Hebbel E. Hoff

Patterns of sinus arrhythmia in patients with lesions of the central nervous system

Abstract Simultaneous recordings of respirations and instantaneous cardiac frequency by means of a cardiotachometer permit visualization of the sinus arrhythmia due to respiration. Observations made on tracings obtained from 102 patients with a variety of neurologic disorders indicate that the typical respiration-heart rate response may be disturbed by lesions affecting the cardioregulatory mechanisms. Decerebration results in prominent periodic waves of acceleration of the heart rate followed by rebound deceleration. These waves coincide with each deep breath or outburst of periodic breathing. A fixed cardiac frequency is indicative of a complete disconnection between the cardiac pacemaker and the regulatory centers of cardiac activity. Cervical spinal cord transections may cause preponderant bradycardia. It is suggested that simultaneous recordings of the pneumogram and the cardiotachogram may yield useful information regarding the integrity of the regulatory centers of cardiac activity.

Effects of Hypertonic Glucose and Mannitol on Plasma Volume.

Summary The influence of hyper tonic glucose and mannitol on blood volume was tested in normovolemic-normotensive and hypovo-lemic-hypotensive dogs. Neither glucose nor mannitol had any effect on the blood volume of normovolemic dogs. In hypovolemic-hypo-tensive dogs, mannitol produced a significant increase in the plasma volume by mobilizing fluid from the extravascular spaces. The fluid entering the circulation was accompanied by a significant amount of protein. Also, plasma volume increased after hemorrhage with glucose, but the increase was small and was not accompanied by protein. Thus, both glucose and mannitol, but particularly the latter, increased the blood volume in hypovolemia.

Defibrillation without A-V Block Using Capacitor Discharge with Added Inductance

Two hundred and seventy-two defibrillations of the ventricles of 17 dogs by capacitor discharge applied directly to the heart were accompanied by A-V block lasting up to 78 seconds. A range of 150 to 475 volts was employed using a 40 microfarad condenser. The duration of the block was proportional to the energy employed for defibrillation. With the minimum energy of 1.8 watt-sec that produced 100% defibrillation in all trials, A-V block was present in 14 of the 17 animals (average duration of A-V block varying from 3 to 18 seconds). That the A-V block is not vagal in origin was demonstrated by atropinization and vagotomy of the animals. Prolongation of the period of fibrillation up to 15 seconds was found not to be a factor in determining the duration of A-V block. Defibrillation with the same energy levels but with the inclusion of an 0.29 henry inductance abolished the A-V block in 115 defibrillations in the same 17 animals. The current waveform measured without inductance was of the capacitor discharge type (unidirectional and exponentially decaying); with the inductance in the circuit the current waveform was a highly damped sinusoidal alternating current consisting of slightly more than two full cycles of about 40 Hz.

A Portable Miniature Transistorized Radio-Frequency Coupled Cardiac Pacemaker

A miniature, transistorized radio-frequency-coupled cardiac pacemaker was developed to eliminate wires penetrating the skin when electrodes are placed on the heart to drive it. The design also eliminates the need for totally implanting a pacemaker with its batteries. The stimulating impulse is transmitted via amplitude modulation to a tuned circuit and detector assembly implanted below the skin. The output of the detector is connected to electrodes directly on the heart, making external control of the heart rate possible. In operation, the pacemaker transmitter is placed on the surface of the body above the receiver implant. The size of the unit is 4×13/4 ×13/2 inches. It weighs three ounces.

Short Distance Broadcasting of Physiological Data

For the transmission of physiological data not requiring complete freedom for the subject, a direct wire system offers many practical advantages including low cost and high reliability. Such a system is particularly well adapted for bedside monitoring and for the usual studies in the clinical laboratory where the patient is required by his illness to be in a fixed position. For general purpose physiological telemetery, it is necessary to transmit a bandwidth extending to zero cycles per second. Experience has demonstrated that such transmission is possible over a direct wire circuit for a distance of at least half a mile. An over-all response time of 100 ?sec provides an adequate bandwidth for the most rapidly changing physiological events.

Claude Bernard on Experimental Medicine—Some Unpublished Notes

One hundred years ago Claude Bernard was at the pinnacle ofhis scientific productivity and his inteEectual powers, ifnot ofhis reputation. Some thirty years earlier he arrived in Paris at the age of twenty-one with the manuscript of a not-too-original play in his pocket and an unsatisfactory and incompleted apprenticeship in pharmacy behind him. He enrolled in the Faculty ofMedicine. There he came under the influence ofMagendie and, gaining his internship in 1839, became Magendie s preparator in 1841. In 1843, at the age of thirty, he obtained the medical degree and completed his first work on the metabolism ofsugar, concluding that sucrose is modified in digestion by demonstrating its presence in the bloodstream only when it was injected intravenously and never when it was ingested. This was followed during the next fifteen years by studies on the function of the pancreas in the digestion of fat, on the metabolism of starvation, on the glycogenic function of the liver and the sugar piqûre, on the localization of the action of curare, and on the vasomotor nerves. In a very early investigation he measured the temperature of the blood in the right and left ventricles of the horse and showed that the blood of the right cavity was warmer than that in the left, disposing thereby of the suggestion of Lavoisier that bodily oxidations take place in the lungs. In so doing he had recourse to catheterization of the cardiac chambers, and, although he was not the first to do so, his report of this procedure had much to do with initiating the chain of events that led from Chauveau and Marey to Forssmann and Cournand.

An improved heart-lung preparation ventilated by negative pressure

Five isolated canine heart-lung preparations were successfully ventilated with intermittent negative pressure in a specially constructed chamber. Improved cardiopulmonary dynamics resulted in increased survival time and improved performance of all preparations. Results obtained with these preparations exceed most of the others reported in the literature. Submitted on May 9, 1960