Postextrasystolic (PES) relaxation of the left ventricle was studied in 24 anesthetized dogs using the time constant (tau) of the left ventricular isovolumic pressure decline as an index of global relaxation velocity. Using programmed atrial stimulation and a control RR interval of 500 msec, the "coupling interval/compensatory pause" was varied from 400/600 msec to 250/750 msec, and left ventri...

BACKGROUND Programming a mechanical ventilator with a biologically variable or fractal breathing pattern (an example of 1/f noise) improves gas exchange and respiratory mechanics. Here we show that fractal ventilation increases respiratory sinus arrhythmia (RSA) -- a mechanism known to improve ventilation/perfusion matching. METHODS Pigs were anaesthetised with propofol/ketamine, paralysed wi...

There is little information on the effects of methyldopa on the human conduction system. His bundle ECGs were obtained in 11 patients before and after the intravenous infusion of 100 mg of methyldopa. Antegrade refractory periods were obtained with the extrastimulus method. The significant results were as follows: the sinus rate was 71 +/- 4 beats per minute before, and 65 +/- 3 beats per minut...

PURPOSE To investigate two apparent anomalies of the human electroretinogram: the "on" and "off" components of the cone based PIII are unequally sized, and transitions from red to green, which are electroretinographically silent, yield reverse transitions (green to red) in which a-waves develop. METHODS Ganzfeld electroretinograms were obtained with intense 100 msec flickering flashes from re...

Recent work has shown that alterations in the dynamic atrioventricular (AV) nodal response to changes in heart rate can significantly modify AV nodal function. The present study was designed to evaluate the nature and potential importance of sympathetic regulation of the rate-dependent properties of the AV node. Selective stimulation protocols and mathematical formulations were used to independ...

During internal defibrillation, potential gradients greater than 100 V/cm occur near defibrillation electrodes. Such strong fields may cause deleterious effects, including arrhythmias. This study determined 1) the effects of such strong fields on the propagation of activation and 2) whether these effects were different for monophasic and biphasic shocks. Voltages and potential gradients during ...

Achieving a 50 msec cognitive cycle in any sufficiently sophisticated cognitive architecture can be a significant challenge. Here an investigation is begun into how to do this within a recently developed graphical architecture that is based on factor graphs (with the summary product algorithm) and piecewise continuous functions. Results are presented from three optimizations that leverage the s...

Background: There are no studies examining the use, safety, efficacy, effective fluence and pulse duration of Laser hair reduction in Nigerians. This study aimed to document duration, number sessions achieve permanent reduction. Methods: A retrospective review removal 87 FitzPatrick skin type V VI patients from January 2017 August 2021 using neodymium-doped yttrium aluminium garnet (Nd:Yag). Th...