Christian Tronstad

• Andersen, Jan-Hugo; Bjerke, Olav; Blakaj, Fatos; Flugsrud, Vilde Moe; Jacobsen, Fredrik Alstad; Jonsson, Marius; Kosaka, Eirik Nobuki; Langstrand, Petter André; Martinsen, Øyvind Grannes; Moen, Alexander Stene; Moen, Emily Qing Zang; Nystad, Øyvind Knutsen; Qureshi, Mahum; Olesen, Eline; Risopatròn, Victor Josè Østrem; Ruud, Simen Kristoffer; Stensø, Nikolai; Winje, Fredrik; Winness, Eirik Vetle; Abie, Sisay Mebre; Joten, Vegard Munkeby; Tronstad, Christian; Elvebakk, Ole & Martinsen, Ørjan Grøttem (2019). Bioimpedance and NIR for non-invasive assessment of blood glucose. Journal of Electrical Bioimpedance.  ISSN 1891-5469.  10, s 133- 138 . doi: 10.2478/joeb-2019-0019
• Aria, Shafa; Elfarri, Yassine; Elvegård, Marius; Gottfridsson, Adam; Grønaas, Halvor; Harang, Sigve Smedsrud; Jensen, Anders; Madland, Thomas Emil Rolland; Martins, Ivar Bruvik; Olstad, Marius Wilhelm; Ryan, Tommy Lee; Shaban, Anwar Nazih; Svenningsen, Øyvind Løken; Sørensen, Andre Djupvik; Ulvestad, Emil Holm; Vister, Ole Martin; Øvergaard, Morten Bratgjerd; Kalvøy, Håvard; Pettersen, Fred-Johan; Odland, Hans Henrik; Joten, Vegard Munkeby; Martinsen, Øyvind Grannes; Tronstad, Christian; Elvebakk, Ole & Martinsen, Ørjan Grøttem (2019). Measuring blood pulse wave velocity with bioimpedance in different age groups. Sensors.  ISSN 1424-8220.  19:850(4), s 1- 10 . doi: 10.3390/s19040850
• Bjørhei, Andreas; Pedersen, Filip T.; Muhammad, Saeed; Tronstad, Christian; Kalvøy, Håvard; Wojniusz, Slawomir; Pabst, Oliver & Sütterlin, Stefan (2019). An investigation on bilateral asymmetry in electrodermal activity. Frontiers in Behavioral Neuroscience.  ISSN 1662-5153.  13(88) . doi: 10.3389/fnbeh.2019.00088 Fulltekst i vitenarkiv.
• Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre I.; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne; Gulseth, Hanne Løvdal; Kalvøy, Håvard; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem (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.
• Martinsen, Tormod; Pettersen, Fred-Johan; Kalvøy, Håvard; Tronstad, Christian; Kvarstein, Gunnvald; Bakken, André; Høgetveit, Jan Olav; Martinsen, Ørjan Grøttem; Grimnes, Sverre & Frich, Lars Inge (2019). Electrosurgery and temperature increase in tissue with a passive metal implant. Frontiers in surgery.  ISSN 2296-875X.  6:8, s 1- 8 . doi: 10.3389/fsurg.2019.00008 Fulltekst i vitenarkiv.
• 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.  ISSN 1891-5469.  10, s 110- 112 . doi: 10.2478/joeb-2019-0016
• Tronstad, Christian; Elvebakk, Ole; Staal, Odd Martin; Kalvøy, Håvard; Høgetveit, Jan Olav; Jenssen, Trond Geir; Birkeland, Kåre I. & Martinsen, Ørjan Grøttem (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
• 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.  ISSN 1891-5469.  10(1), s 139- 145 . doi: 10.2478/joeb-2019-0020
• Tronstad, Christian & Strand-Amundsen, Runar James (2019). Possibilities in the application of machine learning on bioimpedance time-series. Journal of Electrical Bioimpedance.  ISSN 1891-5469.  10(1), s 24- 33 . doi: 10.2478/joeb-2019-0004
• 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.  ISSN 1891-5469.  9, s 52- 58 . doi: 10.2478/joeb-2018-0010 Fulltekst i vitenarkiv.
