Per Steinar Halvorsen

• Antonsen, Lars; Espinoza, Andreas; Halvorsen, Per Steinar; Schalit, Itai; Bergan, Harald & Lilja, Didrik [Vis alle 7 forfattere av denne artikkelen] (2024). The impact of hypovolemia and PEEP on recirculation in venovenous ECMO: an experimental porcine model. Intensive Care Medicine Experimental. ISSN 2197-425X. 12(1). doi: 10.1186/s40635-024-00636-5.
• Qadir, Hemin Ali; Nesaragi, Naimahmed; Halvorsen, Per Steinar & Balasingham, Ilangko (2023). A Multi-channel EEG Data Analysis for Poor Neuro-prognostication in Comatose Patients with Self and Cross-channel Attention Mechanism. I Young, Rosanna Degani (Red.), 2023 Computing in Cardiology . IEEE conference proceedings. ISSN 978-1-6654-5925-9. s. 1–4. doi: 10.22489/CinC.2023.251. Fulltekst i vitenarkiv
• 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
• Nesaragi, Naimahmed; Høiseth, Lars Øivind; Qadir, Hemin Ali; Rosseland, Leiv Arne; Halvorsen, Per Steinar & Balasingham, Ilangko (2023). Non-invasive waveform analysis for emergency triage via simulated hemorrhage: An experimental study using novel dynamic lower body negative pressure model. Biocybernetics and Biomedical Engineering (BBE). ISSN 0208-5216. 43(3), s. 551–567. doi: 10.1016/j.bbe.2023.06.002. Fulltekst i vitenarkiv
• 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
• 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
• Wajdan, Ali; Jahren, Tollef Struksnes; Villegas-Martinez, Manuel; Khan, Faraz Hameed; Halvorsen, Per Steinar & Odland, Hans Henrik [Vis alle 9 forfattere av denne artikkelen] (2022). Automatic Detection of Aortic Valve Events Using Deep Neural Networks on Cardiac Signals From Epicardially Placed Accelerometer. IEEE journal of biomedical and health informatics. ISSN 2168-2194. 26(9), s. 4450–4461. doi: 10.1109/JBHI.2022.3181148. Fulltekst i vitenarkiv
• 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.
• Wisløff-Aase, Kristin; Skulstad, Helge; Haugaa, Kristina Ingrid Helena Hermann; Lingaas, Per Snorre; Beitnes, Jan Otto & Halvorsen, Per Steinar [Vis alle 7 forfattere av denne artikkelen] (2022). Myocardial electrophysiological and mechanical changes caused by moderate hypothermia—A clinical study. Physiological Reports. ISSN 2051-817X. 10:e15259(8), s. 1–10. doi: 10.14814/phy2.15259. Fulltekst i vitenarkiv
• Wisløff-Aase, Kristin; Skulstad, Helge; Beitnes, Jan Otto; Lundblad, Runar; Halvorsen, Per Steinar & Fiane, Arnt Eltvedt [Vis alle 7 forfattere av denne artikkelen] (2022). Left Ventricular Function Changes Induced by Moderate Hypothermia Are Rapidly Reversed after Rewarming - A Clinical Study. Critical Care Medicine. ISSN 0090-3493. 50(1), s. E52–E60. doi: 10.1097/CCM.0000000000005170.
• Krogh, Magnus Reinsfelt; Halvorsen, Per Steinar; Grymyr, Ole-Johannes Holm Nielsen; Bergsland, Jacob; Elle, Ole Jakob & Fosse, Erik [Vis alle 7 forfattere av denne artikkelen] (2021). Continuous Estimation of Acute Changes in Preload Using Epicardially Attached Accelerometers . IEEE Transactions on Biomedical Engineering. ISSN 0018-9294. 68(7), s. 2067–2075. doi: 10.1109/TBME.2020.3020358.
• Storm, Benjamin; Halvorsen, Per Steinar; Skulstad, Helge; Dybwik, Knut Gustav; Schjalm, Camilla & Christiansen, Dorte [Vis alle 11 forfattere av denne artikkelen] (2021). Open chest and pericardium facilitate transpulmonary passage of venous air emboli. Acta Anaesthesiologica Scandinavica. ISSN 0001-5172. 65(5), s. 648–655. doi: 10.1111/aas.13796. Fulltekst i vitenarkiv
• El-Ganainy, Noha; Balasingham, Ilangko; Halvorsen, Per Steinar & Rosseland, Leiv Arne (2020). A New Real Time Clinical Decision Support System Using Machine Learning for Critical Care Units. IEEE Access. ISSN 2169-3536. 8. doi: 10.1109/ACCESS.2020.3030031. Vis sammendrag

  Mean arterial pressure (MAP) is an important clinical parameter to evaluate the health of critically ill patients in intensive care units. Thus, the real time clinical decision support systems detecting anomalies and deviations in MAP enable early interventions and prevent serious complications. The state-of-the-art decision support systems are based on a three-phase method that applies offline training, transfer learning, and retraining at the bedside. Their applicability in critical care units is challenging with delay and inaccuracy. In this article, we propose a real time clinical decision support system forecasting the MAP status at the bedside using a new machine learning structure. The proposed system works in real time at the bedside without requiring the offline phase for training using large datasets. It thereby enables timely interventions and improved healthcare services. The proposed machine learning structure includes two stages. Stage I applies online learning using hierarchical temporal memory (HTM) to enable real time stream processing and provides unsupervised predictions. To the best of our knowledge, this is the first time it is applied to medical signals. Stage II is a long short-term memory (LSTM) classifier that forecasts the status of the patient's MAP ahead of time based on Stage I stream predictions. We perform a thorough performance evaluation of the proposed system and compare it with the state-of-the-art systems employing logistic regression (LR). The comparison shows the proposed system outperforms LR in terms of the classification accuracy, recall, precision, and area under the receiver operation curve (AUROC).

