Publications
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Azulay, Naomi; Singstad, Bjørn-Jostein; Schirmer, Henrik; Løchen, Maja-Lisa; Olsen, Roy Bjørkholt & Jenssen, Trond
[Show all 10 contributors for this article]
(2026).
Exploring hemodynamic measurements from the Tromsø Study for prediction of cardiovascular disease using traditional statistical models and machine learning approaches.
Scientific Reports.
doi:
10.1038/s41598-026-57003-5.
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Abstract In Norway, NORRISK2 is the government-recommended risk model for predicting an individual’s 10-year probability of getting cardiovascular disease (CVD). This study aims to investigate the potential for improvement of CVD prediction by using hemodynamic measurements from a non-invasive beat-to-beat blood pressure monitor, taken as part of pain sensitivity assessment with the cold-pressor test (CPT) during the Tromsø6 Study (2007–2008). Using 6694 recordings, ultra-short-term pulse rate variability (PRV) and baroreflex sensitivity (BRS) obtained during the CPT were added as additional variables into the existing NORRISK2 survival model (extended model). In addition, the time-series data was used in a machine learning (ML) model without the NORRISK2 background variables. Both models were compared to a recalibration of the original NORRISK2 model. The predictions from the recalibrated NORRISK2 model and the ML model were then combined with logistic regression. The statistical models performed similarly on the test set, with an area under the receiver operating characteristic (AUROC) of 0.8 (95% CI: 0.71–0.86), 0.79 (0.71–0.85) and 0.77 (0.69–0.84) (original, recalibrated and extended NORRISK2, respectively). The ML model using only hemodynamic measurements obtained a test set AUROC of 0.73 (0.67–0.80). Combining the NORRISK2 and ML model did not increase the AUROC. Adding ultra-short-term PRV and BRS derived from Tromsø6 did not improve the prediction of the NORRISK2 model either. Although with lower accuracy, the beat-to-beat time series of hemodynamic variables from a CPT had a significant (p < 0.01) ability to predict future CVD without any other person-specific data.
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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.
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Kalvøy, Håvard; Hisdal, Jonny & Tronstad, Christian
(2025).
Toe digit pulsation measurement by impedance plethysmography in miniaturized devices: An early feasibility test.
Journal of Electrical Bioimpedance.
16(1),
p. 150–152.
doi:
10.2478/joeb-2025-0020.
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This early feasibility test explores impedance plethysmography (IPG) for detecting toe pulse waves using a setup suited for miniaturized devices. Conventional tests often miss micro-circulatory impairment, which is critical for wound healing and limb survival. We designed a flexible 3D-printed clamp with Ag/AgCl electrodes positioned on the inner big toe to target the lateral plantar digital artery. 50 kHz impedance measurements were performed on a healthy volunteer using 3D-printed electrode clamp for a tetrapolar configuration. Custom designed flexible electrodes were tested with and without contact gel. Preliminary results suggest that IPG can capture distal pulsatile signals, motivating further exploration of the potential for early detection of peripheral vascular dysfunction.
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Bari, Dindar S.; Rammoo, Mohammed Noor S.; Youssif, Ardawan A.; Najman, Hoger M.; Aldosky, Haval Y. Yacoob & Tronstad, Christian
[Show all 8 contributors for this article]
(2024).
Electrodermal Activity for Quantitative Assessment of Dental Anxiety.
Journal of Sensor and Actuator Networks.
13(6).
doi:
10.3390/jsan13060088.
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In spite of the development in technology and the recent innovations in dentistry, dental anxiety remains a common issue, and accurately assessing it is challenging due to reliance on patients’ self-reports, which are often biased. Hence, this study was undertaken to determine whether dental anxiety can be quantified objectively using the EDA parameters. EDA (skin conductance (SC), skin susceptance (SS), and skin potential (SP)) parameters and heart rate (HR) were recorded from 40 participants during two different sessions (baseline and anxiety). In addition, the Modified Dental Anxiety Scale (MDAS) scale was also used to record the level of anxiety. The physiological data from EDA and HR were compared with the subjective self-reports of anxiety provided on the MDAS to show whether higher EDA and HR readings correspond to higher scores on the MDAS. To elicit dental anxiety, participants were exposed to several film clips associated with dental treatment. EDA signals were compared between the two sessions for all clips and all EDA scores. SC and HR significantly (p < 0.05) increased during the anxiety session compared to the baseline session. The number of fluctuations per minute in the SC, SS, and SP notably increased during the anxiety session. The MDAS results revealed that the participants had dental anxiety when they were exposed to video clips of dental procedures. The study results imply that EDA parameters could be used as a useful tool to monitor dental anxiety, in particular in young children and non-verbal patients or those with intellectual disabilities, which may aid the dentist in the successful management of dental anxiety during treatment. The moment-to-moment EDA data on a patient’s anxiety levels throughout particular dental operations provides a clearer picture of anxiety variations than pre- or post-appointment surveys alone, in addition to offering unbiased tracking of dental anxiety levels over self-reports. This study seeks to encourage further research into the most effective EDA parameters for improving the management of dental anxiety.
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Jerve, Fredrik Wilsbeck; Hjelme, Dag Roar; Kalvøy, Håvard; Allen, John & Tronstad, Christian
(2024).
Exploration of the Conditions for Occurrence of Photoplethysmographic Signal Inversion above the Dorsalis Pedis Artery.
Sensors.
24(20).
doi:
10.3390/s24206505.
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Bari, Dindar S.; Aldosky, Haval Y. Y.; Tronstad, Christian & Martinsen, Ørjan Grøttem
(2024).
Disturbances in Electrodermal Activity Recordings Due to Different Noises in the Environment.
Sensors.
24(16).
doi:
10.3390/s24165434.
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Electrodermal activity (EDA) is a widely used psychophysiological measurement in laboratory-based studies. In recent times, these measurements have seen a transfer from the laboratory to wearable devices due to the simplicity of EDA measurement as well as modern electronics. However, proper conditions for EDA measurement are recommended once wearable devices are used, and the ambient conditions may influence such measurements. It is not completely known how different types of ambient noise impact EDA measurement and how this translates to wearable EDA measurement. Therefore, this study explored the effects of various noise disturbances on the generation of EDA responses using a system for the simultaneous recording of all measures of EDA, i.e., skin conductance responses (SCRs), skin susceptance responses (SSRs), and skin potential responses (SPRs), at the same skin site. The SCRs, SSRs, and SPRs due to five types of noise stimuli at different sound pressure levels (70, 75, 80, 85, and 90 dB) were measured from 40 participants. The obtained results showed that EDA responses were generated at all levels and that the EDA response magnitudes were significantly (p < 0.001) influenced by the increasing noise levels. Different types of environmental noise may elicit EDA responses and influence wearable recordings outside the laboratory, where such noises are more likely than in standardized laboratory tests. Depending on the application, it is recommended to prevent these types of unwanted variation, presenting a challenge for the quality of wearable EDA measurement in real-world conditions. Future developments to shorten the quality gap between standardized laboratory-based and wearable EDA measurements may include adding microphone sensors and algorithms to detect, classify, and process the noise-related EDA.
