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Background/Purpose Few studies have investigated the feasibility of using pudendal neuromodulation to regulate bladder function in spinal cord-injured (SCI) animals. The present study aimed to determine the effects of electrical activation of the pudendal sensory branch on improving voiding functions in rats 6 weeks after a spinal cord injury and to explore the underlying neuromodulatory mechanisms. Methods Two urodynamic measurements were used to assess the effects of electrical stimulation (ES) on bladder and urethral functions: simultaneous recordings of the intravesical pressure (IVP) during continuous isotonic transvesical infusion (i.e., isotonic IVP) and external urethral sphincter (EUS) electromyography (EUS-EMG), and simultaneous recordings of transvesical pressure under isovolumetric conditions (i.e., isovolumetric IVP) and urethral perfusion pressure (UPP). Results Six weeks after the SCI, the rats showed voiding dysfunction, as indicated by abnormal cystometric measurements (e.g., increased volume threshold, increased contraction amplitude, and increased residual volume, and decreased voided volume). The voiding efficiency (VE) decreased to 13% after the SCI, but increased to 22–34% after applying pudendal afferent stimulation. In addition, pudendal stimulation significantly increased the EUS burst period and increased the difference between the UPP and the high-frequency oscillation (HFO) baselines, and changed the time offset between bladder and EUS activities. These findings suggest that pudendal afferent stimulation improved the VE by prolonging the micturition interval, decreased the urethral resistance, and recovered detrusor-sphincter dyssynergia during the voiding phase. Conclusion This study demonstrates the feasibility of using pudendal neuromodulation in chronic SCI rats. These results could aid in developing an advanced neural prosthesis to restore bladder function in clinical settings.

Objective: Tele-assessment techniques can provide healthcare professionals with easily accessible information regarding patients' clinical progress. Recently, kinematic analysis systems have been used to assess rehabilitative outcomes in stroke patients. Kinematic systems, however, are not compatible with tele-assessment. The objective of our study was to develop a tele-assessment system for acquiring kinematic data of forward reaching movements in stroke patients, with an emphasis on cost-effectiveness, portability, and ease of use. Materials and Methods: We selected four healthy control participants and eight hemiplegic stroke patients for our study. The stroke patients were classified as Brunnstrom stage III, stage IV, or stage V. Our tele-assessment system used two three-axes accelerometers, a potentiometer, a multifunctional data acquisition card, and two computers. A standardized kinematic system was applied simultaneously to validate the measurements recorded by our tele-assessment system during five repetitions of forward reaching movements. Results: The correlation coefficients of the reaching displacement, velocity, and acceleration measurements obtained using our tele-assessment system and the standardized kinematic system were 0.956, 0.896, and 0.727, respectively. Differences in the maximum reaching distance and the maximum reaching velocity of forward reaching movements were observed among the study groups. There were no significant differences in the time required to complete the testing session among the study groups. Conclusions: Our tele-assessment system is valid for the evaluation of upper-extremity reaching ability in stroke patients. Further research is needed to investigate the feasibility of the use of the tele-assessment system in patients' homes.

Voltage-controlled neuromuscular electrical stimulation has been considered to be safer in noninvasive applications notwithstanding the fact that voltage-controlled devices purportedly generate forces less predictable than their current-controlled equivalents. This prompted us to evaluate relevant electrical parameters to determine whether forces induced by voltage-controlled stimuli were able to match to those induced by current-controlled ones, which tend to evoke forces that were more predictable. Force magnitudes corresponding to current- and voltage-controlled stimuli were aligned with respect to electric charge (equivalent to average current intensity) and electrical energy (equivalent to average power) of the same stimulation pulse to determine which provided a better coherence. Consistency of forces evaluated with energy was significantly (p

In this research, we employ the technology of computer vision to recognize traffic light. We manipulate the color information of traffic light under HSI color space. And then, adding motor tracking technology, we can trap the traffic light which is subjected to a region of interest (ROI) to the center area of monitor. Meanwhile, we assign different frequency (peach) according to red light or green light to inform the people what state the light is. We develop the algorithm at PC with MATLAB. Then, we port the whole system to DSP platform TI TMS320 DM642 EVM. The result is that in the condition of non-complex environment, the system can distinguish the red light from green light, and also can output audio signal by means of speaker.

