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  • 51.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Pettersson, N-E
    n/a.
    Andersson, K
    n/a.
    Certification of Clinical Engineers in Sweden2009Ingår i: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, VOL 25, PT 12, ISSN 1680-0737, Vol. 25, nr 12, s. 430-431Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Swedish Society for Biomedical Engineering and Physics have certified clinical engineers since 1994. The certification is done on tow levels: Master of science and Bachelor of science. We have in total had 614 applications and certified 341 engineers We have certified a total of 341 persons of which 75 are at the master level and 266 at the bachelor level. We are pleased to note that through the years so many engineers have applied and have get a certification. The interest for applying was very large in the beginning but decreased after some years.

  • 52.
    Ask, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ressner, Marcus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Jansson, Tomas
    Lunds universitet .
    Jurkonis, Rytis
    Kaunas University of Technology, Lithuania .
    Kvikliene, Adriana
    Kaunas University of Technology, Lithuania .
    Hoff, Lars
    Fac of Sience and Engineering, Vestfold University, Horten, Norge .
    Simulation of ultrasound contrast bubble response and the non-linear ultrasound field - combining with in vitro experiments2003Ingår i: New England Doppler Conference,2003, 2003Konferensbidrag (Refereegranskat)
  • 53.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Skogh, Marcus
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Elektriska och mekaniska egenskaper hos EKG-elektroder1974Konferensbidrag (Övrigt vetenskapligt)
  • 54.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Skogh, Marcus
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Undersökning av EKG-elektroders elektriska och mekaniska långtidsegenskaper1974Rapport (Övrigt vetenskapligt)
  • 55.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Skogh, Marcus
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Undersökning av EKG-elektroners elektriska och mekaniska långtidsegenskaper1974Rapport (Övrigt vetenskapligt)
  • 56.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Skogh, Marcus
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tenland, Torsten
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Undersökning av EKG-elektroders elektriska och mekaniska långtidsegenskaper. Kompletterande studie 11975Rapport (Övrigt vetenskapligt)
  • 57.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Sökjer, H.
    Tibbling, Lita
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Mechanisms affecting lower oesophageal sphincter opening and oesophageal retention: A combined X-ray and manometry study1978Ingår i: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 13, nr 7, s. 857-861Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using simultaneous manometry and cineradiography, oesophageal evacuation was studied while contrast medium was infused via a catheter. The distal half of the oesophagus could be filled with contrast medium without triggering peristalsis. The hydrostatic pressure necessary to open the lower oesophageal sphincter (LES) was of approximately the same magnitude as the pressure gradient between oesophagus and LES. No significant relaxation of the LES could be observed at the initiation of swallowing. The LES may be looked upon not only as a sphincter preventing reflux but also as a gate which must be forced open by food.

  • 58.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    A simple device measuring differences in level in the oesophagus1978Ingår i: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 85, nr 3-4, s. 296-297Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    A device for measuring the difference in level between the pressure transducer and a point of measurment is described. It can be used in oesophageal manometry with waterfilled catheters to measure and compensate for superimposed hydrostatic pressure. The practical application of the method is illustrated.

  • 59.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan.
    Clinical evaluation of different fluid-filled systems for oesophageal manometry1979Ingår i: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 14, nr 1, s. 1-5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a clinical study of oesophageal manometry with fluid-filled catheters, both a non-perfused system and a perfused system with a syringe pump have been compared to a system with a low-compliance perfusion pump, which served as a reference. Significantly lower values of motility amplitudes, motility derivatives, and partly of LES pressures, and a time delay of up to 0.5 sec of the amplitude maximum were obtained with the non-perfused system and the system with a syringe pump in comparison to the low-compliance system. Since the oesophageal function can be erroneously evaluated by use of a non-perfused system or a perfused system with a syringe pump, such systems cannot be recommended for clinical use.

  • 60.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Effect of time interval between swallows on esophageal peristalsis.1980Ingår i: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 238, nr 6, s. G485-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Esophageal peristaltic pressure amplitude, peristaltic incidence, speed of peristalsis, and wave duration were investigated as a function of swallow interval. In the distal half of the esophagus, the amplitude decreased at swallow intervals of 8 s and shorter. At intervals of 8 and 4 s, dropouts of contractions that were obtained were most frequent in the distal esophagus and for the 4-s interval. At continuous swallows no contractions were obtained below the upper esophageal sphincter until the end of the swallow sequence, after which a peristaltic wave of high amplitude propagated along the esophagus. The peristaltic speed increased toward a level 5 cm above the lower esophageal sphincter. The peristaltic wave duration was approximately the same in different parts of the esophagus and at different swallow intervals. The findings indicate an impairment of esophageal transport function by short swallow intervals.