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Krispel, Thomas; Badeli, Vahid; Jafarinia, Alireza; Reinbacher-Köstinger, Alice; Tronstad, Christian & Ranftl, Sascha
[Show all 11 contributors for this article]
(2024).
arterioscope.sim: Enabling Simulations of Blood Flow and Its Impact on Bioimpedance Signals.
Bioengineering.
11(12).
doi:
10.3390/bioengineering11121273.
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Objectives: Early detection of cardiovascular diseases and their pre-existing conditions, arteriosclerosis and atherosclerosis, is crucial to increasing a patient’s chance of survival. While imaging technologies and invasive procedures provide a reliable diagnosis, they carry high costs and risks for patients. This study aims to explore impedance plethysmography (IPG) as a non-invasive and affordable alternative for diagnosis. Methods: To address the current lack of large-scale, high-quality impedance data, we introduce arterioscope.sim, a simulation platform that models arterial blood flow and computes the electrical conductivity of blood. The platform simulates bioimpedance measurements on specific body segments using patient-specific parameters. The study investigates how introducing arterial diseases into the simulation affects the bioimpedance signals. Results: The simulation results demonstrate that introducing atherosclerosis and arteriosclerosis leads to significant changes in the computed signals compared to simulations of healthy arteries. Furthermore, simulation of a patient-specific healthy artery strongly correlates with measured signals from a healthy volunteer. Conclusions and significance: arterioscope.sim effectively simulates bioimpedance signals in healthy and diseased arteries and highlights the potential of using these signals for early diagnosis of arterial diseases, offering a non-invasive and cost-effective alternative to traditional diagnostic methods.
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Tronstad, Christian; Amini, Maryam; Olesen, Eline; Qvigstad, Elisabeth; Pabst, Oliver & Martinsen, Tormod
[Show all 11 contributors for this article]
(2022).
Diabetic foot assessment using skin impedance in a custom made sensor-sock.
Journal of Electrical Bioimpedance.
13(1),
p. 136–142.
doi:
10.2478/joeb-2022-0019.
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Abstract Diabetic peripheral neuropathy (DPN) may lead to several changes in the skin, and some of these may influence the skin impedance spectrum. In the present study we have developed a prototype solution for skin impedance spectroscopy at selected skin sites (big toe pulp, heel and toe ball) that was tested in a pilot study on five patients with DPN and five healthy controls. At the big toe, most of the controls had markedly lower impedance than the DPN group, especially in the range of 1-100 kHz. The separation between the groups seems to be weaker at the heel and weakest at the toeball. The results may indicate that monitoring of the skin impedance spectrum may be a method for detection of skin changes associated with DPN, encouraging further studies with the big toe sensor in particular.
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Tronstad, Christian; Amini, Maryam; Bach, Dominik R. & Martinsen, Ørjan Grøttem
(2022).
Current trends and opportunities in the methodology of electrodermal activity measurement.
Physiological Measurement.
ISSN 0967-3334.
43(2).
doi:
10.1088/1361-6579/ac5007.
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Hou, Jie; Strand-Amundsen, Runar James; Tronstad, Christian; Tønnessen, Tor Inge; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem
(2022).
Small intestinal viability assessment using dielectric relaxation spectroscopy and deep learning.
Scientific Reports.
12(1).
doi:
10.1038/s41598-022-07140-4.
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Abstract Intestinal ischemia is a serious condition where the surgeon often has to make important but difficult decisions regarding resections and resection margins. Previous studies have shown that 3 h (hours) of warm full ischemia of the small bowel followed by reperfusion appears to be the upper limit for viability in the porcine mesenteric ischemia model. However, the critical transition between 3 to 4 h of ischemic injury can be nearly impossible to distinguish intraoperatively based on standard clinical methods. In this study, permittivity data from porcine intestine was used to analyze the characteristics of various degrees of ischemia/reperfusion injury. Our results show that dielectric relaxation spectroscopy can be used to assess intestinal viability. The dielectric constant and conductivity showed clear differences between healthy, ischemic and reperfused intestinal segments. This indicates that dielectric parameters can be used to characterize different intestinal conditions. In addition, machine learning models were employed to classify viable and non-viable segments based on frequency dependent dielectric properties of the intestinal tissue, providing a method for fast and accurate intraoperative surgical decision-making. An average classification accuracy of 98.7% was obtained using only permittivity data measured during ischemia, and 96.2% was obtained with data measured during reperfusion. The proposed approach allows the surgeon to get accurate evaluation from the trained machine learning model by performing one single measurement on an intestinal segment where the viability state is questionable.
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Azulay, Naomi; Olsen, Roy Bjørkholt; Nielsen, Christopher Sivert; Stubhaug, Audun; Jenssen, Trond Geir & Schirmer, Henrik
[Show all 9 contributors for this article]
(2022).
Reduced heart rate variability is related to the number of metabolic syndrome components and manifest diabetes in the sixth Tromsø study 2007–2008.
Scientific Reports.
12(1).
doi:
10.1038/s41598-022-15824-0.
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Both diabetes mellitus (DM) and the metabolic syndrome (MetS) are associated with autonomic neuropathy, which predisposes to cardiac events and death. Measures of heart rate variability (HRV) can be used to monitor the activity of the autonomic nervous system (ANS), and there are strong indications that HRV can be used to study the progression of ANS-related diabetes complications. This study aims to investigate diferences in HRV in healthy, MetS and diabetic populations. Based on 7880 participants from the sixth health survey in Tromsø (Tromsø 6, 2007–2008), we found a signifcant negative association between the number of MetS components and HRV as estimated from short-term pulse wave signals (PRV). This decrease in PRV did not appear to be linear, instead it leveled of after the third component, with no signifcant diference in PRV between the MetS and DM populations. There was a signifcant negative association between HbA1c and PRV, showing a decrease in PRV occurring already within the normal HbA1c range. The MetS and DM populations are diferent from healthy controls with respect to PRV, indicating impaired ANS in both conditions. In the future, a study with assessment of PRV measurements in relation to prospective cardiovascular events seems justifed.
