Fred-Johan Pettersen

• Tronstad, Christian; Kleggetveit, Inge Petter; Arora, Tarun; Bakken, André; Nilsen, Kristian Bernhard & Pettersen, Fred-Johan (2025). Advancing possibilities in noninvasive nerve function testing with miniature sensory and motor nerve conduction instrumentation. IEEE Engineering in Medicine and Biology Society. Conference Proceedings. ISSN 1557-170X. doi: 10.1109/EMBC58623.2025.11253218. Fulltekst i vitenarkiv
• AliAbbasi, Easa; Martinsen, Ørjan Grøttem; Pettersen, Fred-Johan; Colgate, James Edward & Basdogan, Cagatay (2024). Experimental Estimation of Gap Thickness and Electrostatic Forces Between Contacting Surfaces Under Electroadhesion. Advanced Intelligent Systems. doi: 10.1002/aisy.202300618. Fulltekst i vitenarkiv Vis sammendrag

  Electroadhesion (EA) is a promising technology with potential applications in robotics, automation, space missions, textiles, tactile displays, and some other fields where efficient and versatile adhesion is required. However, a comprehensive understanding of the physics behind it is lacking due to the limited development of theoretical models and insufficient experimental data to validate them. This article proposes a new and systematic approach based on electrical impedance measurements to infer the electrostatic forces between two dielectric materials under EA. The proposed approach is applied to tactile displays, where skin and voltage-induced touchscreen impedances are measured and subtracted from the total impedance to obtain the remaining impedance to estimate the electrostatic forces between the finger and the touchscreen. This approach also marks the first instance of experimental estimation of the average air gap thickness between a human finger and a voltage-induced capacitive touchscreen. Moreover, the effect of electrode polarization impedance on EA is investigated. Precise measurements of electrical impedances confirm that electrode polarization impedance exists in parallel with the impedance of the air gap, particularly at low frequencies, giving rise to the commonly observed charge leakage phenomenon in EA.

• Lilja, Didrik; Schalit, Itai; Espinoza, Andreas; Nilsen-Hoel, Tom; Larsen, Guttorm & Pettersen, Fred-Johan [Vis alle 7 forfattere av denne artikkelen] (2023). Extracorporeal driveline vibrations to detect left ventricular assist device thrombosis – A porcine model study. The Journal of Heart and Lung Transplantation. ISSN 1053-2498. s. 1–9. doi: 10.1016/j.healun.2023.08.022. Fulltekst i vitenarkiv Vis sammendrag

  Background Pump thrombosis (PT) and related adverse complications contributed to the HeartWare Ventricular Assist Device (HVAD) market withdrawal. Many patients still receive lifelong support, with deficient PT surveillance based on pump power trends. Analysis of pump vibrations is better for detecting PT. Here, we investigated the feasibility of an extracorporeal accelerometer to detect PT from pump vibrations propagated out on the driveline. Methods In a porcine HVAD model (n = 6), an accelerometer was attached to the pump as a reference and another to the driveline for comparisons of signals. In total, 59 thrombi were injected into the heart to induce PT, followed by intermittent thrombus washout maneuvers. Signals were compared visually in spectrograms and quantitatively in third harmonic saliences (S3H) by correlation analysis. Receiver operating characteristic curves expressed the method’s outcome in sensitivity vs specificity, with the overall diagnostic performance in the area under the curve (AUC) score. Results Five experiments had good driveline signal strength, with clear spectrographic relationships between the 2 accelerometers. Third harmonic driveline vibrations were visible 20 vs 30 times in the reference. The comparison in S3H showed a strong correlation and yielded an AUC of 0.85. Notably, S3H proved robust regarding noise and false PT detections. Conclusions An extracorporeal accelerometer on the driveline can be a readily available method for accurate HVAD PT detection before an accelerometer integration with left ventricular assist device is feasible.