  • 61.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Evaluation of a new method for abdominal compression for use in oesophageal investigation.1982Ingår i: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 17, nr 2, s. 269-272Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of conventional extra-abdominal compression with a constant cuff pressure was shown to give various pressures intra-abdominally in different subjects. A feedback system was therefore used, in which the extra-abdominal pressure is controlled by the intra-abdominal pressure. For an intra-abdominal pressure increase of 15 mm Hg the external cuff pressure in 20 subjects varied from 21 to 98 mm Hg. There was, however, an almost linear relationship between increased intra-abdominal pressure and cuff pressure. The extra-abdominal pressure required to obtain a certain intra-abdominal pressure also varied with the size of the cuff. To obtain relevant and comparable results in studies of hiatal incompetence and gastro-oesophageal reflux, the feedback system is recommended and the size of the intra-abdominal cuff should be stated.

  • 62.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Öberg, P.Å.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Bandbreddskrav hos oesophagusmanometriska system.1978Konferensbidrag (Refereegranskat)
  • 63.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Compliance and bandwidth of oesophagus manometry systems1976Konferensbidrag (Övrigt vetenskapligt)
  • 64.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Metodutveckling för oesophagus-diagnostik1976Konferensbidrag (Övrigt vetenskapligt)
  • 65.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Metodutveckling för oesophagus-diagnostik1977Ingår i: Svensk ÖNH-Tidskrift, ISSN 1400-0121, Vol. 1, nr 1, s. 1-1Artikel i tidskrift (Refereegranskat)
  • 66.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, P. Åke
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Static and dynamic characteristics of fluid-filled esophageal manometry systems1977Ingår i: American Journal of Physiology, ISSN 0002-9513, Vol. 233, nr 5, s. E389-E396Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Esophageal manometric systems with water-filled catheters have been characterized by the use of model experiments. The examined parameters have been: catheter dimension, catheter compliance, catheter resistance, pump type, pump compliance, and perfusion flow. Accurate static pressure measurements have been obtained for perfused systems independently of the investigated parameters. The dynamic characteristics vary with catheter diameter and perfusion flow. For catheters with low diameter, a narrow bandwidth is obtained for the investigated perfusion flows. The results have been expressed in terms of an electric model of the measurement system. Perfusion pumps with low compliance are recommended to improve the dynamic properties of the measurement system.

  • 67.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Blood flow measurements1999Ingår i: The measurement instrumentation sensors handbook / [ed] John G. Webster, CRC Press , 1999Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 68.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Pressure integrating transducer for oesophageal manometry.1979Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 17, nr 3, s. 360-364Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A transducer has been designed that gives an integrated measure of the radial pressure profile at a specific level in the oesophagus. The oesophageal pressure is picked up by a semicylinder elastically connected to a transducer housing by means of a slotted semicylinder. The displacement of the semicylinder is sensed by a semiconductor transducer element. The transducer has a linear relation between static pressure and output voltage, flat frequency characteristic and low temperature drift.

  • 69.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik.
    Tibbling, Lita
    ESOPHAGEAL MANOMETRY - DETERMINATION OF BANDWIDTH REQUIREMENTS BY SIGNAL ANALYSIS1980Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 25, nr 5Artikel i tidskrift (Refereegranskat)
  • 70.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Frequency content of esophageal peristaltic pressure.1979Ingår i: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 236, nr 3, s. E296-300Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fourier analysis of esophageal peristaltic pressure waves was performed by computer fast Fourier transform. The highest power spectral density was obtained in the frequency range below 1 Hz. The Fourier analysis showed spectral components up to about 12 Hz in the upper esophageal sphincter (UES). The significance of different frequency components was investigated by low-pass filtering at different cut-off frequencies. A reduction in the amplitude of UES contractions was obtained at a cut-off frequency of 4 Hz, whereas the cut-off frequency of 8 Hz did not show any distortion. For perfused manometry systems, only a low-compliance perfusion pump will have sufficient bandwidth for accurate recording of esophageal peristaltic pressures.

  • 71.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik.
    Ödman, S.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Tenland, T.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Skogh, M.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    ECG Electrodes: A Study of Electrical and Mechanical Long-term Properties1979Ingår i: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 23, nr 2, s. 189-206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The long-term properties of commercially available ECG-electrodes were studied by investigating the parameters: polarization potential, electrical impedance, adhesion, and skin reactions during a period of 7 days. As expected, the most stable polarization potentials were obtained for Ag/AgCl electrodes. Certain simple disposable electrodes showed large polarization potential variations. The most stable electrode impedance was obtained for disposable electrodes with stable adhesion and equipped with an electrode cup or similar. Unchanged adhesion and mechanical properties during the test period were shown by the disposable electrodes with a large self-adhesive collar.