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Jacobsen, Fredrik Alstad; Hafli, Ellen Wold; Tronstad, Christian & Martinsen, Ørjan Grøttem
(2021).
Classification of emotions based on electrodermal activity and transfer learning - a pilot study.
Journal of Electrical Bioimpedance.
12(1),
p. 178–183.
doi:
10.2478/joeb-2021-0021.
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Abstract This paper describes the development, execution and results of an experiment assessing emotions with electrodermal response measurements and machine learning. With ten participants, the study was carried out by eliciting emotions through film clips. The data was gathered with the Sudologger 3 and processed with continuous wavelet transformation. A machine learning algorithm was used to classify the data with the use of transfer learning and random forest classification. The results showed that the experiment lays a foundation for further exploration in the field. The addition of augmented data strengthened the classification and proved that more data would benefit the machine learning algorithm. The pilot study brought to light several areas to help with the expansion of the study for larger scale assessment of emotions with electrodermal response measurements and machine learning for the benefit of fields like psychology.
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Haidl, Felix; Tronstad, Christian; Rosseland, Leiv Arne & Dahl, Vegard
(2021).
Maternal haemodynamics during labour epidural analgesia with and without adrenaline.
Scandinavian Journal of Pain.
ISSN 1877-8860.
21(4),
p. 680–687.
doi:
10.1515/sjpain-2020-0176.
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Objectives Labour is one of the most painful experiences in a woman’s life. Epidural analgesia using low-concentration local anaesthetics and lipophilic opioids is the gold standard for pain relief during labour. Pregnancy in general, particularly labour, is associated with changes in maternal haemodynamic variables, such as cardiac output and heart rate, which increase and peak during uterine contractions. Adrenaline is added to labour epidural solutions to enhance efficacy by stimulating the α2-adrenoreceptor. The minimal effective concentration of adrenaline was found to be 2 μg mL−1 for postoperative analgesia. The addition of adrenaline may also produce vasoconstriction, limiting the absorption of fentanyl into the systemic circulation, thereby reducing foetal exposure. However, adrenaline may influence the haemodynamic fluctuations, possibly adding to the strain on the circulatory system. The aim of this study was to compare the haemodynamic changes after application of labour epidural analgesia with or without adrenaline 2 μg mL−1. Methods This was a secondary analysis of a single-centre, randomised double-blind trial. Forty-one nulliparous women in labour requesting epidural analgesia were randomised to receive epidural solution of bupivacaine 1 mg mL−1, fentanyl 2 μg mL−1 with or without adrenaline 2 μg mL−1. The participants were monitored using a Nexfin CC continuous non-invasive blood pressure and cardiac output monitor. The primary outcomes were changes in peak systolic blood pressure and cardiac output during uterine contraction within 30 min after epidural activation. The effect of adrenaline was tested statistically using a linear mixed-effects model of the outcome variables’ dependency on time, adrenaline, and their interaction. Results After excluding three patients due to poor data quality and two due to a malfunctioning epidural catheter, 36 patients (18 in each group) were analysed. The addition of adrenaline to the solution had no significant effect on the temporal changes in peak systolic blood pressure (p=0.26), peak cardiac output (0.84), or heart rate (p=0.91). Furthermore, no significant temporal changes in maternal haemodynamics (peak systolic blood pressure, p=0.54, peak cardiac output, p=0.59, or heart rate p=0.55) were associated with epidural analgesia during 30 min after epidural activation in both groups despite good analgesia. Conclusions The addition of 2 μg mL−1 adrenaline to the epidural solution is not likely to change maternal haemodynamics during labour.
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Singstad, Bjørn Jostein; Azulay, Naomi; Bjurstedt, Andreas; Bjørndal, Simen Chill; Drageseth, Magnus Flø & Austdal, Lars Peter Engeset
[Show all 21 contributors for this article]
(2021).
Estimation of heart rate variability from finger photoplethysmography during rest, mild exercise and mild mental stress.
Journal of Electrical Bioimpedance.
12(1),
p. 89–102.
doi:
10.2478/joeb-2021-0012.
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Abstract Due to the possibilities in miniaturization and wearability, photoplethysmography (PPG) has recently gained a large interest not only for heart rate measurement, but also for estimating heart rate variability, which is derived from ECG by convention. The agreement between PPG and ECG-based HRV has been assessed in several studies, but the feasibility of PPG-based HRV estimation is still largely unknown for many conditions. In this study, we assess the feasibility of HRV estimation based on finger PPG during rest, mild physical exercise and mild mental stress. In addition, we compare different variants of signal processing methods including selection of fiducial point and outlier correction. Based on five minutes synchronous recordings of PPG and ECG from 15 healthy participants during each of these three conditions, the PPG-based HRV estimation was assessed for the SDNN and RMSSD parameters, calculated based on two different fiducial points (foot point and maximum slope), with and without outlier correction. The results show that HRV estimation based on finger PPG is feasible during rest and mild mental stress, but can give large errors during mild physical exercise. A good estimation is very dependent on outlier correction and fiducial point selection, and SDNN seems to be a more robust parameter compared to RMSSD for PPG-based HRV estimation.
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Wiegerinck, Anouk; Thomsen, Andreas; Hisdal, Jonny; Kalvøy, Håvard & Tronstad, Christian
(2021).
Electrical impedance plethysmography versus tonometry to measure the pulse wave velocity in peripheral arteries in young healthy volunteers: a pilot study.
Journal of Electrical Bioimpedance.
12(1),
p. 169–177.
doi:
10.2478/joeb-2021-0020.
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Abstract The leading cause of health loss and deaths worldwide are cardiovascular diseases. A predictor of cardiovascular diseases and events is the arterial stiffness. The pulse wave velocity (PWV) can be used to estimate arterial stiffness non-invasively. The tonometer is considered as the gold standard for measuring PWV. This approach requires manual probe fixation above the artery and depends on the skills of the operator. Electrical impedance plethysmography (IPG) is an interesting alternative using skin surface sensing electrodes, that is miniaturizable, cost-effective and allows measurement of deeper arteries. The aim of this pilot study was to explore if IPG can be a suitable technique to measure pulse wave velocity in legs as an alternative for the tonometer technique. The PWV was estimated by differences in the ECG-gated pulse arrival times (PAT) at the a. femoralis, a. popliteal, a. tibialis dorsalis and a. dorsalis pedis in nine healthy young adults using IPG and the SphygmoCor tonometer as a reference. The estimated PWV results from bioimpedance and the tonometer were fairly in agreement, and the beat-to-beat variability in PAT was similar. This pilot study indicates that the use of IPG may be a good alternative for estimating PWV in the legs.
