Biomedical subjects

M Sawan

Publications and source records attributed to M Sawan.

12 recordsLinked to original sources

PubMed1997

Proposed new bladder volume monitoring device based on impedance measurement.

A new implantable bladder volume-monitoring device based on the impedance measurement of the detrusor muscle is described. The system is completely autonomous and forms a mixed-signal (analogue/digital) feedback loop with a neuro-stimulator to rectify bladder dysfunctions (incontinence and retention) through neuromuscular stimulation techniques. A programmable instrumentation amplifier and a signal processing block, to eliminate the artefacts caused by the patient's movements, have been designed and tested. The layout for the signal processing block has been realised in 0.8 micron BiCMOS technology.

Electric Impedance↗

PubMed1997

Implantable volume monitor and miniaturized stimulator dedicated to bladder control.

This paper describes a new miniaturized implantable bladder controller that is composed of 4 main parts: a volume monitoring device based on the tomography approach, a fully programmable miniaturized central processor and stimulator, a bidirectional data and power link, and an external controller. The proposed system is intended to restore both normal bladder functions (retention and voiding) to spinal cord injured patients. The system contains a mixed-signal (analog/digital) feedback loop to command the bladder functions through neuromuscular stimulation techniques. The implantable circuitry is powered by a single encoded radiofrequency carried and may have up to 8 independently controlled monopolar (4 bipolar) channels. The microstimulator is able to generate a wide range of stimulation patterns, including selective stimulation waveforms. In addition, an optical link transmits the state of the implant and volume monitoring results to the external controller.

Computer Simulation↗

PubMed1996

Implantable multiprogrammable microstimulator dedicated to bladder control.

An implantable multiprogrammable microstimulator that is intended to restore normal bladder functions (retention and incontinence) to spinal cord injured patients is presented. The implantable microstimulator circuitry is externally controlled and is powered by a single encoded radio frequency carrier and has four bipolar (eight monopolar) independently controlled channels. It offers a higher degree of reprogrammability and flexibility and can be used in any neuromuscular applications. The implant system is adaptable to the patient's needs and to future developments in stimulation algorithms, without changing the implant. Features of the microstimulator include its capabilities to generate a wide range of waveforms and to combine up to four different programmable frequencies in each wave train. By using a forward error detection and correction communication protocol, the reliability of the implant is increased. The chip has been designed for structural testability by means of a scan-based test approach and uses circuit techniques to reduce power consumption and ensure long-term stability.

Electric Stimulation↗

PubMed1996

Stimulator design and subsequent stimulation parameter optimization for controlling micturition and reducing urethral resistance.

An implantable computerized electrical stimulation system designed to induce bladder evacuation in animal models (dogs) after spinal cord transection has been realized and evaluated. This fully programmable system is based on a handheld device and generates a wide range of stimuli through multichannel implantable miniaturized stimulator. Using the new bladder stimulator and inducing reversible fatigue to the external sphincter via the pudendal nerve enables us to reduce the bladder outlet resistance, resulting in the proper emptying of the bladder during stimulation without the need for sacral nerve rhizotomies and the pudendal nerve neurectomies. Four chronically affected dogs were studied to determine the optimal stimulation parameters for inducing a sphincter fatigue that would reliably empty the bladder for the duration of the experiment. These parameters were: maximum amplitude of 1.5 mA +/- 0.5 SD, stimuli composed of a high frequency signal of 200 Hz +/- 50 SD modulated by a low frequency signal of 10 Hz +/- 5 SD, pulse width controlled by a duty-cycle of 20% +/- 10 SD, sacral nerve stimulation of 50 s +/- 25 SD and fatiguing duration of 20 s +/- 5 SD.

Animals↗

PubMed1995

Long-term effect of sphincteric fatigue during bladder neurostimulation.

Commercially available stimulators lack several features, including multiple channel capability and flexible stimulation parameters. These factors limit clinical application. A new computerized electrical stimulator system was developed by our team and evaluated for its efficacy in bladder evacuation in an animal model after spinal cord transection. The system can generate a wide range of stimulation characteristics and has the feature of being a programmable multichannel pacemaker. It has enabled us to induce a reversible fatigue to the external sphincter that results in proper bladder emptying on stimulation. Using this new bladder pacemaker, 8 dogs were studied. We applied the concept of fatiguing of the external sphincter via the pudendal nerve to avoid rhizotomy. We determined the optimal stimulation parameters that can reliably empty the dog's bladder for the duration of the experiment, which lasted for 8 months. The new computerized electrical stimulation system achieved the objective of reducing bladder outlet resistance without the need for sacral rhizotomy.

Animals↗

PubMed1993

A transcutaneous implantable bladder controller.

We describe a computerized experimental system to investigate the effect of early electrical stimulation of the bladder during the spinal shock phase in paraplegic dogs. This system is composed of two main devices; an external part (or controller) based on a portable microcomputer, and a versatile implant (internal) based on a multichannel CMOS microstimulator. Using a new operative technique, this system enabled us to obtain many favorable results.