  • 72. Bader, Dan
    et al.
    Clark, Michael
    Dealey, Carol
    Rithalia, Shyam
    Oomens, Cees
    Goossens, Richard
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Lindgren, Margareta
    Linköpings universitet, Institutionen för medicin och hälsa, Omvårdnad. Linköpings universitet, Hälsouniversitetet.
    Takahashi, Makamoto
    Laboratory measurement of the interface pressures applied by active therapy support surfaces: A consensus document2010Ingår i: Journal of Tissue Viability, ISSN 0965-206X, Vol. 19, nr 1, s. 2-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A key element in pressure ulcer prevention and management is the selection of appropriate pressure redistributing (PR) patient support surfaces for use while seated and in bed. However little explicit guidance exists allowing standardised quantitative comparison of different PR surfaces based upon their ability to redistribute pressure from anatomical landmarks such as the heels and sacrum. In 2008 a working group was established in Europe through the US National Pressure Ulcer Advisory Panel (NPUAP) support surface standardisation initiative (S3I) and under the aegis of the European Pressure Ulcer Advisory Panel with the specific remit of developing test methods for the evaluation of active therapy support surfaces (alternating pressure air mattresses). This report describes a consensus development process to agree test methods appropriate to compare active therapy surfaces based upon their ability to redistribute pressure from the sacrum and the heels.

  • 73. Barclay, Susan A
    et al.
    Eidenvall, Lars
    Karlsson, Matts
    Andersson, Gunnar
    Xiong, Changsheng
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    The shape of the proximal isovelocity surface area varies with regurgitant orifice size and distance from orifice: computer simulation and model experiments with color M-mode technique.1993Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 6, nr 4, s. 433-445Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hemispheric proximal isovelocity surface area method for quantification of mitral regurgitant flow (i.e., Qc = 2 pi r2v), where 2 pi r2 is the surface area and v is the velocity at radius r, was investigated as distance from the orifice was increased. Computer simulations and steady flow model experiments were performed for orifices of 4, 6, and 8 mm. Flow rates derived from the centerline velocity and hemispheric assumption were compared with true flow rates. Proximal isovelocity surface area shape varied as distance from each orifice was increased and could only be approximated from the hemispheric equation when a certain distance was exceeded: > 7, > 10, and > 12 mm for the 4, 6, and 8 mm orifices, respectively. Prediction of relative error showed that the best radial zone at which to make measurements was 5 to 9, 6 to 14 and 7 to 17 mm for the 4, 6, and 8 mm orifices, respectively. Although effects of a nonhemispheric shape could be compensated for by use of a correction factor, a radius of 8 to 9 mm can be recommended without the use of a correction factor over all orifices studied if a deviation in calculated as compared with true flow of 15% is considered acceptable. These measurements therefore have implications for the technique in clinical practice.

  • 74. Bech Hanssen, Odd
    et al.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Caidahl, Kenneth
    The net pressure gradients after pressure recovery can be predicted by Doppler in aortic bileaflet prostheses.2001Ingår i: American Society of Echocardiography,2001, 2001Konferensbidrag (Refereegranskat)
  • 75. Bech-Hansen, Odd
    et al.
    Caidahl, Kenneth
    Wallentin, Ingemar
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Assessment of effective orifice area of prosthetic aortic valves with Doppler echocardiography: An in vivo and in vitro study2001Ingår i: Journal of Thoracic and Cardiovascular Surgery, ISSN 0022-5223, E-ISSN 1097-685X, Vol. 122, nr 2, s. 287-295Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: We sought to evaluate the Doppler assessment of effective orifice area in aortic prosthetic valves. The effective orifice area is a less flow-dependent parameter than Doppler gradients that is used to assess prosthetic valve function. However, in vivo reference values show a pronounced spread of effective orifice area and smaller orifices than expected compared with the geometric area. Methods: Using Doppler echocardiography, we studied patients who received a bileaflet St Jude Medical valve (n = 75, St Jude Medical, Inc, St Paul, Minn) or a tilting disc Omnicarbon valve (n = 46, Medical CV, Incorporated, Inver Grove Heights, Minn). The prosthetic valves were also investigated in vitro in a steady flow model with Doppler and catheter measurements in the different orifices. The effective orifice area was calculated according to the continuity equation. Results: In vivo, there was a wide distribution with the coefficient of variation (SD/mean ╫ 100%) for different valve sizes ranging from 21% to 39% in the St Jude Medical valve and from 25% to 33% in the Omnicarbon valve. The differences between geometric orifice area and effective orifice area in vitro were 1.26 ▒ 0.41 cm2 for St Jude Medical and 1.17 ▒ 0.38 cm2 for Omnicarbon valves. The overall effective orifice areas and peak catheter gradients were similar: 1.35 ▒ 0.37 cm2 and 25.9 ▒ 16.1 mm Hg for St Jude Medical and 1.46 ▒ 0.49 cm2 and 24.6 ▒ 17.7 mm Hg for Omnicarbon. However, in St Jude Medical valves, more pressure was recovered downstream, 11.6 ▒ 6.3 mm Hg versus 3.4 ▒ 1.6 mm Hg in Omnicarbon valves (P = .0001). Conclusions: In the patients, we found a pronounced spread of effective orifice areas, which can be explained by measurement errors or true biologic variations. The in vitro effective orifice area was small compared with the geometric orifice area, and we suspect that nonuniformity in the spatial velocity profile causes underestimation. The St Jude Medical and Omnicarbon valves showed similar peak catheter gradients and effective orifice areas in vitro, but more pressure was recovered in the St Jude Medical valve. The effective orifice area can therefore be misleading in the assessment of prosthetic valve performance when bileaflet and tilting disc valves are compared.

