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  • 151.
    Janerot-Sjöberg, Birgitta
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Ekberg, Stefan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Areskog, M.
    Department of Clinical Physiology, Kalmar Regional Hospital.
    Nylander, Eva
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Swahn, Eva
    Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Cardiology UHL.
    Quantitative digital evaluation of myocardial exercise thallium-201 single-photon emission tomography in post-menopausal women1998In: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 18, no 3, p. 169-177Article in journal (Refereed)
    Abstract [en]

    Quantitative computerized analysis of data from myocardial thallium-201 (201Tl) single-photon emission tomography (SPET) may improve the diagnostic accuracy of coronary heart disease. The reference ranges for post-menopausal women are, however, limited and obtained mainly from patients. To compare reference values from healthy post-menopausal women and to improve the quantitative analysis, 20 women (10 patients with coronary heart disease and previous infarction and 10 age-matched healthy volunteers) were examined immediately post exercise and after a delay. A nine-segment 'bull's-eye' model was used for analysis. At visual evaluation, reproducibility was high (93%), no false-positive results were obtained and in 70% of the patients the SPET was interpreted as abnormal. Using reported reference values for quantitative analysis, all the healthy women had an abnormal result. New reference values based on three different methods of 'normalization' were calculated: the relative activity of segment 3 set to 100%, the segment with the highest activity set to 100% and a least-squares method. They all differed significantly from those that had previously been reported. The frequencies of agreement between visual and quantitative analysis were 84-92% and were highest when segment 3 was used as a reference, but in this case only 40% of the patients with coronary heart disease had an abnormal SPET. Using the least-squares method for handling digital information, the SD of the normal values decreased and 90% of the patients with coronary heart disease were accurately diagnosed. These results provide quantitative digital reference values for healthy post-menopausal women. They verify that quantitative analysis is in diagnostic agreement with visual evaluation, stress the need for local verification of reference ranges and suggest a least-square normalization method for the analysis.

  • 152.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    A neural network for photoplethysmografic respiratory rate monitoring2001In: ECBO,2001, 2001Conference paper (Refereed)
    Abstract [en]

       

  • 153.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    A neural network for photoplethysmographic respiratory rate monitoring2001In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 4434, p. 109-118Conference paper (Other academic)
    Abstract [en]

    The photoplethysmographic signal (PPG) includes respiratory components seen as frequency modulation of the heart rate (respiratory sinus arrhythmia, RSA), amplitude modulation of the cardiac pulse, and respiratory induced intensity variations (RIIV) in the PPG baseline. The aim of this study was to evaluate the accuracy of these components in determining respiratory rate, and to combine the components in a neural network for improved accuracy. The primary goal is to design a PPG ventilation monitoring system. PPG signals were recorded from 15 healthy subjects. From these signals, the systolic waveform, diastolic waveform, respiratory sinus arrhythmia, pulse amplitude and RIIV were extracted. By using simple algorithms, the rates of false positive and false negative detection of breaths were calculated for each of the five components in a separate analysis. Furthermore, a simple neural network (NN) was tried out in a combined pattern recognition approach. In the separate analysis, the error rates (sum of false positives and false negatives) ranged from 9.7% (pulse amplitude) to 14.5% (systolic waveform). The corresponding value of the NN analysis was 9.5-9.6%.

  • 154.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Ahlström, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Länne, Toste
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Pulse wave transit time for monitoring respiration rate2006In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 6, p. 471-478Article in journal (Refereed)
    Abstract [en]

    In this study, we investigate the beat-to-beat respiratory fluctuations in pulse wave transit time (PTT) and its subcomponents, the cardiac pre-ejection period (PEP) and the vessel transit time (VTT) in ten healthy subjects. The three transit times were found to fluctuate in pace with respiration. When applying a simple breath detecting algorithm, 88% of the breaths seen in a respiration air-flow reference could be detected correctly in PTT. Corresponding numbers for PEP and VTT were 76 and 81%, respectively. The performance during hypo- and hypertension was investigated by invoking blood pressure changes. In these situations, the error rates in breath detection were significantly higher. PTT can be derived from signals already present in most standard monitoring set-ups. The transit time technology thus has prospects to become an interesting alternative for respiration rate monitoring. © International Federation for Medical and Biological Engineering 2006.

  • 155.
    Johansson, Anders
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Hök, Bertil
    Sensors for respiratory monitoring2004In: Sensors Applications, Sensors in Medicine and Health Care / [ed] P. Ake Oberg, Tatsuo Togawa & Francis A. Spelman, Weinheim, Germany: WileyVCH Verlag , 2004, 3, p. 161-186Chapter in book (Other academic)
  • 156.
    Johansson, Anders
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Kuiper, Jan-Herman
    Keele University, England Robert Jones and Agnes Hunt Orthopaed Hospital, England .
    Sundqvist, Tommy
    Linköping University, Department of Clinical and Experimental Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
    Persson, Fredrik
    BioOptico AB, Sweden .
    Speier, Craig
    ConMedical Linvatec, CA USA .
    DAlfonso, David
    ConMedical Linvatec, CA USA .
    Richardson, James B
    Keele University, England Robert Jones and Agnes Hunt Orthopaed Hospital, England .
    Öberg, Åke
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Spectroscopic Measurement of Cartilage Thickness in Arthroscopy: Ex Vivo Validation in Human Knee Condyles2012In: Arthroscopy: The Journal of Arthroscopy And Related, ISSN 0749-8063, E-ISSN 1526-3231, Vol. 28, no 10, p. 1513-1523Article in journal (Refereed)
    Abstract [en]

