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Jan Olav Høgetveit

Førsteamanuensis II

E-post j.o.hogetveit@fys.uio.no

Telefon +47 23 07 15 99

Rom Rikshospitalet, Rom D4.3046 (inngang fra D2)

Brukernavn

Besøksadresse Medisinsk-teknologisk avdeling Rikshospitalet Sognsvannsveien 20 0027 Oslo

Postadresse Medisinsk-teknologisk avdeling Postboks 4950 Nydalen 0424 Oslo

Last ned visittkort

Akademiske interesser

Min hovedinteresse har vært medisinsk instrumentering innenfor thoraxkirurgi og trådløs kommunikasjon og interferens. På tross av at det stadig utvikles nye og minimalt invasive kardiologiske prosedyrer er hjerte-lungemaskinen fremdeles helt nødvendig for et stort antall avanserte kirurgiske hjerteprosedyrer. Ved slike prosedyrer er det av avgjørende betydning å holde kontroll på pasientens viktigste fysiologiske parametre uten å påføre pasienten skade, og derfor er det nødvendig å finne nye måletekniske løsninger i nært samarbeid med den aktuelle medisinsk ekspertise. Jeg har særlig vært opptatt av dette tverrfaglige området der spisskompetanse på forskjellige fagområder må kombineres for å oppnå den beste løsningen for pasienten.

Undervisning

http://www.uio.no/studier/emner/matnat/fys/FYS4250/

Høyere utdannelse og arbeidserfaring

Jeg ble utdannet i 1993 som elektroingeniør, Teknisk kybernetikk, ved Oslo Ingeniørhøyskole, og fikk Mastergrad i Elektronikk, Måleteknikk, ved Fysisk Institutt, Universitetet i Oslo i 1997. Masteroppgaven hadde tittelen: "En datapresentasjonsform spesialtilpasset intensivmedisinen", et tema som jeg fortsatte å arbeide med i perioden 1997-1998 ved Institutt for Kirurgisk Forskning der jeg også hadde jobbet med masteroppgaven. I 1998 ble jeg innvilget doktorgradsstipend fra Norges Forskningsråd, og begynte i 1999 å arbeide ved Medisinsk-teknisk avdeling, Rikshospitalet som utviklingsingeniør. Fra 2001 ble jeg leder av Forsknings- og utviklingsseksjonen ved samme avdeling. I 2008 mottok jeg Dr. Scient-graden ved Fysisk Institutt, Universitetet i Oslo med avhandlingen: "Technology Applications for Medical Devices Related to Surgical Operations", og ble så i 2009 utnevnt til Førsteamanuensis ved Fysisk Institutt ved Universitetet i Oslo.

Emneord: Biomedisinsk instrumentering, Medisinsk teknologi, Elektronikk og instrumentering, Bioimpedans, Kirurgisk teknologi

