analyse information from secondary sources to identify current technologies that allow measurement of oxygen saturation and carbon dioxide concentrations in blood and describe and explain the conditions under which these technologies are used.
The Internet is more likely to carry information about current technologies than reference books. Here is a place to begin.
Pulse oximetry Nuffield Department of Anaesthetists, University of Oxford, UK (This site last accessed 12 June 2008)
Assess the reliability by comparing with information from different sources. Information from an organisation, like the World Federation of Societies of Anaesthesiologists, is likely to be more reliable than information from an individual who is not affiliated to any organisation.
Monitoring oxygen and carbon dioxide concentration
One method used by hospitals to monitor blood oxygen and carbon dioxide levels in patient’s blood is to use a pulse oximeter. A small clip with a sensor is attached to the person’s finger, earlobe or toe. A cable connects the sensor to the pulse oximeter machine. The colour of the blood changes according to the amount of oxygen that is dissolved in the blood. Blood that is high in oxygen is bright red while blood low in oxygen is a darker colour. The sensor emits a light signal that passes through the skin. The sensor measures the amount of light absorbed as it passes through the tissue and blood, and transmits the information to the pulse oximeter. A reading is given in a percentage form.
Pulse oximetry is used to monitor the level of oxygen in a person’s blood during heavy sedation or anesthesia. This device is also used when a person is on a ventilator, artificial breathing machine, during stress testing, in sleep laboratories, when checking the body’s response to different medications or to monitor a person with asthma or who is having trouble breathing.
Another method of analysing blood gases is with arterial blood gas (ABG) analysis machines. These can measure the amount of oxygen and carbon dioxide in a sample of blood by monitoring the rate of diffusion of these gases through artificial membranes which are permeable to these gases. When moving through a membrane, oxygen in the blood produces an electrical current while carbon dioxide changes the pH of the solution.