the electrical parameters during reperfusion also follow a characteristic timecourse, depending on the ischemic exposure before pre-reperfusion. The temporal changes in electrical parameters during small intestinal ischemia followed by reperfusion provides important information for assessment of tissue injury.
Amini, Maryam; Hisdal, Jonny & Kalvøy, Håvard (2018). Applications of bioimpedance measurement techniques in tissue engineering. Journal of Electrical Bioimpedance. 9(1), p. 142–158. doi: 10.2478/joeb-2018-0019. Full text in Research Archive Show summary
Rapid development in the field of tissue engineering necessitates implementation of monitoring methods for evaluation of the viability and characteristics of the cell cultures in a real-time, non-invasive and non-destructive manner. Current monitoring techniques are mainly histological and require labeling and involve destructive tests to characterize cell cultures. Bioimpedance measurement technique which benefits from measurement of electrical properties of the biological tissues, offers a non-invasive, label-free and real-time solution for monitoring tissue engineered constructs. This review outlines the fundamentals of bioimpedance, as well as electrical properties of the biological tissues, different types of cell culture constructs and possible electrode configuration set ups for performing bioimpedance measurements on these cell cultures. In addition, various bioimpedance measurement techniques and their applications in the field of tissue engineering are discussed.
Bari, D. S.; Aldosoky, H. Y. Y.; Tronstad, Christian; Kalvøy, Håvard & Martinsen, Ørjan Grøttem (2018). Electrodermal activity responses for quantitative assessment of felt pain. Journal of Electrical Bioimpedance. 9, p. 52–58. doi: 10.2478/joeb-2018-0010. Full text in Research Archive Show summary
Accurate assessment of experienced pain is a well-known problem in the clinical practices. Therefore, a proper method for pain detection is highly desirable. Electrodermal activity (EDA) is known as a measure of the sympathetic nervous system activity, which changes during various mental stresses. As pain causes mental stress, EDA measures may reflect the felt pain. This study aims to evaluate changes in skin conductance responses (SCRs), skin potential responses (SPRs), and skin susceptance responses (SSRs) simultaneously as a result of sequences of electrical (painful) stimuli with different intensities. EDA responses as results of painful stimuli were recorded from 40 healthy volunteers. The stimuli with three different intensities were produced by using an electrical stimulator. EDA responses significantly changed (increased) with respect to the intensity of the stimuli. Both SCRs and SSRs showed linear relationship with the painful stimuli. It was found that the EDA responses, particularly SCRs (p < 0.001) and SSRs (p = 0.001) were linearly affected by the intensity of the painful stimuli. EDA responses, in particular SCRs, may be used as a useful indicator for assessment of experienced pain in clinical settings.
Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre I.; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Frøslie, Kathrine Frey [Show all 10 contributors for this article] (2018). Evaluation of hypoglycaemia with non-invasive sensors in people with type 1 diabetes and impaired awareness of hypoglycaemia. Scientific Reports. 8:14722, p. 1–11. doi: 10.1038/s41598-018-33189-1. Full text in Research Archive Show summary
People with type 1 diabetes and impaired awareness of hypoglycaemia (IAH) are prone to severe hypoglycaemia. Previous attempts to develop non-invasive hypoglycaemia alarm systems have shown promising results, but it is not known if such alarms can detect severe hypoglycaemia in people with IAH. We aimed to explore whether a combination of non-invasive sensors could reliably evaluate hypoglycaemia (plasma glucose (PG) minimum 2.5 mmol/L) in people with IAH. Twenty participants with type 1 diabetes and IAH underwent randomly ordered, single blinded hyperinsulinemic euglycaemic and hyperinsulinemic hypoglycaemic clamps. Sweating, skin temperature, ECG, counterregulatory hormones and symptoms of hypoglycaemia were assessed. Overall, we were not able to detect clamp-induced hypoglycaemia with sufficient sensitivity and specificity for further clinical use. As a post-hoc analysis, we stratified participants according to their ability to identify hypoglycaemic symptoms during hypoglycaemic clamps. Five out of 20 participants could identify such symptoms. These participants had a significantly higher adrenaline response to hypoglycaemia (p < 0.001) and were reliably identified by sensors. Based on our observations, a non-invasive alarm system based on measurement of sweating responses and ECG changes during hypoglycaemia might provide an alert at a plasma glucose concentration around 2.5 mmol/L if an adequate sympatho-adrenal reaction is elicited.