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Hou, Jie; Strand-Amundsen, Runar James; Tronstad, Christian; Høgetveit, Jan Olav; Martinsen, Ørjan Grøttem & Tønnessen, Tor Inge
(2021).
Automatic prediction of ischemia-reperfusion injury of small intestine using convolutional neural networks: A pilot study.
Sensors.
21(19).
doi:
10.3390/s21196691.
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Acute intestinal ischemia is a life-threatening condition. The current gold standard, with evaluation based on visual and tactile sensation, has low specificity. In this study, we explore the feasibility of using machine learning models on images of the intestine, to assess small intestinal viability. A digital microscope was used to acquire images of the jejunum in 10 pigs. Ischemic segments were created by local clamping (approximately 30 cm in width) of small arteries and veins in the mesentery and reperfusion was initiated by releasing the clamps. A series of images were acquired once an hour on the surface of each of the segments. The convolutional neural network (CNN) has previously been used to classify medical images, while knowledge is lacking whether CNNs have potential to classify ischemia-reperfusion injury on the small intestine. We compared how different deep learning models perform for this task. Moreover, the Shapley additive explanations (SHAP) method within explainable artificial intelligence (AI) was used to identify features that the model utilizes as important in classification of different ischemic injury degrees. To be able to assess to what extent we can trust our deep learning model decisions is critical in a clinical setting. A probabilistic model Bayesian CNN was implemented to estimate the model uncertainty which provides a confidence measure of our model decisions.
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Michelsen, Trond Melbye; Tronstad, Christian & Rosseland, Leiv Arne
(2021).
Blood pressure and cardiac output during caesarean delivery under spinal anaesthesia: A prospective cohort study.
BMJ Open.
11(6),
p. 1–9.
doi:
10.1136/bmjopen-2020-046102.
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Objectives We have previously established a method to measure transfer of nutrients between mother, placenta and fetus in vivo. The method includes measurements of maternal and fetal blood flow by Doppler ultrasound prior to spinal anaesthesia. Spinal anaesthesia affects maternal blood pressure and cardiac output. We aimed to determine the effect of spinal anaesthesia in mothers undergoing an elective caesarean section on blood pressure, heart rate and cardiac output, and whether cardiac output levels were comparable before induction of spinal anaesthesia and before delivery. Design Prospective cohort study. Setting Tertiary hospital in Norway. Participants 76 healthy women with uneventful pregnancies undergoing an elective caesarean section. Interventions We induced spinal anaesthesia with a standard prevention of hypotension including intravenous fluid coloading and phenylephrine infusion. Primary and secondary outcome measures Primary outcome measure was maternal cardiac output, and secondary outcome measures were invasive systolic blood pressure and heart rate. We measured heart rate and blood pressure by continuous invasive monitoring with a cannula in the radial artery. Cardiac output was estimated based on continuous arterial waveform. We compared maternal parameters 30 s before induction of spinal anaesthesia to 30 s before delivery. Results Median age at delivery was 34.5 (range 21–43) years and 17 of 76 women were nulliparous. The most prevalent indications were previous caesarean section and maternal request. Among 76 included women, 71 had sufficient data for analysis of endpoints. Median cardiac output was 6.51 (IQR (5.56–7.54) L/min before spinal anaesthesia and 6.40 (5.83–7.56) L/min before delivery (p=0.40)). Median invasive systolic blood pressure increased from 128.5 (120.1–142.7) mm Hg to 134.1 (124.0–146.6) mm Hg (p=0.014), and mean heart rate decreased from 86.0 (SD 13.9) to 75.2 (14.2) (p<0.001). Conclusions Maternal cardiac output at the time of caesarean delivery is comparable to levels before induction of spinal anaesthesia.
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Strand-Amundsen, Runar James; Tronstad, Christian; Elvebakk, Ole; Martinsen, Tormod; Dybwad, Marius & Lingaas, Egil
[Show all 7 contributors for this article]
(2021).
Quantification of aerosol dispersal from suspected aerosol-generating procedures.
European Respiratory Journal Open Research (ERJ Open Research).
doi:
10.1183/23120541.00206-2021.
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Background Oxygen-delivering modalities like humidified high-flow nasal cannula (HFNC) and noninvasive positive-pressure ventilation (NIV) are suspected of generating aerosols that may contribute to transmission of disease such as coronavirus disease 2019. We sought to assess if these modalities lead to increased aerosol dispersal compared to the use of non-humidified low-flow nasal cannula oxygen treatment (LFNC).
Methods Aerosol dispersal from 20 healthy volunteers using HFNC, LFNC and NIV oxygen treatment was measured in a controlled chamber. We investigated effects related to coughing and using a surgical face mask in combination with the oxygen delivering modalities. An aerodynamic particle sizer measured aerosol particles (APS3321, 0.3–20 µm) directly in front of the subjects, while a mesh of smaller particle sensors (SPS30, 0.3–10 µm) was distributed in the test chamber.
Results Non-productive coughing led to significant increases in particle dispersal close to the face when using LFNC and HFNC but not when using NIV. HFNC or NIV did not lead to a statistically significant increase in aerosol dispersal compared to LFNC. With non-productive cough in a room without air changes, there was a significant drop in particle levels between 100 cm and 180 cm from the subjects.
Conclusions Our results indicate that using HFNC and NIV does not lead to increased aerosol dispersal compared to low-flow oxygen treatment, except in rare cases. For a subject with non-productive cough, NIV with double-limb circuit and non-vented mask may be a favourable choice to reduce the risk for aerosol spread.
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Omenås, Ivar Nagelgaard; Tronstad, Christian & Rosseland, Leiv Arne
(2020).
Accuracy and trending abilities of finger plethysmographic blood pressure and cardiac output compared to invasive measurements during caesarean delivery in healthy women: An observational study.
BMC Anesthesiology.
20(157).
doi:
10.1186/s12871-020-01078-8.
