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Weldon School of Biomedical Engineering Faculty Publications

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Elevation Of Ventricular Defibrillation Threshold In Dogs By Antiarrhythmic Drugs, Charles F. Babbs, Gkw Yim, S J. Whistler, W A. Tacker, L A. Geddes Jan 1979

Elevation Of Ventricular Defibrillation Threshold In Dogs By Antiarrhythmic Drugs, Charles F. Babbs, Gkw Yim, S J. Whistler, W A. Tacker, L A. Geddes

Weldon School of Biomedical Engineering Faculty Publications

Effects of antiarrhythmic drugs upon the threshold delivered energy (TDE) and threshold peak current (TPC) for electrical ventricular defibrillation by damped sinusoidal shocks were investigated in 25 pentobarbital-anesthetized dogs. TDE and TPC were increased by the three antiarrhythmic drugs tested. Bolus injections produced a transient rise, and continuous infusions produced a steady rise in defibrillation threshold. The maximal percent elevations in mean defibrillation threshold during the 60 minutes after intravenous drug treatment in groups of n = 5 dogs were: Treatment % increase in TDE % increase in TPC Lidocaine bolus (3 mg/kg) 48 26 Lidocaine (0.5 mg/Kg/min) 99 45 …

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Measurements Of Young's Modulus Of Elasticity Of The Canine Aorta With Ultrasound, D J. Hughes, Charles F. Babbs, L A. Geddes, J D. Bourland Jan 1979

Measurements Of Young's Modulus Of Elasticity Of The Canine Aorta With Ultrasound, D J. Hughes, Charles F. Babbs, L A. Geddes, J D. Bourland

Weldon School of Biomedical Engineering Faculty Publications

We have developed an ultrasonic technique for determining the dynamic Young's modulus of elasticity (E) of the canine aorta in vivo. Young's modulus was measured in the descending thoracic aorta (DTA) and the abdominal aorta (AA) of 12 dogs over a range of mean blood pressures from 40-200 mmHg. The vessels were excised and dynamic moduli were determined in vitro postmortem from pressure-volume curves. The data so obtained were compared to the in vivo values. In vivo and in vitro moduli increased exponentially with mean distending pressure (P). The equation of best fit for these data was of the form …

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Attenuation And Speed Of 10 Mhz Ultrasound In Canine Blood Of Various Packed Cell Volumes At 37c, D J. Hughes, L A. Geddes, Charles F. Babbs, J D. Bourland, V L. Newhouse Jan 1979

Attenuation And Speed Of 10 Mhz Ultrasound In Canine Blood Of Various Packed Cell Volumes At 37c, D J. Hughes, L A. Geddes, Charles F. Babbs, J D. Bourland, V L. Newhouse

Weldon School of Biomedical Engineering Faculty Publications

The attenuation coefficient and the speed of 10 MHz ultrasound were determined in canine blood at 37 oC by a differential path length technique. Blood specimens with packed cell volumes (PCV) ranging from 0 to 53% were prepared by separating the cells from the plasma and mixing the two components. The mean attenuation coefficient increased linearly with packed cell volume, the least squares regression function being  (dB/cm) = 0.992 +0.039 PCV with a standard error of the estimate = 0.255. The speed of 10 MHz ultrasound, c, in millimetres per second, increased with packed cell volume, the regression function …

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Effect Of Pentobarbital Anesthesia On Ventricular Defibrillation Threshold In Dogs, Charles F. Babbs Jan 1978

Effect Of Pentobarbital Anesthesia On Ventricular Defibrillation Threshold In Dogs, Charles F. Babbs

Weldon School of Biomedical Engineering Faculty Publications

The effect of pentobarbital anesthesia upon the minimal voltage and current required for electrical ventricular defibrillation (the defibrillation threshold) was investigated in dogs. Threshold current, energy, and charge in five dogs averaged 2 per cent, 13 per cent, and 6 per cent less under surgical levels of pentobarbital anesthesia than thresholds in the same animals in the awake, unanesthetized state. In dogs given sufficient pentobarbital to produce apnea and supported by mechanical ventilation, threshold current, energy, and charge averaged 3 per cent, 17 per cent, and 2 per cent less than comparable awake values. These differences were far from statistically …

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Temporal Stability And Precision Of Ventricular Defibrillation Threshold Data, Charles F. Babbs, S J. Whistler, G Yim Jan 1978

Temporal Stability And Precision Of Ventricular Defibrillation Threshold Data, Charles F. Babbs, S J. Whistler, G Yim

Weldon School of Biomedical Engineering Faculty Publications

Over two-hundred measurements of the minimum damped sinusoidal current and energy for transchest electrical ventricular defibrillation (ventricular defibrillation threshold) were made to determine the stability and precision of threshold data in 15 pentobarbital-anesthetized dogs. Threshold was determined by repeated trials of fibrillation and defibrillation with successive shocks of diminishing current, each 19% less than that of the preceeding shock. The lowest shock intensity that defibrillated was defined as threshold. In three groups of five dogs each, threshold was measured at intervals of 60, 15, and 5 min. over periods of 8, 5, and 1 hr. respectively. Similar results were obtained …

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Protection Of Ischemic Myocardium By Whole-Body Hypothermia After Coronary Artery Occlusion In Dogs, Dana R. Abendschein, Willis A. Tacker Jr, Charles F. Babbs Jan 1978

Protection Of Ischemic Myocardium By Whole-Body Hypothermia After Coronary Artery Occlusion In Dogs, Dana R. Abendschein, Willis A. Tacker Jr, Charles F. Babbs

Weldon School of Biomedical Engineering Faculty Publications

Anesthetized dogs were cooled to a core body temperature of 26°C or maintained at a body temperature of 37°C during periods of 5 and 10 hours of LAD coronary artery occlusion. Subsequent macroscopic dehydrogenase enzyme mapping showed that ischemic injury was 25 per cent less after 5 hours of coronary occlusion and 20 per cent less after 10 hours of occlusion in hypothermic dogs than in normothermic controls. The heart rate and left ventricular minute work in hypothermic dogs decreased to roughly half the levels measured in normothermic animals, while left ventricular contractility was 10 to 40 per cent lower …

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Evaluation Of The Operating Internal Resistance, Inductance, And Capacitance Of Intact Damped Sine Wave Defibrillators, Charles F. Babbs, S J. Whistler Jan 1978

Evaluation Of The Operating Internal Resistance, Inductance, And Capacitance Of Intact Damped Sine Wave Defibrillators, Charles F. Babbs, S J. Whistler

Weldon School of Biomedical Engineering Faculty Publications

A method is developed for determining actual values of circuit elements in a damped sine wave (Lown waveform) defibrillator, solely from measurements of the output, using two or more power resistors and a storage oscilloscope. If a defibrillator containing capacitance, C, inductance, L, and internal resistance, Ri, is discharged into increasing 5- to 100-ohm resistive loads, R, it is shown for underdamped output waveforms that aˆ = Ri/2L + R/2L and cˆ = CRi + CR, where aˆ = /[t2 tan(t1/t2)], cˆ = 2 aˆ /[ 2 aˆ + (/t2)2], t1 = time from onset to peak, and t2 = …

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