• Espinoza, Andreas Westenvik; Kerans, Viesturs; Bugge, Jan F; Skulstad, Helge & Halvorsen, Per Steinar (2020). Left Ventricular Function During Epinephrine Stimulation and Hypothermia: Effects at Spontaneous and Paced Heart Rates in a Porcine Model. Therapeutic Hypothermia and Temperature Management. ISSN 2153-7658. s. 35–44. doi: 10.1089/ther.2019.0035.
• Wisløff-Aase, Kristin; Kerans, Viesturs; Haugaa, Kristina; Halvorsen, Per Steinar; Skulstad, Helge & Espinoza, Andreas Westenvik (2020). Changes in left ventricular electromechanical relations during targeted hypothermia. Intensive Care Medicine Experimental. ISSN 2197-425X. 8(1). doi: 10.1186/s40635-020-00363-7. Fulltekst i vitenarkiv
• Wajdan, Ali; Krogh, Magnus Reinsfelt; Villegas-Martinez, Manuel; Halvorsen, Per Steinar; Elle, Ole Jacob & Remme, Espen W. (2020). Automatic detection of valve events by epicardial accelerometer allows estimation of the left ventricular pressure trace and pressure–displacement loop area. Scientific Reports. ISSN 2045-2322. 10. doi: 10.1038/s41598-020-76637-7. Fulltekst i vitenarkiv
• Sævik, Marte; Beitnes, Jan Otto; Aaberge, Lars & Halvorsen, Per Steinar (2020). Safety and feasibility of dobutamine stress echocardiography in symptomatic high gradient aortic stenosis patients scheduled for transcatheter aortic valve implantation. Journal of Clinical Ultrasound. ISSN 0091-2751. doi: 10.1002/jcu.22915. Fulltekst i vitenarkiv
• Schalit, Itai; Espinoza, Andreas Westenvik; Pettersen, Fred-Johan; Snartland, Steinar; Ringdal, Mari-Anne I Lindstein & Nilsen-Hoel, Tom [Vis alle 10 forfattere av denne artikkelen] (2020). Detection of thromboembolic events and pump thrombosis in heartware HVAD using accelerometer in a porcine model. ASAIO journal (1992). ISSN 1058-2916. s. 38–48. doi: 10.1097/MAT.0000000000000954.
• Karlsen, Hilde; Bergan, Harald Arne; Halvorsen, Per Steinar; Sunde, Kjetil; Qvigstad, Eirik & Andersen, Geir Øystein [Vis alle 8 forfattere av denne artikkelen] (2019). Esmolol for cardioprotection during resuscitation with adrenaline in an ischaemic porcine cardiac arrest model. Intensive Care Medicine Experimental. ISSN 2197-425X. 7(65), s. 1–14. doi: 10.1186/s40635-019-0279-5. Fulltekst i vitenarkiv
• Wajdan, Ali; Krogh, Magnus Reinsfelt; Villegas-Martinez, Manuel; Halvorsen, Per Steinar; Grymyr, Ole-Johannes Holm Nielsen & Elle, Ole Jacob [Vis alle 7 forfattere av denne artikkelen] (2019). Monitoring cardiac function by accelerometer -Detecting start systole from the acceleration signal makes additional ECG recordings for R-peak detection redundant. IEEE Engineering in Medicine and Biology Society. Conference Proceedings. ISSN 1557-170X. s. 4922–4925. doi: 10.1109/EMBC.2019.8856417. Fulltekst i vitenarkiv
• Lu, Pengfei; Veletic, Mladen; Laasmaa, Martin; Vendelin, Marko; Louch, William Edward & Halvorsen, Per Steinar [Vis alle 8 forfattere av denne artikkelen] (2019). Multi-nodal nano-actuator pacemaker for energy-efficient stimulation of cardiomyocytes. Nano Communication Networks. ISSN 1878-7789. 22:100270, s. 1–11. doi: 10.1016/j.nancom.2019.100270. Fulltekst i vitenarkiv
• Dahle, Gry; Helle-Valle, Thomas Michael; Beitnes, Jan Otto; Espinoza, Andreas Westenvik; Halvorsen, Per Steinar & Rein, Kjell Arne (2019). Single-centre first experience with transapical transcatheter mitral valve replacement with an apical tether: Factors influencing screening outcomes. Interactive Cardiovascular and Thoracic Surgery. ISSN 1569-9293. 28(5), s. 695–703. doi: 10.1093/icvts/ivy343.
• al Batat, Mohammad; Bergsland, Jacob; Arevalo, Hermenegild; Odland, Hans Henrik; Bose, Pritam & Halvorsen, Per Steinar [Vis alle 7 forfattere av denne artikkelen] (2019). Technological and clinical challenges in lead placement for cardiac rhythm management devices. Annals of Biomedical Engineering. ISSN 0090-6964. 48, s. 26–46. doi: 10.1007/s10439-019-02376-0. Fulltekst i vitenarkiv
• Carling, Johan Ulrik; Barkhatov, Leonid; Reims, Henrik Mikael; Storås, Tryggve; Courivaud, Fredric A A & Kazaryan, Airazat M. [Vis alle 10 forfattere av denne artikkelen] (2019). Can we ablate liver lesions close to large portal and hepatic veins with MR-guided HIFU? An experimental study in a porcine model. European Radiology. ISSN 0938-7994. 29(9), s. 5013–5021. doi: 10.1007/s00330-018-5996-8.
• Pischke, Søren; Hestenes, Siv Merete; Johansen, Harald Thidemann; Fure, Hilde; Bugge, Jan F & Espinoza, Andreas Westenvik [Vis alle 12 forfattere av denne artikkelen] (2019). Sepsis causes right ventricular myocardial inflammation independent of pulmonary hypertension in a porcine sepsis model. PLOS ONE. ISSN 1932-6203. 14:e0218624(6). doi: 10.1371/journal.pone.0218624. Fulltekst i vitenarkiv
• El-Ganainy, Noha; Balasingham, Ilangko; Halvorsen, Per Steinar & Rosseland, Leiv Arne (2019). On the performance of hierarchical temporal memory predictions of medical streams in real time. International Symposium on Medical Information and Communication Technology. ISSN 2326-828X. 2019-May:8743902. doi: 10.1109/ISMICT.2019.8743902. Fulltekst i vitenarkiv
• Krogh, Magnus Reinsfelt; Halvorsen, Per Steinar; Elle, Ole Jacob; Bergsland, Jacob & Remme, Espen W. (2019). Dynamic gravity compensation does not increase detection of myocardial ischemia in combined accelerometer and gyro sensor measurements. Scientific Reports. ISSN 2045-2322. 9(1). doi: 10.1038/s41598-018-35630-x. Fulltekst i vitenarkiv
• Schalit, Itai; Espinoza, Andreas Westenvik; Pettersen, Fred-Johan; Thiara, Amrit Paul Singh; Karlsen, Hilde & Sørensen, Gro [Vis alle 9 forfattere av denne artikkelen] (2018). Accelerometer Detects Pump Thrombosis and Thromboembolic Events in an In vitro HVAD Circuit. ASAIO journal (1992). ISSN 1058-2916. 64(5), s. 601–609. doi: 10.1097/MAT.0000000000000699.
• Hyler, Stefan; Espinoza, Andreas Westenvik; Skulstad, Helge; Fosse, Erik & Halvorsen, Per Steinar (2018). Corrigendum to ‘Left ventricular function can be continuously monitored with an epicardially attached accelerometer sensor’ [Eur J Cardiothorac Surg 2014;46:313–20]. European Journal of Cardio-Thoracic Surgery. ISSN 1010-7940. 54(5). doi: 10.1093/ejcts/ezy340.
• Bugge, Jan F; Kerans, Viesturs; Nyrerød, Hans Christian & Halvorsen, Per Steinar (2018). Haemodynamic evaluation and optimisation of brain-dead donors with oesophageal Doppler during organ harvesting: A feasibility study. European Journal of Anaesthesiology. ISSN 0265-0215. 35(11), s. 893–895. doi: 10.1097/EJA.0000000000000876.
• Bergan, Harald Arne; Halvorsen, Per Steinar; Espinoza, Andreas Westenvik; Kerans, Viesturs; Skulstad, Helge & Fosse, Erik [Vis alle 7 forfattere av denne artikkelen] (2018). Left ventricle function during therapeutic hypothermia with beta<sub>1</sub>-adrenergic receptor blockade. Therapeutic Hypothermia and Temperature Management. ISSN 2153-7658. 8(3), s. 156–164. doi: 10.1089/ther.2017.0051.
• Hauge, Karoline Kråkmo; Dahle, Gry; Bendz, Bjørn; Halvorsen, Per Steinar; Abdelnoor, Michael & Mollnes, Tom Eirik [Vis alle 7 forfattere av denne artikkelen] (2018). Reduced inflammatory response by transcatheter, as compared to surgical aortic valve replacement. Scandinavian Cardiovascular Journal. ISSN 1401-7431. 52(1), s. 43–50. doi: 10.1080/14017431.2017.1416157. Fulltekst i vitenarkiv
• Grymyr, Ole-Johannes; Beitnes, Jan Otto; Eidet, Jo; Tølløfsrud, Stein G.; Fiane, Arnt E & Skulstad, Helge [Vis alle 8 forfattere av denne artikkelen] (2017). Detection of intraoperative myocardial dysfunction by accelerometer during aortic valve replacement. Interactive Cardiovascular and Thoracic Surgery. ISSN 1569-9293. 24(2), s. 188–195. doi: 10.1093/icvts/ivw326.
• Krogh, Magnus Reinsfelt; Nghiem, Giang Minh; Halvorsen, Per Steinar; Elle, Ole Jakob; Grymyr, Ole-Johannes & Hoff, Lars [Vis alle 7 forfattere av denne artikkelen] (2017). Gravity compensation method for combined accelerometer and gyro sensors used in cardiac motion measurements. Annals of Biomedical Engineering. ISSN 0090-6964. 45(5), s. 1292–1304. doi: 10.1007/s10439-017-1798-4. Vis sammendrag