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Background In women presenting for caesarean section under spinal anesthesia, continuous measurement of circulatory aspects, such as blood pressure and cardiac output, is often needed. At present, invasive techniques are used almost exclusively. Reliable non-invasive monitoring would be welcome, as it could be safer, less uncomfortable, and quick and easy to apply. We aimed to evaluate whether a non-invasive, finger plethysmographic device, the ccNexFin monitor, can replace invasively measured blood pressure in the radial artery, and whether cardiac output measurements from this device can be used interchangeably with measurements from the mini-invasive LiDCO monitor currently in use at our institution. Methods Simultaneous invasive measurements were compared to ccNexFin in 23 healthy women during elective caesarean section under spinal anesthesia. We used Bland Altman statistics to assess agreement, and polar plot methodology to judge trending abilities with pre-defined limits. Results Mean arterial and systolic pressures showed biases (invasive – ccNexFin) of − 4.3 and 12.2 mmHg, with limits of agreement of − 15.9 – 7.4 and − 11.1 – 35.6, respectively. The ccNexFin trending abilities were within the suggested limits for mean pressure but insufficient for systolic pressure compared to invasive measurements. Cardiac output had a small bias of 0.2 L/min, but wide limits of agreement of − 2.6 – 3.0. The ccNexFin trending abilities compared to the invasive estimated values (LiDCO) were unsatisfactory. Conclusions We consider the ccNexFin monitor to have sufficient accuracy in measuring mean arterial pressure. The limits of agreement for systolic measurements were wider, and the trending ability compared to invasive measurements was outside the recommended limit. The ccNexFin is not reliable for cardiac output measurements or trend in pregnant women for caesarean delivery under spinal anesthesia. Trial registration Registered May 23, 2013, at ClinicalTrials.gov under number NCT01861132 .
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Amini, Maryam; Niemi, Essi Maria; Hisdal, Jonny; Kalvøy, Håvard; Tronstad, Christian & Scholz, Hanne
[Show all 8 contributors for this article]
(2020).
Monitoring the quality of frozen-thawed venous segments using bioimpedance spectroscopy.
Physiological Measurement.
ISSN 0967-3334.
41(4).
doi:
10.1088/1361-6579/ab85b7.
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Objective: Storage at temperatures as low as −80 °C and below (cryopreservation) is considered a method for long-term preservation of cells and tissues, and especially blood vessel segments, which are to be used for clinical operations such as transplantation. However, the freezing and thawing processes themselves can induce injuries to the cells and tissue by damaging the structure and consequently functionality of the cryopreserved tissue. In addition, the level of damage is dependent on the rate of cooling and warming used during the freezing-thawing process. Current methods for monitoring the viability and integrity of cells and tissues after going through the freezing-thawing cycle are usually invasive and destructive to the cells and tissues. Therefore, employing monitoring methods which are not destructive to the cryopreserved tissues, such as bioimpedance measurement techniques, is necessary. In this study we aimed to design a bioimpedance measurement setup to detect changes in venous segments after freezing-thawing cycles in a noninvasive manner. Approach: A bioimpedance spectroscopy measurement technique with a two-electrode setup was employed to monitor ovine jugular vein segments after each cycle during a process of seven freezing-thawing cycles. Main results: The results demonstrated changes in the impedance spectra of the measured venous segments after each freezing-thawing cycle. Significance: This indicates that bioimpedance spectroscopy has the potential to be developed into a novel method for non-invasive and non-destructive monitoring of the viability of complex tissue after cryopreservation.
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Bari, Dindar S.; Aldosky, Haval Y. Yacoob; Tronstad, Christian & Martinsen, Ørjan Grøttem
(2020).
The correlations among the skin conductance features responding to physiological stress stimuli.
Skin Research and Technology.
ISSN 0909-752X.
p. 1–7.
doi:
10.1111/srt.12989.
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Martinsen, Tormod; Pettersen, Fred-Johan; Kalvøy, Håvard; Tronstad, Christian; Kvarstein, Gunnvald & Bakken, André
[Show all 10 contributors for this article]
(2019).
Electrosurgery and temperature increase in tissue with a passive metal implant.
Frontiers in Surgery.
6:8,
p. 1–8.
doi:
10.3389/fsurg.2019.00008.
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<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.
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Aria, Shafa; Elfarri, Yassine; Elvegård, Marius; Gottfridsson, Adam; Grønaas, Halvor & Harang, Sigve Smedsrud
[Show all 25 contributors for this article]
(2019).
Measuring blood pulse wave velocity with bioimpedance in different age groups.
Sensors.
19:850(4),
p. 1–10.
doi:
10.3390/s19040850.
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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.
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Tronstad, Christian; Høgetveit, Jan Olav; Elvebakk, Ole & Kalvøy, Håvard
(2019).
Age-related differences in the morphology of the impedance cardiography signal.
Journal of Electrical Bioimpedance.
10(1),
p. 139–145.
doi:
10.2478/joeb-2019-0020.
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Impedance cardiography (ICG) is a non-invasive method of hemodynamic measurement, mostly known for estimation of stroke volume and cardiac output based on characteristic features of the signal. Compared with electrocardiography, the knowledge on the morphology of the ICG signal is scarce, especially with respect to age-dependent changes in ICG waveforms. Based on recordings from ten younger (20–29 years) and ten older (60–79) healthy human subjects after three different levels of physical activity, the typical interbeat ICG waveforms were derived based on ensemble averages. Comparison of these waveforms between the age groups indicates the following differences: a later initial upward deflection for the younger group, an additional hump in the waveform from many older subjects not presented in the younger group, and a more pronounced second wave in the younger group. The explanation for these differences is not clear, but may be related to arterial stiffness. Further studies are suggested to determine whether these morphological differences have clinical value.
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Bjørhei, Andreas; Pedersen, Filip T.; Muhammad, Saeed; Tronstad, Christian; Kalvøy, Håvard & Wojniusz, Slawomir
[Show all 8 contributors for this article]
(2019).
An investigation on bilateral asymmetry in electrodermal activity.
Frontiers in Behavioral Neuroscience.
13(88).
doi:
10.3389/fnbeh.2019.00088.
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The Multiple Arousal Theory (Picard et al., 2016) was proposed to explain retrospective observations of bilateral differences in electrodermal activities occurring in threat-related high-stake situations. The theory proposes different cortical and subcortical structures to be involved in the processing of various facets of emotional states. Systematic investigations of this effect are still scarce. This study tested the prediction of bilateral electrodermal effects in a controlled laboratory environment where electrodermal activity (EDA) was recorded bilaterally during normal activity and two stress-tasks in 25 healthy volunteers. A visual search stress task with a performance-related staircase algorithm was used, ensuring intersubjectively comparable stress levels across individuals. After completion of the task, a sense of ownership of an attractive price was created and loss aversion introduced to create a high-stake situation. Confirmation of the theory should satisfy the hypothesis of a bilateral difference in EDA between the dominant and non-dominant hand, which is larger during high-stake stressors than during low-stake stressors. The bilateral difference was quantified and compared statistically between the two stress-tasks, revealing no significant difference between them nor any significant difference between the stress tasks and the period of normal activity. Subgroup analysis of only the participants with maximum self-rating of their desire to win the price (n = 7) revealed neither any significant difference between the two tasks nor between the stress-tasks and the period of normal activity. Although the theory was not confirmed by this study, eight cases suggestive of bilateral difference within the recordings were identified and are presented. Because the study is limited in using one of several possible operationalizations of the phenomenon, it is not possible to draw a general conclusion on the theory. Nevertheless, the study might contribute to a better understanding and encourage systematic review and hypothesis development regarding this new theory. Possible explanations and suggestions for future pathways to systematically investigate the Multiple Arousal Theory are discussed.
