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Biomedical subjects

N P Reddy

Publications and source records attributed to N P Reddy.

At least 19 recordsLinked to original sources
PubMed1997

Fractal analysis of surface EMG signals from the biceps.

Nonlinear analysis techniques are necessary to understand the complexity of the EMG. The purpose of the present study was to determine the fractal dimension of surface EMG obtained from the biceps brachii of normal subjects during isokinetic flexion-extension of the arm. The measurements were obtained with different loading conditions on the arm and for various rates of flexion-extension. Fractal dimensions of the surface EMG signals were calculated for each of these conditions. ANOVA results showed statistically significant differences between the fractal dimensions calculated for different loading conditions and rates of flexion-extensin (P < or = 0.005). Linear regression analysis showed a correlation coefficient of 0.99 between the fractal dimension and the load, and a correlation coefficient of 0.98 between the fractal dimension and the rate of flexion-extension. The results of the study show that the fractal dimension can be used along with other parameters to characterize the EMG signal.

Algorithms↗
PubMed1996

Surface EMG measurements at the throat during dry and wet swallowing.

Within the sphere of dysphagia management, there is a growing need for the development of noninvasive methods of quantification of swallowing disorders. The purpose of the present investigation was to determine if surface electromyogram (EMG) at the throat could be measured during swallowing. Surface EMG was measured from 35 normal human subjects during dry and wet swallowing. The EMG signals recorded were highpass filtered using digital fourth order highpass Butterworth filter to eliminate baseline variations. Spectral analysis was performed on the filtered signals. The mean power values of the surface EMG signals were then calculated. Paired t-test between the mean power values of surface EMG during dry and wet swallowing showed a statistically significant difference (p < 0.005). The results of the study confirmed the hypothesis that surface EMG at the throat during swallowing could be measured. Mean power of surface EMG measurement provides a reliable noninvasive measure of swallowing.

Deglutition↗
PubMed1995

A mathematical model of flow through the terminal lymphatics.

Proper understanding of the mechanisms of fluid absorption and flow through the terminal lymphatics is essential for the control of several pathological conditions such as edema, bedsores and cancer. A mathematical model of the terminal lymphatics was developed using the principles of mechanics. Computer simulation results substantiate the hypothesis that fluid absorption and flow through the terminal lymphatics occur due to suction mechanisms of the adjacent contractile lymphatic segments and due to periodic fluctuations in the interstitial fluid pressure. In addition, the results suggested that increasing the length of a terminal lymphatic vessel beyond a certain limit does not cause further increase in fluid flow into the terminal lymphatic.

Biomedical Engineering↗
PubMed1995

Three-dimensional finite element stress analysis of the polypropylene, ankle-foot orthosis: static analysis.

An asymmetric 3-dimensional finite element model (FEM) of the ankle-foot orthosis (AFO) together with the ankle-foot complex was developed using the computer aided design (CAD) program PATRAN. Static analysis of normal and pathological motions of the ankle-foot complex such as the "drop-foot" problem were conducted using the FEM program ADINA. A total of 313 three dimensional solid elements and 10 truss elements were used. Heel strike and toe-off condition were simulated. Results revealed that the peak compressive stress (1.6 MPa) in the AFO model occurred in the heel regions of the AFO and the maximum tensile stress (0.8 MPa) occurred in the neck region of the AFO during toe-off. Parametric analyses revealed that the model was sensitive to the elastic moduli of the AFO and of the soft tissue, but was relatively insensitive to the ligament stiffness. The results confirmed the hypothesis that peak stresses in the orthosis occur in the heal and neck regions of the orthosis.

Ankle Joint↗
PubMed1995

A fuzzy logic diagnosis system for classification of pharyngeal dysphagia.