With the aging of the population and the increasing patient preference for receiving care in their own homes, remote home care is one of the fastest growing areas of health care in Taiwan and many other countries. Many remote home-monitoring applications have been developed and implemented to enable both formal and informal caregivers to have remote access to patient data so that they can respond instantly to any abnormalities of in-home patients. The aim of this technology is to give both patients and relatives better control of the health care, reduce the burden on informal caregivers and reduce visits to hospitals and thus result in a better quality of life for both the patient and his/her family. To facilitate their widespread adoption, remote home-monitoring systems take advantage of the low-cost features and popularity of the Internet and PCs, but are inherently exposed to several security risks, such as virus and denial-of-service (DoS) attacks. These security threats exist as long as the in-home PC is directly accessible by remote-monitoring users over the Internet. The purpose of the study reported in this paper was to improve the security of such systems, with the proposed architecture aimed at increasing the system availability and confidentiality of patient information. A broker server is introduced between the remote-monitoring devices and the in-home PCs. This topology removes direct access to the in-home PC, and a firewall can be configured to deny all inbound connections while the remote home-monitoring application is operating. This architecture helps to transfer the security risks from the in-home PC to the managed broker server, on which more advanced security measures can be implemented. The pros and cons of this novel architecture design are also discussed and summarized.

Block of the external urethral sphincter contractions by using high frequency electrical stimulation of the pudendal nerves is a potential method for inhibiting detrusor sphincter dyssynergia. Most researchers use high frequency electrical stimulation at frequencies between 2kHz to 20kHz, but the parameters and mechanism of this block are not well understood. This paper demonstrated the use of radio frequency electrical stimulation (500kHz) as a method to block the external urethral sphincter contractions and improved voiding efficiency by electrical stimulation of unilateral pudendal nerve efferent axons. The most efficient waveform for conduction was 500kHz (with 0.2 to 1mA) constant-current biphasic sinusoidal, voiding efficiency increased from 53 to 71-92%. These results raise the possibility that using radio frequency electrical stimulation to block external urethral sphincter contraction may provide a new approach for improving voiding in spinal cord injured patients.

Control strategies are the chief attraction in the field of rehabilitation engineering, and especially in a functional electrical stimulation (FES) system, a reliable control method is important for paralyzed patients to restore lost their functions. In this paper, we have presented a demonstration of the control strategy, which is based on the patient-driven loop, used in a non-invasive FES system for hand function restoration. With the patient-driven loop control, hemiplegic patients could use their residual capabilities, such as shoulder movements in their sound extremities, the myoelectric signals generated from different muscles, etc, to operate the FES system. Here we have chosen the most common and acceptable signals as the input sources, i.e. electromyographic (EMG) signals, to control a non-invasive FES system, generating the electrical stimuli to excite the paralyzed muscles. In addition, EMG signals recorded by the sensors in the electrical stimulator can serve both as the trigger of the system and as the adjustment of the electrical stimulation parameters, thereby improving the system's performance and reliability. From the experimental results, subjects can successfully use their residual capabilities to control the FES system and restore their lost hand functions as well. On the other hand, from the viewpoints of rehabilitation and psychology, hemiplegics will benefit greatly by using their residual capabilities to regain their lost functions. It is believed that the patient-driven loop control is very useful, not only for the FES system in this study, but also for other assistive devices. By the control strategy proposed in this paper, we deeply hope that patients will benefit greatly and regain their self-confidence.