    Purpose: To evaluate the accuracy of articular cartilage thickness measurement when implementing a new technology based on spectroscopic measurement into an arthroscopic camera. Methods: Cartilage thickness was studied by ex vivo arthroscopy at a number of sites (N = 113) in human knee joint osteoarthritic femoral condyles and tibial plateaus, removed from 7 patients undergoing total knee replacement. The arthroscopic image spectral data at each site were used to estimate cartilage thickness. Arthroscopically derived thickness values were compared with reference cartilage thickness as measured by 3 different methods: needle penetration, spiral computed tomography scanning, and geometric measurement after sample slicing. Results: The lowest mean error (0.28 to 0.30 mm) in the regression between arthroscopic and reference cartilage thickness was seen for reference cartilage thickness less than 1.5 mm. Corresponding values for cartilage thickness less than 2.0 and 2.5 mm were 0.32 to 0.40 mm and 0.37 to 0.47 mm, respectively. Cartilage thickness images-created by pixel-by-pixel regression model calculations applied to the arthroscopic images-were derived to demonstrate the clinical use of a camera implementation. Conclusions: On the basis of this investigation on osteoarthritic material, when one is implementing the spectroscopic method for estimating cartilage thickness into an arthroscopic camera, errors in the range of 0.28 to 0.30 mm are expected. This implementation does not, however, influence the fact that the spectral method performs less well in the cartilage thickness region from 1.5 to 2.5 mm and cannot assess cartilage thicker than 2.5 mm. Clinical Relevance: Imaging cartilage thickness directly in the arthroscopic camera video stream could serve as an interesting image tool for in vivo cartilage quality assessment, in connection with cartilage diagnosis, repair, and follow-up.

  • 157.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Larsby, Birgitta
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Neuroscience and Locomotion, Technical Audiology.
    Tamura, Toshiyo
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Fallförebyggande sensor för äldre2005In: National Medical Convent,2005, 2005Conference paper (Refereed)
  • 158.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Nilsson, Lena
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Kalman, Sigga
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Respiratory monitoring using photoplethysmography - evaluation in the postoperative care unit1998In: Annual International Conference of th IEEE Engineering in Medicine and Biology Society,1998, 1998Conference paper (Refereed)
  • 159.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Strömberg, Tomas
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Influence of tidal volume and thoraco-abdominal separation on the respiratory induced variation of the photoplethysmogram2000In: Journal of clinical monitoring and computing, ISSN 1387-1307, E-ISSN 1573-2614, Vol. 16, no 8, p. 575-581Article in journal (Refereed)
    Abstract [en]

    Objective. The present study was aimed at determining the relative influences of tidal volume and thoraco-abdominal separation (relative thoracic and abdominal contribution to the tidal volume) on the respiratory induced intensity variation (RIIV) of the photoplethysmographic signal. The effects were studied in two body positions. Methods. Respiratory inductive plethysmography was used or quantifying thoraco-abdominal separation and for assessing tidal volumes. 10 subjects were trained to perform widely varying degrees of thoraco-abdominal separation at different tidal volumes. The relationship between the RIIV signal peak-to-peak value (measured at the forearm), and the tidal volume and thoraco-abdominal separation was investigated in two body positions with the use of multiple linear regression. Results. Larger tidal volume and more thoracic contribution to respiration were found to increase the RIIV peak-to-peak value (p < 0.0005). In the supine position, the tidal volume influence was stronger than that of thoraco-abdominal separation, and in the sitting position, the opposite was seen. Conclusions. The effects on the RIIV signal following changes in thoraco-abdominal separation and tidal volume are of the same order of magnitude. In the supine position, the influence of thoracic versus abdominal contribution to the tidal volume is not as significant as in the sitting position. Photoplethysmography is a promising technique for combined monitoring of several respiratory parameters, including tidal volume. In situations where the relative thoracic and abdominal contribution are likely to vary, the tidal volume information becomes less reliable.

  • 160.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Sundqvist, Tommy
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Molecular and Clinical Medicine, Medical Microbiology.
    Kuiper, J-H
    Inst of Science and Technology in Medicine Keele University Medical School, UK.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    IN VITRO Imaging of human cartilage - contrast improvement by optical wavelength selection2005In: Nordic Baltic Conference Biomedical Engineering and Medical Physics,2005, Umeå: IFMBE , 2005, p. 172-Conference paper (Refereed)
  • 161.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Estimation of respiratory volumes from the photoplethysmographic signal1997In: World Congress on Medical Physics and Biomedical Engineering,1997, 1997Conference paper (Refereed)
  • 162.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Uppskattning av andningsvolym med fotopletysmografi1996In: National Medical Convent,1996, 1996Conference paper (Refereed)
  • 163.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Sedin, Gunnar
    Uppsala .
    Monitoring of the heart and respiratory rates using photoplethysmography - Evaluation on neonates1998In: BIOS Europe98,1998, 1998Conference paper (Other academic)
  • 164.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Sedin, Gunnar
    Akademiska sjukhuset Uppsala.
    New perspectives in biooptical assessment of ventilation in neonatal care2000In: Int Conf on Fetal Neonatal physiological Measurement,2000, 2000Conference paper (Refereed)
  • 165.
    Johansson, Anders
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Sundqvist, Tommy
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Molecular and Clinical Medicine, Medical Microbiology.
    Sundberg, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Assessment of cartilage thickness utilising reflectance spectroscopy2002In: Nordic Baltic Conference on Biomedical Engineering,2002, 2002Conference paper (Refereed)
    Abstract [en]

      

  • 166. Johansson, K E
    et al.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Boeryd, B
    Fransson, S G
    Tibbling, Lita
    Oesophagitis, signs of reflux, and gastric acid secretion in patients with symptoms of gastro-oesophageal reflux disease.1986In: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 21, no 7, p. 837-847Article in journal (Refereed)
    Abstract [en]