  • 76. Bech-Hanssen, O
    et al.
    Caidahl, K
    Wallentin, I
    Brandberg, J
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Aortic prosthetic valve design and size: Relation to Doppler echocardiographic findings and pressure recovery - An in vitro study2000Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 13, nr 1, s. 39-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The extent to which Doppler echocardiography information can be used in the assessment of prosthesis hemodynamic performance is still controversial. The goals of our study were to assess the importance of valve design and size both on Doppler echocardiography findings and on pressure recovery in a fluid mechanics model. We performed Doppler and catheter measurements in the different orifices of the bileaflet St Jude (central and side orifices), the monoleaflet Omnicarbon (major and minor orifices), and the stented Biocor porcine prosthesis. Net pressure gradients were predicted from Doppler flow velocities, assuming either independence or dependence of valve size. The peak Doppler estimated gradients (mean +/- SD for sizes 21 to 27) were 21 +/- 10.3 rum Hg for St Jude, 18 +/- 9.3 mm Hg for Omnicarbon, and 37 +/- 14.5 mm Hg for Biocor (P <.05 for St Jude and Omnicarbon vs Biocor). The pressure recovery (proportion of peak catheter pressure) was 53% +/- 8.6% for central-St Jude, 29% +/- 8.9% for side-St Jude, 20% +/- 5.6% for major-Omnicarbon, 23% +/- 7.4% for minor-Omnicarbon, and 18% +/- 3.6% for Biocor (P <.05 for central-St Jude and side-St Jude vs Omnicarbon and Biocor). Valve sizes (2) significantly influenced pressure recovery (y in percentage) (central-St Jude: y = 3.7x - 35.9, r = 0.88, P =.0001, major-Omnicarbon: y = 2.1x - 30.3, r = 0.85, P =.0001). By assuming dependence of valve size, Doppler was able to predict net pressure gradients in St Jude with a mean difference between net catheter and Doppler-predicted gradient of - 3.8 +/- 2.5 mm Hg. In conclusion, prosthetic value design and size influence the degree of pressure recovery, making Doppler gradients potentially misleading in both the assessment of hemodynamic performance and the comparison of one design with another. The preliminary results indicate that net gradient can be predicted from Doppler gradients,

  • 77. Bech-Hanssen, O
    et al.
    Caidahl, K
    Wallentin, I
    Brandberg, J
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Aortic prosthetic valve design and size: relation to Doppler echocardiographic findings and pressure recovery- an in vitro study.2000Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 13, nr 1, s. 39-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The extent to which Doppler echocardiography information can be used in the assessment of prosthesis hemodynamic performance is still controversial. The goals of our study were to assess the importance of valve design and size both on Doppler echocardiography findings and on pressure recovery in a fluid mechanics model. We performed Doppler and catheter measurements in the different orifices of the bileaflet St Jude (central and side orifices), the monoleaflet Omnicarbon (major and minor orifices), and the stented Biocor porcine prosthesis. Net pressure gradients were predicted from Doppler flow velocities, assuming either independence or dependence of valve size. The peak Doppler estimated gradients (mean +/- SD for sizes 21 to 27) were 21 +/- 10.3 mm Hg for St Jude, 18 +/- 9.3 mm Hg for Omnicarbon, and 37 +/- 14.5 mm Hg for Biocor (P <.05 for St Jude and Omnicarbon vs Biocor). The pressure recovery (proportion of peak catheter pressure) was 53% +/- 8.6% for central-St Jude, 29% +/- 8. 9% for side-St Jude, 20% +/- 5.6% for major-Omnicarbon, 23% +/- 7.4% for minor-Omnicarbon, and 18% +/- 3.6% for Biocor (P <.05 for central-St Jude and side-St Jude vs Omnicarbon and Biocor). Valve sizes (x) significantly influenced pressure recovery (y in percentage) (central-St Jude: y = 3.7x - 35.9, r = 0.88, P =.0001; major-Omnicarbon: y = 2.1x - 30.3, r = 0.85, P =.0001). By assuming dependence of valve size, Doppler was able to predict net pressure gradients in St Jude with a mean difference between net catheter and Doppler-predicted gradient of -3.8 +/- 2.5 mm Hg. In conclusion, prosthetic valve design and size influence the degree of pressure recovery, making Doppler gradients potentially misleading in both the assessment of hemodynamic performance and the comparison of one design with another. The preliminary results indicate that net gradient can be predicted from Doppler gradients.