This article introduces the modification of a self-developed prototype electrical stimulator. In addition, we describe our new design of a versatile and user-friendly toolbox based on the LabVIEW environment that will enable clinical users and physicians to easily go on to further applications and research. The prototype electrical stimulator is based on the digital signal processor, and the drive stage of the previous model has also been improved by using a modified constant-current circuit. Moreover, we use LabVIEW to implement the man-machine interface and to develop a user-friendly toolbox. This system is versatile and feasible from the viewpoint of the hardware and software designs. With the virtual instrument in the toolbox, the man-machine interface is easy for users to implement and helpful in their further research. Furthermore, this toolbox includes many units and parameters, such as waveform types, currents, stimulation time, and others. The system can be considered a versatile and full-featured stimulator for various applications, with its high flexibility in stimulation patterns and multi-channel designs. The proposed system can produce suitable electrical stimulation by tuning the parameters in the interface. The procedure described above can also be implemented in man-machine interfaces for different research purposes.

We had proposed a novel and fast Electrocardiogram (ECG) signal compression algorithm for non-uniform sampling in time domain [1]. It meets the real-time requirement for clinical application. Moreover, the compression performance is stable and uniform even for abnormal ECG signals. A criterion called sum square difference (SSD) is defined as an error test equation. The algorithm using SSD to calculate error tolerance is applied to the records in MIT-BIH database (with 11-bit resolution and 360 Hz sampling rate). It belongs to the threshold-limited algorithm but [1] does not mention much about this kind of algorithm. In this paper we provide more comparisons among SSD, Fan, scan-along polygonal approximation (SAPA), maximum enclosed area (MEA), and optimization algorithm (OPT) using the two measures called sample compression ratio (SCR) and percent root mean squared difference (PRD) with proper mean offset that [1] does not adopt. The results show SSD outperforms the mentioned algorithms with the same computational complexity O(n). Moreover, the comparison with the best but time-consuming coder OPT (O (n3)) shows how much the algorithm can be improved.

Owing to the improvement of computing power, computer-aided multi-unit acquisition and separation rapidly proliferated during the last two decades. To utilize this technology is, however, not easy since task-specific designs are usually mandatory. To overcome this obstacle, a commercial data acquisition system was used to evaluate whether it is possible to accomplish the task of multi-unit acquisition without the aid of these devices. As the results shown that the technique of spike-trigger acquisition can provide the capability to reduce the data amount to 2% while compared with that sampled by continuous acquisition. However, the interval between two consecutive spikes cannot be shorter than 5 ms. This suggests that special designed devices are still necessary.

This study aims to establish an electronic wheelchair system in Taiwan that conforms to multiple master-multiple slave (M3S) standards. The proposed system could enhance the safety and convenience of people with disabilities.The M3S-based head-controlled electric wheelchair consists of three parts: (A) the input device, (B) the output device, and (C) the safety device. Head movement can be used as the input control to cause the tilting device to produce a corresponding level of analog voltage (backwardforward/leftright) which is then transmitted to the analogy/digital conversion module to control the output device (wheelchair's motor). Ten subjects with C5 incompleted spinal cord injury were recruited in the clinical assessment. They were randomly assigned into groups A and B. In the group A, the subjects were assigned to operate the head-controlled wheelchair system with M3S standard before operating the head-controlled wheelchair system without M3S standard. In the group B, the subjects were assigned to operate the head-controlled wheelchair system without M3S standard before operating the head-controlled wheelchair system with M3S standard. Two subjects in the group B drop off due to their personal reasons.The time cost for group A in completing tasks 1, 2, and 3 with the M3S and without the M3S were insignificant (p0.05). The time cost for completing in group B was insignificant (p0.05). Thus, the wheelchair operating time is depended on the proficiency of the subjects, not the M3S standard added.The time cost for subjects to operate the wheelchair was determined by their proficiency, not the M3S standard control added to the system. However, the M3S-based system did realize the safety mechanism and complex auxiliary tools with and without the plug-in and play function.