    In a study comprising 100 patients referred to a surgical clinic with symptoms suggestive of gastro-oesophageal reflux disease the value of different diagnostic procedures was investigated. Positive acid perfusion and 24-h pH tests were the commonest findings. Forty-nine per cent showed a normal oesophageal mucosa or diffuse oesophagitis at endoscopy. The severity of heartburn and regurgitation did not differ between patients with normal oesophageal mucosa and oesophagitis of various severities. The severity of macroscopic oesophagitis was significantly correlated to the total reflux time, the presence of reflux or a hiatal hernia at radiology, an open cardia or reflux at endoscopy, pressure transmission or reflux and low lower oesophageal sphincter pressure at manometry. Gastric hypersecretion was found in 66% of the patients. Gastric acid secretion was not correlated to the severity of oesophagitis or to the findings at 24-h pH test. In patients with severe oesophagitis the sensitivity for radiologic, manometric, and endoscopic signs of incompetence of the gastro-oesophageal junction was 94%.

  • 167. JOHANSSON, KE
    et al.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    EDWALL, G
    Tibbling, Lita
    A PORTABLE UNIT FOR 24-HOUR ESOPHAGEAL PH MONITORING WITH ANTIMONY ELECTRODES1981In: ACTA CHIRURGICA SCANDINAVICA, ISSN 0001-5482, no 506Article in journal (Refereed)
  • 168.
    Jönsson, Björn
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Vascular surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Laurent, Claes
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Eneling, Martin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Skau, Tommy
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Automatic ankle pressure measurements using PPG in ankle-brachial pressure index determination2005In: Scandinavian Cardiovascular Journal,2005, Sweden: Taylor & Francis , 2005, p. 13-Conference paper (Refereed)
  • 169.
    Jönsson, Björn
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Vascular surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Laurent, Claes
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Eneling, Martin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Skau, Tommy
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Automatisk ankeltryckmätning med PPG för bestämning av ankel-armindex (ABP)2005In: Svensk Kirurgi,2005, 2005, p. 23-Conference paper (Refereed)
  • 170.
    Jönsson, Björn
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Vascular surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Laurent, Claes
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Skau, Tommy
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    A new probe for ankle systolic pressure measurements using photopethysmography2004In: International Angiology,2004, 2004, p. 186-186Conference paper (Other academic)
  • 171.
    Karlsson, Annika M.
    et al.
    Linköping University, Department of Medical and Health Sciences, Pharmacology. Linköping University, Faculty of Health Sciences.
    Bjuhr, Katarina
    Linköping University, Department of Medical and Health Sciences, Pharmacology. Linköping University, Faculty of Health Sciences.
    Testorf, Martin
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Öberg, Åke
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Lerner, Ethan
    Bunsen Rush Laboratories, Dallas, TX, USA.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Svensson, Samuel P.S.
    Linköping University, Department of Medical and Health Sciences, Pharmacology. Linköping University, Faculty of Health Sciences.
    Biosensing of opioids using frog melanophores2002In: Biosensors and Bioelectronics, ISSN 0956-5663, Vol. 17, no 4, p. 331-335Article in journal (Refereed)
    Abstract [en]

    Spectacular color changes of fishes, frogs and other lower vertebrates are due to the motile activities of specialized pigment containing cells. Pigment cells are interesting for biosensing purposes since they provide an easily monitored physiological phenomenon. Melanophores, containing dark brown melanin pigment granules, constitute an important class of chromatophores. Their melanin-filled pigment granules may be stimulated to undergo rapid dispersion throughout the melanophores (cells appear dark), or aggregation to the center of the melanophores (cells appear light). This simple physiological response can easily be measured in a photometer. Selected G protein coupled receptors can be functionally expressed in cultured frog melanophores. Here, we demonstrate the use of recombinant frog melanophores as a biosensor for the detection of opioids. Melanophores were transfected with the human opioid receptor 3 and used for opiate detection. The response to the opioid receptor agonist morphine and a synthetic opioid peptide was analyzed by absorbance readings in an aggregation assay. It was shown that both agonists caused aggregation of pigment granules in the melanophores, and the cells appeared lighter. The pharmacology of the expressed receptors was very similar to its mammalian counterpart, as evidenced by competitive inhibition by increasing concentrations of the opioid receptor inhibitor naloxone. Transfection of melanophores with selected receptors enables the creation of numerous melanophore biosensors, which respond selectively to certain substances. The melanophore biosensor has potential use for measurement of substances in body fluids such as saliva, blood plasma and urine.

  • 172. Karlsson, M
    et al.
    Brandberg, J
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Computer simulation for improved assessment of mitral regurgitation.1997In: COMPUTERS IN CARDIOLOGY 1997, VOL 24, 1997, Vol. 24, p. 169-170Conference paper (Refereed)
    Abstract [en]

    Since valvular regurgitation is one of the most common malfunctions of the heart the quantification of valvular regurgitation by means of non-invasive methods is desired. However existing methods for quantitative assessment is far from perfect. The aim of this paper is to study the proximal velocity field for non-stationary flow and non-planar geometries by computer simulation, which were performed using the FIDAP package to numerically solve the governing equations. A plexiglass in-vitro model similar to the computer model was used for comparison and the same results were obtained. We have found that it is possible to refine the PISA method and standardize flow calculations. Further improvements will hopefully create a tool for the echocardiographer that will facilitate evaluation and clinical applicability of the PISA approach.

