J Biomech Eng. 1977;99(1):1-2. doi:10.1115/1.3426262.
Commentary by Dr. Valentin Fuster


J Biomech Eng. 1977;99(1):3-8. doi:10.1115/1.3426266.

A new approach for evaluating advanced concepts for knee-joint control in above-knee prostheses involves the use of a simulator prosthesis which can be worn by an amputee and controlled electronically to emulate proposed future prostheses. A critical element in this system is the knee-torque controller. Realization of a powerful, lightweight, easily controlled transducer was essential to the successful development of the simulator system. This paper presents the design of such a controller and evaluates its performance. Brief examples of studies in which the new system has been applied are given. The proven viability of the device suggests that similar actuators might aid other prosthesis/orthesis studies.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1977;99(1):9-13. doi:10.1115/1.3426269.

A five-parameter transfer function has been used to characterize the input impedance of the human systemic circulation. Aortic pressure and flow measurements obtained at cardiac catheterization are employed to evaluate the model parameters in individual patients. The appropriate parameters are chosen using a standard optimization technique to minimize the difference between pressures computed from the model and the measured values. Impedance parameters calculated for 19 patients showed considerable variation with no apparent correlation with the type of heart disease. The model is useful in describing the loading of the left ventricle produced by the systemic circulation. It may also have application to the study of vascular disease.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1977;99(1):14-19. doi:10.1115/1.3426261.

Inlet and outlet pressures and flows were obtained over a wide range of operating conditions for a pneumatically driven sac-type artificial ventricle connected to a mechanical mock circulatory system. The load presented to the ventricle by the mock circulatory system was found to be characterized by a linear resistance and capacitance. A dynamic model for the ventricle which accounted for instantaneous pressures and flows was developed. The outlet port is characterized by an inertance and square law resistance; the inlet port is characterized by a nonlinear resistance dependent on the type of valve. The input to the model is the time varying sac pressure. The model predicts the fill-limited and ejection-limited modes of the artificial ventricle.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1977;99(1):20-25. doi:10.1115/1.3426263.

Bioengineering aspects of headgear design are surveyed to illustrate the interactions and contributions of different engineering disciplines to military headgear design. Illustrations are drawn from the fields of anthropometry, human factors, heat transfer, acoustics, and applied mechanics. In addition, a helmet design procedure is described which takes into consideration such interactions. The procedure was successfully used in the design and development of a new ballistic protective infantry helmet. This methodology is equally applicable to the design of civilian head protective devices. Possible applications are pointed out.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1977;99(1):26-32. doi:10.1115/1.3426264.

A pulsed ultrasound Doppler velocity meter has been used to map the time varying velocity waveforms in the exposed left coronary arteries of anesthetized ponies. Velocity measurements were made without invading the vessels or disturbing the hemodynamic patterns. Typical recordings of velocity waveforms and calculated velocity profiles in the main, descending and circumflex branches are presented. Marked velocity fluctuations in the frequency range of 5 to 10 Hz were measured in the major coronary branches and may influence the stability of the flow and the development of separated flows. Peak Reynolds numbers normally ranged from 300 to 600 and the Womersley unsteadiness parameter based on the heart frequency was usually less than 4.0. Maximum shear rates at the wall were estimated from the calculated velocity profiles and ranged from 400 to 600 sec−1 .

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1977;99(1):33-39. doi:10.1115/1.3426265.

A mathematical model of a sac-type artificial ventricle is presented. The model, derived from the mass conservation and energy equations of a deformable control volume, is used in a digital simulation study of a latex ventricle in mock circulation. The hinged disk valves mounted within the ventricle are modelled as nonlinear resistive elements with flow regurgitation. The simulation results are compared with experimental measurements.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1977;99(1):40-44. doi:10.1115/1.3426267.

The relationship between fracture strength in bending, bending stiffness and bone mineral content for 56 fresh canine radii, ulnae and tibiae was determined from three- and four-point bending tests on a MTS testing machine and from measurements of bone mineral content at the fracture site using the Norland-Cameron Bone Mineral Analyzer. The high correlation of bending stiffness (0.962) and mineral content (0.901) with fracture bending moment permits estimates of fracture strength using current noninvasive methods of measuring stiffness and mineral content.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1977;99(1):45-53. doi:10.1115/1.3426268.

Temperature of the gas stream and mucosa were measured in the upper and lower trachea and right and left main bronchi of several anesthetized, intubated and mechanically respired mongrel dogs. Airway temperatures were measured using an airway sensor probe instrumented with microthermistors. Each thermistor was integrated into an especially designed. Wheatstone bridge whose signal of millivolts was displayed on a calibrated polygraph recorder. Diving respiratory conditions were simulated by utilization of an appropriate ventilatory periodic flow through an endotracheal airway which by-passed the efficient gas conditioning nasal turbinates of the dog. Deep diving respiratory environmental conditions of gas temperature, density and thermal capacitance (ρCp ) were simulated in a hyperbaric chamber. The temperatures recorded during in vivo periodic positive pressure ventilation were applied to a quasi-steady flow model based upon the morphological dimensions of the Weibel model. An empirical mathematical model of inspiratory sensible heat loss was verified and slightly modified to better reflect the overall dimensionless heat transfer relationship Nu = 0.302 (RePr)0.786 that existed in the major bronchial airways of the experimental subject. The design of the experimental instrumentation is explained in detail, as is the basic mathematical model. Significance of the experimental findings is discussed.

Commentary by Dr. Valentin Fuster

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