Multichannel recording provides integral information about electrical brain activities at one instant in time. In this study, multielectrode probes were fabricated to record the thalamic field potentials (FPs) responding to the electrical stimulation of nerve at the rat tail. At first, the number of sweeps used to form the evoked FP average and the spatial sampling density were determined by using cross-correlation functions, which were then statistically analyzed. The difference was significant at P< 0.05, if the number of sweeps for averaging was more than 50 and the spatial interval between two consecutive recording sites was less than 50 m in the anteroposterior, mediolateral and ventrodorsal directions. The responsive area was distributed vertically in the thalamus (ventral posterior lateral (VPL) nucleus); therefore, the recording sites were arranged in one linear array. Sixteen recording sites, which were 50 m apart from each other, were distributed in the ventrodorsal direction. A 16-channel silicon probe was fabricated by using a standard photolithography process and laser micromachining techniques. The probe provides capabilities to record multiple thalamic evoked FPs and multiunit activities simultaneously. © 2004 Elsevier B.V. All rights reserved.

This study describes an eyeglass-type infrared-based communication board for the nonspeaking with quadriplegia.This system is composed of four major components: a headset, an infrared transmitting module, an infrared receiving/signal-processing module, and a main controller, the Intel-8951 microprocessor. This design concept was based on the use of an infrared remote module fastened to the eyeglasses which could allow the convenient control of the input motion on the keys of a communication board, which are all modified with infrared receiving/signal-processing modules. For system evaluation, 12 subjects (all men, 21-45 years old, six normal subjects as the control group and six nonspeaking with quadriplegia as the experimental group) were recruited.The average accuracy of the control group and the experimental group were 93.1 +/- 4.3% and 89.7 +/- 5.5%, respectively. The average time cost of the control group and the experimental group were 78.3 +/- 8.7 s and 89.9 +/- 10.2 s, respectively. An independent t-test revealed that the differences in the average accuracy and the average time cost of the control group and the experimental group were not significant (p0.05).The increase of opportunity to communicate using the infrared-based communication board would help people with multiple disabilities to socialize actively.

This paper proposes a segmented average method that combines the derived non-linear response (DNLR) and linear-averaging methods to increase the reproducibility of transiently evoked otoacoustic emissions (TEOAEs). In this method, the DNLR method is used at the 2.5-P-ms segment of each TEOAE signal, and the linear-averaging method is used from P to 20 ms. This exploits the reduced-artefact advantage of the DNLR method and the high-reproducibility advantage of the linear-averaging method. To evaluate the performance of the proposed method, 26 normal ears were tested, with P selected as 8 ms. Each TEOAE signal obtained was decomposed into three scales using the discrete wavelet transform. Then the similarities and differences between the signals obtained with this method and with the DNLR method were assessed. The results show that the average reproducibility of the TEOAE signals increases from 78.1% to 88.7% when applying the proposed method.SumarioEste articulo propone un metodo segmentado promedio que co...

Purpose : This study proposes image processing and microprocessor technology for use in developing a head movement image (HMI)-controlled computer mouse system for the spinal cord injured (SCI). Method : The system controls the movement and direction of the mouse cursor by capturing head movement images using a marker installed on the user's headset. In the clinical trial, this new mouse system was compared with an infrared-controlled mouse system on various tasks with nine subjects with SCI. Results : The results were favourable to the new mouse system. The differences between the new mouse system and the infrared-controlled mouse were reaching statistical significance in each of the test situations ( p

The proposed system for long-term uterine contraction monitoring includes a pressure sensor and a portable monitor. The pressure sensor converts uterine activities into frequency variations from 1 to 2 MHz. The portable monitor is a microcontroller-based embedded system. We chose the 89c52 microcontroller because of its intelligence and functionality. A CMOS counter serves as a frequency down-converter for scaling down the frequency variation from 50 to 100 kHz.