  • 173.
    Karlsson, Matts
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Engvall, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Orifice flow in stenotic and regurgitant valve lesions - Modelling and computer simulations1994In: Biofluid mechanics, Southhampton: Computational Mechanics Publications , 1994Chapter in book (Other academic)
  • 174.
    Karlsson, Matts
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Lindström, K
    Elmqvist, Håkan
    CORTECH tutor - a distributed biomedical engineering graduate training initiative1999In: The 1st Joint Meeting of BMES and EMBS,1999, 1999Conference paper (Other academic)
  • 175.
    Kvikliene, Adriana
    et al.
    Institute of Biomedical Engineering, Kaunas University of Technology, K. Donelaicio st. 73, Kaunas LT-3006, Lithuania.
    Jurkonis, Rytis
    Institute of Biomedical Engineering, Kaunas University of Technology, K. Donelaicio st. 73, Kaunas LT-3006, Lithuania.
    Ressner, Marcus
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Hoff, Lars
    Faculty of Science and Engineering, Vestfold University College, P.O. Box 2243, N-3103 Tønsberg, Norway.
    Jansson, Tomas
    Department of Electrical Measurements, Lund University, P.O. Box 118, SE-221 00, Lund, Sweden.
    Janerot Sjöberg, Birgitta
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Lukosevicius, Arunas
    Institute of Biomedical Engineering, Kaunas University of Technology, K. Donelaicio st. 73, Kaunas LT-3006, Lithuania.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles: simulation and experiment2004In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 42, no 01-Sep, p. 301-307Article in journal (Refereed)
    Abstract [en]

    The propagation of diagnostic ultrasonic imaging pulses in tissue and their interaction with contrast micro bubbles is a very complex physical process, which we assumed to be separable into three stages: pulse propagation in tissue, the interaction of the pulse with the contrast bubble, and the propagation of the scattered echo. The model driven approach is used to gain better knowledge of the complex processes involved. A simplified way of field simulation is chosen due to the complexity of the task and the necessity to estimate comparative contributions of each component of the process. Simulations are targeted at myocardial perfusion estimation. A modified method for spatial superposition of attenuated waves enables simulations of low intensity pulse pressure fields from weakly focused transducers in a nonlinear, attenuating, and liquid-like biological medium. These assumptions enable the use of quasi-linear calculations of the acoustic field. The simulations of acoustic bubble response are carried out with the Rayleigh-Plesset equation with the addition of radiation damping. Theoretical simulations with synthesised and experimentally sampled pulses show that the interaction of the excitation pulses with the contrast bubbles is the main cause of nonlinear scattering, and a 2-3 dB increase of second harmonic amplitude depends on nonlinear distortions of the incident pulse. (C) 2004 Elsevier B.V. All rights reserved.

  • 176.
    Källman, Ulrika
    et al.
    Linköping University, Department of Medical and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences.
    Bergstrand, Sara
    Linköping University, Department of Medical and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences.
    Ek, Anna-Christina
    Linköping University, Department of Medical and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Acute Health Care.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Lindberg, Lars-Göran
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Lindgren, Margareta
    Linköping University, Department of Medical and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences.
    Different lying positions and their effects on tissue blood flow and skin temperature in older adult patients2013In: Journal of Advanced Nursing, ISSN 0309-2402, E-ISSN 1365-2648, Vol. 69, no 1, p. 133-144Article in journal (Refereed)
    Abstract [en]

    Aim. To report a study to compare the effects of different lying positions on tissue blood flow and skin temperature in older adult patients. This article reports the evaluation of study design and procedures. Background. To reduce risk of pressure ulcers, repositioning of immobile patients is a standard nursing practice; however, research into how different lying positions effect tissue microcirculation is limited. Design. Descriptive comparative design. Methods. From MarchOctober 2010, 20 inpatients, aged 65 years or older, were included in the study. Tissue blood flow and skin temperature were measured over bony prominences and in gluteus muscle in four supine and two lateral positions. Results. The blood flow over the bony prominence areas was most influenced in the superficial skin and especially in the 30 degrees lateral position, where the blood flow decreased significantly in comparison with the supine positions. There were significant individual differences in blood flow responses, but no common trend was identified among the patients considered at risk for pressure ulcer development. The study procedure worked well and was feasible to perform in an inpatient population. Conclusion. The lying positions seem to influence the tissue blood flow over the bony prominences in different ways in older adult inpatients, but further study is needed to confirm the results and to make recommendations to clinical practice. The study procedure worked well, although some minor adjustments with regard to heat accumulation will be made in future studies.

  • 177.
    Källman, Ulrika
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences. Södra Älvsborgs Sjukhus, Borås, Sweden .
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Bergstrand, Sara
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences.
    Ek, Anna-Cristina
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Acute Health Care in Linköping.
    Fredrikson, Mats
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Lindgren, Margareta
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences.
    The Effects of Different Lying Positions on Interface Pressure, Skin Temperature, and Tissue Blood Flow in Nursing Home Residents2015In: Biological Research for Nursing, ISSN 1099-8004, E-ISSN 1552-4175, Vol. 17, no 2, p. 142-151Article in journal (Refereed)
    Abstract [en]

    Background: Although repositioning is considered an important intervention to prevent pressure ulcers, tissue response during loading in different lying positions has not been adequately explored.

    Aim: To compare the effects of different lying positions on interface pressure, skin temperature, and tissue blood flow in nursing home residents.

    Method: From May 2011 to August 2012, interface pressure, skin temperature, and blood flow at three tissue depths were measured for 1 hr over the sacrum in 30 supine tilt and 0 supine positions and over the trochanter major in 30lateral and 90lateral positions in 25 residents aged 65 years or older. Measurement of interface pressure was accomplished using a pneumatic pressure transmitter connected to a digital manometer, skin temperature using a temperature sensor, and blood flow using photoplethysmography and laser Doppler flowmetry.

    Results: Interface pressure was significantly higher in the 0supine and 90lateral positions than in 30supine tilt and 30 lateral positions. The mean skin temperature increased from baseline in all positions. Blood flow was significantly higher in the 30 supine tilt position compared to the other positions. A hyperemic response in the post pressure period was seen at almost all tissue depths and positions.