Hou, Jie; Liavåg, Olav Magnus Ivar; Færden, Ida Høy; Martinsen, Ørjan Grøttem; Tønnessen, Tor Inge & Line, Pål Dag [Vis alle 10 forfattere av denne artikkelen] (2022). Utilization of dielectric properties for assessment of liver ischemia-reperfusion injury in vivo and during machine perfusion. Scientific Reports. 12(1). doi: 10.1038/s41598-022-14817-3. Fulltekst i vitenarkiv Vis sammendrag
Abstract There is a shortage of donor livers and patients consequently die on waiting lists worldwide. Livers are discarded if they are clinically judged to have a high risk of non-function following transplantation. With the aim of extending the pool of available donor livers, we assessed the condition of porcine livers by monitoring the microwave dielectric properties. A total of 21 livers were divided into three groups: control with no injury (CON), biliary injury by hepatic artery occlusion (AHEP), and overall hepatic injury by static cold storage (SCS). All were monitored for four hours in vivo, followed by ex vivo plurithermic machine perfusion (PMP). Permittivity data was modeled with a two-pole Cole–Cole equation, and dielectric properties from one-hour intervals were analyzed during in vivo and normothermic machine perfusion (NMP). A clear increasing trend in the conductivity was observed in vivo in the AHEP livers compared to the control livers. After four hours of NMP, separations in the conductivity were observed between the three groups. Our results indicate that dielectric relaxation spectroscopy (DRS) can be used to detect and differentiate liver injuries, opening for a standardized and reliable point of evaluation for livers prior to transplantation.
Hou, Jie; Strand-Amundsen, Runar James; Tronstad, Christian; Tønnessen, Tor Inge; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem (2022). Small intestinal viability assessment using dielectric relaxation spectroscopy and deep learning. Scientific Reports. 12(1). doi: 10.1038/s41598-022-07140-4. Fulltekst i vitenarkiv Vis sammendrag
Abstract Intestinal ischemia is a serious condition where the surgeon often has to make important but difficult decisions regarding resections and resection margins. Previous studies have shown that 3 h (hours) of warm full ischemia of the small bowel followed by reperfusion appears to be the upper limit for viability in the porcine mesenteric ischemia model. However, the critical transition between 3 to 4 h of ischemic injury can be nearly impossible to distinguish intraoperatively based on standard clinical methods. In this study, permittivity data from porcine intestine was used to analyze the characteristics of various degrees of ischemia/reperfusion injury. Our results show that dielectric relaxation spectroscopy can be used to assess intestinal viability. The dielectric constant and conductivity showed clear differences between healthy, ischemic and reperfused intestinal segments. This indicates that dielectric parameters can be used to characterize different intestinal conditions. In addition, machine learning models were employed to classify viable and non-viable segments based on frequency dependent dielectric properties of the intestinal tissue, providing a method for fast and accurate intraoperative surgical decision-making. An average classification accuracy of 98.7% was obtained using only permittivity data measured during ischemia, and 96.2% was obtained with data measured during reperfusion. The proposed approach allows the surgeon to get accurate evaluation from the trained machine learning model by performing one single measurement on an intestinal segment where the viability state is questionable.
Hou, Jie; Strand-Amundsen, Runar James; Hødnebø, Stina; Tønnessen, Tor Inge & Høgetveit, Jan Olav (2021). Assessing ischemic injury in human intestine ex vivo with electrical impedance spectroscopy. Journal of Electrical Bioimpedance. 12(1), s. 82–88. doi: 10.2478/joeb-2021-0011. Fulltekst i vitenarkiv Vis sammendrag
