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Biomedical subjects

D J Griffiths

Publications and source records attributed to D J Griffiths.

At least 91 records · Page 5Linked to original sources
PubMed1980

Urodynamic investigation of the wide ureter.

Pressure flow studies constitute a valuable advancement in the investigation of wide ureters without reflux. However, these studies do not in themselves allow the determination of the adequacy of urine transport into the bladder. Radiological examination during perfusion is necessary to assess peristalsis and antiperistalsis, to determine the outflow to the bladder and to judge the geometric changes. Case studies reveal that it is difficult to assess the outflow to the bladder from measurements of renal pelvic pressure and of inflow.

Adult↗
PubMed1979

The assessment of prostatic obstruction from urodynamic measurements and from residual urine.

One hundred and seventeen males over the age of 55 were investigated for possible prostatic obstruction. About half of the cases in this series could have been objectively classified as unobstructed or obstructed from the maximum flow rate alone. In about two-thirds of the cases obstruction could be satisfactorily assessed from the maximum flow rate together with the detrusor pressure at maximum flow. It was not helpful to combine these 2 measurements into a single urethral resistance factor. In the remaining one-third of the cases, obstruction could be objectively assessed only from a plot of detrusor pressure against flow rate throughout micturition. In many of these cases both the pressure and the flow rate were low and the main peculiarity was that the contractile power of the bladder was weak. Residual urine is a sign of an abnormality of bladder function rather than the direct result of urethral obstruction.

Humans↗
PubMed1979

Contractility of the urinary bladder.

Measurements have been made in vitro of the active mechanical properties of complete pig bladders, electrically stimulated to contract. The results are described with the aid of a model of the bladder wall consisting of a contractile element in series with an elastic element. For the contractile element the active force depends on the velocity of shortening. This relation is well described by a classical Hill equation, provided force is normalized by dividing it by the isometric force at the same bladder volume. The force-extension relation of the series elastic element is non-linear and can be described by an elastic modulus which depends monoexponentially on the extension. In the light of these findings the limitations of existing clinical methods of assessing bladder contractility, and the possibility of developing new methods, are discussed.

Animals↗
PubMed1977

Urodynamic assessment of bladder function.

Bladder function in micturition may be studied, without interference from the urethra, through 2 parameters, Piso and Q, which are measures respectively of the maximum pressure and of the maximum flow rate that the bladder can generate, i.e. of its intrinsic strength and speed. These parameters may be determined in a standard urodynamic investigation if the patient interrupts voiding for a short time with the external sphincter. The normal ranges of Piso and Q depend only slightly on age and sex and seem to be as follows: Piso, 50 to 100(+)cm H2O in both sexes; Q, 35 to 120 ml s-1 in males, 20 to 80 ml s-1 in females. There are significant differences in both parameters between different groups of patients. Many females, with stress or urge incontinence or with urgency, have bladders which seem to be weaker than normal (low Piso). The majority of proximally obstructed males, and many who have been surgically relieved of obstruction, have bladders which are significantly slower than normal but are of normal strength (low Q, normal Piso). Therefore the characteristic response of the detrusor to obstruction appears to be not the expected mechanical hypertrophy (Turner Warwick et al., 1973) but reduction in intrinsic speed. In contrast, a few proximally obstructed males and most males with a history of primary enuresis (persisting after 6 years of age) have bladders of normal speed and of strength significantly greater than normal (normal Q, high Piso), suggesting true mechanical hypertrophy of the detrusor. Females with a history of primary enuresis do not show this pattern so clearly. Since these sex- and disease-related differences must surely be of clinical significance, and since it is so easy to measure Piso and Q by the method given in section (e) of the Appendix, those who are concerned with clinical urodynamics are urged to investigate bladder function in this or some equivalent way (e.g. that proposed by Schäfer and Melchior (1975)).

Female↗
PubMed1977

Flow rate versus bladder volume. An alternative way of presenting some features of the micturition of healthy males.

By transforming uroflowmetrograms from curves of flow rate versus time into curves of flow rate versus instantaneous bladder volume, additional information about the variation of the flow rate during voiding is obtained. These curves show that, within a certain volume range, the maximum flow rate is more or less independent of the voided volume. A second volume-independent parameter is the maximum contraction velocity, which can be calculated from the flow rate and the instantaneous bladder volume. This parameter is presumably a measure of the physiological maximum contraction velocity of the detrusor muscle.

Adult↗
PubMed1976

Measurement of the elasticity of the male urethral meatus by urinary drop spectrometry.

The urinary stream breaks up into drops shortly after leaving the external meatus. For normal males the frequency of the drops is related in a characteristic way to the flow rate. From this relation the elastic properties of an elastic constriction near the external meatus are calculated, using a theory of flow through distensible tubes. The elastic constriction behaves as if rigid at low flow rates, but distends elastically at flow rates above a critical value. This theoretical result is verified by observations of the stream emerging from a mechanical model, constructed with similar elastic properties. Functional meatal stenosis is associated with a lack of distensibility at the higher flow rates, which is reflected clinically in a changed relation between drop frequency and flow rate. Measurement of the relation, by the urinary drop spectrometer, offers a quick, non-invasive way of diagnosing this type of urethral obstruction.

Elasticity↗