    Conclusion: The 30supine tilt position generated less interface pressure and allowed greater tissue perfusion, suggesting that this position is the most beneficial.

  • 178.
    Laurent, Claes
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Measure the pressure and measure it right, at the brachial artery with infrared light2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the development and assessment of an optical probe and instrument based on photoplethysmography (PPG) for monitoring of systolic blood pressure on the upper arm. The development procedure steps have included investigation of best probe position above the brachial artery, probe location underneath the occlusion cuff and also assessment of the ability of infrared light to mirror a blood flow related signal from a deeper vascular depth where the brachial artery is found. In addition, a digital PPG instrument has been developed and adapted to requirements from both a technical and clinical perspective. Design of algorithms for automatic blood pressure determination has been performed and used but they are not fully optimised yet. The technique was assessed in a study and the correlation factor, r=o.95. The difference between blood pressure obtained using the PPG method and invasive blood pressure was 3.9 ± 9.1 mmHg (mean± SD), n=19.

    The work in this thesis demonstrates that PPG in combination with a specially designed probe can monitor the systolic blootl pressure at the upper arm. A robust algorithm for automatic pressure determination and presentation and a probe permanently integrated within the cuff is a prerequisite for the coming technical development. Recent technological developments facilitate ambulatory monitoring systems within which fields our system is clearly adaptable.

    List of papers
    1. Noninvasive monitoring of systolic blood pressure on the arm utilizing photoplethysmography (PPG): clinical report
    Open this publication in new window or tab >>Noninvasive monitoring of systolic blood pressure on the arm utilizing photoplethysmography (PPG): clinical report
    Show others...
    2004 (English)In: Proc. SPIE 5318, Advanced Biomedical and Clinical Diagnostic Systems II / [ed] Gerald E. Cohn; Warren S. Grundfest; David A. Benaron; Tuan Vo-Dinh, Bellingham WA, USA: SPIE , 2004, p. 99-Conference paper, Published paper (Refereed)
    Abstract [en]

    A soft (silicone) probe, containing six light emitting diodes (880 nm) and three photo detectors, utilizes photoplethysmography (PPG) to monitor pulsations from the brachialis artery under an occluding cuff during deflation. When the arterial pulse returns, measured by PPG, the corresponding pressure in the cuff is determined. This pressure is assumed to equal the systolic pressure. An assessment trial was performed on 21 patients (9 women and 12 men, aged 27-69) at the Neuro-Intensive care unit. Since the patients were already provided with arterial needles, invasive blood pressure could be used as the reference. By choosing a threshold, for detecting pulses, as a fraction (4%) of the maximum amplitude, the systolic blood pressure was underestimated (-0.57 mmHg, SD 12.1). The range of systolic pressure for the patients was 95.5 - 199.0 mmHg, n=14. The method is promising, but improvements still have to be made in order to improve the technique.

    Place, publisher, year, edition, pages
    Bellingham WA, USA: SPIE, 2004
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-22175 (URN)10.1117/12.529092 (DOI)1305 (Local ID)1305 (Archive number)1305 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-11-13
    2. Non-invasive measurement of systolic blood pressure on the arm utilising photoplethysmography: development of the methodology
    Open this publication in new window or tab >>Non-invasive measurement of systolic blood pressure on the arm utilising photoplethysmography: development of the methodology
    2005 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 43, no 1, p. 131-135Article in journal (Refereed) Published
    Abstract [en]

    Photoplethysmography (PPG) can be used to measure systolic blood pressure at the brachial artery. With a specially designed probe, positioned in the most distal position beneath a pressure cuff on the upper arm, this is possible. The distance between the light source (880 nm) and the photodetector was 20 mm. A test was performed on neuro-intensive care patients by determining blood pressure from the PPG curves, and, when it was compared with systolic blood pressure obtained from inserted indwelling arterial catheters, a correlation factor of r=0.95 was achieved. The difference between blood pressure obtained using PPG and invasive blood pressure measurement was 3.9±9.1 mmHg (mean±SD), n=19. The depth to the brachial artery was 13.9±4.1 mm (mean±SD), n=18. A digital PPG system utilising pulsating light was also developed.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-29570 (URN)10.1007/BF02345134 (DOI)000226938000020 ()14945 (Local ID)14945 (Archive number)14945 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
  • 179.
    Laurent, Claes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Jönsson, Björn
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Vascular surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Vegfors, Magnus
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Eneling, M
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Nonivasive monitoring of systolic blood pressuire on the arm utilizing photoplethysmpgraphy (PPG)2004In: Proceedings of SPIE jfr 1998-2000 SPIE proceedings ISSN 1017-2653, ISSN 1605-7422, p. 99-107Article in journal (Refereed)
  • 180.
    Laurent, Claes
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Jönsson, Björn
    Linköping University, Department of Medicine and Care, Vascular surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery. Linköping University, Faculty of Health Sciences.
    Vegfors, Magnus
    Linköping University, Department of Medicine and Care, Anaesthesiology. Linköping University, Faculty of Health Sciences.
    Eneling, Martin
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Lindberg, Lars-Göran
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Noninvasive monitoring of systolic blood pressure on the arm utilizing photoplethysmography (PPG): clinical report2004In: Proc. SPIE 5318, Advanced Biomedical and Clinical Diagnostic Systems II / [ed] Gerald E. Cohn; Warren S. Grundfest; David A. Benaron; Tuan Vo-Dinh, Bellingham WA, USA: SPIE , 2004, p. 99-Conference paper (Refereed)
    Abstract [en]

    A soft (silicone) probe, containing six light emitting diodes (880 nm) and three photo detectors, utilizes photoplethysmography (PPG) to monitor pulsations from the brachialis artery under an occluding cuff during deflation. When the arterial pulse returns, measured by PPG, the corresponding pressure in the cuff is determined. This pressure is assumed to equal the systolic pressure. An assessment trial was performed on 21 patients (9 women and 12 men, aged 27-69) at the Neuro-Intensive care unit. Since the patients were already provided with arterial needles, invasive blood pressure could be used as the reference. By choosing a threshold, for detecting pulses, as a fraction (4%) of the maximum amplitude, the systolic blood pressure was underestimated (-0.57 mmHg, SD 12.1). The range of systolic pressure for the patients was 95.5 - 199.0 mmHg, n=14. The method is promising, but improvements still have to be made in order to improve the technique.