• Lilja, Didrik; Schalit, Itai; Espinoza, Andreas; Fiane, Arnt Eltvedt; Dahle, Gry & Sandbu, Helen Littorin [Vis alle 11 forfattere av denne artikkelen] (2023). Detection of inflow obstruction in left ventricular assist devices by accelerometer: A porcine model study. The Journal of Heart and Lung Transplantation. ISSN 1053-2498. 42(8), s. 1005–1014. doi: 10.1016/j.healun.2023.03.017. Fulltekst i vitenarkiv Vis sammendrag

  Background Left ventricular assist devices (LVAD) provide circulatory blood pump support for severe heart failure patients. Pump inflow obstructions may lead to stroke and pump malfunction. We aimed to verify in vivo that gradual inflow obstructions, representing prepump thrombosis, are detectable by a pump-attached accelerometer, where the routine use of pump power (PLVAD) is deficient. Method In a porcine model (n = 8), balloon-tipped catheters obstructed HVAD inflow conduits by 34% to 94% in 5 levels. Afterload increases and speed alterations were conducted as controls. We computed nonharmonic amplitudes (NHA) of pump vibrations captured by the accelerometer for the analysis. Changes in NHA and PLVAD were tested by a pairwise nonparametric statistical test. Detection sensitivities and specificities were investigated by receiver operating characteristics with areas under the curves (AUC). Results NHA remained marginally affected during control interventions, unlike PLVAD. NHA elevated during obstructions within 52-83%, while mass pendulation was most pronounced. Meanwhile, PLVAD changed far less. Increased pump speeds tended to amplify the NHA elevations. The corresponding AUC was 0.85-1.00 for NHA and 0.35-0.73 for PLVAD. Conclusion Elevated NHA provides a reliable indication of subclinical gradual inflow obstructions. The accelerometer can potentially supplement PLVAD for earlier warnings and localization of pump.

• Lilja, Didrik; Schalit, Itai; Espinoza, Andreas Westenvik; Pettersen, Fred-Johan; Elle, Ole Jakob & Halvorsen, Per Steinar (2022). Detection of inflow obstruction in left ventricular assist devices by accelerometer: An in vitro study. Medical Engineering and Physics. ISSN 1350-4533. 110. doi: 10.1016/j.medengphy.2022.103917. Fulltekst i vitenarkiv Vis sammendrag

  Inflow obstruction in left ventricular assist devices (LVAD) may lead to embolic stroke and pump malfunction. We investigated if an accelerometer detected graded LVAD inflow obstructions. Detection performances were compared to the current continuous surveillance routine based on the pump power consumption (PLVAD). In ten mock circuit experiments, four different-sized pendulating balloons obstructed HVAD™ inflow conduits cross-section areas by 14%-75%. Nonharmonic amplitudes (NHA) of continuous signals from a triaxial accelerometer attached to the LVAD were compared against single-point PLVAD values, using load and speed alterations as control interventions. We analyzed the NHA band power with a pairwise nonparametric statistical test. The detection performances were analyzed by receiver operating characteristics with areas under the curves (AUC). The NHA remained unaffected during load alterations. In contrast, NHA increased significantly from the 27% obstruction level (AUC≥0.82), an effect amplified by increased pump speed. PLVAD did not change significantly below the maximal 75% obstruction level (AUC≤0.36). In conclusion, NHA detected the inflow obstructions much better than PLVAD. The technique may provide a future monitoring modality of any pendulating obstructive inflow pathology.

