F6.iv · Ventilation-Perfusion Relationships

This viva discussed arterial blood gases, dead space, the measurement of carbon dioxide and capnography.

This Viva tested knowledge of respiratory physiology. It explored the understanding of ventilation and perfusion of the lung, dead space and moved on to discuss capnography.

This Viva tested knowledge of respiratory physiology and measurement. It explored understanding of capnography and moved on to discuss dead space.

This focused upon knowledge of aspects of respiratory physiology, measurement and oxygen delivery. Candidates were shown a chest X-ray, and told it represented complete collapse of the left lung. The opening question was what processes might contribute to hypoxia in that patient. It viva then went on to examine knowledge of shunt, dead space and measurement of oxygen. Overall most candidates performed well, with overall the depth of knowledge of the physiological mechanisms of hypoxia being the area of weakness.

The initial information given to the candidates was - In this station you will be asked to draw and discuss a capnograph tracing. Draw a graph of partial pressure of CO2 versus time, from a ventilated patient, i.e. a ‘capnograph tracing’. This viva explored the candidates’ knowledge in relation to the following points Capnograph trace and information that can be ascertained from it Methods used to measure partial pressure of CO2 and the underlying principles ETCO2 and PaCO2 relationships and factors that influence it Capnograph and deadspace Examination feedback: General there was a lack of depth in the understanding of the capnograph. Specifically what it measures, principles of measurements and an understanding of deadspace.