Impedance-gradient electrode reduces skin irritation induced by transthoracic defibrillation.

A new type of disposable external defibrillation electrode has been developed to reduce the skin irritation commonly associated with defibrillation and synchronised cardioversion. This design employs an impedance gradient to reduce the proportion of current delivered to the electrode periphery. The temperature distribution under the new electrode was compared with that of four other types of commercially available electrodes after repeated high-energy biphasic defibrillation discharges to domestic swine.

Self-sealing, large bore arterial punctures: a counterintuitive new phenomenon.

The human femoral artery can bleed dangerously following the removal of a catheter uring cardiac catheterization. In this study, a modified technique of needle insertion, simply inserting the needle bevel-down instead of the standard bevel-up approach, was tested as a means to reduce bleeding after catheter removal. Large bore needle punctures were made in surgically exposed arteries of anesthetized pigs using either a standard technique (45 degree approach, bevel up) or a modified technique (25 degree approach, bevel down).

Electroventilation with monopolar and bipolar intratracheal electrodes.

Unlabelled: Electroventilation is the technique of producing inspiration with stimuli applied to inspiratory muscles by using strategically placed electrodes on or within the body. We conducted studies using the dog to determine the efficacy of monopolar and bipolar intratracheal electrodes for electroventilation. Bipolar electrodes were able to produce an inspired volume greater than a spontaneous tidal volume in all seven dogs, but monopolar electrodes were able to in only three of seven dogs.

Electrophysiological control of ventricular rate during atrial fibrillation.

Thirteen anesthetized canine subjects (17-29 kg) were used to demonstrate that mild cervical left vagal stimulation could control ventricular rate effectively during atrial fibrillation (AF). Two studies are presented. The first study used six subjects to demonstrate the inverse relationship between (manually applied) left vagal stimulation and ventricular excitation (R wave) rate during AF.

Characterization of atrioventricular nodal response to electrical left vagal stimulation.

The dynamic effect of left vagal stimulation on atrioventricular conduction was studied in six isofluorane-anesthetized dogs ranging in weight from 22 to 29 kg. The cervical vagus nerve trunks were left intact and no beta-adrenergic blockade was produced so that any influences of the sympathetic nervous system and autonomic reflex activity could be observed. Atrial pacing was used to control the heart rate while single, short trains of left vagal stimulation were delivered and timed to occur at different instances during the cardiac cycle.

Skin-temperature distribution under a new type of defibrillating electrode.

The temperature rises under a new type of x-ray-transparent, improved current-density-distribution defibrillation electrode applied to pig skin were measured at four sites with fiberoptic thermal probes. Three anesthetized pigs, ranging in weight from 79 to 92 lb, were used. Temperature-time curves were obtained and the maximum temperature was identified.

Post-mortem changes after lead extraction from the ovine coronary sinus and great cardiac vein.

We investigated in sheep, non-thoracotomy extraction of leads which had been chronically implanted in the right atrium (RA), coronary sinus/great cardiac vein (CS/GCV) and right ventricle (RV) for atrial implantable defibrillation. Clinical success of extraction as well as gross and histologic findings in the heart are reported. Six of nine sheep had successful extractions.

Maintenance of atrial fibrillation in anesthetized and unanesthetized sheep using cholinergic drive.

Atrial fibrillation (AF) was induced electrically and the duration of AF was measured in six isoflurane-anesthetized sheep (weight range 54.5-72.7 kg), and in five unanesthetized sheep (weight range 60-75 kg).

End-tidal CO2, CO2 production, and O2 consumption as early indicators of approaching hyperthermia.

To illustrate the abilities of several physiologic events to indicate a change in metabolic status, dinitrophenol was used to induce hyperthermia. Ten dogs were divided into two groups, one being mechanically ventilated and the other allowed to breathe spontaneously. End-tidal CO2 (ETCO2) and CO2 production, O2 consumption, mean blood pressure, and rectal temperature were monitored continuously in both groups.

A pressure-sensitive mat for measuring contact pressure distributions of patients lying on hospital beds.

The authors describe a novel system for sensing and displaying the distribution of contact pressure caused by a patient's lying on a hospital bed. The system includes a flexible, pressure-sensitive mat, electronics to activate the mat, a small computer to process data, and a color video display. The present prototypes can sense pressure at 1,536 discrete locations in a rectangular grid of 24 x 64 nodes, each node representing an area of 4 cm2.

Oxygen uptake and mean blood pressure as indicators of induced hyperthermia.

This dog study was designed to identify which of two measurements (oxygen consumption, mean blood pressure) tracked the onset of hyperthermia as reflected by rectal temperature. The animals were anesthetized, paralyzed, and mechanically ventilated. Hyperthermia was induced with 2,4-dinitrophenol (5 mg/kg) injected intravenously in 5 dogs.

End-tidal carbon dioxide concentration, carbon dioxide production, heart rate, and blood pressure as indicators of induced hyperthermia.

In 4 spontaneously breathing, barbiturate-anesthetized dogs, hyperthermia was induced with 2,4-dinitrophenol while rectal temperature, heart rate, mean blood pressure, end-tidal carbon dioxide, and carbon dioxide production (milliliters per minute) were measured continuously. The latter was determined with a pneumotachygraph (to obtain respired volume) and an infrared carbon dioxide analyzer that measured inspired and expired carbon dioxide concentration. Of the five physiologic measurements, the increase in carbon dioxide production preceded the increase in rectal temperature by more than 120 seconds.

Simple canine model of arterial thrombosis with endothelial injury suitable for investigation of thrombolytic agents.

Three separate studies were done to evaluate a new canine model of arterial thrombosis with endothelial injury. Endothelial injury was produced by exposing the luminal surface of a 2-cm segment of femoral artery to 100 degrees C saline for 5 min. There was no disruption of proximal or distal blood flow with this model, and thrombolysis was continuously monitored by measuring 125I-labelled fibrin gamma emissions from the thrombus.

Gastric insufflation during IAC-CPR and standard CPR in a canine model.

This study was undertaken to determine the effect of interposed abdominal compressions (IAC) during cardiopulmonary resuscitation (CPR) on gastric insufflation when the airway is not secured with an endotracheal tube. A canine model was used in which a common ventilation pressure was applied to separate cuffed esophageal and tracheal tubes. Gas entering the stomach was collected by a pre-placed gastrostomy tube leading to a bell spirometer.

The prediction of the impedance of the thorax to defibrillating current.

In this paper a technique for predicting thoracic impedance to defibrillator pulses is described. The impedance to low-current (1.0 mA) high-frequency (10-500kHz) sinusoidal current is used as an indicator of the impedance of the thorax to high-current, damped sinusoidal waveform pulses.