  A miniaturized accelerometer fixed to the heart can be used for monitoring of cardiac function. However, an accelerometer cannot differentiate between acceleration caused by motion and acceleration due to gravity. The accuracy of motion measurements is therefore dependent on how well the gravity component can be estimated and filtered from the measured signal. In this study we propose a new method for estimating the gravity, based on strapdown inertial navigation, using a combined accelerometer and gyro. The gyro was used to estimate the orientation of the gravity field and thereby remove it. We compared this method with two previously proposed gravity filtering methods in three experimental models using: (1) in silico computer simulated heart motion; (2) robot mimicked heart motion; and (3) in vivo measured motion on the heart in an animal model. The new method correlated excellently with the reference (r2 > 0.93) and had a deviation from reference peak systolic displacement (6.3 ± 3.9 mm) below 0.2 ± 0.5 mm for the robot experiment model. The new method performed significantly better than the two previously proposed methods (p < 0.001). The results show that the proposed method using gyro can measure cardiac motion with high accuracy and performs better than existing methods for filtering the gravity component from the accelerometer signal.

• Bergan, Harald Arne; Halvorsen, Per Steinar; Skulstad, Helge; Fosse, Erik & Bugge, Jan F (2016). Does therapeutic hypothermia during extracorporeal cardiopulmonary resuscitation preserve cardiac function? Journal of Translational Medicine. ISSN 1479-5876. 14(1). doi: 10.1186/s12967-016-1099-y.
• Eidet, Jo; Dahle, Gry; Bugge, Jan F; Bendz, Bjørn; Rein, Kjell Arne & Aaberge, Lars [Vis alle 10 forfattere av denne artikkelen] (2016). Long-term outcomes after transcatheter aortic valve implantation: The impact of intraoperative tissue Doppler echocardiography. Interactive Cardiovascular and Thoracic Surgery. ISSN 1569-9293. 23(3), s. 403–409. doi: 10.1093/icvts/ivw159.
• Tjulkins, Fjodors; Nguyen Thai, Anh Tuan; Andreassen, Erik; Hoff, Lars; Grymyr, Ole-Johannes & Halvorsen, Per Steinar [Vis alle 7 forfattere av denne artikkelen] (2016). An Implantable Accelerometer-based Heart Monitoring Device with Improved Positional Stability. Journal of Medical Devices. ISSN 1932-6181. 10(4). doi: 10.1115/1.4034574. Vis sammendrag

  This paper reports recent results from an ongoing effort to develop an implantable accelerometer-based heart-monitoring device for ischemia monitoring. The latest device prototype utilizes a new and more compact accelerometer (1.2 × 1.5 × 0.8 mm3), a prototype device from Bosch SensorTec, Reutlingen, Germany. This paper presents the fabrication and testing of the device, including an explorative study of the effect of the capsule shape on the stability of the implanted device in the heart tissue. The stability study indicated sufficient stability of the device and a higher resistance to retraction for one of the capsule designs. The device was able to carry out acceleration monitoring and it meets the leakage current requirements of the IEC60601 standard.

• Secerbegovic, Alma; Bergsland, Jacob; Halvorsen, Per Steinar; Suljanović, Nermin; Mujčić, Aljo & Balasingham, Ilangko (2016). Blood pressure estimation using video plethysmography. IEEE International Symposium on Biomedical Imaging. ISSN 1945-7928. 2016-June, s. 461–464. doi: 10.1109/ISBI.2016.7493307.
• Gottås, André; Arnestad, Marianne; Halvorsen, Per Steinar; Bachs, Liliana Casulleras & Høiseth, Gudrun (2016). Pharmacokinetics of heroin and its metabolites in vitreous humor and blood in a living pig model. Forensic Toxicology. ISSN 1860-8965. 34, s. 277–285. doi: 10.1007/s11419-016-0315-z.
• Eidet, Jo; Dahle, Gry; Bugge, Jan F; Bendz, Bjørn; Rein, Kjell Arne & Aaberge, Lars [Vis alle 10 forfattere av denne artikkelen] (2016). Intraoperative improvement in left ventricular peak systolic velocity predicts better short-term outcome after transcatheter aortic valve implantation. Interactive Cardiovascular and Thoracic Surgery. ISSN 1569-9293. 22(1), s. 5–12. doi: 10.1093/icvts/ivv277.
• Kerans, Viesturs; Espinoza, Andreas Westenvik; Skulstad, Helge; Halvorsen, Per Steinar; Edvardsen, Thor & Bugge, Jan F (2015). Systolic left ventricular function is preserved during therapeutic hypothermia, also during increases in heart rate with impaired diastolic filling. Intensive Care Medicine Experimental. ISSN 2197-425X. 3(1), s. 1–17. doi: 10.1186/s40635-015-0041-6.
• Nguyen Thai, Anh Tuan; Tjulkins, Fjodors; Aasmundtveit, Knut Eilif; Hoivik, Nils; Hoff, Lars & Grymyr, Ole-Johannes [Vis alle 8 forfattere av denne artikkelen] (2015). Development of a Multifunctional Implantable Heart Monitoring Device. Journal of Microelectronics and Electronic Packaging. ISSN 1551-4897. 12(4), s. 171–180. doi: 10.4071/imaps.476. Vis sammendrag

  Early detection of cardiac complications after heart surgery is a crucial demand in clinical surveillance facilities. The use of accelerometer devices fixated to the heart has been demonstrated as a promising method for the detection of myocardial ischemia with high sensitivity and specificity. One of the most important challenges in developing heart implantable accelerometer devices is to minimize any tissue trauma. In this study, a new approach in making a heart muscle implantable accelerometer sensor is described. An overall diameter of 2 mm is achieved by encapsulating a miniaturized three-axis MEMS accelerometer (similar to the BMA355) from Bosch Sensortec GmbH, Germany. The design of the sensor features a simple implantation procedure, which aims to be similar to the medical procedure of temporary pacing wire attachment. The device remained in place in the heart muscle without the need for additional attachment or fixation. The essential clinical requirements for implantable devices, especially heart implantable sensors, are also taken into account in this study. Additional safety enhancement is realized by adding a galvanic isolator, which ensures electrical safety.