• 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, s 298- 307 . doi: 10.1159/000492275
• Bruehl, Stephen; Bjørkholt Olsen, Roy; Tronstad, Christian; Sevre, Knut; Burns, John W; Schirmer, Henrik; Nielsen, Christopher Sivert; Stubhaug, Audun & Rosseland, Leiv Arne (2018). Chronic pain-related changes in cardiovascular regulation and impact on comorbid hypertension in a general population: the Tromsø study. Pain.  ISSN 0304-3959.  159(1), s 119- 127 . doi: 10.1097/j.pain.0000000000001070 Fulltekst i vitenarkiv.
• Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre I.; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne; Frøslie, Kathrine Frey; Godang, Kristin; Kalvøy, Håvard; Martinsen, Ørjan Grøttem & Gulseth, Hanne Løvdal (2018). Evaluation of hypoglycaemia with non-invasive sensors in people with type 1 diabetes and impaired awareness of hypoglycaemia. Scientific Reports.  ISSN 2045-2322.  8:14722, s 1- 11 . doi: 10.1038/s41598-018-33189-1 Fulltekst i vitenarkiv.
• Strand-Amundsen, Runar James; Tronstad, Christian; Kalvøy, Håvard; Ruud, Tom Erik; Høgetveit, Jan Olav; Martinsen, Ørjan Grøttem & Tønnessen, Tor Inge (2018). Small intestinal ischemia and reperfusion - Bioimpedance measurements. Physiological Measurement.  ISSN 0967-3334.  39(2) . doi: 10.1088/1361-6579/aaa576 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.
• 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), s 108- 116 . doi: 10.1111/srt.12397
• 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.  s 9- 12 . doi: 10.1109/EMBC.2017.8036750
• Pabst, Oliver; Tronstad, Christian; Grimnes, Sverre; Fowles, Don C. & Martinsen, Ørjan Grøttem (2017). Comparison between the AC and DC measurement of electrodermal activity. Psychophysiology.  ISSN 0048-5772.  54(3), s 374- 385 . doi: 10.1111/psyp.12803
• Pabst, Oliver; Tronstad, Christian & Martinsen, Ørjan Grøttem (2017). Instrumentation, electrode choice and challenges in human skin memristor measurement. IEEE Engineering in Medicine and Biology Society. Conference Proceedings.  ISSN 1557-170X.  s 1844- 1848 . doi: 10.1109/EMBC.2017.8037205
• Strand-Amundsen, Runar James; Reims, Henrik Mikael; Tronstad, Christian; Kalvøy, Håvard; Martinsen, Ørjan Grøttem; Høgetveit, Jan Olav; Ruud, Tom Erik & Tønnessen, Tor Inge (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
• 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.  s 3997- 4000 . doi: 10.1109/EMBC.2017.8037732
• Nygaard, Kent Inge; Thiara, Amrit Paul Singh; Tronstad, Christian; Ringdal, Mari-Anne I Lindstein & Fiane, Arnt E (2016). VAVD vacuum may cause bubble transgression in membrane oxygenators. Perfusion.  ISSN 0267-6591.  31(8), s 648- 652 . doi: 10.1177/0267659116651345
• Strand-Amundsen, Runar James; Tronstad, Christian; Kalvøy, Håvard; Gundersen, Yngvar; Krohn, Claus Danckert; Aasen, Ansgar Oddne; Holhjem, Lars; Reims, Henrik Mikael; Martinsen, Ørjan Grøttem; Høgetveit, Jan Olav; Ruud, Tom Erik & Tønnessen, Tor Inge (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 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.