Abstract Electrical impedance spectroscopy is a well-established tool for monitoring changes in the electrical properties of tissue. Most tissue and organ types have been investigated in various studies. As for the small intestine, there are several published studies conducted on pig and rat models. This study investigates the changes in passive electrical properties of the complete wall of the human intestine non-invasively during ischemia. We aim to use the passive electrical properties to assess intestinal viability. The bioimpedance measurements were performed using a two-electrode set-up with a Solartron 1260 Impedance/gain-phase analyser. The small intestinal samples were resected from patients who underwent pancreaticoduodenectomy. Impedance measurements were conducted following resection by placing the electrodes on the surface of the intestine. A voltage was applied across the intestinal sample and the measured electrical impedance was obtained in the ZPlot software. Impedance data were further fitted into a Cole model to obtain the Cole parameters. The P y value was calculated from the extracted Cole parameters and used to assess the cell membrane integrity, thus evaluate the intestinal viability. Eight small intestinal segments from different patients were used in this study and impedance measurements were performed once an hour for a ten-hour period. One hour after resection, the impedance decreased, then increased the next two hours, before decreasing until the end of the experiment. For all the intestinal segments, the P y values first increased and reached a plateau which lasted for 1 - 2 hours, before it decreased irreversibly. The time interval where P y value reached the maximum is consistent with reported viable/non-viable limits from histological analysis.
Hou, Jie; Strand-Amundsen, Runar James; Tronstad, Christian; Høgetveit, Jan Olav; Martinsen, Ørjan Grøttem & Tønnessen, Tor Inge (2021). Automatic prediction of ischemia-reperfusion injury of small intestine using convolutional neural networks: A pilot study. Sensors. 21(19). doi: 10.3390/s21196691. Fulltekst i vitenarkiv Vis sammendrag
Acute intestinal ischemia is a life-threatening condition. The current gold standard, with evaluation based on visual and tactile sensation, has low specificity. In this study, we explore the feasibility of using machine learning models on images of the intestine, to assess small intestinal viability. A digital microscope was used to acquire images of the jejunum in 10 pigs. Ischemic segments were created by local clamping (approximately 30 cm in width) of small arteries and veins in the mesentery and reperfusion was initiated by releasing the clamps. A series of images were acquired once an hour on the surface of each of the segments. The convolutional neural network (CNN) has previously been used to classify medical images, while knowledge is lacking whether CNNs have potential to classify ischemia-reperfusion injury on the small intestine. We compared how different deep learning models perform for this task. Moreover, the Shapley additive explanations (SHAP) method within explainable artificial intelligence (AI) was used to identify features that the model utilizes as important in classification of different ischemic injury degrees. To be able to assess to what extent we can trust our deep learning model decisions is critical in a clinical setting. A probabilistic model Bayesian CNN was implemented to estimate the model uncertainty which provides a confidence measure of our model decisions.
Tronstad, Christian; Martinsen, Tormod; Olsen, Morten; Rosseland, Leiv Arne; Pettersen, Fred-Johan & Martinsen, Ørjan Grøttem [Vis alle 8 forfattere av denne artikkelen] (2020). Splitting one ventilator for multiple patients - a technical assessment. arXiv.org. ISSN 2331-8422. Fulltekst i vitenarkiv
Martinsen, Tormod; Pettersen, Fred-Johan; Kalvøy, Håvard; Tronstad, Christian; Kvarstein, Gunnvald & Bakken, André [Vis alle 10 forfattere av denne artikkelen] (2019). Electrosurgery and temperature increase in tissue with a passive metal implant. Frontiers in Surgery. 6:8, s. 1–8. doi: 10.3389/fsurg.2019.00008. Fulltekst i vitenarkiv Vis sammendrag
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.