  • 78.
    Bech-Hanssen, O.
    et al.
    Department of Clinical Physiology, Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden.
    Gjertsson, P.
    Gjertsson, P..
    Houltz, E.
    Department of Clinical Physiology, Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära.
    Caidahl, K.
    Caidahl, K..
    Net Pressure Gradients in Aortic Prosthetic Valves can be Estimated by Doppler2003Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 16, nr 8, s. 858-866Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: In aortic prosthetic valves, both the Doppler-estimated gradients and orifice areas are misleading in the assessment of hemodynamic performance. The parameter of major interest is the net pressure gradient after pressure recovery (PR). We, therefore, investigated, in vitro, our ability to predict the net pressure gradient and applied the formulas in a representative patient population with 2 different valve designs. Methods: We studied the St Jude Medical (SJM) standard valve (size 19-27) and SJM Biocor (size 21-27) in an in vitro steady-flow model with simultaneous Doppler-estimated pressure and catheter pressure measurements. Using echocardiography, we also studied patients who received the SJM (n = 66) and SJM Biocor (n = 45). Results: In the SJM, we observed PR both within the prosthesis and aorta, whereas in the SJM Biocor, PR was only present in the aorta. We estimated the PR within the valve and within the aorta separately from echocardiographic in vitro data, combining a regression equation (valve) with an equation on the basis of fluid mechanics theory (aorta). The difference between estimated and catheter-obtained net gradients (mean ± SD) was 0.6 ± 1.6 mm Hg in the SJM and - 0.2 ± 1.9 mm Hg in the SJM Biocor. When these equations were applied in vivo, we found that PR had an overall value of 57 ± 7% of the peak Doppler gradient in the SJM and 33 ± 9% in the SJM Biocor. Conclusions: The in vitro results indicate that it is possible to predict the net pressure gradient by Doppler in bileaflet and stented biologic valves. Our data indicate that important PR is also present in stented biologic valves.

  • 79. Bolger, A F
    et al.
    Eidenvall, L
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Understanding continuous-wave Doppler signal intensity as a measure of regurgitant severity.1997Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 10, nr 6, s. 613-622Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Continuous-wave Doppler signal intensity is commonly expected to reflect the severity of mitral regurgitation. Physical principles predict that alignment of the imaging beam, flow velocity, and turbulence can also be important or even dominant determinants of continuous-wave Doppler signal intensity. The reliability of tracking regurgitant severity with continuous-wave Doppler signal intensity was assessed in vitro with varying volume, velocity, turbulence, and beam alignment. The conditions wherein continuous-wave Doppler signal intensity increased with regurgitant volume were specific but poorly predictable combinations of orifice size, flow volume, and perfect beam alignment. Under other conditions flow velocity and turbulence effects dominated, and continuous-wave Doppler signal intensity did not reflect changing regurgitant volume. Continuous-wave Doppler signal intensity-based impressions of regurgitant severity may be unreliable and even misleading under some circumstances.

  • 80. Bolger, Ann
    et al.
    Eidenvall, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Understanding continuous wave Doppler signal intensity as a measure of regurgitant severity1997Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 10, s. 613-622Artikel i tidskrift (Refereegranskat)
  • 81.
    Bolger, Ann F
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Eidenvall, Lars
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    THE MULTIPLE DETERMINANTS OF CONTINUOUS WAVE SIGNAL INTENSITY1992Ingår i: Circulation, ISSN 0009-7322, E-ISSN 1524-4539, Vol. 86, nr 4, SArtikel i tidskrift (Refereegranskat)
  • 82.
    Brandberg, Joakim
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Chew, M.
    Anaesthesia & Intensive Care and Cardiothoracic Surgery, The Institute for Experimental Clinical Research, Skejby Sygehys, Aarhus, Denmark.
    Bjærum, S.
    Department of Physiology and Biomedical Engineering, Trondheim University, Norway.
    Torp, Hans
    Department of Physiology and Biomedical Engineering, Trondheim University, Norway.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Janerot Sjöberg, Birgitta
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    How many planes are necessary for accurate cardiac output measurement using surface integration of velocity vectors (SIVV) in the left ventricular outflow tract? Pediatric applicationManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Flow measurements with surface integration of velocity vectors, (SIVV) is a three dimensional approach where velocities measured by colour Doppler from several two-dimensional imaging planes are gathered and flow is automatically calculated. With SIVV no assumptions regarding the Doppler insonation angle, area changes and flow profile are necessary, thus avoiding such errors. Numerical simulations have shown that an elliptic area less than 1:2 in major minor axis relation needs at least two equidistant (preferably four) planes for accurate measurements. The purpose of this study was to evaluate this finding in a controlled in vitro environment and in high quality in vivo observations. A Plexiglass® pulsatile flow model was used where the outflow tract allows for insertion of an artificial valve. A total of 12 images were acquired with an increment of 15o at three flow rates (0.9- 3.0 1/min). A series of piglets (13.5-17 kg) were stemotomized, and a 5MHz phased array transthoracic probe placed at the apex with the beam directed towards the left ventricular outflow tract, (LVOT) simulating the transoesophageal transgastric or transthoracic apical view. Epicardial images were acquired in 4 planes (45o increments). Ten high quality sequences at different cardiac output levels (0.9 - 2.1 1/min) were selected and compared to ultrasound transit time (TT) cardiac output measurement. The results show that for the in-vitro case, at least two planes were necessary for measurements with an error of <10%. In-vivo, four planes were required for errors of <20%. Our study confirms the theoretical assumption that at least two planes are preferable to obtain accurate flow measurements from colour Doppler data.

