A method for the estimation of regurgitant blood flow in aortic incompetence Part II

It seems likely that the technique described is capable of measuring the regurgitant flow in the arm of a patient suffering from aortic incompetence. Whether this percentage backflow is equal to that at the aortic orifices is not known for certain. It seems likely however that a close approximation may exist in many cases particularly if the degree of regurgitation is severe and the arteries are dilated. The clinical assessment of the degree of aortic incompetence is roughly paralleled by the plethsmographic assessment. It is hoped to reveal a closer correlation by means of animal experiments, where the degree of aortic incompetence may be varied at will, and where the arterial and venous pressure and flow may be recorded by direct techniques, with simultaneous plethysmographic measurement. Cardiac catheterisation via the femoral artery together with the dye technique of Braunwald and Morrow combines descriptive (though not necessarily interpretive) simplicity of regurgitant flow with accessory information on aortic stenosis and mitral lesions. The plethymographic technique on the other hand does not involve any surgical intervention and may therefore be more conveniently performed as often as required. It may well, under certain specified conditions, provide a more accurate assessment of the percentage aortic regurgitant flow, and for this reason it is hoped that it may be developed for routine clinical use (AU)

A method for the estimation of regurgitant blood flow in aortic incompetence - Part 1

The introduction to this paper outlines the historical approach to the condition of aortic incompetence in man. The accompanying 'visible pulsation' which was described by Corrigan in 1832, has been attributed both to aortic regurgitant flow and to changes in the peripheral vascular system which are often present in this disease. Thus Stewart in 1908 stated that in severe cases 'the volume of blood that regurgitates is negligible', while Wiggers in 1931 believed that 'in advanced stages of the disease a large reflux obtains'. It is now generally believed that regurgitant flow may be considerable. Mackey had observed in 1960 that the forearm blood flow of a patient with aortic incompetence as measured by plethysmography, was critically related to the occlusive collecting pressure, often being maximal in the region of 80 mm to 100 mm Hg. It was felt that these high pressures the occlusive cuff was acting in a valve-like manner in that it prevented the reflux of arterial blood at pressures below that of the cuff. Conversely there is also obstruction to forward flow at these pressures and the technique described in this paper was developed to allow the normal forward flow of blood into the arm but to prevent any subsequent backflow. This technique consists of a 'pulsating' arterially occlusive cuff which is timed from the R wave of the electrocardiogram and is only inflated during the regurgitant phase of the cardiac cycle. Results indicate that in severe cases regurgitant flow in the arm may amount to 60 per cent of the initial forward flow, while patients diagnosed clinically as having moderate incompetence have backflows ranging from 10 to 40 per cent. These figures are in good agreement with those obtained on the same patients using the dye technique of Braunwald and Marrow (AU)

The use of B-thiopropionic acid for the analysis of mixtures of adrenaline and noradrenaline in plasma by the flourometric trihydroxyindole method

The use of B-thiopropionic acid for the stabilisation of the flourescence of the final solutions in the trihydroxyindole method of analysis of adrenaline and noradrenaline is described. Reliable plasma analysis with a methodological error of about ñ0.1 ng may be achieved using this thio-acid, and the Turner 111 flourometer (AU)

An investigation to devise an index for the measurement of the degree of aortic incompetence - abstract

From earlier investigations it seemed that under certain conditions a pneumatic cuff acted like a valve on the peripheral blood vessels in a limb when it was inflated to certain pressures. It was therefore decided to see whether a pneumatic cuff could be employed as a valve on the brachial artery in aortic incompetence , and by obstructing the regurgitant flow of blood provide a means of measuring its volume. The procedure adopted was to measure forearm and hand blood flow plethysmographically and examine the influence of various pneumatic cuff pressures on this blood flow. It was interesting to observe in some instances how effectively this approach increased the forward flow. However, a cuff with a steady pressure is unlikely to be a satisfactory "valve", and it was therefore decided to improve on this approach by having a pressure cuff in which the pressure could be quickly applied and released at any desired point in the cardiac cycle. Thus, in aortic incompetence where regurgitation was likely to occur, the cuff could be released only during the ejection phase and applied for the remainder, or regurgitant part, of the cardiac cycle. The basis of this technique was to employ an electrocardiograph and trigger from its R-wave a sliding pneumatic valve which applied or released the pressure at pre-determined times during the cardiac cycle. The use of this approach has been compared with the earlier technique and has produced greater forward flows, as measured plethysmographically, in the forearm and hand. The purpose of this communication is to describe these techniques and demonstrate the results obtained by the two methods in measuring regurgitation in the brachial artery in aortic incompetence. It is hoped that an accurate index of aortic incompetence may be eventually obtained by the use of these techniques (AU)

An investigation into the processes underlying the alpha rythm of the human electroencephalogram

The visual reaction time and the behaviour of the alpha rhythm during this test was examined. Normally the alpha rhythm, a sinusoidal electrical charge of about 10 cycles per second, disappears about 0.3-0.5 seconds after a light appears in front of a subject in a darkened room (alpha rhythm disappearance time). Other stimuli such as sound and touch are less effective in stopping this rhythm. Experiments were carried out to determine whether the disappearance of the alpha rhythm bore any relationship to the complexity of the visual reaction time test employed. The response of a subject to a simple reaction time test was much shorter (0.15-0.2 seconds) than the alpha rhythm disappearance time. The visual reaction time to various pattern of light was then investigated. This was found to vary between 0.3 and 0.5 seconds and so seemed to parallel the alpha rhythm disappearance time. However, examination of the individual records showed that the relationship was not a direct one. The records showed that the response to a complex visual stimulus in some subjects occurred before the disappearance of the alpha rhythm disappearance time. These results suggest that the alpha rhythm per se has little to do with visual perception or the motor responses derived from this. Experiments were then carried out by the author to examine whether the alpha rhythm disappearance time to a visual stimulus could be conditioned to a sound stimulus and this proved to be the case. The subject learned subconsciously to block his alpha rhythm with a sound stimulus by the formation of a conditioned response to this stimulus. The rhythm was not only depressed in the occipital (visual) but also in the temporal (auditory) and frontal areas. This also lends support to the idea that the alpha generator is sub-cortical. The author believes that the alpha rhythm may result from the to and fro passage of impulses in the postulated cortico- thalamic feedback system; thus, loss of consciousness or sleep which are accompanied by slower waves of about 3 cycles per second (delta waves) might be due to the lenghtening of this pathway or the inexcitability of one of its components (Summary)