• Martinsen, Ørjan Grøttem; Pabst, Oliver; Tronstad, Christian & Grimnes, Sverre (2015). Sources of error in AC measurement of skin conductance. Journal of Electrical Bioimpedance.  ISSN 1891-5469.  6(1), s 49- 53 . doi: 10.5617/jeb.2640
• Pischke, Søren Erik; Hyler, Stefan; Tronstad, Christian; Bergsland, Jacob; Fosse, Erik; Halvorsen, Per Steinar; Skulstad, Helge & Tønnessen, Tor Inge (2015). Myocardial tissue CO2 tension detects coronary blood flow reduction after coronary artery bypass in real-time. British Journal of Anaesthesia.  ISSN 0007-0912.  114(3), s 414- 422 . doi: 10.1093/bja/aeu381
• Tronstad, Christian; Omenås, Ivar Nagelgaard & Rosseland, Leiv Arne (2015). An improved artifact removal algorithm for continuous cardiac output and blood pressure recordings. IEEE Engineering in Medicine and Biology Society. Conference Proceedings.  ISSN 1557-170X.  2015-November, s 5968- 5972 . doi: 10.1109/EMBC.2015.7319751
• Tronstad, Christian; Staal, Odd Martin; Saelid, Steinar & Martinsen, Ørjan Grøttem (2015). Model- based filtering for artifact and noise suppression with state estimation for electrodermal activity measurements in real time. IEEE Engineering in Medicine and Biology Society. Conference Proceedings.  ISSN 1557-170X.  s 2750- 2753 . doi: 10.1109/EMBC.2015.7318961
• Nordbotten, Bernt Jørgen; Tronstad, Christian; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2014). Estimation of skin conductance at low frequencies using measurements at higher frequencies for EDA applications. Physiological Measurement.  ISSN 0967-3334.  35(6), s 1011- 1018 . doi: 10.1088/0967-3334/35/6/1011
• Tronstad, Christian; Helsing, Per; Tønseth, Kim Aleksander; Grimnes, Sverre & Polesie, Anne Lene Krogstad (2014). Tumescent suction curettage vs. curettage only for treatment of axillary hyperhidrosis evaluated by subjective and new objective methods. Acta Dermato-Venereologica.  ISSN 0001-5555.  94(2), s 215- 220 . doi: 10.2340/00015555-1671
• Tronstad, Christian & Pripp, Are Hugo (2014). Statistical methods for bioimpedance analysis. Journal of Electrical Bioimpedance.  ISSN 1891-5469.  5(1), s 14- 27 . doi: 10.5617/jeb.830
• 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), s 1074- 1083 . doi: 10.1007/s10439-013-0743-4
• 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), s 1070- 1078 . doi: 10.1111/psyp.12092
• Pischke, Søren Erik; Tronstad, Christian; Holhjem, Lars; Halvorsen, Per Steinar & Tønnessen, Tor Inge (2012). Perioperative detection of myocardial ischaemia/reperfusion with a novel tissue CO2 monitoring technology. European Journal of Cardio-Thoracic Surgery.  ISSN 1010-7940.  42(1), s 157- 163 . doi: 10.1093/ejcts/ezr278
• Pischke, Søren Erik; Tronstad, Christian; Holhjem, Lars; Line, Pål Dag; Haugaa, Håkon & Tønnessen, Tor Inge (2012). Hepatic and Abdominal Carbon Dioxide Measurements Detect and Distinguish Hepatic Artery Occlusion and Portal Vein Occlusion in Pigs. Liver transplantation.  ISSN 1527-6465.  18(12), s 1485- 1494 . doi: 10.1002/lt.23544
• Grimnes, Sverre; Jabbari, Azar; Martinsen, Ørjan Grøttem & Tronstad, Christian (2011). Electrodermal activity by DC potential and AC conductance measured simultaneously at the same skin site. Skin research and technology.  ISSN 0909-752X.  17(1), s 26- 34 . doi: 10.1111/j.1600-0846.2010.00459.x
• Nordbotten, Bernt Jørgen; Tronstad, Christian; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2011). Evaluation of algorithms for calculating bioimpedance phase angle values from measured whole-body impedance modulus. Physiological Measurement.  ISSN 0967-3334.  32(7), s 755- 765 . doi: 10.1088/0967-3334/32/7/S03
• 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), s 2371- 2382 . doi: 10.1007/s10439-010-9989-2
• Tronstad, Christian; Grimnes, Sverre; Martinsen, Ørjan Grøttem; Amundsen, Vegar & Wojniusz, Slawomir (2010). PC-based instrumentation for electrodermal activity measurement. Journal of Physics: Conference Series.  ISSN 1742-6588.  224 . doi: 10.1088/1742-6596/224/1/012093 Vis sammendrag