• Grymyr, Ole-Johannes; Nguyen Thai, Anh Tuan; Tjulkins, Fjodors; Espinoza, Andreas Westenvik; Remme, Espen W. & Skulstad, Helge [Vis alle 9 forfattere av denne artikkelen] (2015). Continuous monitoring of cardiac function by 3-dimensional accelerometers in a closed-chest pig model. Interactive Cardiovascular and Thoracic Surgery. ISSN 1569-9293. 21(5), s. 573–582. doi: 10.1093/icvts/ivv191. Vis sammendrag

  OBJECTIVES Cardiac wall motions reflect systolic and diastolic function. We have previously demonstrated the ability of a miniaturized three-axis (3D) accelerometer to monitor left ventricular function in experimental models and in patients. The main aim of this study was to investigate the clinical utility of the method for monitoring the left and right ventricular function during changes in global and regional cardiac function in a postoperative closed-chest situation. METHODS In 13 closed-chest pigs, miniaturized 3D accelerometers were placed on the left ventricle in the apical and basal regions and in the basal region of the right ventricle. An epicardial 3D motion vector was calculated from the acceleration signals in each heart region. Peak systolic velocity along this 3D vector (3D Vsys) was compared with the positive time derivative of the left and right ventricular pressure and with cardiac index during changes in global LV function (unloading, fluid loading, esmolol, dobutamine) and with ultrasound during regional left ventricular dysfunction (3-min occlusion of the left anterior descending coronary artery). RESULTS Significant and typical changes in accelerometer 3D Vsys were seen in all heart regions during changes in global cardiac function. 3D Vsys reflected the left and right ventricular contractility via significant correlations with the positive time derivative of the left and right ventricular pressure, r = 0.86 and r = 0.72, and with cardiac index r = 0.82 and r = 0.73 (all P < 0.001), respectively. The miniaturized accelerometers also detected regional dysfunction, but showed reduced ability to localize ischaemia as the 3D Vsys in all heart regions showed similar reductions during coronary artery occlusion. CONCLUSIONS Miniaturized 3D accelerometers placed on the heart can assess global and regional function in a closed-chest model. The technique may be used for continuous postoperative monitoring after cardiac surgery.

• Bergan, Harald Arne; Halvorsen, Per Steinar; Skulstad, Helge; Edvardsen, Thor; Fosse, Erik & Bugge, Jan F (2015). Successful ECMO-cardiopulmonary resuscitation with the associated post-arrest cardiac dysfunction as demonstrated by MRI. Intensive Care Medicine Experimental. ISSN 2197-425X. 3. doi: 10.1186/s40635-015-0061-2. Fulltekst i vitenarkiv
• Eidet, Jo; Dahle, Gry; Bugge, Jan F; Bendz, Bjørn; Rein, Kjell Arne & Fosse, Erik [Vis alle 8 forfattere av denne artikkelen] (2015). Transcatheter aortic valve implantation and intraoperative left ventricular function: A myocardial tissue Doppler imaging study. Journal of Cardiothoracic and Vascular Anesthesia. ISSN 1053-0770. 29(1), s. 115–120. doi: 10.1053/j.jvca.2014.10.016.
• Espinoza, Andreas Westenvik; Neumann, Kirill; Halvorsen, Per Steinar; Sundset, Arve; Kongerud, Johny & Fosse, Erik (2015). Critical airway obstruction: Challenges in airway management and ventilation during therapeutic bronchoscopy. Journal of Bronchology & Interventional Pulmonology. ISSN 1944-6586. 22(1), s. 41–47. doi: 10.1097/LBR.0000000000000127.
• Hyler, Stefan; Pischke, Søren Erik; Halvorsen, Per Steinar; Espinoza, Andreas Westenvik; Bergsland, Jacob & Tønnessen, Tor Inge [Vis alle 8 forfattere av denne artikkelen] (2015). Continuous monitoring of regional function by a miniaturized ultrasound transducer allows early quantification of low-grade myocardial ischemia. Journal of the American Society of Echocardiography. ISSN 0894-7317. 28(4), s. 486–494. doi: 10.1016/j.echo.2014.12.014.
• Floor, Pål Anders; Chavez-Santiago, Raul; Brovoll, Sverre; Aardal, Øyvind; Bergsland, Jacob & Grymyr, Ole-Johannes [Vis alle 10 forfattere av denne artikkelen] (2015). In-body to on-body Ultrawideband propagation model derived from measurements in living animals. IEEE journal of biomedical and health informatics. ISSN 2168-2194. 19(3), s. 938–948. doi: 10.1109/JBHI.2015.2417805. Fulltekst i vitenarkiv Vis sammendrag

  Ultra wideband (UWB) radio technology for wireless implants has gained significant attention. UWB enables the fabrication of faster and smaller transceivers with ultra low power consumption, which may be integrated into more sophisticated implantable biomedical sensors and actuators. Nevertheless, the large path loss suffered by UWB signals propagating through inhomogeneous layers of biological tissues is a major hindering factor. For the optimal design of implantable transceivers, the accurate characterization of the UWB radio propagation in living biological tissues is indispensable. Channel measurements in phantoms and numerical simulations with digital anatomical models provide good initial insight into the expected path loss in complex propagation media like the human body, but they often fail to capture the effects of blood circulation, respiration, and temperature gradients of a living subject. Therefore, we performed UWB channel measurements within 1-6 GHz on two living porcine subjects because of the anatomical resemblance with an average human torso. We present for the first time a path loss model derived from these invivo measurements, which includes the frequency-dependent attenuation. The use of multiple on-body receiving antennas to combat the high propagation losses in implant radio channels was also investigated.