  • 83.
    Brandberg, Joakim
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Chew, Michelle
    University of Aarhus Denmark.
    Hasenkam, Michael
    Aarhus University Hospital Aarhus, Denmark.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Cardiac output measurement using ultrasound in a paediatric model: In-vivo validation of the surface integration of velocity vectros (SIVV) technique1999Ingår i: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 19, nr 3, s. 198-198Artikel i tidskrift (Refereegranskat)
  • 84.
    Brandberg, Joakim
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Janerot Sjöberg, Birgitta
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Increased accuracy of echocardiographic measurement of flow using automated spherical integration of multiple plane velocity vectors1999Ingår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 25, nr 2, s. 249-257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The calculation of blood flow in the heart by surface integration of velocity vectors (SIVV) using Doppler ultrasound is independent of the angle. Flow is normally calculated from velocity in a spherical thick shell with its center located at the ultrasound transducer. In a numerical simulation, we have shown that the ratio between minor and major axes of an elliptic flow area substantially influences the accuracy of the estimation of flow in a single scan plane. The accuracy of flow measurements by SIVV can be improved by calculating the mean of the values from more than one scan plane. We have produced an automated computer program that includes an antialiasing procedure. We confirmed an improvement of flow measurements in a pulsatile hydraulic flow model, the 95% confidence interval for single estimations being reduced from 20% to 10% (p < 0.05) using the newly developed software. We think that the SIVV method has important implications for clinical transthoracic echocardiography.

  • 85.
    Brandberg, Joakim
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Wodlin, Peter
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Sun, Y
    The SIVV technique for quantifying cardiovascular flows in vivo1996Ingår i: Congress of the European Society of Cardiology,1996, 1996Konferensbidrag (Refereegranskat)
  • 86.
    Brandberg, Joakim
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Wodlin, Peter
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Sun, Y
    In vivo estimation of cardiovascular flows with surface integration of velocity vectors from color Doppler imaging1996Ingår i: Annual International Conference of the IEEE Engineering in Medicine and Biology Society,1996, IEEE , 1996Konferensbidrag (Refereegranskat)
  • 87.
    Brandberg, Joakim
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Karlsson, Matts
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk modellering och simulering.
    Eidenvall, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Automated calculation of regrgitation from proximal 2D Doppler data1996Ingår i: Congress of the European Society of Cardiology,1996, 1996Konferensbidrag (Refereegranskat)
  • 88.
    Brandberg, Joakim
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Karlsson, Matts
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk modellering och simulering.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Integration of proximal velocities (IPROV) - An improvment of the pisa method for estimation of regurgitant flow.1998Ingår i: European Soc for Noninvasive Cardiovascular Dynamics,1998, 1998, s. 161-161Konferensbidrag (Övrigt vetenskapligt)
  • 89.
    Brandberg, Joakim
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård. Linköpings universitet, Hälsouniversitetet.
    Asp, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Karlsson, Matts
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik. Linköpings universitet, Tekniska högskolan.
    Non-stationary flow through non-planar circular constrictions: application to mitral valve diseaseManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Quantification of valvular malfunctions by means of noninvasive methods is presently far from perfect. Since valvular regurgitation is common, a simple and reliable method for quantitative assessment is desired. In this paper the proximal isovelocity surface area method, (PISA) was studied. Numerical simulations for non-stationary flow and non-planar circular geometries were compared with ultrasound measurements in an invitro model with the same geometry and similar flow characteristics. Three different valvular geometries were used: planar, reversed cone and funnel. In the numerical simulation special emphasis was given to the influence from the angle of the valvular leaflets on the proximal surface area. We found both numerically and experimentally that there is support to use the hemispherical velocity profile assumption for the geometries investigated except for the funnel case. Here the actual geometry at the funnel inlet should be considered instead of the half-sphere approximation.

  • 90.
    Chew, Michelle
    et al.
    Departments of Anaesthesia and Intensive Care, Institute of Experimental Clinical Research, Skejby Sygehus, Aarhus University Hospital, Denmark.
    Brandberg, Joakim
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Bjarum, Steinar
    Department of Biomerical Engineering, Trondheim University, Norway.
    Baek-Jensen, Katrine
    Institute of Experimental Clinical Research, Skejby Sygehus, Aarhus University Hospital, Denmark.
    Sloth, Erik
    Departments of Anaesthesia and Intensive Care, Skejby Sygehus, Aarhus University Hospital, Denmark.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Hasenkam, J. Michael
    Department of Cardiothoracic Surgery, Skejby Sygehus, Aarhus University Hospital, Denmark.
    Janerot Sjöberg, Birgitta
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    Pediatric cardiac output measurement using surface integration of velocity vectors: an in vivo validation study2000Ingår i: Critical Care Medicine, ISSN 0090-3493, E-ISSN 1530-0293, Vol. 28, nr 11, s. 3664-3671Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective: To test the accuracy and reproducibility of systemic cardiac output (CO) measurements using surface integration of velocity vectors (SIVV) in a pediatric animal model with hemodynamic instability and to compare SIVV with traditional pulsed-wave Doppler measurements.