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), s. 139–145. doi: 10.2478/joeb-2019-0020. Fulltekst i vitenarkiv Vis sammendrag
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.
Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre I.; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Gulseth, Hanne Løvdal [Vis alle 9 forfattere av denne artikkelen] (2019). A multiparameter model for non-invasive detection of hypoglycemia. Physiological Measurement. ISSN 0967-3334. 40(8), s. 1–14. doi: 10.1088/1361-6579/ab3676. Fulltekst i vitenarkiv Vis sammendrag
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 [Vis alle 8 forfattere av denne artikkelen] (2019). Non-invasive prediction of blood glucose trends during hypoglycemia. Analytica Chimica Acta. ISSN 0003-2670. 1052, s. 37–48. doi: 10.1016/j.aca.2018.12.009. Fulltekst i vitenarkiv
Strand-Amundsen, Runar James; Tronstad, Christian; Reims, Henrik Mikael; Reinholt, Finn P.; Høgetveit, Jan Olav & Tønnessen, Tor Inge (2018). Machine learning for intraoperative prediction of viability in ischemic small intestine. Physiological Measurement. ISSN 0967-3334. 39(10), s. 1–16. doi: 10.1088/1361-6579/aae0ea. Fulltekst i vitenarkiv Vis sammendrag
Objective: Evaluation of intestinal viability is essential in surgical decision-making in patients with acute intestinal ischemia. There has been no substantial change in the mortality rate (30-93%) of patients with acute mesenteric ischemia (AMI) since the 1980’s. As the accuracy from the first laparotomy alone is 50%, the gold standard is a second-look laparotomy, increasing the accuracy to 87-89%. This study investigates the use of machine learning to classify intestinal viability and histological grading in pig jejunum, based on multivariate time-series of bioimpedance sensor data. Approach: We have previously used a bioimpedance sensor system to acquire electrical parameters from perfused, ischemic and reperfused pig jejunum (7 + 15 pigs) over 1-16 hours of ischemia and 1-8 hours of reperfusion following selected durations of ischemia. In this study we compare the accuracy of using end-point bioimpedance measurements with a feedforward neural network (FNN), versus the accuracy when using a recurrent neural network with long short-term memory units (LSTM-RNN) with bioimpedance data history over different periods of time. Main results: Accuracies in the range of what has been reported clinically can be achieved using FNN’s on a single bioimpedance measurement, and higher accuracies can be achieved when employing LSTM-RNN on a sequence of data history. Significance: Intraoperative bioimpedance measurements on intestine of suspect viability combined with machine learning can increase the accuracy of intraoperative assessment of intestinal viability. Increased accuracy in intraoperative assessment of intestinal viability has the potential to reduce the high mortality and morbidity rate of the patients.
Strand-Amundsen, Runar James; Reims, Henrik Mikael; Reinholt, Finn P.; Ruud, Tom Erik; Yang, Runkuan & Høgetveit, Jan Olav [Vis alle 7 forfattere av denne artikkelen] (2018). Ischemia/reperfusion injury in porcine intestine - Viability assessment. World Journal of Gastroenterology (WJG). ISSN 1007-9327. 24(18), s. 2009–2023. doi: 10.3748/wjg.v24.i18.2009. Fulltekst i vitenarkiv
Strand-Amundsen, Runar James; Tronstad, Christian; Kalvøy, Håvard; Ruud, Tom Erik; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem [Vis alle 7 forfattere av denne artikkelen] (2018). Small intestinal ischemia and reperfusion - Bioimpedance measurements. Physiological Measurement. ISSN 0967-3334. 39(2). doi: 10.1088/1361-6579/aaa576. Fulltekst i vitenarkiv Vis sammendrag
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.
Strand-Amundsen, Runar James; Reims, Henrik Mikael; Tronstad, Christian; Kalvøy, Håvard; Martinsen, Ørjan Grøttem & Høgetveit, Jan Olav [Vis alle 8 forfattere av denne artikkelen] (2017). Ischemic small intestine - In vivo versus ex vivo bioimpedance measurements. Physiological Measurement. ISSN 0967-3334. 38(5), s. 715–728. doi: 10.1088/1361-6579/aa67b7. Fulltekst i vitenarkiv