• Grymyr, Ole-Johannes; Remme, Espen W.; Espinoza, Andreas Westenvik; Skulstad, Helge; Elle, Ole Jakob & Fosse, Erik [Vis alle 7 forfattere av denne artikkelen] (2015). Assessment of 3D motion increases the applicability of accelerometers for monitoring left ventricular function. Interactive Cardiovascular and Thoracic Surgery. ISSN 1569-9293. 20(3), s. 329–337. doi: 10.1093/icvts/ivu404.
• Pischke, Søren Erik; Hyler, Stefan; Tronstad, Christian; Bergsland, Jacob; Fosse, Erik & Halvorsen, Per Steinar [Vis alle 8 forfattere av denne artikkelen] (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.
• Tjulkins, Fjodors; Nguyen Thai, Anh Tuan; Andreassen, Erik; Aasmundtveit, Knut Eilif; Høivik, Nils Deneke & Hoff, Lars [Vis alle 9 forfattere av denne artikkelen] (2015). Fabrication and assembly of MEMS accelerometer-based heart monitoring device with simplified, one step placement. Journal of Medical Engineering & Technology. ISSN 0309-1902. 39(1), s. 69–74. doi: 10.3109/03091902.2014.981307. Vis sammendrag

  An accelerometer-based heart monitoring system has been developed for real-time evaluation of heart wall movement. In this paper, assembly and fabrication of an improved device is presented along with system characterization and test data from an animal experiment. The new device is smaller and has simplified the implantation procedure compared to earlier prototypes. Leakage current recordings were well below those set by the corresponding standards.

• Tjulkins, Fjodors; Nguyen Thai, Anh Tuan; Andreassen, Erik; Hoivik, Nils; Aasmundtveit, Knut Eilif & Hoff, Lars [Vis alle 9 forfattere av denne artikkelen] (2014). MEMS-based implantable heart monitoring system with integrated pacing function, 2014 IEEE 64th Electronic Components and Technology Conference (ECTC), 27-30 May 2014, Florida, USA. IEEE conference proceedings. ISSN 978-1-4799-2406-6. s. 139–144. doi: 10.1109/ECTC.2014.6897279. Vis sammendrag

  Miniaturized accelerometer-based implantable heart monitoring systems may increase safety during cardiac surgery. Such systems can provide sustained monitoring compared to imaging techniques. During ischemia, changes in acceleration occur instantly and before changes can be observed by electrocardiography. This may allow earlier detection of adverse events like graft occlusion. Recent designs have been made to meet requirements for postoperative use by easy and safe removal. However, the implantation procedure has been too complicated. The system presented in this paper is a reworked package in which a 3-axis accelerometer is placed inside a stainless steel capsule fabricated by additive manufacturing (3D printing). A needle attached to the package allows for easy implantation. In addition, the metallic capsule makes it possible to use the device as a pacing lead. The system demonstrates easy implantation. Furthermore, in conjunction with a second electrode, pacing and electrical potential sensing functionality is demonstrated.

• Nguyen Thai, Anh Tuan; Tjulkins, Fjodors; Aasmundtveit, Knut Eilif; Hoivik, Nils; Hoff, Lars & Grymyr, Ole-Johannes [Vis alle 8 forfattere av denne artikkelen] (2014). Packaging of a Multifunctional Implantable Heart Monitoring Device. I Courtois, Bernard; Karam, Jean Michel; Marcelli, Romolo; Megherbi, Souhil; Mita, Yoshio; Nouet, Pascal & Yeh, J. Andrew (Red.), Symposium on Design, test, Integration & Packaging of MEMS/MOEMS, Cannes, France, 1-4 April, 2014. EDA Publishing Association. ISSN 9782355000287. s. 322–327. doi: 10.1109/dtip.2014.7056657.
• Courivaud, Fredric A A; Kazaryan, Airazat M.; Lund, Alice; Orszagh, Vivian C; Svindland, Aud & Marangos, Irina Pavlik [Vis alle 11 forfattere av denne artikkelen] (2014). Thermal fixation of swine liver tissue after magnetic resonance-guided high-intensity focused ultrasound ablation. Ultrasound in Medicine and Biology. ISSN 0301-5629. 40(7), s. 1564–1577. doi: 10.1016/j.ultrasmedbio.2014.02.007.
• Hestenes, Siv Merete; Halvorsen, Per Steinar; Skulstad, Helge; Remme, Espen; Espinoza, Andreas Westenvik & Hyler, Stefan [Vis alle 10 forfattere av denne artikkelen] (2014). Advantages of strain echocardiography in assessment of myocardial function in severe sepsis: An experimental study. Critical Care Medicine. ISSN 0090-3493. 42(6), s. e432–e440. doi: 10.1097/CCM.0000000000000310.
• Hyler, Stefan; Espinoza, Andreas Westenvik; Skulstad, Helge; Fosse, Erik & Halvorsen, Per Steinar (2014). Left ventricular function can be continuously monitored with an epicardially attached accelerometer sensor. European Journal of Cardio-Thoracic Surgery. ISSN 1010-7940. 46(2), s. 313–320. doi: 10.1093/ejcts/ezt653.
• Espinoza, Andreas Westenvik; Kerans, Viesturs; Opdahl, Anders; Skulstad, Helge; Halvorsen, Per Steinar & Bugge, Jan F [Vis alle 8 forfattere av denne artikkelen] (2013). Effects of Therapeutic Hypothermia on Left Ventricular Function Assessed by Ultrasound Imaging. Journal of the American Society of Echocardiography. ISSN 0894-7317. 26(11), s. 1353–1363. doi: 10.1016/j.echo.2013.06.021.
• 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.
• Remme, Espen W.; Hoff, Lars; Halvorsen, Per Steinar; Opdahl, Anders; Fosse, Erik & Elle, Ole Jakob (2012). Simulation model of cardiac three dimensional accelerometer measurements. Medical Engineering and Physics. ISSN 1350-4533. 34(7), s. 990–998. doi: 10.1016/j.medengphy.2012.04.015. Vis sammendrag

  A miniaturized accelerometer sensor attached to the heart may be applied for monitoring cardiac motion. Proper understanding of the sensor measurements is required for successful development of algorithms to process the signal and extract clinical information. In vivo testing of such sensors is limited by the invasive nature of the procedure. In this study we have developed a mathematical simulation model of an accelerometer attached to the heart so that testing initially may be performed on realistic, simulated measurements. Previously recorded cardiac motion by sonomicrometric crystals was used as input to the model. The three dimensional motion of a crystal attached to the heart served as the simulated motion of the accelerometer, providing the translational acceleration components. A component of gravity is also measured by the accelerometer and fused with the translational acceleration. The component of gravity along an accelerometer axis varies when the axis direction slightly rotates as the accelerometer moves during the cardiac cycle. This time-varying gravity component has substantial effects on the accelerometer measurements and was included in the simulation model by converting the motion to prolate spheroidal coordinates where the axis rotation could be found. The simulated accelerometer signal was filtered and integrated to velocity and displacement. The resulting simulated motion was consistent with previous accelerometer recordings during normal and ischemic conditions as well as for alterations of accelerometer orientation and patient positions. This suggests that the model could potentially be useful in future testing of algorithms to filter and process accelerometer measurements.