    Design: Prospective, comparative study.

    Setting: Animal research laboratory at a university medical center.

    Subjects: Eight piglets weighing 10-15 kg.

    Interventions: Hemodynamic instability was induced by using inhalation of isoflurane and infusions of colloid and dobutamine.

    Measurements: SIVV CO was measured at the left ventricular outflow tract, the aortic valve, and ascending aorta. Transit time CO was used as the reference standard.

    Results: There was good agreement between SIVV and transit time CO. At high frame rates, the mean difference ± 2 sd between the two methods was 0.01 ± 0.27 L/min for measurements at the left ventricular outflow tract, 0.08 ± 0.26 L/min for the ascending aorta, and 0.06 ± 0.25 L/min for the aortic valve. At low frame rates, measurements were 0.06 ± 0.25, 0.19 ± 0.32, and 0.14 ± 0.30 L/min for the left ventricular outflow tract, ascending aorta, and aortic valve, respectively. There were no differences between the three sites at high frame rates. Agreement between pulsed-wave Doppler and transit time CO was poorer, with a mean difference ± 2 sd of 0.09 ± 0.93 L/min. Repeated SIVV measurements taken at a period of relative hemodynamic stability differed by a mean difference ±2 sd of 0.01 ± 0.22 L/min, with a coefficient of variation = 7.6%. Intraobserver coefficients of variation were 5.7%, 4.9%, and 4.1% at the left ventricular outflow tract, ascending aorta, and aortic valve, respectively. Interobserver variability was also small, with a coefficient of variation = 8.5%.

    Conclusions: SIVV is an accurate and reproducible flow measurement technique. It is a considerable improvement over currently used methods and is applicable to pediatric critical care.

  • 91.
    Chew, Michelle
    et al.
    Departments of Anaesthesia and Intensive Care, Aarhus, Denmark.
    Brandberg, Joakim
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Canard, Peter
    Institute of Experimental Clinical Research, Skejby Sygehus, Aarhus University Hospital, Aarhus, Denmark.
    Sloth, Erik
    Departments of Anaesthesia and Intensive Care, Aarhus, Denmark.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Hasenkam, Michael
    Department of Cardiothoracic and Vascular Surgery, Aarhus, Denmark.
    Doppler flow measurement using surface integration of velocity vectors (Sivv): in vitro validation2000Ingår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 26, nr 2, s. 255-262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blood flow measurement using an improved surface integration of velocity vectors (SIVV) technique was tested in in vitro phantoms. SIVV was compared with true flow (12–116 mL/s) in a steady-state model using two angles of insonation (45° and 60°) and two vessel sizes (internal diameter = 11 and 19 mm). Repeatability of the method was tested at various flow rates for each angle of insonation and vessel. In a univentricular pulsatile model, SIVV flow measured at the mitral inlet was compared to true flow (29–61 mL/s). Correlation was excellent for the 19-mm vessel (r2= 0.99). There was a systematic bias but close limits of agreement (mean ± 2 SD = −24.1% ± 7.6% at 45 °; +16.4% ± 11.0% at 60 °). Using the 11-mm vessel, a quadratic relationship was demonstrated between between SIVV and true flow (r2 = 0.98–0.99), regardless of the angle of insonation. In the pulsatile system, good agreement and correlation were shown (r2 = 0.94, mean ± 2 SD = −4.7 ± 10.1%). The coefficients of variation for repeated SIVV measurements ranged from 0.9% to 10.3%. This method demonstrates precision and repeatability, and is potentially useful for clinical measurements.