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. Fulltekst i vitenarkiv
Strand-Amundsen, Runar James; Tronstad, Christian; Kalvøy, Håvard; Gundersen, Yngvar; Krohn, Claus Danckert & Aasen, Ansgar Oddne [Vis alle 12 forfattere av denne artikkelen] (2016). In vivo characterization of ischemic small intestine using bioimpedance measurements. Physiological Measurement. ISSN 0967-3334. 37(2), s. 257–275. doi: 10.1088/0967-3334/37/2/257. Fulltekst i vitenarkiv Vis sammendrag
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.
Pettersen, Fred Johan & Høgetveit, Jan Olav (2015). Optically isolated current source. Journal of Electrical Bioimpedance. 6(1), s. 18–21. doi: 10.5617/jeb.2571. Fulltekst i vitenarkiv Vis sammendrag
There is a need for isolated current sources for use in selected bio- impedance measurement circuits. The requirement for good isolation is particularly important in medical settings because of safety concerns. A new circuit for producing voltage-controlled current is presented. Measurements have been made on a prototype and simulations have been done on a SPICE model. The presented circuit is an H-bridge where the output devices are the output photodiodes of high-linearity optocouplers. Five operational amplifiers, four high linearity optocouplers, and passive components are used. Output current capability is ±35 μA with an output impedance that is more than 1 MΩ. It is possible to achieve bandwidths above 1 MHz for small load impedances. This circuit is well suited for medical applications thanks to the isolation in the optocouplers.
Pettersen, Fred Johan; Martinsen, Tormod; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem (2015). Unintentional heating at implants when using electrosurgery. IEEE Engineering in Medicine and Biology Society. Conference Proceedings. ISSN 1557-170X. s. 5805–5808. doi: 10.1109/EMBC.2015.7319711. Fulltekst i vitenarkiv
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), s. 1067–1082. doi: 10.1088/0967-3334/35/6/1067. Fulltekst i vitenarkiv
Pettersen, Fred Johan & Høgetveit, Jan Olav (2011). From 3D tissue data to impedance using Simpleware ScanFE+IP and COMSOL Multiphysics – a tutorial. Journal of Electrical Bioimpedance. 2, s. 13–32. doi: 10.5617/jeb.173. Fulltekst i vitenarkiv
Høgetveit, Jan Olav; Saatvedt, Kjell; Norum, Hilde Margrethe; Kristiansen, Frode; Elvebakk, Ole & Dahle, Gry [Vis alle 7 forfattere av denne artikkelen] (2011). Central venous catheters may be a potential source of massive air emboli during vascular procedures involving extracorporeal circulation: an experimental study. Perfusion. ISSN 0267-6591. 26(4), s. 341–346. doi: 10.1177/0267659111403644. Fulltekst i vitenarkiv
Pettersen, Fred Johan; Martinsen, Ørjan Grøttem; Grimnes, Sverre & Høgetveit, Jan Olav (2010). Impedance measurement set-up based on off-the-shelf PXI modules. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 224. doi: 10.1088/1742-6596/224/1/012002. Fulltekst i vitenarkiv
Høgetveit, Jan Olav; Kristiansen, Frode & Røislien, Jo (2009). A novel method for indirectly monitoring arterial pO(2) during cardiopulmonary bypass. Journal of Medical Engineering & Technology. ISSN 0309-1902. 33(7), s. 567–574. doi: 10.1080/03091900903071897. Fulltekst i vitenarkiv
Imenes, Kristin; Aasmundtveit, K; Husa, EM; Høgetveit, Jan Olav; Halvorsen, Steinar & Elle, Ole Jakob [Vis alle 9 forfattere av denne artikkelen] (2007). Assembly and packaging of a three-axis micro accelerometer used for detection of heart infarction. Biomedical microdevices. ISSN 1387-2176. 9, s. 951–957. doi: 10.1007/s10544-007-9082-2. Fulltekst i vitenarkiv
Imenes, Kristin; Aasmundtveit, Knut E.; Husa, Ellen Marie; Høgetveit, Jan Olav; Halvorsen, Steinar & Elle, Ole Jakob [Vis alle 9 forfattere av denne artikkelen] (2007). Assembly and packaging of a three-axis micro accelerometer used for detection of heart infarction. Biomedical microdevices. ISSN 1387-2176. 9, s. 951–957. Fulltekst i vitenarkiv Vis sammendrag