• Wester, Torjus; Häggblad, Erik; Ahmed, Zaheer; Barratt-Due, Andreas; Kvernebo, Mari Skylstad & Halvorsen, Per Steinar [Vis alle 8 forfattere av denne artikkelen] (2011). Assessments of skin and tongue microcirculation reveals major changes in porcine sepsis. Clinical Physiology and Functional Imaging. ISSN 1475-0961. 31(2), s. 151–158. doi: 10.1111/j.1475-097X.2010.00994.x.
• Ahmed, Zaheer; Häggblad, Erik; Wester, Torjus; Kvernebo, Mari Skylstad; Halvorsen, Per Steinar & Kvernebo, Knut (2011). Diffuse reflectance spectroscopy: Systemic and microvascular oxygen saturation is linearly correlated and hypoxia leads to increased spatial heterogeneity of microvascular saturation. Microvascular Research. ISSN 0026-2862. 81(3), s. 245–251. doi: 10.1016/j.mvr.2011.02.004.
• Johansson, Martin L.; Thomsen, Peter; Hultén, Leif; Halvorsen, Per Steinar; Fosse, Erik & Edwin, Bjørn (2011). Integration between a percutaneous implant and the porcine small bowel. Journal of Biomedical Materials Research. Part B - Applied biomaterials. ISSN 1552-4973. 98B(1), s. 101–109. doi: 10.1002/jbm.b.31838.
• Espinoza, Andreas Westenvik; Halvorsen, Per Steinar; Skulstad, Helge; Lundblad, Runar; Bugge, Jan Frederik & Hoff, Lars [Vis alle 8 forfattere av denne artikkelen] (2011). Automated detection of myocardial ischaemia by epicardial miniature ultrasound transducers - a novel tool for patient monitoring during cardiac surgery. European Journal of Cardio-Thoracic Surgery. ISSN 1010-7940. 39(1), s. 53–59. doi: 10.1016/j.ejcts.2010.03.067. Vis sammendrag

  Objectives: Early detection of myocardial ischaemia in cardiac surgery is important. We have developed an ultrasonic system for continuous myocardial monitoring by use of miniature transducers. The aim of this study was to investigate the system's ability to detect ischaemia in patients undergoing off-pump coronary artery bypass grafting (CABG), and whether automated signal analysis could detect ischaemia. Methods: In 10 patients scheduled for CABG, ultrasound transducers were fixed to the epicardium in the area supplied by left anterior descending artery (LAD), and in a remote area for control. M-mode images with measurements of wall-thickening velocities were presented in real time and systolic (S?) and post-systolic velocities (PSVs) were recorded. An automated algorithm for ischaemia detection was developed, using end-systolic wall thickening as a fraction of total wall thickening. Registrations were made at baseline and during LAD occlusion. Echocardiographic strain was used as reference. Results: Nine of 10 patients developed ischaemia during LAD occlusion, with resulting decrease in systolic and increase in post-systolic wall-thickening velocities (P < 0.001). In these nine patients, Vdiff shifted below zero with no overlap between baseline and LAD occlusion (P < 0.001). The automated wall-thickening fraction was reduced from 0.93 ± 0.05 to 0.57 ± 0.15 (P = 0.001). A cut-off value of 0.85 could completely separate normal from ischaemic myocardium in all patients. Conclusion: The ultrasonic system detected regional ischaemia during LAD occlusion. An automated analysis algorithm demonstrated excellent ability to detect ischaemia. This technology can develop into a useful tool to detect ischaemia in cardiac surgery.

• Espinoza, Andreas Westenvik; Halvorsen, Per Steinar; Hoff, Lars; Skulstad, Helge; Fosse, Erik & Ihlen, Halfdan [Vis alle 7 forfattere av denne artikkelen] (2010). Detecting myocardial ischaemia using miniature ultrasonic transducers - a feasibility study in a porcine model. European Journal of Cardio-Thoracic Surgery. ISSN 1010-7940. 37(1), s. 119–126. doi: 10.1016/j.ejcts.2009.05.013. Vis sammendrag

  Background: Detection of myocardial ischaemia during and after cardiac surgery remains a challenge. Echocardiography is more sensitive in ischaemia detection than echocardiography (ECG) and haemodynamic monitoring, but demands repeated examinations for monitoring over time. We have developed and validated an ultrasonic system that permits continuous real-time assessment of myocardial ischaemia using miniature epicardial ultrasound transducers. Methods: In an open-chest porcine model (n = 8), prototype ultrasound transducers were fixed on the epicardium in the left anterior descending and circumflex coronary artery supply regions, providing continuous measurement of transmural myocardial velocities. Peak systolic velocity and post-systolic velocity were recorded simultaneously with ECG, left ventricular pressure and arterial pressure. Two-dimensional (2D) echocardiographic strain was used as a reference. Global changes were induced by infusing fluid, epinephrine, nitroprusside and esmolol. Regional changes were induced by occluding the left anterior descending coronary artery (LAD). Subsequent LAD stenosis was performed in a subgroup, with flow reduction to 50% of baseline level and further to occlusion. Results: Systolic velocity in the LAD region decreased during LAD occlusion (0.9 +/- 0.1 to 0.1 +/- 0.1 cm s¯¹, P < 0.01), whereas post-systolic velocity increased (0.3 +/- 0.1 to 2.3 +/- 0.1 cm s¯¹, P < 0.01). No changes occurred in the circumflex coronary artery (CX) region. Severe ischaemia was confirmed by reduction in 2D echocardiography strain calculations. Changes in myocardial velocities assessed by miniature transducer during ischaemia differed from changes during all global interventions. Significant reduction in systolic velocity occurred at 50% LAD flow (0.9 +/- 0.1 to 0.5 +/- 0.1 cm s¯¹, P = 0.02) with further decrease on following occlusion (0.0 +/- 0.0 cm s¯¹, P < 0.01). Post-systolic velocity increased both from baseline to 50% LAD flow, and further to occlusion. Conclusion: The epicardial transducers provided continuous assessment of regional myocardial function and detected ischaemia with high sensitivity and specificity. Further development of this system may provide a useful tool for myocardial monitoring during and after cardiac surgery. (C) 2009 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

• Wester, Torjus; Häggblad, Erik; Ahmed, Zaheer; Barratt-Due, Andreas; Kvernebo, Mari Skylstad & Halvorsen, Per Steinar [Vis alle 8 forfattere av denne artikkelen] (2010). Assessments of skin and tongue microcirculation reveals major changes in porcine sepsis. Clinical Physiology and Functional Imaging. ISSN 1475-0961. doi: 10.1111/j.1475-097X.2010.00994.x..
• Halvorsen, Per Steinar; Remme, Espen W.; Espinoza, Andreas Westenvik; Skulstad, Helge; Lundblad, Runar & Bergsland, Jacob [Vis alle 11 forfattere av denne artikkelen] (2010). Automatic real-time detection of myocardial ischemia by epicardial accelerometer. Journal of Thoracic and Cardiovascular Surgery. ISSN 0022-5223. 139(4), s. 1026–1032. doi: 10.1016/j.jtcvs.2009.05.031. Vis sammendrag