Bari, Dindar S.; Aldosky, Haval Y. Yacoob; Tronstad, Christian; Kalvøy, Håvard & Martinsen, Ørjan Grøttem (2018). Influence of relative humidity on electrodermal levels and responses. Skin Pharmacology and Physiology. ISSN 1660-5527. 31, p. 298–307. doi: 10.1159/000492275. Full text in Research Archive
Kalvøy, Håvard; Tronstad, Christian; Ullensvang, Kyrre; Steinfeldt, Thorsten & Sauter, Axel Rudolf (2017). Detection of needle to nerve contact based on electric bioimpedance and machine learning methods. IEEE Engineering in Medicine and Biology Society. Conference Proceedings. ISSN 1557-170X. p. 9–12. doi: 10.1109/EMBC.2017.8036750. Full text in Research Archive
Bari, D. S.; Aldosky, H. Y. Y.; Tronstad, Christian; Kalvøy, Håvard & Martinsen, Ørjan Grøttem (2017). Electrodermal responses to discrete stimuli measured by skin conductance, skin potential, and skin susceptance. Skin Research and Technology. ISSN 0909-752X. 24(1), p. 108–116. doi: 10.1111/srt.12397. Full text in Research Archive
Tronstad, Christian; Elvebakk, Ole; Kalvøy, Håvard; Bjørgaas, Marit Ragnhild Rokne & Martinsen, Ørjan Grøttem (2017). Detection of sympathoadrenal discharge by parameterisation of skin conductance and ECG measurement. IEEE Engineering in Medicine and Biology Society. Conference Proceedings. ISSN 1557-170X. p. 3997–4000. doi: 10.1109/EMBC.2017.8037732. Full text in Research Archive
Strand-Amundsen, Runar James; Reims, Henrik Mikael; Tronstad, Christian; Kalvøy, Håvard; Martinsen, Ørjan Grøttem & Høgetveit, Jan Olav [Show all 8 contributors for this article] (2017). Ischemic small intestine - In vivo versus ex vivo bioimpedance measurements. Physiological Measurement. ISSN 0967-3334. 38(5), p. 715–728. doi: 10.1088/1361-6579/aa67b7. Full text in Research Archive
Pettersen, Fred Johan; Martinsen, Ørjan Grøttem; Høgetveit, Jan Olav; Kalvøy, Håvard & Odland, Hans Henrik (2016). Bioimpedance spectroscopy of temporal impedance changes in a beating heart. Biomedical Engineering & Physics Express. 2. doi: 10.1088/2057-1976/2/6/065015. Full text in Research Archive
Strand-Amundsen, Runar James; Tronstad, Christian; Kalvøy, Håvard; Gundersen, Yngvar; Krohn, Claus Danckert & Aasen, Ansgar Oddne [Show all 12 contributors for this article] (2016). In vivo characterization of ischemic small intestine using bioimpedance measurements. Physiological Measurement. ISSN 0967-3334. 37(2), p. 257–275. doi: 10.1088/0967-3334/37/2/257. Full text in Research Archive Show summary
The standard clinical method for the assessment of viability in ischemic small intestine is still visual inspection and palpation. This method is non-specific and unreliable, and requires a high level of clinical experience. Consequently, viable tissue might be removed, or irreversibly damaged tissue might be left in the body, which may both slow down patient recovery. Impedance spectroscopy has been used to measure changes in electrical parameters during ischemia in various tissues. The physical changes in the tissue at the cellular and structural levels after the onset of ischemia lead to time-variant changes in the electrical properties. We aimed to investigate the use of bioimpedance measurement to assess if the tissue is ischemic, and to assess the ischemic time duration. Measurements were performed on pigs (n = 7) using a novel two-electrode setup, with a Solartron 1260/1294 impedance gain-phase analyser. After induction of anaesthesia, an ischemic model with warm, full mesenteric arterial and venous occlusion on 30 cm of the jejunum was implemented. Electrodes were placed on the serosal surface of the ischemic jejunum, applying a constant voltage, and measuring the resulting electrical admittance. As a control, measurements were done on a fully perfused part of the jejunum in the same porcine model. The changes in tan δ (dielectric parameter), measured within a 6 h period of warm, full mesenteric occlusion ischemia in seven pigs, correlates with the onset and duration of ischemia. Tan δ measured in the ischemic part of the jejunum differed significantly from the control tissue, allowing us to determine if the tissue was ischemic or not (P < 0.0001, F = (1,75.13) 188.19). We also found that we could use tan δ to predict ischemic duration. This opens up the possibility of real-time monitoring and assessment of the presence and duration of small intestinal ischemia.