In coronary artery bypass grafting there is a risk of graft occlusion which may result in myocardial infarction. A three-axis acceleration sensor may give additional information about heart function during surgery and the first postoperative days. This paper describes the assembly and packaging of a three-axis micro acceleration sensor for use in clinical trials. The sensor was connected to a cable for power supply and signal output and moulded in silicone. Testing of the encapsulation showed leakage currents well below the 10 mu A limit for direct cardiac applications. A hydrogen peroxide gas plasma method was used for sterilization. In animal experiments the sensor was sutured to the heart and no fatigue failures ensued due to the cycling strain forces from the heart. The sensor has been qualified for clinical trials.
Øyri, Karl; Balasingham, Ilangko; Samset, Eigil; Høgetveit, Jan Olav & Fosse, Erik (2006). Wireless continuous arterial blood pressure monitoring during surgery: a pilot study. Anesthesia and Analgesia. ISSN 0003-2999. 102(2), s. 478–483. Fulltekst i vitenarkiv
Samset, Eigil; Høgetveit, Jan Olav; Cate, Gerben Ten & Hirschberg, Henry (2005). Integrated neuronavigation system with intraoperative image updating. Minimally Invasive Neurosurgery. ISSN 0946-7211. 48(2), s. 73–76. Fulltekst i vitenarkiv
Elle, Ole Jakob; Samset, Eigil; Bakken, Andre; Høgetveit, Jan Olav & Fosse, Erik (2000). Head-tracking in scopic surgical procedures using Robot-held camera and head-mounted stereoscopic display. I Lemke, Heinz U.; Vannier, Michael W.; Inamura, Kiyonari; Farman, Allan G. & Doi, Kunio (Red.), Procedings of the 14th International Congress and Exhibition - Computer Assisted Radiology and Surgery (CARS 2000), ICS 1214. ISSN 9780444505361. s. 121–127. Fulltekst i vitenarkiv Vis sammendrag
Compared to open surgery, endoscopic surgery is associated with less patient trauma, less risk for infections and reduced overall cost related convalescence time of the patient. However, the introduction of endoscopic surgery has some disadvantages compared to open surgery. The loss of depth perception using 2D-videoscopes makes the endoscopic skill and experience of the surgeon very important. This drawback has led to the development of 3D-videoscopes, cameras and Head Mounted Displays (HMD). HMD¿s helps the surgeon to be immersed by the video images. It has been observed that many surgeons, using head-mounted displays on 3D-vision system, turn their head in an awkward position during the procedure possibly to change the sight of view. Development of motion sickness while using the head mounted displays has also been reported. Intuitively the view changes according to the movement of the head and body. When this does not happen, the brain might misinterpret this contradictory information. In this study a prototype of a Head-Tracker is developed to overcome these problems related to the use of head mounted displays in scopic surgery. The proposed system tracks the head movements of the surgeons and direct the resulting signals from these sensed movements to a robot that holds the camera. Thus, the camera movement is coupled to the head movement, which gives the expected change of view.
Sveen, Ola Halvor; Høgetveit, Jan Olav & Aasen, Ansgar Oddne (1997). EWICUM, an early warning monitoring system for data presentation in the ICU. I Faist, Eugen (Red.), The Immune Consequences of Traum, Shock and Sepsis. Monduzzi editore, Italy. ISSN 9788832303049. s. 717–720. Fulltekst i vitenarkiv Vis sammendrag
A PC-based computer system is operating on-line performing real-time data collection, handling and presentation. The PC has a big data display screen in the ICU near to the patient beds. Analyses results are collected from many sources via the hospital data network. Several clinical scoring systems (APACHE II and III, SAPS II, LOD, PFI) are supported, indices are calculated automatically. The graphed results emphasise parameters and indices of maximal importance for the evaluation of critically ill patients (sepsis, severe trauma, major surgery, transplantations). The system combines scoring systems and key parameter evaluations in several important biological systems.