This paper proposes the development of a surface electromyographic (SEMG)-controlled telephone interface for the disabled. The system is composed of three major components: (1) a SEMG receiving/signal-processing module; (2) a row-column scanning interface for the telephone dialling pad; and (3) a main controller, the Intel-8951 microprocessor. The design concept was based on the idea of using a SEMG generated by the disabled and converting it into a trigger pulse. This could allow convenient control of the dialing motion in the row-column scanning keys of a telephone dialling pad. People with disabilities are competent for certain kinds of work such as being a telephone operator. The increase of opportunities to perform a job for the disabled would help them live independently.

An Electrogastrography (EGG) recorder is proposed in this paper. This recorder consists of a microcontroller, an interfacing circuit for the RS-232, amplifiers and filters for signal conditioning, and a control program for EGG acquisition. An EGG signal, filtered between 0.015 and 0.5 Hz, was used to evaluate the performance of this system. The results suggest that this system is useful both in the hardware circuits and in the analyzing software. The complete system is versatile and cheap. Thus, it will be helpful for other laboratories with limited financial budget. Furthermore, circuits are described in detail for this purpose.

Using a homemade electrogastrography (EGG) system, we studied the characteristics of the myoelectrical rhythm in Chinese patients with nonulcer dyspepsia (NUD). Based on short-term Fourier transformation, recorded slow waves could be automatically analyzed to obtain the following parameters: dominant frequency/power, percent of normal frequency (2–4 cpm), power ratio, etc. EGG parameters, Helicobacter pylori status, histological examination of gastric mucosa, and dyspeptic symptoms were recorded in 27 NUD patients. Compared to 32 healthy controls, the Chinese NUD patients had abnormal postprandial EGG parameters including a lower percentage of regular 2–4 cpm slow waves (70.10 ± 2.97% vs 79.08 ± 2.95%, P < 0.05), a lower level of increment of dominant power (0.62, ± 0.91 vs 3.76 ± 0.58 dB, P < 0.05), lower power ratio (1.42 ± 0.28 vs 2.79 ± 0.39, P < 0.05) and a higher instability coefficient (0.36 ± 0.03 vs 0.26 ± 0.03, P < 0.05). However, Helicobacter pylori infection and its associated gastritis did not influence any EGG parameters in NUD patients. Six main dyspeptic symptoms and total symptom score had no correlation with any EGG parameters. In conclusion, Chinese NUD patients may have abnormal postprandial stomach myoelectrical activity, but these EGG abnormalities are not a direct result of Helicobacter pylori infection and its related gastritis and do not contribution to the dyspeptic symptoms.

Using a homemade electrogastrography (EGG) system, we studied the characteristics of myoelectrical rhythm in gastric cancer (GC) patients. Based on a short-term Fourier transform, recorded slow waves could be automatically analyzed to obtain the following parameters: dominant frequency/power, percent of normal rhythm (2.4-3.7 cpm), power ratio, etc. Fifty histologically confirmed GC patients (34 men, 16 women) were enrolled before surgical intervention to measure their fasting and postprandial EGG parameters for 30 min. The cancerous parameters of GC patients were then obtained postoperatively. In addition, 46 healthy subjects were enrolled for comparison. When compared to controls, GC patients had the following characteristics: absence of postprandial increase in dominant frequency (GC: 3.04 +/- 0.47 vs 3.07 +/- 0.44 cpm, NS; controls: 3.02 +/- 0.31 vs 3.21 +/- 0.25 cpm, P < 0.001), marked power response after meal (P < 0.05), and obvious power ratio (4.58 +/- 7.38 vs 2.27 +/- 2.05, P < 0.05). Multivariate analysis indicated that advanced GC was the factor responsible for the obvious dominant power enhancement after meal (P < 0.05). Other demographic, clinical, and cancerous factors did not influence EGG parameters. We conclude that apparent arrhythmia is not encountered in GC patients, although they mainly exhibit obvious postprandial power response. Advanced GC is likely responsible for this power enhancement on EGG recording.