Animals↗

PubMed1992

Effect of early bladder stimulation on spinal shock: experimental approach.

The period of spinal shock which frequently follows spinal cord injury is associated with bladder areflexia and urinary retention. We studied the effect of early bladder electric stimulation on detrusor activity during the spinal shock phase in the dog. The animals had a spinal cord section at T10 vertebra, and their bladder management was assigned to one of the three following groups: intermittent catheterization, indwelling catheterization, and electric bladder stimulation. The parameters for evaluating each treatment included: blood chemistry, and radiographic and urodynamic tests. The most important finding was the early return of detrusor activity in the group of animals treated by early electric stimulation of the bladder.

Animals↗

PubMed1992

Electrical stimulation induced sphincter fatigue during voiding.

The stimulation of the sacral nerves to induce voiding is often associated with simultaneous contraction of the striated sphincter rendering micturition difficult or impossible. Rhizotomy of some sacral nerves was found to be necessary to facilitate voiding with stimulation. An main objective in the present experiment was to evaluate the feasibility of achieving the same result using electrical stimulation to fatigue the sphincter. In order to compare the effect of rhizotomy and fatiguing striated sphincter, the bladder outlet resistance was measured. S2 nerves were stimulated with 3 V, 35 Hz and 100 microseconds duration for 5 to 10 sec. Following S2 nerves stimulation the pudendal nerve was stimulated till we obtained sphincteric fatigue. The optimal parameter to induce sphincter fatigue were 3 V, 100-500 Hz and 100 microseconds. for 15-20 sec. The combined pressure-flow studies showed that fatiguing the sphincter via the pudendal nerve using these parameters was as good as cutting it in achieving bladder emptying with stimulation.

Animals↗

PubMed1992

Role of electric stimulation in bladder evacuation following spinal cord transection.

Neural stimulation is potentially a valuable therapeutic tool in the treatment of neurogenic bladder with detrusor areflexia. We studied 20 dogs in different groups, up to eight months, and compared the effect of electric stimulation with intermittent catheterization, specially during spinal shock phase. We found that early stimulation hastened the return of detrusor activity. When stimulation was delayed, the bladder could still regain its activity, and when the pace-maker was turned off, the detrusor activity was gradually decreased. Neurostimulation can completely empty bladder up to eight months. The lowest A.Ch. content in detrusor muscle was found in intermittent catheterization group and in this group the detrusor strips showed marked supersensitivity to urecholine stimulation than the bladders managed by electric stimulation. Also, we found that electric stimulation reduced the complications caused by intermittent catheterization and protected kidney function.

Animals↗

PubMed1992

Computerized transcutaneous control of a multichannel implantable urinary prosthesis.

In the present paper we describe a personal computer interface of a multichannel implantable urinary prosthesis. This system is composed of two main parts: the first one is internal and consists of an implant using a 4-microns CMOS gate array chip controlling a wide variety of waveforms via eight monopolar channels. The second, an external controller featuring a versatile software, a PCB card plugged in a portable microcomputer, and a radiofrequency-coupled technique. This device is used to transmit the power, the data and the synchronization clock to the implant by a simple binary signal modulating a 20 MHz carrier. We also report the features of implant encapsulation and electrode design and fabrication. In the experimental phase, we studied the effect of early electric stimulation of the bladder during the spinal shock phase in the dog. We present the operative techniques that enabled us to perform chronic electrostimulation of the sacral roots and discuss the results.

Animals↗

PubMed1989

The effect of early bladder stimulation on spinal shock: a preliminary report.

The period of spinal shock which frequently follows spinal cord injury is associated with bladder areflexia and urinary retention. We studied the effect of early bladder electric stimulation on detrusor activity during the spinal shock phase in the dog. The animals had a spinal cord section at T10 vertebra and their bladder management was assigned to one of the three following groups: intermittent catheterization, indwelling catheterization and electric bladder stimulation. The parameters for evaluating each treatment included: blood chemistry, radiographic and urodynamic tests. The salient feature was the early return of detrusor activity in the group of animals treated by early electric stimulation of the bladder.

Animals↗

PubMedDate not supplied

A new bladder stimulator--hand-held controller and miniaturized implant: preliminary results in dogs.

A new urinary-tract stimulator that is intended to restore normal bladder function to patients who have spinal-cord injuries is described. The system is composed of two principal parts. The first, which is external, consists of a hand-held device based on an inductive-coupling technique. This controller incorporates all the circuitry necessary to transmit data transdermally. The second, a fully programmable implantable device, includes a complementary metal oxide semiconductor gate-array integrated circuit controlling eight monopolar (or four bipolar) stimulation channels. To protect the tissues and the device, three different biocompatible polymers encapsulate the implant. In the experimental phase, the authors investigated the effect of early electrical stimulation of the bladder during the spinal-shock phase in paraplegic dogs. In addition, using the stimulator, they localized the parameters of stimulation that give the best results in terms of effective bladder pressure and voiding a high volume of urine.

Animals↗