  • 181.
    Laurent, Claes
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Jönsson, Björn
    Linköping University, Department of Medicine and Care, Vascular surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery. Linköping University, Faculty of Health Sciences.
    Vegfors, Magnus
    Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN. Linköping University, Faculty of Health Sciences.
    Lindberg, Lars-Göran
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Non-invasive measurement of systolic blood pressure on the arm utilising photoplethysmography: development of the methodology2005In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 43, no 1, p. 131-135Article in journal (Refereed)
    Abstract [en]

    Photoplethysmography (PPG) can be used to measure systolic blood pressure at the brachial artery. With a specially designed probe, positioned in the most distal position beneath a pressure cuff on the upper arm, this is possible. The distance between the light source (880 nm) and the photodetector was 20 mm. A test was performed on neuro-intensive care patients by determining blood pressure from the PPG curves, and, when it was compared with systolic blood pressure obtained from inserted indwelling arterial catheters, a correlation factor of r=0.95 was achieved. The difference between blood pressure obtained using PPG and invasive blood pressure measurement was 3.9±9.1 mmHg (mean±SD), n=19. The depth to the brachial artery was 13.9±4.1 mm (mean±SD), n=18. A digital PPG system utilising pulsating light was also developed.

  • 182.
    Laurent, Claes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Jönsson, Björn
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Vascular surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Vegfors, Magnus
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Non-invasive monitoring of systolic blood preassure on arm utilizing photoplethysmography (PPG)2000In: World Congress of Medical Physics and Biomedical Engineering,2000, Springer-Verlag , 2000, p. 131-135Conference paper (Refereed)
    Abstract [en]

    Photoplethysmography (PPG) can be used to measure systolic blood pressure at the brachial artery. With a specially designed probe, positioned in the most distal position beneath a pressure cuff on the upper arm, this is possible. The distance between the light source (880 nm) and the photodetector was 20 mm. A test was performed on neuro-intensive care patients by determining blood pressure from the PPG curves, and, when it was compared with systolic blood pressure obtained from inserted indwelling arterial catheters, a correlation factor of r=0.95 was achieved. The difference between blood pressure obtained using PPG and invasive blood pressure measurement was 3.9±9.1 mmHg (mean±SD), n=19. The depth to the brachial artery was 13.9±4.1 mm (mean±SD), n=18. A digital PPG system utilising pulsating light was also developed.

  • 183. Lepper, W
    et al.
    Flachskampf, F A
    Köhler, J
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Hanrath, P
    [Overestimation of regurgitation velocities of intact mechanical heart valve prostheses and other small orifices with 10 mm2 Doppler echocardiography].1997In: Zeitschrift für Kardiologie, ISSN 0300-5860, E-ISSN 1435-1285, Vol. 86, no 5, p. 354-362Article in journal (Refereed)
    Abstract [de]

    A systematic evaluation of the accuracy of continuous wave echo Doppler measurements across prosthetic valve leakages and regurgitant lesions has not been performed. Continuous echo Doppler velocity measurements in an in vitro, steady flow model, across the leaks of 12 intact mechanical prostheses and across six circular nozzles (area, 0.5-20 mm2) at pressure drops between 30 and 105 mm Hg were analyzed and compared to the velocities predicted by the modified Bernoulli equation. Laser Doppler anemometry of flow velocities through the nozzles was performed in addition. Despite excellent correlation, there was substantial overestimation of "Bernoulli predicted"-velocities by echo Doppler in the prosthetic leaks (mean +12.3 +/- 9.4%; range, 90.3-143.4%). Also in nozzles < or = 10 mm2, but not in those > 20 mm2, an overestimation of the "Bernoulli predicted"-velocities was observed (mean +6.2 +/- 2%). Laser Doppler anemometry of flow velocities through the nozzles showed slightly lower values than predicted by the Bernoulli equation. This effect apparently is due to transit time effects leading to spectral broadening and should be taken into account when using echo Doppler measurements in very small (< 10 mm2) orifices, such as mild to moderate regurgitant lesions and prosthetic valve leakage.

  • 184.
    Lindberg, Lars-Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Fridolin, Ivo
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Magnusson, M
    Non-invasive optical dialysate monitoring1999In: Congress of the European Renal Association, European Dialysis and Transplant Association,1999, 1999Conference paper (Refereed)
  • 185.
    Lindberg, Lars-Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Lennmarken, Claes
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Intensive Care UHL.
    Vegfors, Magnus
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Pulse oximetry-clinical implications and recent technical developments1995In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 39, p. 279-287Article in journal (Refereed)
  • 186.
    Lindberg, Lars-Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Vegfors, Magnus
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Lennmarken, Claes
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Intensive Care UHL.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Pulse oximeter signal at various blood flow conditions in an In vitro model1995In: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 33, p. 87-91Article in journal (Refereed)
  • 187.
    Ljungvall, Ingrid
    et al.
    Swedish University of Agriculture Science.
    Ahlström, Christer
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Hoglund, Katja
    Swedish University of Agriculture Science.
    Hult, Peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Kvart, Clarence
    Swedish University of Agriculture Science.
    Borgarelli, Michele
    Kansas State University.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Haggstrom , Jens
    Swedish University of Agriculture Science.
    Use of signal analysis of heart sounds and murmurs to assess severity of mitral valve regurgitation attributable to myxomatous mitral valve disease in dogs2009In: AMERICAN JOURNAL OF VETERINARY RESEARCH, ISSN 0002-9645 , Vol. 70, no 5, p. 604-613Article in journal (Refereed)
    Abstract [en]

    Objective-To investigate use of signal analysis of heart sounds and murmurs in assessing severity of mitral valve regurgitation (mitral regurgitation [MR]) in dogs with myxomatous mitral valve disease (MMVD).

