Biomedical subjects

Julio Benítez Navío

Publications and source records attributed to Julio Benítez Navío.

5 recordsLinked to original sources

PubMed2004

[The bases of urodynamics: analysis of stability of the solutions for the equation defining detrusor behaviour].

OBJECTIVES: In this article we develop the analysis of stability of the solution(s) of the differential equation describing detrusor behaviour as a forced and overcushioned tensor. We followed the theories of Lyapunov about stability. Therefore, we used a matricial method which is more didactical and also analytically more graphic. Solutions are placed in the Trace-Determinant (T-D) plane. This work represents a previous study to the one about detrusor as a dispersing system. And about which we would have to perform an analysis, first from the point of view of the Hamiltonian systems, then from the point of view of chaos. METHODS/RESULTS: We worked on the equation which has been widely described in previous articles in the series of publications titled "the bases of urodynamics". In previous articles, we gave results after applying other methods different from the ones that are usually employed to solve differential equations. We used the matricial method for the analysis of stability of solutions because of its greater didactical clarity. CONCLUSIONS: We conclude that we are in an unstable balance until the moment right before to start voiding. Once voiding is initiated, we are in front of a system with a drain, which at the same time is a fountain. Then we pass from a Hamiltonian dispersing system to a chaotic one. But this is another question...

Humans↗

PubMed2003

[Urodynamic fundamentals, flow curve and urethral echo-Doppler. (Calculation of the urination strength and spectral power].

OBJECTIVES: We present the calculation of two parameters of practical interest for the urologists, which help to understand bladder phenomena. They are the real (total) power developed during micturition, and the spectral power of the flow curve, considered this as a finite time discrete signal. METHODS: We use Doppler ultrasound to calculate the propelling power of the urine towards the exterior. The calculation of the spectral power is included among the auxiliary calculus methods employed for the calculation of the contractile power in those cases in which the flow curve has several humps; we could only calculate the real power in one of them because the Doppler only measured the speed in one curl. RESULTS: We report one case with several curls in the flow curve, in which we could only test speed in one of the curls. The calculation of the spectral power allows us to compare curls and to calculate the total power just by addition. CONCLUSIONS: These two power measures are the expression of the same phenomenon, but they are different, showing one the micturition process from the flow curve and the other one from bladder contraction. We believe it is interesting to know them as a useful work tool. In the same way, the usefulness of Doppler ultrasound to obtain the values of urine speed through the urethra is demonstrated, a necessary data for the calculation of the bladder contractile power.

Algorithms↗

PubMed2003

[Rationale of Doppler urodynamics and urodynamics. What does Doppler contribute to urodynamics?].

OBJECTIVES: To make an analysis of the usefulness of urodynamic tests and what can be obtained from them. METHODS: We also perform and analytical deduction of those parameters that define detrusor behavior, such as the constant defining bladder compliance, the bladder elastic constant, in its tensile properties, and we found the expression of resistances and calculate the abdominal pressure formula; therefore we don't need to introduce a rectal catheter to know the value of those parameters that define bladder dynamics. RESULTS: Although they are provisional, they allow foreseeing a promising future for this application of a well-known device. CONCLUSIONS: Currently, we can only define the bladder behaviour, its resistances, the detrusor drive and compliance with the only discomfort of a perineal Doppler ultrasound. Time will open new possibilities.

Humans↗

PubMed2002

[Urodynamics foundations: contractile potency and urethral doppler].

OBJECTIVES: To calculate the bladder softening factor, elastic constant and contractile potency. METHODS: For the analysis we considered bladder behavior like that of a spring. See articles 1 and 2 published in this issue. Using flowmetry, Doppler ultrasound and abdominal pressure (Transrectal pressure register catheter) an analytical solution that permits calculation of factors defining bladder behavior was looked for. Doppler ultrasound allows us to know urine velocity through the prostatic urethra and, therefore, to calculate bladder contractile potency. RESULTS: Equations are solved reaching an analytical solution that allows calculating those factors that define bladder behavior: Bladder contractile potency, detrusor elastic constant, considering it behaves like a spring, and calculation of muscle resistance to movement. All thanks to Doppler ultrasound that allows to know urine speed. CONCLUSIONS: The bladder voiding phase is defined with the aforementioned factors; storage phase behavior can be indirectly inferred. Only uroflowmetry curves, Doppler ultrasound and abdominal pressure value are used. We comply with the so called non invasive urodynamics although for us it is just another phase in the biomechanical study of the detrusor muscle. Main conclusion is the addition of Doppler ultrasound to the urodynamist armamentarium as an essential instrument for the comprehension of bladder dynamics and calculation of bladder behavior defining factors. It is not a change in the focus but in the methods, gaining knowledge and diminishing invasion.

Mathematics↗

PubMedDate not supplied

[Urodynamic paradigms: from renaissance fibrilar theory to current Doppler-flowmetry].

UNLABELLED: To perform a historical introduction and a review of the mathematical model, emphasizing that our mathematical model may be the solution to the viscoelastic model. It is evident that the same experiment has been repeated over half a century, with similar results in all cases. We also show one of the projects we are working on: the electro-vesicogram for the evaluation of the filling phase, and Doppler uroflowmetry for the study of the voiding phase. METHODS: We have chosen and studied in depth the results Dr. Virseda presents in his thesis of one of the experiments performed in relation to the viscoelastic model. After applying analytical methods we reach a differential equation we suppose defines detrusor behaviour, as it has been explained by the viscoelastic model. The solution of this equation by means of the Laplace's transform enables to obtain the values of the incognitas set by urodynamics. Besides, we analyzed the behaviour of solutions' stability using a matricial method following the Lyapunov theory. The former may solve the incognitas for the voiding phase. We used urethral Doppler with simultaneous uroflowmetry to obtain the data equations demanded; this is what we named "Doppler uroflowmetry". The filling phase was studied by superficial electromiography. We named it "electrovesicogram". We attach images for both Doppler wave and electrovesicogram. They both are the projects we are working on. RESULTS: Currently we can only explain the methodology we are following. Indeed, this article is the first of a series in which we aim to explain the methodology we are following in detail: Doppler wave capture; mounting process photogram by photogram, and vectorization and cleaning of the wave, either Doppler or flow waves; treatment in autocad to obtain the vector; and management of the vector with the matalab software, which gives us the results we are looking for. CONCLUSIONS: It is intuitive to deduct the usefulness of these methods as not invasive techniques in the urodynamic diagnosis. We have our illusions in these projects which open a window to the future.

Biophysics↗