This study investigates the optimal external parameters for using an ultrasound applicator for treating bone tumors. This system utilized spherically arranged applicators such as scanned focused ultrasound, and spherically focused multielement applicators. The power deposition pattern is modeled as geometric gain with exponential attenuation. The specific absorption rate ratio (SARR) criteria have been used to determine the proper heating domain of ultrasound driving frequency and therapeutic tumor diameter. The results demonstrate that the optimal driving frequency depends on tumor depth, ultrasound absorption of bone marrow, and diameter of bone, but it is independent of the acoustic window area and SARR. The treatable diameter of bone tumor increased when the absorption ratio of bone marrow to tumor, acoustic window of surface skin, and diameter of bone were elevated. However, the treatable diameter of bone tumor decreased when muscle thickness, SARR of bone tumor site to the surface skin, bone marrow, and bone declined. To deliver the ultrasound energy into the tumor site and to avoid the potential damage to the normal tissue as much as possible, the specific absorption rate (SAR) in the bone tumor site has to be three times higher than that in the surface skin, tumor/marrow, and marrow/bone interfaces. The temperature distributions can verify the SARR criteria in this model. This study provides the information for choosing the optimal operating frequency of the ultrasound transducer and the acoustic window on the skin surface, and for designing the ultrasound applicator for clinical implementation.

This paper describes a portable speech controller system for persons with a vision impairment to adjust the channel frequency of a radio set via speech commands. The speech commands are recognized on a general-purpose digital signal processor using a hidden Markov model (HMM), and are used to remotely control radio channel changes.

External ultrasound hyperthermia is considered to be a very flexible modality for heating deep-seated tumors owing to its penetration and focusing ability. However, using this flexibility requires that many complicated, interacting decisions be made to obtain optimal treatment. This paper presents the feasibility of arranging multiple-focused ultrasound transducers to produce an appropriate heating pattern for a specific treatment, based on the optimal scan parameters obtained from an optimization algorithm. The variable scan parameters of the heating system optimized are the transducer tilt and rotation angles, focal depth, scan radius, and output acoustical power. After obtaining the optimal scan parameters, multiple transducers are systematically arranged according to these scan parameters. Three-dimensional ultrasound power deposition and temperature distribution for a specific treatment are calculated for this multiple ultrasound transducer system. A more uniform temperature distribution in the treatment region for a large, highly perfused tumor can be achieved by scanning the system with respect to the central scan axis and/or swinging the transducers inwards and outwards. The maximum heating depth of focused ultrasound transducers used in this heating system is also studied. Simulation results demonstrate that the optimal arrangement of this multiple-focused ultrasound transducer system is highly promising for heating deep, large, and highly perfused tumors.

Because the relations between electromyographic signal (EMG) and anisometric joint torque remain unpredictable, the aim of this study was to determine the relations between the EMG activity and the isokinetic elbow joint torque via an artificial neural network (ANN) model. This 3-layer feed-forward network was constructed using an error back-propagation algorithm with an adaptive learning rate. The experimental validation was achieved by rectified, low-pass filtered EMG signals from the representative muscles, joint angle and joint angular velocity and measured torque. Learning with a limited set of examples allowed accurate prediction of isokinetic joint torque from novel EMG activities, joint position, joint angular velocity. Sensitivity analysis of the hidden node numbers during the learning and testing phases demonstrated that the choice of numbers of hidden node was not critical except at extreme values of those parameters. Model predictions were well correlated with the experimental data (the mean root-mean-square-difference and correlation coefficient gamma in learning were 0.0290 and 0.998, respectively, and in three different speed testings were 0.1413 and 0.900, respectively). These results suggested that an ANN model can represent the relations between EMG and joint torque/moment in human isokinetic movements. The effect of different adjacent electrode sites was also evaluated and showed the location of electrodes was very important to produce errors in the ANN model.

Compared with a single-frequency system, the multiple-frequency system has an additional function to combine power patterns of different frequencies. This function increases the availability of power patterns to treat various shapes and depths of tumors. Therefore, we proposed a system with the ability to drive ultrasonic phased arrays of multiple resonant frequencies for ultrasound hyperthermia.

