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Biomedical subjects

G D Moskowitz

Publications and source records attributed to G D Moskowitz.

16 recordsLinked to original sources
PubMed1989

The theoretical development of a multichannel time-series myoprocessor for simultaneous limb function detection and muscle force estimation.

This paper details the theoretical development and simulation of a complete time-series myoprocessor which provides reliable and economical predictions of both the magnitude and direction of limb motion from the spectral content of the surface EMG. Treating multiple channels of surface EMG as a vector-valued autoregressive process incorporates spatially distributed information which extends the operating range of parallel filtering limb function classifiers and reduces their sensitivity to modeling conditions. Active joint moment is estimated simultaneously from the pooled variance of the prewhitened EMG generated during the classification procedure. Estimation from the prewhitened sequence imposes no additional computational requirements and extends optimal myoprocessors to include multiple channels of serially dependent data. Such a system may be applied to the control of actively powered prostheses or orthoses.

Artificial Limbs↗
PubMed1989

The experimental demonstration of a multichannel time-series myoprocessor: system testing and evaluation.

A multichannel time-series myoprocessor which combines the advantages of the parallel filtering limb function classifiers of Doerschuk et al. and the "optimal myoprocessor" muscle force estimators described by Hogan et al. have been developed and evaluated experimentally. Magnitudes and directions of knee movements were identified accurately and robustly from EMG sites intermediate to the major thigh muscles of intact individuals. Electrode placement criteria were tested, and system performance and sensitivity to contraction level as functions of channel number were computed. By including spatially distributed information into the structure of the processor, gains in accuracy and reliability over systems with fewer channels were demonstrated. Operating range increased with the number of channels included in the processor. Joint moment was estimated from multiple channels of temporally correlated data, extending and generalizing previously reported techniques. Identifying the parameters of AR models of the EMG at low levels of contraction resulted in more robust classification and joint moment estimation. Optimal electrode position could not be predicted a priori. The system may be applicable to the proportional control of myoelectric prostheses.

Adult↗
PubMed1984

Passive and active components of the internal moment developed about the ankle joint during human ambulation.

The internal moment developed about a joint during a functional activity is the result of contraction of muscles and the visco-elastic properties of the joint and its surrounding soft tissues. In this study, the contribution of each one of these mechanisms to the total internal moment developed about the ankle joint during human level walking was assessed. The results indicate that during normal level walking the internal moment about the ankle is mainly due to contraction of muscles surrounding the joint. The contribution of the passive component was found to be negligible. These results, however, were found to be different for the pathological case tested. The results indicated that in a subject with a mild equinus ankle deformity, a substantial portion (21%) of the total internal moment was contributed by the passive resistance of the joint and its surrounding structures.

Adult↗
PubMed1981

Instrumentation for measuring cardiac output by direct Fick method during liquid ventilation.

A closed-circuit fluorocarbon oxygenation system was designed and incorporated into an existing liquid breathing system (LBS) to allow measurement of an animal's oxygen consumption during liquid ventilation. This enabled simultaneous determination of cardiac output by the direct Fick method. A series of seven in-vivo experiments were conducted in which the oxygen consumption and cardiac output of adult cats (2.3 +/- 0.1 kg body wt SEM) were measured during both spontaneous gas breathing (Fio2 = 0.80 in the control animals) and fluorocarbon liquid (FC-80) ventilation using the LBS. On conversion to liquid ventilation, cardiac output and oxygen consumption were found to decrease significantly, by 40% (P less than 0.02) and 18.6% (P less than 0.05), respectively, from control values for gas breathing. Use of the closed-loop fluorocarbon oxygenation system provided for total recovery of vaporized fluorocarbon (greater than 750 ml/h) and of oxygen (18 liter/min STPD), which were otherwise discarded in previous experiments with liquid ventilation.

Animals↗
PubMed1978

Positive end expiratory pressure: effects on lung mechanics of premature lambs.

Pulmonary mechanics were determined at 0, 3, 6, and 10 cm H2O positive and expiratory pressure (PEEP) in premature lambs at a mean gestational age of 134 days. Functional residual capacity increased (p less than 0.005) by 7% (1.6 ml/kg) per cm H2O PEEP. Dynamic lung compliance and specific compliance significantly decreased by 10% (0.11 ml/cm H2O/kg) and 9% (0.0051 l/cm H2O) per cm H2O PEEP, respectively, for PEEP above 3 cm H2O level. Inspiratory lung resistance increased significantly (p less than 0.05) only between 0 and 6 cm H2O PEEP while expiratory lung resistance increased (p less than 0.05) between 0 cm H2O PEEP and all higher levels. The data suggest that PEEP in excess of 3 cm H2O produces undesirable effects on lung mechanics in premature lambs. These results may be important in predicting contraindications and potential complications of positive pressure breathing in the newborn.

Animals↗
PubMed1978

Pulmonary lavage in preterm lambs.

Pulmonary function was studied before and after bilateral lung lavage with oxygenated FC-80 fluorocarbon liquid in seven perterm lambs, 134 days of gestation. Measurements of transpulmoary pressure, airflow, tidal volume, and functional residual capacity (FRC) enabled calculation of lung resistance and compliance, specific compliance, and work of breathing. Immediately postlavage, arterial oxygen tension (PaO2) decreased significantly (P less than 0.05) by 41% from control values. In addition, at 1 hr postlavage, lung compliance significantly decreased (P less than 0.01) by 43% from control levels. Lung resistance, FRC work of breathing arterial carbon dioxide tension, and pH postlavage were not significantly different from prelavage values. The mean volume of FC-80 remaining in the lungs at 1 hr postlavage was 32% of the instilled volume. These data indicate that lung lavage with a low surface tension liquid has a relatively small effect on lung mechanics of the premature lung.

Animals↗
PubMed1977

Instrumentation for measuring functional residual capacity in small animals.

A system for measuring functional residual capacity (FRC) by the dilution method was evaluated to determine its suitability for use in neonates and small animals. The system makes use of rapid, automatically triggered valves for precise closure at end expiration. Results of a theoretical error analysis and experimental in vitro tests are presented and indicate that the measuring error in FRC is related to the FRC-to-initial rebreathing bag volume ratio. With a 200-ml bag volume one standard deviation of the calculated error was 16% for a 50-ml, 9.1% for a 100-ml, and 5.8% for a 200-ml FRC.

Animals↗
PubMedDate not supplied

Liquid breathing trials and animal studies with a demand-regulated liquid breathing system.

Experimental results of in vivo animal tests conducted on a demand-regulated liquid breathing system are presented. When a liquid replaces gas as the medium in which oxygen and carbon dioxide are transported, several problems not typical in gas respiration occur. The increased mass and viscosity of a liquid as compared with a gas necessitate some means of mechanical assistance. The lower diffusion rates of gases in liquids as compared with gas rates places several constraints on the design of a mechanically assisted liquid breathing system. The liquid breathing system reported in this study has been designed to be demand-regulated, i.e., the animal has control over cycling the pumps which mechanically assist the circulation of an oxygenated liquid to and from the lungs. This system consists of a gas-operated diaphragm pump, demand controller, liquid regenerator with heater and gas scrubber, and ancillary equipment. A demand controller is described which obtains a control signal from an esophageal balloon catheter in the animal and governs operation of the pneumatically driven diaphragm pump.

Airway Resistance↗