Identification and classification of the dysphagic patient at risk of aspiration is important from a clinical point of view. Recently, we have developed techniques to quantify various biomechanical parameters that characterize the dysphagic patient, and have developed an expert system to classify patients based on these measurements. The purpose of the present investigation was to develop a fuzzy logic diagnosis system for classification of the patient with pharyngeal dysphagia into four categories of risk for aspiration. Non-invasive acceleration and swallow pressure measurements were obtained and five parameters were extracted from these measurements. A set of membership functions were defined for each parameter. The measured parameter values were fuzzified and fed to a rule base which provided a set of output membership values corresponding to each of the categories. The set of output values were defuzzified to obtain a continuous measure of classification. The fuzzy system was evaluated using the data obtained from 22 subjects. There was a complete agreement between the fuzzy system classification and the clinician's classification in 18 of the 22 patients. The fuzzy system overestimated the risk by half a category in two patients and underestimated by half a category in two patients. The fuzzy logic diagnosis system, together with the biomechanical measures, provides a tool for continued patient assessment on a daily basis to identify the patient who needs further videofluorography examination.

Biomechanical Phenomena↗
PubMed1995

Stress distribution in the ankle-foot orthosis used to correct pathological gait.

Abnormal motion of the ankle-foot complex presents a major problem in the rehabilitation of stroke patients. These patients often develop drop foot, a problem involving excessive and uncontrolled plantar flexion. An ankle-foot orthosis (AFO) is prescribed to constrain and inhibit this abnormal motion. The purpose of this investigation was to simulate the drop foot problem to determine the stress distribution in the orthosis. A quasi-static 3-D finite element analysis of the AFO complex was conducted using ADINA. Results confirmed the hypotheses that the maximum peak stress occurs in the neck, heel, and side-arc region of the AFO. However, the neck region of the AFO experienced the largest amount of stress. High stress concentration in the neck region observed in the present analysis is consistent with the common clinical observation that AFOs break down in the neck region.

Ankle Joint↗
PubMed1994

Design and development of portable biofeedback systems for use in oral dysphagia rehabilitation.

The management of dysphagia presents a major problem in the comprehensive rehabilitation of stroke and head injury patients. Dysphagia is a disorder of the swallowing process. Oral dysphagia refers to abnormalities in the oral phase of the swallowing mechanism. The oral phase of the swallowing mechanism is important for the proper triggering of the swallowing reflex. Current techniques in oral dysphagia rehabilitation include oro-motor exercises using tongue depressors and mouth-care swabs. There is thus a need for a better therapeutic method for oral dysphagia. The purpose of this paper is to report the development of audio-visual biofeedback devices for treating oral dysphagia. Portable biofeedback devices rendering feedback of biomechanical parameters characterizing the oral phase were developed and evaluated in preliminary clinical trials. A patient progress index (PPI) was developed and used to quantify the overall patient progress. The devices demonstrated good patient acceptability.

Biofeedback, Psychology↗
PubMed1994

A theoretical model of infant incubator dynamics.

A spatially lumped mathematical model was developed and used for a computer simulation of the neonate-incubator system for parametric analysis of the factors that influence neonatal thermo-regulation. The simulation examined the effects of the following parameters: (1) size of the infant; (2) respiratory rate; (3) metabolic rate; (4) heart rate; (5) thermal properties of the mattress; (6) specific heat capacity of the incubator wall; (7) air flow rate; (8) heater control mechanisms.

Air Movements↗
PubMed1994

Toward classification of dysphagic patients using biomechanical measurements.

Identification of a patient at risk of aspiration is a major problem in the rehabilitation of the dysphagic patient. The present methods of diagnosis are based on clinical evaluation or videofluorography or fiberoptic endoscopic examination of swallowing (FEES). Recently, we developed biomechanical techniques for noninvasive quantitative assessment of the dysphagic patient. The purpose of the present investigation was to assess the clinical validity of the technique. In a double-blind study, both biomechanical test results and videofluorography (including bedside evaluation) results were used to independently classify the patients into four categories of risk for aspiration. Of the 36 patients studied, there was complete agreement between the biomechanical and clinical classifications in 21 patients. In 11 patients, the biomechanical technique overestimated the risk by one category, and underestimated the risk by one category in four patients. The biomechanical technique presents a useful tool for continued patient assessment; however, further studies are needed.

Adult↗
PubMed1992

Stress distribution in a physical buttock model: effect of simulated bone geometry.