  A PC-based EDA measuring system is presented. The system is composed of a laptop with a PCMCIA DAQ-card running LabVIEW® software, a small front-end with a dual op-amp IC and a few passive components, and three skin-surface electrodes. The electrode system gives a monopolar measurement below the measuring electrode regardless of the electrode sizes, unless very small. Usage of the system is demonstrated by measurements from a mental stress experiment on 17 volunteers. There was a significant correlation (R=0.51, p<0.001) between the self-assessed stress-level and the EDA response frequency. The system allows easy on-site customization in software of measuring parameters, signal-quality monitoring and non-linearity detection in real time. We believe that the most suited use for the system is for stationary experimental purposes where this flexibility is desired. The system is easy to reproduce by engineers interested in doing EDA research.

• Tronstad, Christian; Johnsen, Gorm Krogh; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2010). A study on electrode gels for skin conductance measurements. Physiological Measurement.  ISSN 0967-3334.  31(10), s 1395- 1410 . doi: 10.1088/0967-3334/31/10/008
• Tronstad, Christian; Pischke, Søren Erik; Holhjem, L; Tønnessen, Tor Inge; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2010). Early detection of cardiac ischemia using a conductometric pCO(2) sensor: real-time drift correction and parameterization. Physiological Measurement.  ISSN 0967-3334.  31(9), s 1241- 1255 . doi: 10.1088/0967-3334/31/9/013

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• Pabst, Oliver; Martinsen, Ørjan Grøttem; Tronstad, Christian & Wilson, Steven Ray Haakon (2018). Electrical properties of human skin: From linear recordings of exogenous electrodermal activity to non-linear memristor measurements. Series of dissertations submitted to the Faculty of Mathematics and Natural Sciences, University of Oslo.. 1971.
• 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.  s 71
• Pabst, Oliver; Tronstad, Christian; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2016). Comparison between AC and DC exosomatic EDA measuring methods. Proceedings of the 16th International Conference on Electrical Bioimpedance.  s 65
• 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
• 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.
• Elvebakk, Ole; Tronstad, Christian; Gulseth, Hanne Løvdal; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne; Høgetveit, Jan Olav; Martinsen, Ørjan Grøttem & Birkeland, Kåre I. (2015). Physiological and symptomatic responses to hypoglycemia in patients with impaired awareness.
• Tronstad, Christian; Staal, Odd Martin; Sælid, Steinar & Martinsen, Ørjan Grøttem (2015). Model-based filtering for artifact and noise suppression with state estimation for electrodermal activity measurements in real time.
• 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.
• 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.
• Nordbotten, Bernt Jørgen; Tronstad, Christian; Martinsen, Ørjan Grøttem & Grimnes, Sverre (2013). Estimation of skin conductance at low frequencies from measurements at higher frequencies for EDA application.
• 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.
• Tronstad, Christian; Kalvøy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem (2013). Sweat production estimated by bioimpedance and bioelectrical signals.
• 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
• Tronstad, Christian (2012). Developments in biomedical sensors based on electrical impedance- Improvements in electrodes, instrumentation and signal processing technology for new and existing biomedical sensors for clinical use.
• 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

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