    Animals-77 client-owned dogs.

    Procedures-Cardiac sounds were recorded from dogs evaluated by use of auscultatory and echocardiographic classification systems. Signal analysis techniques were developed to extract 7 sound variables (first frequency peak, murmur energy ratio, murmur duration > 200 Hz, sample entropy and first minimum of the auto mutual information function of the murmurs, and energy ratios of the first heart sound [S1] and second heart sound [S2]).

    Results-Significant associations were detected between severity of MR and all sound variables, except the energy ratio of S1. An increase in severity of MR resulted in greater contribution of higher frequencies, increased signal irregularity, and decreased energy ratio of S2. The optimal combination of variables for distinguishing dogs with high-intensity murmurs from other dogs was energy ratio of S2 and murmur duration > 200 Hz (sensitivity, 79%; specificity, 71%) by use of the auscultatory classification. By use of the echocardiographic classification, corresponding variables were auto mutual information, first frequency peak, and energy ratio of S2 (sensitivity, 88%; specificity, 82%).

    Conclusions and Clinical Relevance-Most of the investigated sound variables were significantly associated with severity of MR, which indicated a powerful diagnostic potential for monitoring MMVD. Signal analysis techniques could be valuable for clinicians when performing risk assessment or determining whether special care and more extensive examinations are required.

  • 188.
    Ljungvall, Ingrid
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Ahlström, Christer
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Höglund, Katja
    Hult, Peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Kvart, Clarence
    Borgarelli, Michele
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Häggström, Jens
    Assessing mitral regurgitation attributable to myxomatous mitral valve disease in dogs using signal analysis of heart sounds and murmurs2008Article in journal (Refereed)
  • 189.
    Loyd, Dan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Doppler prediction of transvalvular gradient and stenotic orifice area.1988In: American Journal of Cardiology, ISSN 0002-9149, E-ISSN 1879-1913, Vol. 61, no 11, p. 958-959Article in journal (Refereed)
  • 190.
    Loyd, Dan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    MITRAL PRESSURE HALF-TIME TECHNIQUE FOR ASSESSING SEVERITY OF MITRAL-STENOSIS - ESSENTIAL PARAMETERS1989In: IMAGES OF THE TWENTY-FIRST CENTURY, PTS 1-6, 1989, Vol. 11Conference paper (Refereed)
    Abstract [en]

    The flow through a stenotic mitral valve, which is mainly determined by the cross-sectional area of the valve and the pressure difference across it, is discussed. The gradient half-time is an attempt to describe the area from the decline in transmitral pressure difference alone. The gradient half-time increases with increasing severity of the stenosis. Besides the area of the mitral valve, there are other factors influencing the gradient half-time. Such factors are the transported volume and the initial pressure gradient. The compliance of the cardiac chambers and the pulmonary venous flow also influence the gradient half-time, but through changes in the pressure difference across the valve. The problem can therefore be analyzed either with or without inclusion of compliance in the calculations

  • 191.
    Loyd, Dan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Pressure half-time does not always predict mitral valve area correctly.1988In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 1, no 5, p. 313-321Article in journal (Refereed)
    Abstract [en]

    A theory is presented elucidating factors that influence the pressure half-time. By combining the Bernoulli and continuity equations and making certain assumptions about the shape of the atrioventricular pressure difference decay, it can be shown that valve area, volume transported across that area, and initial pressure difference influence the pressure half-time according to a formula in which the pressure half-time is related to V/(Ao square root of delta po), where V is the transported volume across the orifice with the area Ao, and delta po is the initial pressure difference across that area. In a subsequent hydraulic model experiment pressure half-time was determined for three different hole areas, with various initial volumes and initial pressure gradients. We did not obtain a unique relation between the pressure half-time and area. Instead the results supported our theory, and we found a close linear relationship between area and V/(T0.5 square root of delta po) (correlation coefficient [r] = 0.998), as predicted in the theory (T0.5 = pressure half-time). Clinical examples in which the pressure half-time may be misleading in the assessment of severity of mitral stenosis are presented.

  • 192.
    Loyd, Dan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    BARCLAY, SA
    XIONG, Changsheng
    ANDERSSON, Gunnar
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    ECHOCARDIOGRAPHIC ASSESSMENT OF HEART-VALVE REGURGITANT FLOW USING THE FLOW CONVERGENCE METHOD1991In: PROCEEDINGS OF THE ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOL 13, PTS 1-5, 1991, p. 191-192Conference paper (Refereed)
  • 193.
    Loyd, Dan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    KARLSSON, M
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    ERLANDSON, BE
    HYPERTHERMIA OF THE PROSTATE FROM A HEAT TRANSFER POINT OF VIEW1994In: PROCEEDINGS OF THE 16TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY - ENGINEERING ADVANCES: NEW OPPORTUNITIES FOR BIOMEDICAL ENGINEERS, PTS 1&2, 1994, Vol. 2, p. 768-769Conference paper (Refereed)
    Abstract [en]

