David Adler

Fetal Movements Recorder, Use and Indications

A new device for recording fetal movements is presented. This device is composed of 2 sensors, incorporating a highly sensitive piezoelectric material. It is sensitive to rapid straining forces such as fetal movements and relatively insensitive to steady, slow movements such as uterine contractions and maternal respiratory movements. In this study of 20 women, the sensors were placed on 2 different zones of the abdomen, usually above the umbilicus. There was a good correlation between fetal movements recorded by the device and those felt by the patients. Seventy percent of all observed fetal movements recorded by the device were registered simultaneously by the women. The device recorded 90.4% and the women recorded 79.7% of all such movements.

The contractile element behaviour as force generator and shortening generator—A well-defined representation of the contractile element in Hill's model

Abstract The importance of a unique and well-defined behaviour of the contractile element (CE) in Hills model is discussed. Two alternative models of CE as a shortening generator and as a force generator are described and analyzed. The consequences of the analysis are: (1) the two models are mathematically equivalent and the mechanical behaviour of the sarcomere can be simulated by a model of a non ideal generator, composed of an ideal generator connected to an intersarcomeric compliance which serves as an “internal load”, (2) the suggested model enables the determination of the ratio between the intersarcomeric and extrasarcomeric compliances indirectly from available experiments of the sarcomere shortening during isometric and unloaded contractions, (3) cardiac and to a greater extent skeletal muscle behaviour are closer to that of an ideal force generator than to that of an ideal shortening generator.

Measurement of Fetal Movements by Moving-Coil Transducer

A transducer for the detection of fetal movements is described. The transducer is based on a coil moving in a magnetic field. It produces a signal as a result of fetal movements which create changes on the matemal anterior abdomen. The transducer is not affected by slow movements, maternal respiration, and uterine contractions. The sensitivity of the transducer in comparison with other means of fetal movement assessment is discussed.

Evaluation of time-dependent and quantitative properties of contraction from left ventricular pressure

SummarySeveral mechanical indices predicted from a model of cardiac muscle contraction are tested. In thein-vivo canine heart, dp/dtmax and t-dp/dt, the time, interval from onset of contraction to dp/dtmax, were measured. The product of these parameters Ap=t-dp/dt×dp/dtmax was calculated. t-dp/dt was shortened when heart rate was elevated and remained constant when ventricular end diastolic volume was changed. Ap increased with augmentation of ventricular end diastolic volume. To achieve constant muscle length when heart rate is changed, analogous tension measurements (assigned as dT/dtmax, t-dT/dt and AT) of prestretched Walton Brodie strain-gauge arch had been taken instead of pressure measurements. In the experiments in which Tmax, maximal isometric tension, was not changed for various heart rates, AT was also unchanged. These results are consistent with the predictions that t-dp/dt and Ap can be used as two independent mechanical indices: 1) t-dp/dt for the evaluation of the “time-dependent properties” of contraction and 2) Ap, for the evaluation of the “quantitative properties” of contraction. The advantages of applying these two mechanical indices for use in the intact ejecting heart, instead of the well-established parameters Vmax and Po are emphasized.ZusammenfassungIn der vorliegenden Studie werden verschiedene mechanische Indizes getestet, die auf der Grundlage eines Modells der Herzmuskelkontraktion entwickelt wurden. Beim Hundeherzen in vivo wurden dP/dtmax und t-dp/dt, das Zeitintervall vom Beginn der Kontraktion bis zur maximalen Druckanstiegesgeschwindigkeit, gemessen und das Produkt aus diesen Parametern Ap=t-dp/dt×dp/dtmax berechnet. t-dp/dt nahm mit steigender Herzfrequenz ab, war jedoch unabhängig von Veränderungen des enddiastolischen Ventrikelvolumens Dagegen stieg Ap mit Zunahme eine konstante Muskellänge zu erreichen, wurden mit Hilfe eines Dehnungsmeßstreifens anstelle der Druckmessungen analoge Spannungsmessungen (dT/dtmax, t-dT/dt und AT) durchgeführt. Wurde die maximale isometrische Spannung bei unterschiedlichen Herzfrequenzen nicht verändert, so war auch At konstant. Diese Ergebnisse sprechen dafür, daß t-dp/dt und Ap als zwei unabhängige mechanische Indizes verwendet werden können: 1. t-dp/dt für die Bewertung der „zeitabhängigen Eigenschaften” der Kontraktion und 2. Ap für die Bewertung der „quantitativen Eigenschaften” der Kontraktion. Die Vorteile einer Anwendung dieser beiden mechanischen Indizes für den Gebrauch beim intakten Herzen anstelle der weit verbreiteten Parameter Vmax und Po werden betont.