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Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre I.; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Gulseth, Hanne Løvdal
[Show all 9 contributors for this article]
(2019).
A multiparameter model for non-invasive detection of hypoglycemia.
Physiological Measurement.
ISSN 0967-3334.
40(8),
p. 1–14.
doi:
10.1088/1361-6579/ab3676.
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Objective: Severe hypoglycemia is the most serious acute complication for people with type 1 diabetes (T1D). Approximately 25% of people with T1D have impaired ability to recognize impending hypoglycemia, and nocturnal episodes are feared. Approach: We have investigated the use of non-invasive sensors for detection of hypoglycemia based on a mathematical model which combines several sensor measurements to identify physiological responses to hypoglycemia. Data from randomized single-blinded euglycemic and hypoglycemic glucose clamps in 20 participants with T1D and impaired awareness of hypoglycemia was used in the analyses. Main results: Using a sensor combination of sudomotor activity at three skin sites, ECG-derived heart rate and heart rate corrected QT interval, near-infrared and bioimpedance spectroscopy; physiological responses associated with hypoglycemia could be identified with an F1 score accuracy up to 88%. Significance: We present a novel model for identification of non-invasively measurable physiological responses related to hypoglycemia, showing potential for detection of moderate hypoglycemia using a wearable sensor system
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Martinsen, Ørjan Grøttem; Kalvøy, Håvard; Bari, Dindar S. & Tronstad, Christian
(2019).
A circuit for simultaneous measurements of skin electrical conductance, susceptance, and potential.
Journal of Electrical Bioimpedance.
10,
p. 110–112.
doi:
10.2478/joeb-2019-0016.
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A circuit is presented that enables measurement of skin electrical conductance, susceptance, and potential simultaneously beneath the same monopolar electrode. Example measurements are shown to confirm the function of the circuit. The measurements are also in accordance with earlier findings that changes in skin conductance and potential do not always correspond and hence contain unique information.
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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),
p. 1–16.
doi:
10.1088/1361-6579/aae0ea.
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Objective: Evaluation of intestinal viability is essential in surgical decision-making in patients with acute intestinal ischemia. There has been no substantial change in the mortality rate (30-93%) of patients with acute mesenteric ischemia (AMI) since the 1980’s. As the accuracy from the first laparotomy alone is 50%, the gold standard is a second-look laparotomy, increasing the accuracy to 87-89%. This study investigates the use of machine learning to classify intestinal viability and histological grading in pig jejunum, based on multivariate time-series of bioimpedance sensor data. Approach: We have previously used a bioimpedance sensor system to acquire electrical parameters from perfused, ischemic and reperfused pig jejunum (7 + 15 pigs) over 1-16 hours of ischemia and 1-8 hours of reperfusion following selected durations of ischemia. In this study we compare the accuracy of using end-point bioimpedance measurements with a feedforward neural network (FNN), versus the accuracy when using a recurrent neural network with long short-term memory units (LSTM-RNN) with bioimpedance data history over different periods of time. Main results: Accuracies in the range of what has been reported clinically can be achieved using FNN’s on a single bioimpedance measurement, and higher accuracies can be achieved when employing LSTM-RNN on a sequence of data history. Significance: Intraoperative bioimpedance measurements on intestine of suspect viability combined with machine learning can increase the accuracy of intraoperative assessment of intestinal viability. Increased accuracy in intraoperative assessment of intestinal viability has the potential to reduce the high mortality and morbidity rate of the patients.
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Strand-Amundsen, Runar James; Tronstad, Christian; Kalvøy, Håvard; Ruud, Tom Erik; Høgetveit, Jan Olav & Martinsen, Ørjan Grøttem
[Show all 7 contributors for this article]
(2018).
Small intestinal ischemia and reperfusion - Bioimpedance measurements.
Physiological Measurement.
ISSN 0967-3334.
39(2).
doi:
10.1088/1361-6579/aaa576.
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Objective: Trans-intestinal bioimpedance measurements have previously been used to investigate changes in electrical parameters during 6h of ischemia in the small intestine. Knowledge is lacking regarding the time course of trans-intestinal bioimpedance parameters during reperfusion. As reperfusion is an important part in the clinical treatment of intestinal ischemia, we need to know how it affects the bioimpedance measurements. Approach: We performed bioimpedance measurements, using a two-electrode setup on selected segments of the jejunum in 15 pigs. A controlled voltage signal was applied while measuring the resulting current. In each pig, five or six 30 cm segments of the jejunum were made ischemic by clamping the mesenteric arteries and veins creating segments with ischemia from 1–16h duration. Reperfusion was initiated at selected time intervals of ischemia, and measured for 5–15h afterwards. Main results: The tan δ parameter (loss tangent) was different (p < 0.016) comparing ischemic and control tissue for the duration of the experiment (16h). Comparing the control tissue 30 cm from the ischemic area with the control tissue 60 cm from the ischemic tissue, we found that the mean tan δ amplitude in the frequency range (3900–6300 Hz) was significantly higher (p < 0.036) in the proximal control after 10h of experiment duration. After reperfusion, the time development of tanδm (loss tangent maximum over a frequency range) amplitude and frequency overlapped and periodically increased above the tanδm in the ischemic intestine. Dependent on the ischemic duration pre-reperfusion, the initial increase in tan δ stabilizes or increases drastically over time, compared to the tan δ amplitude of the ischemic tissue. Significance: As during ischemia, the electrical parameters during reperfusion also follow a characteristic timecourse, depending on the ischemic exposure before pre-reperfusion. The temporal changes in electrical parameters during small intestinal ischemia followed by reperfusion provides important information for assessment of tissue injury.
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Bari, D. S.; Aldosoky, H. Y. Y.; Tronstad, Christian; Kalvøy, Håvard & Martinsen, Ørjan Grøttem
(2018).
Electrodermal activity responses for quantitative assessment of felt pain.
Journal of Electrical Bioimpedance.
9,
p. 52–58.
doi:
10.2478/joeb-2018-0010.
