| 1. |
- Ask, Per, et al.
(author)
-
A SHORT-TIME-DELAY URINARY FLOWMETER
- 1985
-
In: Neurourology and Urodynamics. - : Wiley. - 0733-2467 .- 1520-6777. ; 4:3, s. 247-256
-
Journal article (peer-reviewed)abstract
- A urinary flowmeter has been designed, using a quickly rotating disc and a balance principle. The flowmeter has a fast and accurate response to changing flows. The time delay of the flowmeter is less than about 0.25 s. The improved accuracy in recording urinary flow using the presented flowmeter should make it possible to extract more information from the detrusor pressure and urinary flow relations, relevant for assessing lower urinary tract function.
|
|
| 2. |
- Ask, Per, et al.
(author)
-
Accuracy and choice of procedures in 24-hour oesophageal pH monitoring with monocrystalline antimony electrodes.
- 1986
-
In: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 24:6, s. 602-608
-
Journal article (peer-reviewed)abstract
- In 24 h pH monitoring, the evaluation is dependent on the absolute accuracy of the pH measurements. Several sources of error exist, such as the chemical composition of calibration buffers and reference electrode gel and the effect of temperature on both the pH and the reference electrodes. We investigated the magnitude of these errors for the monocrystalline antimony electrode. Similar analysis applies to other types of pH electrodes. The errors we found are important when choosing a calibration procedure. We recommend a calibration procedure in which the pH and reference electrodes are both put in a beaker with the calibration buffers prior to and after the 24 h measurements. The calibration buffers and the electrode gel should have a specially selected ion composition where, for example, the Cl-ion concentration is critical. Corrections for differences in temperature between the calibration and the in situ measurements must be added. The pH measurements can be checked by performing in situ calibration.
|
|
| 3. |
- Ask, Per
(author)
-
Measurement techniques for urodynamic investigations.
- 1989
-
In: Critical reviews in biomedical engineering. - 0278-940X .- 1943-619X. ; 17:5, s. 413-449
-
Journal article (peer-reviewed)abstract
- Important measurement techniques for investigating lower urinary tract function are flow and pressure measurements. The demands on urinary flowmeters and the measurement principles of balance type, rotating disc, dipstick, and air-displacement type are described. Urological pressure measurements are performed in the bladder, in the urethra, and in the abdominal cavity. Various fluid-filled and microtransducer systems are reviewed and demands for performance given. Differences in measuring a mechanical pressure, like in the urethra, and a fluid pressure in the bladder are discussed. Electromyography (EMG) technique is used to investigate various neurological disturbances in the lower urinary tract. The electrode technique is also described. Furthermore, techniques for incontinence detection are reviewed.
|
|
| 4. |
|
|
| 5. |
- Ask, Per, et al.
(author)
-
THEORETICAL AND EXPERIMENTAL-ANALYSIS OF AORTIC COARCTATION
- 1989
-
In: IMAGES OF THE TWENTY-FIRST CENTURY, PTS 1-6. ; , s. 103-103
-
Conference paper (peer-reviewed)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
|
|
| 6. |
- Johansson, K. E., et al.
(author)
-
Oesophagitis, signs of reflux, and gastric acid secretion in patients with symptoms of gastro-oesophageal reflux disease
- 1986
-
In: Scandinavian Journal of Gastroenterology. - Oslo : Informa Healthcare. - 0036-5521 .- 1502-7708. ; 21:7, s. 837-847
-
Journal article (peer-reviewed)abstract
- 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%.
|
|
| 7. |
|
|
| 8. |
- Loyd, Dan, et al.
(author)
-
MITRAL PRESSURE HALF-TIME TECHNIQUE FOR ASSESSING SEVERITY OF MITRAL-STENOSIS - ESSENTIAL PARAMETERS
- 1989
-
In: IMAGES OF THE TWENTY-FIRST CENTURY, PTS 1-6.
-
Conference paper (peer-reviewed)abstract
- 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
|
|
| 9. |
- Loyd, Dan, et al.
(author)
-
Pressure half-time does not always predict mitral valve area correctly.
- 1988
-
In: Journal of the American Society of Echocardiography. - 0894-7317 .- 1097-6795. ; 1:5, s. 313-321
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 10. |
|
|