• Schalit, Itai; Espinoza, Andreas Westenvik; Pettersen, Fred-Johan; Skulstad, Helge; Fosse, Erik & Fiane, Arnt Eltvedt [Vis alle 7 forfattere av denne artikkelen] (2022). Improved Detection of Thromboembolic Complications in Left Ventricular Assist Device by Novel Accelerometer-Based Analysis. ASAIO journal (1992). ISSN 1058-2916. 68(9), s. 1117–1125. doi: 10.1097/MAT.0000000000001654. Fulltekst i vitenarkiv
• 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

  <i>Importance</i>: 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.<p> <p><i>Objective</i>: To determine the temperature of tissue close to metal implants during electrosurgery in an <i>in-vitro</i> model.<p> <p><i>Design, Setting, and Participants</i>: Thirty tissue samples (15 with a metal implant placed in center, 15 controls without implant) were placed in an <i>in vitro</i> 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.<p> <p><i>Main Outcomes and Measures</i>: 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.<p> <p><i>Results</i>: 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).<p> <p><i>Conclusions and Relevance</i>: 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 [Vis alle 25 forfattere av denne artikkelen] (2019). Measuring blood pulse wave velocity with bioimpedance in different age groups. Sensors. 19:850(4), s. 1–10. doi: 10.3390/s19040850. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Pettersen, Fred-Johan (2018). On sensitivity in transfer impedance measurements. Journal of Electrical Bioimpedance. 9(1), s. 159–162. doi: 10.2478/joeb-2018-0020. 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
• 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
• 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

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• Edemann-Callesen, Henriette; Huus, Christel Mie Lykke; Karstoft, Caroline; Bjarnadóttir, Elín; Bikic, Aida & Jeppesen, Pia [Vis alle 13 forfattere av denne artikkelen] (2025). External trigeminal nerve stimulation versus sham stimulation for attention deficit hyperactivity disorder in children and adolescents aged 7–17 years: study protocol for a pilot and feasibility randomized clinical trial. doi: 10.1007/s00787-025-02786-7. Fulltekst i vitenarkiv Vis sammendrag

  External trigeminal nerve stimulation (eTNS) is a non-invasive technique involving external cutaneous stimulation of the trigeminal nerve. In 2019, the Monarch eTNS device was approved as a treatment for children with attention-deficit/hyperactivity disorder (ADHD). The Monarch eTNS device is designed to be applied at home, which offers a certain level of convenience but also necessitates a high degree of compliance and acceptability from the families. To assess the feasibility of – and pilot a larger randomized clinical trial investigating the Monarch eTNS device versus sham for patients aged 7 to 17 years with ADHD. We will conduct a parallel-group, sham-controlled, feasibility randomised clinical trial. We will include 60 children and adolescents (aged 7 to 17 years) diagnosed with ADHD from three clinical sites in Denmark. Patients will be randomised to 4 weeks of active versus sham eTNS. Feasibility outcomes include completion of the trial; the number of eligible participants who consent to inclusion; treatment compliance; acceptability of the intervention and completion. Adverse events will be monitored throughout the trial. Exploratory clinical outcomes include ADHD core symptoms (primary) and several secondary outcomes. Autonomic functions will be evaluated by means of heart rate variability, using a heart rate sensor. This trial will allow us to evaluate the feasibility of conducting a larger randomised clinical trial investigating the use of eTNS as a home-based, non-pharmacological intervention for children and adolescents diagnosed with ADHD.

• 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
• Pettersen, Fred Johan; Martinsen, Tormod; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem (2015). Unintentional heating at implants when using electrosurgery. Fulltekst i vitenarkiv
• Abir, R.; Pettersen, Fred Johan; Martinsen, Ørjan Grøttem & Rabbani, K. S. (2013). Effect of a spherical object in 4 electrode Focused Impedance Method (FIM): measurement and simulation. Fulltekst i vitenarkiv
• Pettersen, Fred Johan; Ferdous, Humayra & Martinsen, Ørjan Grøttem (2013). Simulation of 6-electrode and 8-electrode Focused Impedance Method (FIM) using Comsol Multiphysics – A comparative study. Fulltekst i vitenarkiv
• Pettersen, Fred-Johan (2017). Bioimpedance as a tool in cardiac resyncronisation therapy. Universitetet i Oslo. Fulltekst i vitenarkiv

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