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Øyri, Karl; Balasingham, Ilangko & Høgetveit, Jan Olav (2003). Den trådløse pasienten. Scandinavian conference in Health Informatics. ISBN 9788271175078. 5 s. Fulltekst i vitenarkiv

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Strand-Amundsen, Runar James; Tronstad, Christian; Martinsen, Ørjan Grøttem; Høgetveit, Jan Olav; Ruud, TE & Tønnessen, Tor Inge (2016). Bioimpedance - in vivo vs in vitro ischemic small intestine. Proceedings of the 16th International Conference on Electrical Bioimpedance. s. 53–53. Fulltekst i vitenarkiv
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. Fulltekst i vitenarkiv
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. s. 73–73. Fulltekst i vitenarkiv
Elvebakk, Ole; Tronstad, Christian; Gulseth, Hanne Løvdal; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Høgetveit, Jan Olav [Vis alle 8 forfattere av denne artikkelen] (2015). Physiological and symptomatic responses to hypoglycemia in patients with impaired awareness. Fulltekst i vitenarkiv
Pettersen, Fred Johan; Martinsen, Tormod; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem (2015). Unintentional heating at implants when using electrosurgery. Fulltekst i vitenarkiv
Elvebakk, Ole; Tronstad, Christian; Høgetveit, Jan Olav; Jenssen, Trond Geir; Bjørgaas, Marit & Martinsen, Ørjan Grøttem (2013). Sweating reactions due to hypoglycemia detected by skin AC conductance. Fulltekst i vitenarkiv
Tronstad, Christian; Elvebakk, Ole; Høgetveit, Jan Olav; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Martinsen, Ørjan Grøttem (2013). Monitoring of sweat activity for detection of severe hypoglycemia – A pilot study. Fulltekst i vitenarkiv
Imenes, Kristin; Aasmundtveit, Knut E.; Husa, Ellen Marie; Høgetveit, Jan Olav; Halvorsen, Steinar & Elle, Ole Jakob [Vis alle 8 forfattere av denne artikkelen] (2007). Packaging of an implantable accelerometer for measurements of heart motion. Fulltekst i vitenarkiv
Høgetveit, Jan Olav; Øyri, Karl; Balasingham, Ilangko & Sveen, Ola Halvor (2003). Implications ofUsing Invasive Wireless Blood Preesure-Sensors in a Clinical Environment. Fulltekst i vitenarkiv
Aasen, Ansgar Oddne; Næss, Leif; Høgetveit, Jan Olav & Sveen, Ola Halvor (2002). Ewicum, a Unique ICU Monitoring System for Early Warning and Decision Support. Fulltekst i vitenarkiv
Elle, Ole Jakob; Samset, Eigil; Bakken, Andre; Høgetveit, Jan Olav & Fosse, Erik (2000). Head-tracking in scopic surgical procedures using Robot-held camera and head-mounted stereoscopic display. Fulltekst i vitenarkiv Vis sammendrag
Sammendrag Compared to open surgery, endoscopic surgery is associated with less patient trauma, less risk for infections and reduced overall cost related convalescence time of the patient. However, the introduction of endoscopic surgery has some disadvantages compared to open surgery. The loss of depth perception using 2D-videoscopes makes the endoscopic skill and experience of the surgeon very important. This drawback has led to the development of 3D-videoscopes, cameras and Head Mounted Displays (HMD). HMD¿s helps the surgeon to be immersed by the video images. It has been observed that many surgeons, using head-mounted displays on 3D-vision system, turn their head in an awkward position during the procedure possibly to change the sight of view. Development of motion sickness while using the head mounted displays has also been reported. Intuitively the view changes according to the movement of the head and body. When this does not happen, the brain might misinterpret this contradictory information. In this study a prototype of a Head-Tracker is developed to overcome these problems related to the use of head mounted displays in scopic surgery. The proposed system tracks the head movements of the surgeons and direct the resulting signals from these sensed movements to a robot that holds the camera. Thus, the camera movement is coupled to the head movement, which gives the expected change of view.
Høgetveit, Jan Olav; Sveen, Ola Halvor & Aasen, Ansgar Oddne (1998). EWICUM - Early Warning Intensive Care Unit Monitoring System. Fulltekst i vitenarkiv
Sveen, Ola Halvor; Høgetveit, Jan Olav & Aasen, Ansgar Oddne (1997). EWICUM, an Early Warning Monitorng System for Data Presentation in the ICU. Fulltekst i vitenarkiv
Sveen, Ola Halvor; Høgetveit, Jan Olav & Aasen, Ansgar Oddne (1997). EWICUM, Early Warning Intensive Care Unit Monitoring System. Fulltekst i vitenarkiv