Mechanical stresses developed in the tissue during sitting or reclining could cause bedsores in paralyzed individuals. Cushions are usually prescribed to redistribute the stresses. Two two-dimensional physical models of the buttock were developed and used to study whether the stress distribution is different with round- and flat-base bone core geometries and to find out whether the relative cushion responses are dependent on loading direction and bone core geometries. In these models, PVC gel simulated the soft tissue and a wooden core simulated the bony prominence. One model had a round-base core and the other had a flat-base bone core. A grid etched on the model allowed strain measurements, and stress calculations. The sharp-base bone core model generated large regions of high shear stress during vertical and inclined loading. However, the round-base core produced maximum compressive stress during vertical loading. The relative cushion responses were dependent on bone core geometry and loading direction.

Air↗
PubMed1992

A lumped parameter mathematical model of the splanchnic circulation.

A lumped parameter mathematical model to describe the propulsion of blood in the splanchnic circulation was developed by integrating the principles of mechanics and physiology. A set of governing equations by derived by specifically considering the contractility of the portal vein, hepatic vein, liver sinusoids, and of the draining lymphatics. These equations were then simulated on a computer. The present simulation results substantiate previous experimental observations that hepatic venous pressure leads to portal hypertension and increased liver interstitial fluid volume.

Blood Pressure↗
PubMed1991

Noninvasive acceleration measurements to characterize the pharyngeal phase of swallowing.

Swallowing disorder (dysphagia) presents a major problem in the rehabilitation of stroke and head injured patients. In the present investigation, a new technique is developed for noninvasive assessment of the pharyngeal phase of the swallowing mechanism. Acceleration was measured with two ultra-miniature accelerometers placed on the skin over the throat. Simultaneously, the swallow suction pressure was monitored. Swallowing in normal individuals gave rise to a characteristic acceleration pattern which was quite reproducible, and was in phase with the swallow pressure. In dysphagic patients, the acceleration response was either absent or significantly delayed. The accelerometry technique provides a tool for continuing patient assessment and demonstrating the clinical improvements.

Biomechanical Phenomena↗
PubMed1990

Biomechanical measurements to characterize the oral phase of dysphagia.

Dysphagia is a disorder of the swallowing mechanism and presents a major problem in the rehabilitation of stroke patients and head injured patients. The authors have identified several biomechanical parameters that characterize the oral musculature and have developed techniques to quantify these parameters in normal and dysphagic patients. These parameters include lip closure pressure, lip interface shear force, tongue thrust, and swallow pressure. Significant differences were found in each of these parameters measured in normal and dysphagic patients. The quantitative measurements may aid the physician in choosing the appropriate therapy during the course of recovery.

Biomechanical Phenomena↗
PubMed1989

A technique for quantitative assessment of three-dimensional motion with applications to human joints.

A technique is developed for quantitative measurement of general three-dimensional motion, and this technique is applied to the kinematics of anatomical joints. The spatial locations of three orthogonal points representing coordinate frames on each member of the joint are measured during motion of the joint by photo encoders of a three-dimensional mechanical pointer. Kinematic calculations are used to derive, from the experimentally collected data, the six orthogonal components of the motion of one member relative to the other. The accuracy of this technique is presented. Applications to the knee and ankle are discussed.

Ankle Joint↗
PubMed1987

A stochastic compartmental model of bone cells.

Cellular dynamics play an important role in bone remodelling. The mesenchymal cells, osteoclasts, osteoblasts and osteocytes are the four types of bone cells, which mediate bone remodelling involving bone formation and resorption throughout the human life-span. A stochastic compartmental model of bone cells is formulated in the present analysis assuming these four types of cells to be in four distinct compartments. The cumulant generating function is first derived using the transition parameters for intercompartmental diffusion. Equations for the mean, variance and covariance for the number density of these cells are then derived from the partial differential equation for the cumulant generating function. The simulation results are consistent with previous experimental observations.

Bone Development↗
PubMed1986

A simple coding method for computer storage and handling of drug information.

An ever-growing body of knowledge in pharmacology has created a need for devising improved methods for handling drug information. We have developed an eleven digit comprehensive cardiovascular number to represent vital information on the effects of a drug on the cardiovascular system. Each digit of the number signifies an important cardiovascular phenomenon, and can vary from 0 to 9. This coding method provides a simple technique for computer handling of vital information on the effects of pharmacoactive agents in a semi-quantitative manner. Using this procedure, similar numbers for neuromuscular and immune systems can be easily developed.

Cardiovascular Physiological Phenomena↗