    The finite element method is used to analyse the heat transfer at hyperthermia treatment of the prostate. The microwave antenna is enclosed in a water cooled intra urethral catheter. The purpose of this study is modeling and simulation of the temperature field during local microwave hyperthermal treatment of the prostate. Numerical calculations of the temperature field and the heat flux are necessary in order to get better knowledge of possibilities and restrictions of the method. The influence on the treatment from an incorrect location of the antenna has been studied. The location of the antenna is essential for a successful treatment. The effect of possible phase change processes associated with the heating is included in the analysis. A phase transition has a significant influence on the shape and the propagation speed of the temperature field. For the combination of microwave heating of the tissue and heat transfer from it there exists a transition zone of finite size instead of a transition front

  • 194.
    Loyd, Dan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    KARLSSON, Matts
    ANDERSSON, Gunnar
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Hyperthermia treatment of the prostate - A complex heat transfer problem1993In: NUMERICAL METHODS IN THERMAL PROBLEMS, VOL VIII, PTS 1 AND 2, 1993, p. 1239-1250Conference paper (Refereed)
  • 195.
    Loyd, Dan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Erlandsson, B-E
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Computer analysis of hyperthermia treatment of the prostate1997In: Advances in Engineering Software, ISSN 0965-9978, E-ISSN 1873-5339, Vol. 28, p. 347-351Article in journal (Refereed)
  • 196.
    Loyd, Dan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    KARLSSON, Matts
    ERLANDSSON, Björn Erik
    SJODIN, Jan Gunnar
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Heat transfer analysis of hyperthermia treatment of the prostate1995In: COMPUTER SIMULATIONS IN BIOMEDICINE, 1995, p. 617-624Conference paper (Refereed)
  • 197.
    Lönn, Urban
    et al.
    Thoraxklin Universitetssjukhuset, Linköping.
    Wulff, J
    Keck, K-Y
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Peterzén, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Intensive Care UHL.
    Ahn, Henrik Casimir
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Thoracic Surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Flow characteristics of the hemopump: An experimental in Vitro study1997In: Annals of Thoracic Surgery, ISSN 0003-4975, E-ISSN 1552-6259, Vol. 63, no 1, p. 162-166Article in journal (Refereed)
  • 198.
    Naslund, J.
    et al.
    Näslund, J., Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden.
    Pettersson, Jonas
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering.
    Lundeberg, T.
    Rehabilitation Medicine University Clinic Stockholm, Danderyds Hospital, Stockholm, Sweden.
    Linnarsson, D.
    Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Non-invasive continuous estimation of blood flow changes in human patellar bone2006In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 6, p. 501-509Article in journal (Refereed)
    Abstract [en]

    A photoplethysmographic (PPG) technique to assess blood flow in bone tissue has been developed and tested. The signal detected by the PPG consists of a constant-level (DC) component - which is related to the relative vascularization of the tissue - and a pulsatile (AC) component - which is synchronous with the pumping action of the heart. The PPG probe was applied on the skin over the patella. The probe uses near-infrared (804 nm) and green (560 nm) light sources and the AC component of the PPG signals of the two wavelengths was used to monitor pulsatile blood flow in the patellar bone and the overlying skin, respectively. Twenty healthy subjects were studied and arterial occlusion resulted in elimination of PPG signals at both wavelengths, whereas occlusion of skin blood flow by local surface pressure eliminated only the PPG signal at 560 nm. In a parallel study on a physical model with a rigid tube we showed that the AC component of the PPG signal originates from pulsations of blood flow in a rigid structure and not necessarily from volume pulsations. We conclude that pulsatile blood flow in the patellar bone can be assessed with the present PPG technique. © International Federation for Medical and Biological Engineering 2006.

  • 199.
    Naslund, J.
    et al.
    Näslund, J., Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden, Nobels väg 8, Stockholm, SE-17177, Sweden.
    Walden, M.
    Department of Orthopaedics, Hässleholm Hospital, Hässleholm, Sweden.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Decreased pulsatile blood flow in the patella in patellofemoral pain syndrome2007In: American Journal of Sports Medicine, ISSN 0363-5465, E-ISSN 1552-3365, Vol. 35, no 10, p. 1668-1673Article in journal (Refereed)
    Abstract [en]

    Background: Anterior knee pain without clinical and radiologic abnormalities has primarily been explained from a purely structural view. A recently proposed biologic and homeostatic explanation questions the malalignment theory. No objective measurement of the pathophysiology responsible for changes in local homeostasis has been presented. Hypothesis: Flexing the knee joint interferes with the perfusion of the patellar bone in patellofemoral pain syndrome. Study Design: Case control study, Level of evidence, 4. Methods: Pulsatile blood flow in the patella was measured continuously and noninvasively using photoplethysmography. Measurements were made with the patient in a resting position with knee flexion of 20°and after passive knee flexion to 90°. In total, 22 patients with patellofemoral pain syndrome were examined bilaterally, and 33 subjects with healthy knees served as controls. Results: The pulsatile blood flow in the patient group decreased after passive knee flexion from 20°to 90°(systematic change in position, or relative position [RP] = -0.32, 95% confidence interval for RP, -0.48 to -0.17), while the response in the control group showed no distinct pattern (RP = 0.17, 95% confidence interval for RP, -0.05 to 0.31). The difference between the groups was significant (P =.0002). The median change in patients was -26% (interquartile range, 37). Conclusions: Pulsatile patellar blood flow in patellofemoral pain syndrome patients is markedly reduced when the knee is being flexed, which supports the previous notion of an ischemic mechanism involved in the pathogenesis of this pain syndrome. © 2007 American Orthopaedic Society for Sports Medicine.

  • 200.
    Nilsson, Gert
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Salerud, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Tenland, T.
    Wahlberg, J.E.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Laser Doppler Flowmetry A New Technique for Noninvasive Assessment of Skin Blood Flow.1983In: Cosmetics and toiletries, ISSN 0361-4387, Vol. 99, no 3, p. 97-108Article in journal (Refereed)
    Abstract [en]

      

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