  Objective: Myocardial ischemia may be detected with epicardial accelerometers. We developed and tested automated algorithms for real-time detection of myocardial ischemia by accelerometer measurements in both experimental and clinical settings. Methods: In 10 pigs, an accelerometer was fixed to the epicardium in the area perfused by left anterior descending coronary artery. Acceleration and electrocardiogram were simultaneously recorded, and the QRS complex was automatically detected for exact timing of systole. Peak circumferential velocity and displacement were automatically calculated from epicardial acceleration signal within 150 milliseconds after peak R on electrocardiography. Global myocardial function was reduced by esmolol infusion, and regional function was altered by temporary left anterior descending occlusion. Automated ischemia detection analyses were tested in 7 patients during off-pump coronary artery bypass grafting. Left anterior descending coronary artery was occluded for 3 minutes before grafting. In both models, echocardiographic myocardial circumferential strain was used to confirm ischemia. Results: Systolic displacement changed most during left anterior descending occlusion. Negative displacement during ischemia was found in pigs (11.5 ± 2.3 to ?1.2 ± 2.8 mm, P < .01); regional hypokinesia was found in clinical study (12.8 ± 8.1 to 3.5 ± 4.4 mm, P < .01). Ischemia was confirmed by echocardiography in both settings. Esmolol infusion induced smaller changes in automated accelerometer measurements than did left anterior descending occlusion (P < .01). Conclusions: Automatic real-time detection of myocardial ischemia with epicardial accelerometer was feasible. Automated ischemia detection analysis may be used for continuous monitoring of myocardial ischemia during cardiac surgery.

• Remme, Espen; Hoff, Lars; Halvorsen, Per Steinar; Nærum, Edvard; Skulstad, Helge & Fleischer, Lars Albert [Vis alle 8 forfattere av denne artikkelen] (2009). Validation of cardiac accelerometer sensor measurements. Physiological Measurement. ISSN 0967-3334. 30(12). Vis sammendrag

  In this study we have investigated the accuracy of an accelerometer sensor designed for the measurement of cardiac motion and automatic detection of motion abnormalities caused by myocardial ischaemia. The accelerometer, attached to the left ventricular wall, changed its orientation relative to the direction of gravity during the cardiac cycle. This caused a varying gravity component in the measured acceleration signal that introduced an error in the calculation of myocardial motion. Circumferential displacement, velocity and rotation of the left ventricular apical region were calculated from the measured acceleration signal. We developed a mathematical method to separate translational and gravitational acceleration components based on a priori assumptions of myocardial motion. The accuracy of the measured motion was investigated by comparison with known motion of a robot arm programmed to move like the heart wall. The accuracy was also investigated in an animal study. The sensor measurementswere compared with simultaneously recorded motion from a robot arm attached next to the sensor on the heart and with measured motion by echocardiography and a video camera. The developed compensation method for the varying gravity component improved the accuracy of the calculated velocity and displacement traces, giving very good agreement with the reference methods.

• Halvorsen, Per Steinar; Fleischer, Lars Albert; Espinoza, Andreas; Elle, Ole Jakob; Hoff, Lars & Skulstad, Helge [Vis alle 8 forfattere av denne artikkelen] (2009). Detection of myocardial ischaemia by epicardial accelerometers in the pig. British Journal of Anaesthesia. ISSN 0007-0912. 102(1), s. 29–37. Vis sammendrag

  Conclusions. Myocardial ischaemia can be detected with epicardial three-axis accelerometers. The accelerometer had the ability to distinguish ischaemia from interventions altering global myocardial function. This novel technique may be used for continuous real-time monitoring of myocardial ischaemia during and after cardiac surgery.

• Bergsland, Jacob; Lingaas, Per Snorre; Skulstad, Helge; Hol, Per Kristian; Halvorsen, Per Steinar & Andersen, Rune [Vis alle 11 forfattere av denne artikkelen] (2009). Intracoronary Shunt Prevents Ischemia in Off-Pump Coronary Artery Bypass Surgery. Annals of Thoracic Surgery. ISSN 0003-4975. 87(1), s. 54–60. doi: 10.1016/j.athoracsur.2008.08.032.
• Remme, Espen W.; Hoff, Lars; Halvorsen, Per Steinar; Nærum, Edvard; Skulstad, Helge & Fleischer, Lars Albert [Vis alle 8 forfattere av denne artikkelen] (2009). Validation of Cardiac Accelerometer Sensor Measurements. Physiological Measurement. ISSN 0967-3334. 30(12), s. 1429–1444. doi: 10.1088/0967-3334/30/12/010.
• Espinoza, Andreas Westenvik; Halvorsen, Per Steinar; Hoff, Lars; Skulstad, Helge; Fosse, Erik & Ihlen, Halfdan [Vis alle 7 forfattere av denne artikkelen] (2009). Detecting myocardial ischaemia using miniature ultrasonic transducers - a feasibility study in a porcine model. European Journal of Cardio-Thoracic Surgery. ISSN 1010-7940. 37, s. 119–126. doi: 10.1016/j.ejcts.2009.05.013.
• Fleischer, Lars Albert; Halvorsen, Per Steinar; Hoff, Lars; Fosse, Erik & Elle, Ole Jakob (2008). Epicardial acceleration signal measured using a single chip 3-axis accelerometer, Proceedings of 14th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics. Springer. ISSN 1680-0737. s. 221–224.
• Halvorsen, Per Steinar; Espinoza, Andreas; Fleischer, Lars Albert; Elle, Ole Jakob; Hoff, Lars & Lundblad, Runar [Vis alle 10 forfattere av denne artikkelen] (2008). Feasibility of a three-axis epicardial accelerometer in detecting myocardial ischemia in cardiac surgical patients. Journal of Thoracic and Cardiovascular Surgery. ISSN 0022-5223. 136(6), s. 1496–1502. Vis sammendrag

  Conclusions: The epicardial accelerometer detects myocardial ischemia with great accuracy. This novel technique has potential to improve monitoring of myocardial ischemia during cardiac surgery.

• 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.
• Elle, Ole Jakob; Halvorsen, Steinar; Gulbrandsen, Martin Gunnar; Aurdal, Lars; Bakken, Andre & Samset, Eigil [Vis alle 7 forfattere av denne artikkelen] (2005). Early recognition of regional cardiac ischemia using a 3-axis accelerometer sensor. Physiological Measurement. ISSN 0967-3334. 26, s. 429–440.
• Mathisen, Lars; Andersen, Marit Helen; Hol, Per Kristian; Tennøe, Bjørn; Lund, Christian & Russell, David [Vis alle 11 forfattere av denne artikkelen] (2005). Preoperative cerebral ischemic lesions predict physical health status after on-pump coronary artery bypass surgery. Journal of Thoracic and Cardiovascular Surgery. ISSN 0022-5223. 130(6), s. 1691–1697. doi: 10.1016/j.jtcvs.2005.08.008.
• Skjelland, Mona; Bergsland, Jacob; Lundblad, Runar; Lingaas, Per Snorre; Rein, Kjell Arne & Halvorsen, Steinar [Vis alle 10 forfattere av denne artikkelen] (2005). Cerebral microembolization during off-pump coronary artery bypass surgery with the Symmetry aortic connector device. Journal of Thoracic and Cardiovascular Surgery. ISSN 0022-5223. 130(6), s. 1581–1585. doi: 10.1016/j.jtcvs.2005.08.015.
• Bergsland, Jacob; Hol, Per Kristian; Lingås, Per Snorre; Lundblad, Runar; Rein, Kjell Arne & Andersen, Rune [Vis alle 12 forfattere av denne artikkelen] (2004). Intraoperative and intermediate-term angiographic results of coronary artery bypass surgery with Symmetry proximal anastomotic device. Journal of Thoracic and Cardiovascular Surgery. ISSN 0022-5223. 128(5), s. 718–724.

