| 1. |
- Andersson, Roger, 1967-, et al.
(författare)
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Cross-sectional changes in an asymmetric tube with bearing on non-invasive pressure measurements
- 2003
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Ingår i: Technology and Health Care. - 0928-7329 .- 1878-7401. ; 11:1, s. 11-20
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Tidskriftsartikel (refereegranskat)abstract
- This study aims at investigating the radial dimensional changes, as a result of an applied intraluminal pressure for an elastic tube with non-uniform cross section. The study is related to a method for non-invasive pressure measurement using the extracorporeal tube as part of the sensor. The intended application is for monitoring of pressure in the blood and dialysate tubes during haemodialysis. The intention is to find a tube cross-section geometry that results in an expansion of the tube so that it is suitable to use as a component in a pressure sensor. The tube should have high radial compliance and expand in a well-defined manner to be able to transfer the intraluminal pressure to a transducer element sensing the radial force. Radial expansion was studied experimentally for tubes with different cross-section geometries. For small tube expansions the resolution in the experimental measurements was not sufficient to study the radial expansion. In this case, numerical simulation was performed. We conclude that a tube with essentially elliptic outer surface and circular inner surface, with a relation of 1:2 between the size of the thin and thick wall, results in a radial expansion upon application of pressure indicating that this tube is suitable for use as part of a sensor.
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| 2. |
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| 3. |
- Andersson, R, et al.
(författare)
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Pressure sensed non-invasively directly on the extra corporeal bloodline tube
- 2001
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Ingår i: PROCEEDINGS OF THE 23RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-4. - 0780372115 ; , s. 3179-3181
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Konferensbidrag (refereegranskat)abstract
- To clinically measure blood pressure at extra corporeal bloodlines involves a hazard due to the infection risk and a risk for thrombosis formation. The aim was to design a non-invasive pressure sensor, measuring directly on a tube section. A modified tube cross-section was used to improve sensitivity. Using the developed sensing principle, a consistent relation (r=0.999) was obtained between pressure and output signal. The output was stable and an acceptable drift within the temperature-range. The method shows great promise for applications in monitoring of the dialysis process.
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| 4. |
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| 5. |
- Ask, Per, et al.
(författare)
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Bio-acoustic signals from stenotic tube flow : state of the art and perspectives for future methodological development.
- 1995
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 33:5, s. 669-675
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Tidskriftsartikel (refereegranskat)abstract
- To study the degree of stenosis from the acoustic signal generated by the turbulent flow in a stenotic vessel, so-called phonoangiography was first suggested over 20 years ago. A reason for the limited use of the technique today may be that, in the early work, the theory of how to relate the spectrum of the acoustic signal to the degree of the stenosis was not clear. However, during the last decade, the theoretical basis for this and other biological tube flow applications has been clarified. Now there is also easy access to computers for frequency analysis. A further explanation for the limited diagnostic use of bio-acoustic techniques for tube flow is the strong competition from ultrasound Doppler techniques. In the future, however, applications may be expected in biological tube flow where the non-invasive, simple and inexpensive bio-acoustic techniques will have a definite role as a diagnostic method.
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| 6. |
- Ask, Per, 1950-, et al.
(författare)
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Bioacoustic signals from stenotic tube flow
- 1995
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Ingår i: Medical & Biological Engineering & Computing. - : Springer. - 0140-0118 .- 1741-0444. ; 33, s. 669-675
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Tidskriftsartikel (refereegranskat)
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| 7. |
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| 8. |
- Ask, Per, et al.
(författare)
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THEORETICAL AND EXPERIMENTAL-ANALYSIS OF AORTIC COARCTATION
- 1989
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Ingår i: IMAGES OF THE TWENTY-FIRST CENTURY, PTS 1-6. ; , s. 103-103
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Konferensbidrag (refereegranskat)abstract
- Aortic coarctation, which could severely influence the haemodynamic conditions of the body, is discussed. A theory has been developed which relates the pressure drop over the coarctation to the flow. This theory indicates that the pressure drop across the actual coarctation is related to the flow squared. For the collateral flow the expected pressure drop is either linearly or quadratically related to the flow. Model experiments and patient data support the present theoretical model
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| 9. |
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| 10. |
- Barclay, Susan A, et al.
(författare)
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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.
- 1993
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Ingår i: Journal of the American Society of Echocardiography. - 0894-7317 .- 1097-6795. ; 6:4, s. 433-445
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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