Biomedical subjects

E D Gommer

Publications and source records attributed to E D Gommer.

4 recordsLinked to original sources

PubMed1999

Validity of a non-invasive determination of the isovolumetric bladder pressure during voiding in men with LUTS.

Invasive pressure flow analysis is the gold standard for discriminating between hypocontractile bladder muscle function and infravesical obstruction in male patients with lower urinary tract symptoms. Here a non-invasive method to determine the isovolumetric bladder pressure to judge contractility is presented. This is based on interruption of urine flow by sudden occlusion of a specially fixed condom catheter. The pressure inside the condom is recorded and used to estimate the isovolumetric bladder pressure. Combined with, for example, home uroflowmetry, this non-invasive method may overcome some of the disadvantages (e.g., invasiveness, cost) of the conventional pressure flow test. To determine the isovolumetric bladder pressure reliably with this non-invasive method, two constraints have to be met. First, the bladder neck and urethra have to remain open after occlusion of the condom catheter. This was tested combining the non-invasive test with radiography in five patients. Second, a steady state has to be reached, i.e., the flow in the urethra, due to the elastic properties of the biological and the condom systems, should come to a stop when the bladder pressure and the condom pressure equilibrate. This was investigated by comparing the non-invasively recorded condom pressure with the simultaneously invasively recorded intravesical pressure in 52 patients. In these patients, three different methods of condom fixation were evaluated. The results show that the bladder neck and urethra remain open during the test. However, a steady state is often not reached. In more than 80% of the cases with the best condom fixation, the bladder pressure has not stabilized, although the condom pressure reached a plateau. Therefore, this method of sudden occlusion is not yet clinically applicable for determining the isovolumetric bladder pressure. Neurourol. Urodynam. 18:477-486, 1999.

Humans↗

PubMed1998

A non-invasive method for bladder electromyography in humans.

No convincing correlation of bladder EMG in humans to simultaneously measured intravesical pressure has been reported in the literature. In most studies on bladder EMG the electrodes contact the bladder wall itself. This causes problems in the discrimination between very small extracellular signals, reflecting actual membrane potential changes of bladder muscle cells, and large electro-mechanical artefact caused by electrode movement as the tissue contracts. Aim of this study is to investigate whether bladder EMG can be performed non-invasively with Ag-AgCl surface electrodes that are placed on the abdominal skin of healthy volunteers. Bipolar electrode signals are obtained in a diagonal, vertical and horizontal direction of the abdominal electrodes. A conventional urodynamic investigation is performed according to International Continence Society standards simultaneously with bladder EMG. This new method shows that voiding is accompanied by a slow voltage change in bipolar electrode signals. The contribution of abdominal and other striated muscle activity to the bipolar electrode signals can clearly be distinguished from the slow voltage changes related to voiding. Free flowmetry shows that the electrical activity picked up by the abdominal electrodes is related to bladder emptying. In pressure/flow studies a relation between the electrical activity and the detrusor pressure is found. The present results suggest that the slow voltage changes found during bladder contraction are caused by summed membrane potential changes of bladder muscle cells, but this concept needs further testing. Also, validation for clinical use remains to be established.

Electromyography↗

PubMed1997

A method for the electromyographic mapping of the detrusor smooth muscle.

Various methods for detrusor EMG in the living mammal have been described in the literature. These methods do insufficiently take into account signal components that are caused by movement between the electrodes and the bladder wall. Reliable detrusor EMG has not been achieved yet. This study investigates the feasibility of a new experimental set-up, in which the electrical activity of the detrusor smooth muscle can be examined. In six rabbits, after cervical dislocation, laparotomy and after excision of the heart, electrical signals of the detrusor muscle are measured with 240 electrodes. The electrodes are positioned on the serosal surface of the filled and isovolumetric bladder. During the recordings, no bladder contractions are deliberately evoked by any stimulus. Consistent results in all six animals show a repetitive spike pattern on multiple electrodes with a repetition frequency of 1.2 Hz. Spikes are triphasic and have a mean duration of 0.47 s (STD = 0.15 s, n = 40) and a mean amplitude of 0.29 mV (STD = 0.07 mV, n = 40). On adjacent electrodes a time shift between the spikes is found, suggesting the propagation of electrical activity across the detrusor surface. The maximum conduction velocity of an arbitrary spike front in the direction of propagation is approximately 30 mm/s. In two animals slow waves are found on the edge of the highpass filter setting. Extensive control experiments are executed to validate the set-up and to interpret the data obtained by the animal experiments. The bladder is still able to contract thirty minutes post mortem. The heart, as a distant signal source, generates a signal that is present on all electrodes and shows no detectable time shift from one electrode to any other. Motion imposed on the electrodes relative to the bladder wall does not reproduce the slow waves and spikes found in the animal experiments. The control experiments support that the results of the animal experiments show electrical activity originating from the detrusor muscle itself. With the experimental set-up described in this paper, nearly artefact free detrusor EMG can be recorded. An electromyographic map of a considerable detrusor smooth muscle area can be obtained.

Animals↗

PubMed1995

Ambulatory urodynamics.

Ambulatory monitoring of lower and upper urinary tract continues to develop. The addition of electronic urine-loss measurements to indicate the exact time-related loss is an important new feature. In the near future, quantitative urine-loss measurements will become available. The additional possibility of plugging in a flowmeter completes the technique with respect to pressure-flow analysis. At present, however, ambulatory urodynamics is still confined to specialized urodynamic centers. Ambulatory urodynamic monitoring has shown that de-novo detrusor instability after a suspension operation is frequently missed as a preoperative diagnosis of detrusor overactivity. The first steps are being taken toward giving a quantitative analysis of detrusor activity during the filling phase. This justifies a more widespread use of this ambulatory monitoring.

Female↗