Se alle arbeider i Cristin

• Høiseth, Gudrun; Gottås, André; Berg, Thomas; Arnestad, Marianne; Halvorsen, Per Steinar & Bachs, Liliana Casulleras (2017). Urinary kinetics of heroin metabolites in pigs shortly after intake. Journal of Analytical Toxicology. ISSN 0146-4760. 41(5), s. 451–454. doi: 10.1093/jat/bkx017.
• Bugge, Jan F; Espinoza, Andreas & Halvorsen, Per Steinar (2016). Hypothermia Is Not an Inotropic Drug. Critical Care Medicine. ISSN 0090-3493. 44(12). doi: 10.1097/CCM.0000000000002048.
• Mørk, Bjørn Erik; Aanestad, Margunn; Hoholm, Thomas & Halvorsen, Per Steinar (2013). "Høyteknologisk innovasjon, tverrfaglighet og ekspertise".
• Halvorsen, Per Steinar; Espinoza, Andreas Westenvik; Fiane, Arnt E & Fosse, Erik (2013). Continuous Monitoring of Right Ventricular Function with a 3-Axis Accelerometer during Left Ventricular Assist Device Implantation. The Journal of Heart and Lung Transplantation. ISSN 1053-2498. 32(4), s. S161–S162.
• Hoff, Lars; Imenes, Kristin; Fleischer, Lars Albert; Halvorsen, Per Steinar; Espinoza, Andreas & Remme, Espen [Vis alle 8 forfattere av denne artikkelen] (2010). Microsensors for continuous monitoring of heart function.
• Halvorsen, Per Steinar; Espinoza, Andreas Westenvik; Skulstad, Helge; Bugge, Jan Frederik; Elle, Ole Jakob & Fosse, Erik (2010). EPICARDIAL DISPLACEMENTS BY A 3-AXIS ACCELEROMETER SENSOR DETECT LEFT VENTRICULAR DYSFUNCTION DURING CORONARY ARTERY OCCLUSION. Intensive Care Medicine. ISSN 0342-4642. 36, s. S351–S351.
• Hyler, Stefan; Pischke, Søren Erik; Halvorsen, Per Steinar; Espinoza, Andreas Westenvik; Hestenes, Siv Merete & Bergsland, Jacob [Vis alle 8 forfattere av denne artikkelen] (2010). Systolic and postsystolic velocities quantify low grade myocardial ischaemia by a miniaturized epicardial ultrasonic sensor. European Heart Journal. ISSN 0195-668X. 31, s. 45–45.
• Hestenes, Siv Merete; Halvorsen, Per Steinar; Skulstad, Helge; Espinoza, Andreas Westenvik; Hyler, Stefan & Bugge, Jan F [Vis alle 9 forfattere av denne artikkelen] (2010). Right ventricular strain reduction in an experimental model of sepsis is closely related to increasing afterload conditions. European Heart Journal. ISSN 0195-668X. 31, s. 747–748.
• Espinoza, Andreas Westenvik; Skulstad, Helge; Kerans, Viesturs; Halvorsen, Per Steinar; Opdahl, Anders & Bugge, Jan F [Vis alle 7 forfattere av denne artikkelen] (2010). Moderate hypothermia causes increased left ventricular wall stiffness and delayed filling in a porcine model. European Heart Journal. ISSN 0195-668X. 31, s. 123–123.
• Espinoza, Andreas Westenvik; Kerans, Viesturs; Halvorsen, Per Steinar; Opdahl, Anders; Bugge, Jan F & Skulstad, Helge [Vis alle 7 forfattere av denne artikkelen] (2010). Impaired diastolic filling reduces the frequency force reserve during therapeutic hypothermia in an experimental model. European Heart Journal. ISSN 0195-668X. 31, s. 724–724.
• Hyler, S; Halvorsen, Per Steinar; Espinoza, Andreas; Hoff, Lars; Edvardsen, T. & Skulstad, Helge [Vis alle 7 forfattere av denne artikkelen] (2009). REAL TIME MONITORING OF LEFT VENTRICULAR PERFORMANCE WITH AN EPICARDIAL ACCELEROMETER SENSOR. Intensive Care Medicine. ISSN 0342-4642. s. 236–236. Vis sammendrag

  INTRODUCTION. Left ventricular stroke work (LVSW) measured with a pulmonary artery catheter is considered the clinical gold standard method for assessment of global cardiac function. However, only intermittent measurements are achievable by the use of this technique. A miniaturized accelerometer sensor provides continuous real time information of myocardial movement and has shown excellent ability for continuous detection of myocardial ischemia. The aim of this study was to evaluate whether measures from an epicardial accelerometer sensor could represent LVSW. CONCLUSION. Alterations in circumferential peak systolic velocities measured by an epicardial accelerometer were closely correlated to changes in LVSW during interventions affecting global cardiac function. Peak systolic velocity generated from an epicardial accelerometer sensor could therefore be used to quantify LV performance continuously and in real time. This technique may be a powerful tool for continuous monitoring of myocardial contraction during and after cardiac surgery.

• Hyler, Stefan; Halvorsen, Per Steinar; Espinoza, Andreas Westenvik; Hoff, L; Edvardsen, Thor & Skulstad, Helge [Vis alle 7 forfattere av denne artikkelen] (2009). REAL TIME MONITORING OF LEFT VENTRICULAR PERFORMANCE WITH AN EPICARDIAL ACCELEROMETER SENSOR. Intensive Care Medicine. ISSN 0342-4642. 35, s. 236–236.
• Espinoza, Andreas Westenvik; Kerans, Viesturs; Opdahl, Anders; Halvorsen, Per Steinar; Skulstad, Helge & Hoff, L [Vis alle 8 forfattere av denne artikkelen] (2009). Moderate hypothermia induces severe diastolic changes in a porcine model.
• Mathisen, Lars; Andersen, Marit Helen; Hol, Per Kristian; Tennøe, Bjørn; Lund, Christian & Russell, David [Vis alle 11 forfattere av denne artikkelen] (2005). Pre- and postoperative cerebral lesions as predictors of health status after coronary artery bypass surgery.
• Lingaas, Per Snorre; Krohg-Sørensen, Kirsten; Solberg, Steinar; Edwin, Bjørn; Halvorsen, Steinar & Fosse, Erik (2004). Laparaskopisk aortakirurgi. Vitenskapelige forhandlinger - De norske kirurgiske foreninger. ISSN 0801-5902.
• Halvorsen, Per Steinar & Fosse, Erik (2010). Continuous monitoring of left ventricular function by epicardial 3-axis accelerometers. Unipub forlag. ISSN 978-82-8072-364-2.

Se alle arbeider i Cristin