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Maths and physics for anaesthetists : blood gas analysis.
Hill, D. W
Blood Gas Analysis
In the second of two lectures, Reader in Medical Physics, Dr DW Hill, making use of a large array of animated diagrams, talks about the combination of maths and physics which control how anaesthesia affects the human body. The two lectures provide a highly detailed, although technical look at the mechanics of respiration and blood flow - this part focuses on the analysis of blood gases. For those not well-versed in medical physics, the many illustrations and the clear explanation of the subject make this lecture quite accessible.
Segment 1 Hill narrates over a film of surgery taking place in an operating theatre. He describes how the measurement of blood gases and the pH of a patient's blood is frequently checked during anaesthesia. Hill talks to camera about which systems are the most efficient for measuring blood gas pH - the pH value is the measure of its acidity or alkalinity. Hill demonstrates how this can be measured using electrode potentials and how this can be applied to the study of blood pH levels - he uses animated models to illustrate this. Time start: 00:00:00:00 Time end: 00:06:19:00 Length: 00:06:19:00 Segment 2 Hill continues to discuss, and demonstrate, how pH electrode potentials can be used to measure blood pH levels during anaesthesia. He shows a film in which a pH electrode pair are demonstrated practically. Time start: 00:06:19:00 Time end: 00:09:26:00 Length: 00:03:06:00 Segment 3 Hill shows graphs and a film demonstrating how to make accurate measurements of blood gas pH using a blood pH meter, he describes the way the meter works in depth. He then shows the correct method of taking blood for pH testing as arterial blood must be used and this must be taken from one of the arteries deep in the wrist. Hill now refers to two films: the first shows how blood pH is measured on a non-automatic blood gas analyser machine, the second shows how blood pH is measured on an automatic blood gas analyser machine. After this, Hill shows a table comparing blood gas levels. He then introduces the new technique of direct reading PCO2 electrodes - a sensitive glass electrode which can measure the pH of a blood sample when prepared in a sodium bicarbonate solution. Time start: 00:09:26:00 Time end: 00:17:34:00 Length: 00:08:08:00 Segment 4 Hill shows a film demonstrating the PCO2 glass electrode technique for testing blood gas pH levels. He then introduces the polarographic oxygen electrode which works in a similar way. A film is shown to demonstrate this method. A further film shows demonstrations of both automatic and manual blood gas analysers. Hill then sums up the lecture, reminding the viewer that accurate blood testing and the correct use of blood gas analysis machines is essential to maintain the health of a patient during anaesthesia, or during time in intensive care. Time start: 00:17:34:00 Time end: 00:24:37:06 Length: 00:07:03:06
Presented by DW Hill, Reader in Medical Physics. Produced by David R Clark and Michael Tomlinson. Film extract provided by courtesy of Dr JT Wright, Bio-engineering and Medical Physics Unit, University of Liverpool. Made for British Postgraduate Medical Federation. Made by University of London, Audio-Visual Centre.
This video is one of around 310 titles, originally broadcast on Channel 7 of the ILEA closed-circuit television network, given to Wellcome Trust from the University of London Audio-Visual Centre shortly after it closed in the late 1980s. Although some of these programmes might now seem rather out-dated, they probably represent the largest and most diversified body of medical video produced in any British university at this time, and give a comprehensive and fascinating view of the state of medical and surgical research and practice in the 1970s and 1980s, thus constituting a contemporary medical-historical archive of great interest. The lectures mostly take place in a small and intimate studio setting and are often face-to-face. The lecturers use a wide variety of resources to illustrate their points, including film clips, slides, graphs, animated diagrams, charts and tables as well as 3-dimensional models and display boards with movable pieces. Some of the lecturers are telegenic while some are clearly less comfortable about being recorded; all are experts in their field and show great enthusiasm to share both the latest research and the historical context of their specialist areas.