  • 92.
    Chew, Michelle
    et al.
    Malmö University.
    Brandberg, Joakim
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Sloth, Erik
    Aarhus University Hospital.
    Hasenkam, J. Michael
    Aarhus University Hospital.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Colour Doppler flow measurements using surface integration of velocity vectors (SIVV): Effect of colour flow gain, pulse repetition frequency and number of imaging planes2008Ingår i: Open medical imaging journal, ISSN 1874-3471, Vol. 2, s. 56-61Artikel i tidskrift (Refereegranskat)
  • 93.
    Chew, Michelle
    et al.
    Faculty of Health Science University of Aarhus, Denmark.
    Brandberg, Joakim
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Sloth, Erik
    Aarhus University Hospital Aarhus Denmark.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Hasenkam, Michael
    Aarhus University Hospital Aarhus Denmark.
    Noninvasive cardiac output measurement using Doppler echocardiography; current status and future perspective using Surface Integration of Velocity Vectors (SIVV)1999Ingår i: Danish Society of Anesthesiologists,1999, 1999Konferensbidrag (Övrigt vetenskapligt)
  • 94.
    Chew, Michelle
    et al.
    University of Aarhus Denamrk.
    Brandberg, Joakim
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Sloth, Erik
    Aarhus University Hospital Aarhus Denmark.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Non-invasive cardiac output measurement using colour Doppler ultrasound - the SIVV approach1999Ingår i: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 114, s. 91-92Artikel i tidskrift (Refereegranskat)
  • 95. Chew, Michelle S
    et al.
    Brandberg, Joakim
    Canard, P
    Sloth, E
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hasenkam, J Michael
    Doppler flow measurement using surface integration of velocity vectors (SIVV): in vitro validation.2000Ingår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 26, nr 2, s. 255-262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blood flow measurement using an improved surface integration of velocity vectors (SIVV) technique was tested in in vitro phantoms. SIVV was compared with true flow (12-116 mL/s) in a steady-state model using two angles of insonation (45 degrees and 60 degrees ) and two vessel sizes (internal diameter = 11 and 19 mm). Repeatability of the method was tested at various flow rates for each angle of insonation and vessel. In a univentricular pulsatile model, SIVV flow measured at the mitral inlet was compared to true flow (29-61 mL/s). Correlation was excellent for the 19-mm vessel (r(2)= 0.99). There was a systematic bias but close limits of agreement (mean +/- 2 SD = -24.1% +/- 7.6% at 45 degrees; +16.4% +/- 11.0% at 60 degrees ). Using the 11-mm vessel, a quadratic relationship was demonstrated between between SIVV and true flow (r(2) = 0.98-0.99), regardless of the angle of insonation. In the pulsatile system, good agreement and correlation were shown (r(2) = 0.94, mean +/- 2 SD = -4.7 +/- 10.1%). The coefficients of variation for repeated SIVV measurements ranged from 0.9% to 10.3%. This method demonstrates precision and repeatability, and is potentially useful for clinical measurements.

  • 96. Chew, MS
    et al.
    Brandberg, Joakim
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Cannard, p
    Sloth, E
    Hasenkam, JM
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Evaluation of the surface integration of velocity vectors (SIVV) method in tubular flow model1998Ingår i: European Soc for Noninvasive cardiovascular dynamics,1998, 1998, s. 161-161Konferensbidrag (Övrigt vetenskapligt)
  • 97.
    Danbolt, Christina
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neurovetenskap. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Klinisk patologi och klinisk genetik.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Filosofiska fakulteten.
    Grahn, Lita Tibbling
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Validation and characterization of the computerized laryngeal analyzer (CLA) technique.1999Ingår i: Dysphagia (New York. Print), ISSN 0179-051X, E-ISSN 1432-0460, Vol. 14, nr 4, s. 191-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study was to investigate the response characteristics of the Computerized Laryngeal Analyzer (CLA) and the validity of the noninvasive CLA method to detect swallowing-induced laryngeal elevation correctly. Two healthy adults and two experimental models were used in the study. The CLA technique identified all swallowing events but was unable to discriminate between swallowing and other movements of the tongue or the neck. The computer program produced a derivated response to a square wave signal. Stepwise bending increments of the sensor displayed a linear amplitude response. The degree of laryngeal elevation could not be estimated with the CLA technique, and it was not possible to draw any reliable conclusions from the recordings as to whether the larynx was moving upward or downward.

  • 98.
    Danbolt, Christina
    et al.
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Tibbling Grahn, Lita
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Validation and characterization of the computerized laryngeal analyzer (CLA) technique1999Ingår i: Dysphagia (New York. Print), ISSN 0179-051X, E-ISSN 1432-0460, Vol. 14, nr 4, s. 191-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study was to investigate the response characteristics of the Computerized Laryngeal Analyzer (CLA) and the validity of the noninvasive CLA method to detect swallowing-induced laryngeal elevation correctly. Two healthy adults and two experimental models were used in the study. The CLA technique identified all swallowing events but was unable to discriminate between swallowing and other movements of the tongue or the neck. The computer program produced a derivated response to a square wave signal. Stepwise bending increments of the sensor displayed a linear amplitude response. The degree of laryngeal elevation could not be estimated with the CLA technique, and it was not possible to draw any reliable conclusions from the recordings as to whether the larynx was moving upward or downward.

  • 99. EIDENVALL, L
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    DETERMINATION OF REGURGITANT FLOW IN A PULSATILE MODEL BY INTEGRATING VELOCITIES FROM THE ENTIRE 3D PROXIMAL VELOCITY-FIELD1993Ingår i: Circulation, ISSN 0009-7322, E-ISSN 1524-4539, Vol. 88, nr 4, 2Artikel i tidskrift (Refereegranskat)
  • 100.
    Eidenvall, Lars
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Determination of regurgitant flow and volume by integrating actual proximal velocities over hemispheres (IPROV) in two orthogonal planes1996Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 9, nr 4, s. 527-538Artikel i tidskrift (Refereegranskat)
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