This paper reports on the development of an eyeglass- type infrared (IR)-controlled computer interface for the disabled. This system may serve to assist those who suffer from spinal cord injuries or other handicaps to operate a computer. This system is comprised of three major components: 1) an infrared transmitting module, 2) an infrared receiving/signal-processing module, and 3) a main controller, the Intel-8951 microprocessor. The infrared transmitting module utilizes tongue-touch circuitry which is converted to an infrared beam and a low power laser (0.1 mW) beam. The infrared receiving/signal-processing module, receives the infrared beam and fine tunes the unstable infrared beam into standard pulses which are used as control signals. The main controller is responsible for detecting the input signals from the infrared receiving/signal-processing module and verifying these signals with the mapping table in its memory. After the signal is verified, it is released to control the keys of the computer keyboard and mouse interface. This design concept was mainly based on the idea that the use of an infrared remote module fastened to the eyeglasses could allow the convenient control of the input motion on the keys of a computer keyboard and mouse which are all modified with infrared receiving/signal-processing modules. The system is designed for individuals with spinal cord injuries and disabled in which the subjects' movement are severely restricted. The infrared transmitting module can be easily mounted on eyeglasses or artificial limbs.

Complexity C can characterize the order or disorder of a time series and was used to discriminate between normal and abnormal electroencephalograms (EEG) in this study. Two classified groups of 20 ...

The pi-sharing theory developed by Lawrence and Johnson (1986) is extended to handle square multivariable continuous-time systems, and for the most essential part of finding usable pi-coefficients, LMI formulations are utilized such that for any finite-dimensional LTI systems, time-invariant pi-coefficients can be obtained easily. Furthermore, pi-coefficients are derived for sector-bounded nonlinearities, and the extended pi-sharing theory is applied to the multivariable Lur'e problem. With this approach, not only can a Lur'e system with known sector bounds on nonlinearities be checked for stability, but also the maximal bounds ensuring stability can be found under some conditions.

An elastance-resistance model has long been used to assess the systolic mechanical behavior of the ventricular pump under anin situ, open-chest experiment. However, there is difficulty in the clinical application of such a model because of the required isovolumetric signal that is obtained by occluding the ascending aorta in diastole. In this study, we determine the characteristics of an elastance-resistance model in the absence of isovolumetric measurement to quantify the physical properties of the left ventricle. A high-fidelity multisensor catheter was used to record the left ventricular pressure and ascending aortic flow in nine anaesthetized, closed-chest dogs. The isovolumetric pressure was estimated from the instantaneous pressure of an ejecting contraction by a curve-fitting technique. Thus, the parameters in the characterization of systolic pumping mechanics could be inferred by the used of fitting this elastance-resistance model. The results showed that the maximal systolic elastance was 7.3±2.8 mmHg and theoretical maximum flow was 494±194 ml s−1. These data were compatible with other reports in the literature. Moreover, in every dog studied the maximal systolic elastance was smaller than the end-systolic elastance which was determined by using the end-systolic pressure-volume relation. We suggested that an elastance-resistance model with theestimatedisovolumetric pressure has the potential to measure the intrinsic systolic mechanics of the left ventricle in a closed-chest cardiovascular system.

The authors discuss a two-model multilayer neural network controller for adaptive control of mean arterial blood pressure (MABP) using sodium nitroprusside. A model with an autoregressive moving average (ARMA), representing the dynamics of the system, and a modified backpropagation training algorithm are used to design the control system to meet specified objectives of design (settling time and undershoot/overshoot) and clinical constraints. The controller is associated with a weighting-determinant unit (WDU) to determine and update the output weighting factor of the parallel two-model neural network for adequate control action and a control-signal modification unit (CMU) to comply with clinical constraints and to suppress the effect of adverse noise and to improve the WDU performance. Extensive computer simulations indicate satisfactory performance and robustness of the proposed controller in the presence of much noise, over the full range of plant parameters, uncertainties, and large variations of parameters.