Kalvøy, Håvard; Aliau-Bonet, C; Pallas-Areny, R. & Martinsen, Ørjan Grøttem (2015). Effects of stray capacitance to ground in three electrode monopolar needle bioimpedance measurements. IEEE Engineering in Medicine and Biology Society. Conference Proceedings. ISSN 1557-170X. 2015-November, p. 7542–7545. doi: 10.1109/EMBC.2015.7320137. Full text in Research Archive
Kalvøy, Håvard & Sauter, Axel Rudolf (2015). Detection of intraneural needle-placement with multiple frequency bioimpedance monitoring: a novel method. Journal of clinical monitoring and computing. ISSN 1387-1307. doi: 10.1007/s10877-015-9698-3. Full text in Research Archive
Pettersen, Fred Johan; Ferdous, Humayra; Kalvøy, Håvard; Martinsen, Ørjan Grøttem & Høgetveit, Jan Olav (2014). Comparison of four different FIM configurations - A simulation study. Physiological Measurement. ISSN 0967-3334. 35(6), p. 1067–1082. doi: 10.1088/0967-3334/35/6/1067. Full text in Research Archive
Tronstad, Christian; Kalvøy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2013). Improved Estimation of Sweating Based on Electrical Properties of Skin. Annals of Biomedical Engineering. ISSN 0090-6964. 41(5), p. 1074–1083. doi: 10.1007/s10439-013-0743-4. Full text in Research Archive
Haugan, Berit; Langerud, Anne Kathrine; Kalvøy, Håvard; Frøslie, Kathrine Frey; Riise, Else & Kapstad, Heidi (2013). Can we trust the new generation of infrared tympanic thermometers in clinical practice? Journal of Clinical Nursing (JCN). ISSN 0962-1067. 22(5-6), p. 698–709. doi: 10.1111/j.1365-2702.2012.04077.x. Full text in Research Archive
Tronstad, Christian; Kalvøy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2013). Waveform difference between skin conductance and skin potential responses in relation to electrical and evaporative properties of skin. Psychophysiology. ISSN 0048-5772. 50(11), p. 1070–1078. doi: 10.1111/psyp.12092. Full text in Research Archive
Kvaløy, Håvard; Johnsen, Gorm Krogh; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2011). New method for separation of electrode polarization impedance from measured tissue impedance. Open Biomedical Engineering Journal. 5, p. 8–13. doi: 10.2174/1874120701105010008. Full text in Research Archive
Høyum, Per; Kvaløy, Håvard; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2010). A finite element model of needle electrode spatial sensitivity. Physiological Measurement. ISSN 0967-3334. 31(10), p. 1369–1379. doi: 10.1088/0967-3334/31/10/006. Full text in Research Archive
Kalvøy, Håvard; Høyum, Per; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2010). From impedance theory to needle electrode guidance in tissue. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 224. doi: 10.1088/1742-6596/224/1/012072. Full text in Research Archive
Høyum, Per; Kalvøy, Håvard; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2010). Finite element model of needle electrode sensitivity. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 224(1). Full text in Research Archive
Kalvøy, Håvard; Tronstad, Christian; Nordbotten, Bernt Jørgen; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2010). Electrical Impedance of Stainless Steel Needle Electrodes. Annals of Biomedical Engineering. ISSN 0090-6964. 38(7), p. 2371–2382. doi: 10.1007/s10439-010-9989-2. Full text in Research Archive
Martinsen, Ørjan Grøttem; Kalvøy, Håvard; Grimnes, Sverre; Nordbotten, Bernt Jørgen; Hol, Per Kristian & Fosse, Erik [Show all 8 contributors for this article] (2010). Invasive electrical impedance tomography for blood vessel detection. Open Biomedical Engineering Journal. 4, p. 135–137. doi: 10.2174/1874120701004010135. Full text in Research Archive
Sauter, Axel Rudolf; Dodgson, Michael; Kvaløy, Håvard; Grimnes, Sverre; Stubhaug, Audun & Klaastad, Øivind (2009). Current Threshold for Nerve Stimulation Depends on Electrical Impedance of the Tissue: A Study of Ultrasound-Guided Electrical Nerve Stimulation of the Median Nerve. Anesthesia and Analgesia. ISSN 0003-2999. 108(4), p. 1338–1343. doi: 10.1213/ane.0b013e3181957d84. Full text in Research Archive
Kvaløy, Håvard; Nordbotten, Bernt Jørgen; Tronstad, Christian; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2009). Impedance properties of stainless steel needle electrodes. International Federation for Medical and Biological Engineering Proceedings. ISSN 1680-0737. 25, p. 380–383. Full text in Research Archive