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Accurate assessment of experienced pain is a well-known problem in the clinical practices. Therefore, a proper method for pain detection is highly desirable. Electrodermal activity (EDA) is known as a measure of the sympathetic nervous system activity, which changes during various mental stresses. As pain causes mental stress, EDA measures may reflect the felt pain. This study aims to evaluate changes in skin conductance responses (SCRs), skin potential responses (SPRs), and skin susceptance responses (SSRs) simultaneously as a result of sequences of electrical (painful) stimuli with different intensities. EDA responses as results of painful stimuli were recorded from 40 healthy volunteers. The stimuli with three different intensities were produced by using an electrical stimulator. EDA responses significantly changed (increased) with respect to the intensity of the stimuli. Both SCRs and SSRs showed linear relationship with the painful stimuli. It was found that the EDA responses, particularly SCRs (p < 0.001) and SSRs (p = 0.001) were linearly affected by the intensity of the painful stimuli. EDA responses, in particular SCRs, may be used as a useful indicator for assessment of experienced pain in clinical settings.
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Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre I.; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Frøslie, Kathrine Frey
[Show all 10 contributors for this article]
(2018).
Evaluation of hypoglycaemia with non-invasive sensors in people with type 1 diabetes and impaired awareness of hypoglycaemia.
Scientific Reports.
8:14722,
p. 1–11.
doi:
10.1038/s41598-018-33189-1.
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People with type 1 diabetes and impaired awareness of hypoglycaemia (IAH) are prone to severe hypoglycaemia. Previous attempts to develop non-invasive hypoglycaemia alarm systems have shown promising results, but it is not known if such alarms can detect severe hypoglycaemia in people with IAH. We aimed to explore whether a combination of non-invasive sensors could reliably evaluate hypoglycaemia (plasma glucose (PG) minimum 2.5 mmol/L) in people with IAH. Twenty participants with type 1 diabetes and IAH underwent randomly ordered, single blinded hyperinsulinemic euglycaemic and hyperinsulinemic hypoglycaemic clamps. Sweating, skin temperature, ECG, counterregulatory hormones and symptoms of hypoglycaemia were assessed. Overall, we were not able to detect clamp-induced hypoglycaemia with sufficient sensitivity and specificity for further clinical use. As a post-hoc analysis, we stratified participants according to their ability to identify hypoglycaemic symptoms during hypoglycaemic clamps. Five out of 20 participants could identify such symptoms. These participants had a significantly higher adrenaline response to hypoglycaemia (p < 0.001) and were reliably identified by sensors. Based on our observations, a non-invasive alarm system based on measurement of sweating responses and ECG changes during hypoglycaemia might provide an alert at a plasma glucose concentration around 2.5 mmol/L if an adequate sympatho-adrenal reaction is elicited.
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Bari, Dindar S.; Aldosky, Haval Y. Yacoob; Tronstad, Christian; Kalvøy, Håvard & Martinsen, Ørjan Grøttem
(2018).
Influence of relative humidity on electrodermal levels and responses.
Skin Pharmacology and Physiology.
ISSN 1660-5527.
31,
p. 298–307.
doi:
10.1159/000492275.
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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.
p. 1844–1848.
doi:
10.1109/EMBC.2017.8037205.
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Kalvøy, Håvard; Tronstad, Christian; Ullensvang, Kyrre; Steinfeldt, Thorsten & Sauter, Axel Rudolf
(2017).
Detection of needle to nerve contact based on electric bioimpedance and machine learning methods.
IEEE Engineering in Medicine and Biology Society. Conference Proceedings.
ISSN 1557-170X.
p. 9–12.
doi:
10.1109/EMBC.2017.8036750.
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Bari, D. S.; Aldosky, H. Y. Y.; Tronstad, Christian; Kalvøy, Håvard & Martinsen, Ørjan Grøttem
(2017).
Electrodermal responses to discrete stimuli measured by skin conductance, skin potential, and skin susceptance.
Skin Research and Technology.
ISSN 0909-752X.
24(1),
p. 108–116.
doi:
10.1111/srt.12397.
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Tronstad, Christian; Elvebakk, Ole; Kalvøy, Håvard; Bjørgaas, Marit Ragnhild Rokne & Martinsen, Ørjan Grøttem
(2017).
Detection of sympathoadrenal discharge by parameterisation of skin conductance and ECG measurement.
IEEE Engineering in Medicine and Biology Society. Conference Proceedings.
ISSN 1557-170X.
p. 3997–4000.
doi:
10.1109/EMBC.2017.8037732.
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Strand-Amundsen, Runar James; Tronstad, Christian; Kalvøy, Håvard; Gundersen, Yngvar; Krohn, Claus Danckert & Aasen, Ansgar Oddne
[Show all 12 contributors for this article]
(2016).
In vivo characterization of ischemic small intestine using bioimpedance measurements.
Physiological Measurement.
ISSN 0967-3334.
37(2),
p. 257–275.
doi:
10.1088/0967-3334/37/2/257.
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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.
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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),
p. 648–652.
doi:
10.1177/0267659116651345.
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Pabst, Oliver; Tronstad, Christian; Grimnes, Sverre; Fowles, Don C. & Martinsen, Ørjan Grøttem
(2016).
Comparison between the AC and DC measurement of electrodermal activity.
Psychophysiology.
ISSN 0048-5772.
54(3),
p. 374–385.
doi:
10.1111/psyp.12803.
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Martinsen, Ørjan Grøttem; Pabst, Oliver; Tronstad, Christian & Grimnes, Sverre
(2015).
Sources of error in AC measurement of skin conductance.
Journal of Electrical Bioimpedance.
6(1),
p. 49–53.
doi:
10.5617/jeb.2640.
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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.
p. 2750–2753.
doi:
10.1109/EMBC.2015.7318961.
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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,
p. 5968–5972.
doi:
10.1109/EMBC.2015.7319751.
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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),
p. 1011–1018.
doi:
10.1088/0967-3334/35/6/1011.
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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),
p. 215–220.
doi:
10.2340/00015555-1671.
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Tronstad, Christian; Kalvøy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem
(2013).
Improved Estimation of Sweating Based on Electrical Properties of Skin.
Annals of Biomedical Engineering.
ISSN 0090-6964.
41(5),
p. 1074–1083.
doi:
10.1007/s10439-013-0743-4.
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Tronstad, Christian; Kalvøy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem
(2013).
Waveform difference between skin conductance and skin potential responses in relation to electrical and evaporative properties of skin.
Psychophysiology.
ISSN 0048-5772.