Sveen, Ola Halvor; Høgetveit, Jan Olav & Aasen, Ansgar Oddne (1997). EWICUM - Early Warning Intensive Care Unit Monitoring. Fulltekst i vitenarkiv
Sveen, Ola Halvor; Høgetveit, Jan Olav & Aasen, Ansgar Oddne (1997). The EWICUM Data Presentation System. Fulltekst i vitenarkiv
Aasen, Ansgar Oddne; Solberg, Rigmor; Høgetveit, Jan Olav & Sveen, Ola Halvor (1997). Protease cascades in intraabdominal infection. Fulltekst i vitenarkiv
Aasen, Ansgar Oddne; Sveen, Ola Halvor & Høgetveit, Jan Olav (1996). Data Presentation in the Surgical Intensive Care Unit. Development of a Data Presentation System for Critical Biochemical Variables and Scoring Systems. Fulltekst i vitenarkiv
Sveen, Ola Halvor; Høgetveit, Jan Olav & Aasen, Ansgar Oddne (1996). An intensive care unit data presentation system for critical biochemical variables and scoring systems. Fulltekst i vitenarkiv
Mirtaheri, Peyman; Gunnlaugsdottir, Helga; Høgetveit, Jan Olav & Hellström, Lars-Gösta (2013). Spectroscopic determination of pH in an arterial line from a Heart-lung machine. KTH, School of Technology and Health (STH. Fulltekst i vitenarkiv Vis sammendrag
There is a need for a real-time, non-invasive method to monitor blood pH in a patient lineduring cardiopulmonary bypass, as today’s methods are both invasive and time consuming.Blood pH is an indicator of physiological and biochemical activity in the body and needs to be kept within a relatively narrow range, typically between 7.35-7.45. A pH value outside thisrange can be critical for the patient and therefore needs to be carefully monitored throughoutthe course of cardiopulmonary bypass. In this study the feasibility of using spectroscopicmethods for indirect measurement of pH was investigated, and both transmission andreflectance spectroscopy were tested. The results showed that NIR reflectance spectroscopy isa feasible technique for blood pH monitoring during cardiopulmonary bypass. A strongcorrelation was found between measured pH values and spectral output in the wavelengthrange 800-930 nm. It was suggested that by means of the statistical partial least squareregression method, a model could be created with three regression factors with across-validated R^2 of 0.906 and a prediction error RMSEP of 0.089 pH units. The results presented here form a foundation for further analysis and experiments with larger sample setand more controlled experimental environment.
Gudbrands, Heidi Kittilsen; Mirtaheri, Peyman & Høgetveit, Jan Olav (2012). Noninvasiv pH-måling ved bruk av hjertelungemaskin. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag
Målet med denne studien var å avklare om spektrometri er en egnet metode for kontinuerlig monitorering av pH-nivået i pasientens blod ved bruk av hjertelungemaskin (HML) under kirurgiske prosedyrer. Rapporten gir en innføring i noen av områdene som inngår i forsøkene, så som pH, spektrofotometri, bølgelengder, lyskilder og hjertelungemaskin. Den belyser også flere sider av blodets egenskaper. Rapporten inneholder også alle detaljer rundt oppsettet for forsøkene, gjennomføring og resultater av disse. Resultatene viser at bølgelengdeområdet for måling av pH i arterielt blod ligger mellom ca. 700 og 850 nm, og at spektrometri kan være en egnet metode for kontinuerlig monitorering av pH-nivået i pasientens blod ved bruk av HLM under kirurgiske prosedyrer, men må utredes nærmere og utvides med kliniske studier for å kvalitetssikre metoden.
Høgetveit, Jan Olav (2008). Information Technology Applications for Medical Devices Related to Surgical Operations. Universitetet i Oslo. Fulltekst i vitenarkiv
Høgetveit, Jan Olav (1997). En datapresentasjonsform spesialtilpasset intensivmedisinen. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag
I intensivbehandling av alvorlig syke pasienter står legene ovenfor store mengder tilgjengelige data for hver pasient. Datapresentesjonssystemet som ble utviklet i hovedoppgaven, samler inn data automatisk fra perifere enheter, lagrer og bearbeider de innsamlede data for å gjøre materialet oversiktelig og enkelt tilgjengelig for brukerne. Formålet er å kunne gjøre tilgjengelig personell på intensivavdelingen oppmerksomme på en uheldig utvikling så tidlig som mulig slik at riktig behandling kan settes iverk på et tidlig stadium i sykdomsforløpet.

Se alle arbeider i NVA

Publisert 4. nov. 2010 12:19 - Sist endret 14. nov. 2011 13:18

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