Tronstad, Christian; Krogstad, Anne Lene; Kvaløy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2009). Skin AC conductance levels and responses in axillary hyperhidrosis patients. International Federation for Medical and Biological Engineering Proceedings. ISSN 1680-0737. 25, p. 349–351. Full text in Research Archive
Kvaløy, Håvard; Frich, Lars Inge; Grimnes, Sverre; Martinsen, Ørjan Grøttem; Hol, Per Kristian & Stubhaug, Audun (2009). Impedance-based tissue discrimination for needle guidance. Physiological Measurement. ISSN 0967-3334. 30(2), p. 129–140. doi: 10.1088/0967-3334/30/2/002. Full text in Research Archive
Kalvøy, Håvard; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2008). Determination of tissue type surrounding a needle tip by electrical bioimpedance. IEEE Engineering in Medicine and Biology Society. Conference Proceedings. ISSN 1557-170X. p. 2285–2286. Full text in Research Archive
Kalvøy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2007). Needle position determined by tissue impedance. International Federation for Medical and Biological Engineering Proceedings. ISSN 1680-0737. 17, p. 205–208. Full text in Research Archive

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Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre Inge; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Frøslie, Kathrine Frey [Show all 10 contributors for this article] (2019). Author Correction: Evaluation of Hypoglycaemia with Non-Invasive Sensors in People with Type 1 Diabetes and Impaired Awareness of Hypoglycaemia (Scientific Reports, (2018), 8, 1, (14722), 10.1038/s41598-018-33189-1). Scientific Reports. 9(1). doi: 10.1038/s41598-019-42218-6. Full text in Research Archive
Tronstad, Christian; Elvebakk, Ole; Martinsen, Ørjan Grøttem; Kalvøy, Håvard & Høgetveit, Jan Olav (2016). Bioimpedance for prediction of hypoglycemic trends. Proceedings of the 16th International Conference on Electrical Bioimpedance. Full text in Research Archive
Pettersen, Fred Johan; Martinsen, Ørjan Grøttem; Høgetveit, Jan Olav; Flattum, M.; Kalvøy, Håvard & Odland, Hans Henrik (2016). Using pacemaker leads for bioimpedance and electromyography. Proceedings of the 16th International Conference on Electrical Bioimpedance. p. 73–73. Full text in Research Archive
Kalvøy, Håvard; Sauter, Axel Rudolf; Tronstad, Christian & Martinsen, Ørjan Grøttem (2016). Neural tissue discrimination with machine learning methods. Proceedings of the 16th International Conference on Electrical Bioimpedance. p. 71–71. Full text in Research Archive
Kalvøy, Håvard; Aliau-Bonet, C.; Pallas-Areny, R. & Martinsen, Ørjan Grøttem (2015). Effects of stray capacitance to ground in three electrode monopolar needle bioimpedance measurements. Full text in Research Archive
Kalvøy, Håvard; Tronstad, Christian; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2013). Simultaneous measurement of DC potential and AC conductance to monitor electrodermal activity at a single electrode. Full text in Research Archive
Amoussou-Guenou, Kuassi M.; Houndetoungan, G. D.; Fachinan, O. H.; Kalvøy, Håvard & Martinsen, Ørjan Grøttem (2013). Comparison of two filtration methods in erythrocyte deformability: determination measurement using impedancemetry. Full text in Research Archive
Tronstad, Christian; Kalvøy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2013). Sweat production estimated by bioimpedance and bioelectrical signals. Full text in Research Archive
Tronstad, Christian; Kvaløy, Håvard; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2012). New parameters of electrodermal activity and estimation of sweat production. International Federation for Medical and Biological Engineering Proceedings. ISSN 1680-0737. 39. Full text in Research Archive
Kvaløy, Håvard; Tronstad, Christian; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2012). Electrodermal activity measured as DC potential and AC conductance at the same electrode. International Federation for Medical and Biological Engineering Proceedings. ISSN 1680-0737. 39. Full text in Research Archive
Kalvøy, Håvard; Grimnes, Sverre; Martinsen, Ørjan Grøttem & Høyum, Per (2006). Current distribution and impedance in monopolar needle electrode systems. Full text in Research Archive
Kalvøy, Håvard (2010). Needle Guidance in Clinical Applications based on Electrical Impedance. Universitetet i Oslo. Full text in Research Archive

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Published Apr. 14, 2011 10:31 AM - Last modified Apr. 14, 2011 12:37 PM

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Oslo Bioimpedance Group