50(11),
p. 1070–1078.
doi:
10.1111/psyp.12092.
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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),
p. 1485–1494.
doi:
10.1002/lt.23544.
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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),
p. 157–163.
doi:
10.1093/ejcts/ezr278.
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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),
p. 26–34.
doi:
10.1111/j.1600-0846.2010.00459.x.
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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),
p. 755–765.
doi:
10.1088/0967-3334/32/7/S03.
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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),
p. 1241–1255.
doi:
10.1088/0967-3334/31/9/013.
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Kalvøy, Håvard; Tronstad, Christian; Nordbotten, Bernt Jørgen; Grimnes, Sverre & Martinsen, Ørjan Grøttem
(2010).
Electrical Impedance of Stainless Steel Needle Electrodes.
Annals of Biomedical Engineering.
ISSN 0090-6964.
38(7),
p. 2371–2382.
doi:
10.1007/s10439-010-9989-2.
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Tronstad, Christian; Grimnes, Sverre; Martinsen, Ørjan Grøttem; Amundsen, Vegar & Wojniusz, Slawomir
(2010).
PC-based instrumentation for electrodermal activity measurement.
Journal of Physics: Conference Series (JPCS).
ISSN 1742-6588.
224.
doi:
10.1088/1742-6596/224/1/012093.
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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.
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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),
p. 1395–1410.
doi:
10.1088/0967-3334/31/10/008.
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Kildal, Emilie Smith-Meyer; Quintana, Daniel; Szabo, Attila; Tronstad, Christian; Andreassen, Ole & Nærland, Terje
[Show all 7 contributors for this article]
(2023).
Heart rate monitoring to detect acute pain in non-verbal patients: a study protocol for a randomized controlled clinical trial.
BMC Psychiatry.
23(1).
doi:
10.1186/s12888-023-04757-1.
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Background Autism entails reduced communicative abilities. Approximately 30% of individuals with autism have intellectual disability (ID). Some people with autism and ID are virtually non-communicative and unable to notify their caregivers when they are in pain. In a pilot study, we showed that heart rate (HR) monitoring may identify painful situations in this patient group, as HR increases in acutely painful situations. Objectives This study aims to generate knowledge to reduce the number of painful episodes in non-communicative patients’ everyday lives. We will 1) assess the effectiveness of HR as a tool for identifying potentially painful care procedures, 2) test the effect of HR-informed changes in potentially painful care procedures on biomarkers of pain, and 3) assess how six weeks of communication through HR affects the quality of communication between patient and caregiver. Methods We will recruit 38 non-communicative patients with autism and ID residing in care homes. Assessments: HR is measured continuously to identify acutely painful situations. HR variability and pain-related cytokines (MCP-1, IL-1RA, IL-8, TGFβ1, and IL-17) are collected as measures of long-term pain. Caregivers will be asked to what degree they observe pain in their patients and how well they believe they understand their patient’s expressions of emotion and pain. Pre-intervention: HR is measured 8 h/day over 2 weeks to identify potentially painful situations across four settings: physiotherapy, cast use, lifting, and personal hygiene. Intervention: Changes in procedures for identified painful situations are in the form of changes in 1) physiotherapy techniques, 2) preparations for putting on casts, 3) lifting techniques or 4) personal hygiene procedures. Design: Nineteen patients will start intervention in week 3 while 19 patients will continue data collection for another 2 weeks before procedure changes are introduced. This is done to distinguish between specific effects of changes in procedures and non-specific effects, such as caregivers increased attention. Discussion This study will advance the field of wearable physiological sensor use in patient care. Trial registration Registered prospectively at ClinicalTrials.gov (NCT05738278).
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Elvebakk, Ole; Tronstad, Christian; Birkeland, Kåre Inge; Jenssen, Trond Geir; Bjørgaas, Marit Ragnhild Rokne & Frøslie, Kathrine Frey
[Show all 10 contributors for this article]
(2019).
Author Correction: Evaluation of Hypoglycaemia with Non-Invasive Sensors in People with Type 1 Diabetes and Impaired Awareness of Hypoglycaemia (Scientific Reports, (2018), 8, 1, (14722), 10.1038/s41598-018-33189-1).
Scientific Reports.
9(1).
doi:
10.1038/s41598-019-42218-6.
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Strand-Amundsen, Runar James; Tronstad, Christian; Martinsen, Ørjan Grøttem; Høgetveit, Jan Olav; Ruud, TE & Tønnessen, Tor Inge
(2016).
Bioimpedance - in vivo vs in vitro ischemic small intestine.
Proceedings of the 16th International Conference on Electrical Bioimpedance.
p. 53–53.
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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.
p. 65–65.
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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.
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Kalvøy, Håvard; Sauter, Axel Rudolf; Tronstad, Christian & Martinsen, Ørjan Grøttem
(2016).
Neural tissue discrimination with machine learning methods.
Proceedings of the 16th International Conference on Electrical Bioimpedance.
p. 71–71.
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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.
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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.
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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.
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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.
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Tronstad, Christian; Kalvøy, Håvard; Grimnes, Sverre & Martinsen, Ørjan Grøttem
(2013).
Sweat production estimated by bioimpedance and bioelectrical signals.
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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.
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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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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.
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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.
Universitetet i Oslo.
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This thesis is all about applying an electrical voltage to human skin and measuring the corresponding electrical current. A recording (on any tissue) is non-linear when the electrical properties are affected by the applied signal itself; The measurement is linear otherwise. Non-linear measurements on human skin initiate a very new field of research. Dependent on the polarity of the applied voltage, the sweat inside the ducts is moved towards the skin surface or towards deeper skin layers. Here we confirmed that the sweat ducts are memristors (memory resistor) and found that information can actually be stored inside. If you are a forgetful person, this might be a way to store your bank pin number in the future. A second memristor can be found in the stratum corneum (the tissue in the outer layer of the skin that surrounds the sweat ducts). However, the voltage-current characteristics recorded from human skin vary largely among subjects with potential applications in Diagnostics. Further, we found that human skin can act as a frequency doubler and halve-wave rectifier. An example of linear measurements will be given as an introduction. Changes in sweating due to sympathetic nervous activity are subject of (linear) electrodermal activity (EDA) recordings. Here, the test subjects were asked to do continuous subtractions and deep breaths, to stimulate their sweat activity. By doing so, it was possible to find out that EDA recordings using the alternating current (AC) method are comparable with recordings using the direct current (DC) method.
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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.
Universitetet i Oslo.
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Published
Dec. 6, 2011 1:08 PM
- Last modified
Sep. 10, 2012 12:51 PM