O2 and CO2 levels in blood

Oxygen saturation is the percentage of haemoglobin that is saturated with oxygen CO2 produces carbonic acid and the acid dissociates H+ ions in plasma, and this is the basis of measurement of Co2 concentration in blood.

Can be measured- Invasively- by removal of blood sample from the patient Non-invasively- with no removal of blood

The Conditions It Is Used Technology How it Works The Conditions It Is Used Pulse oximeter Measures O2 Device like a peg sits on the finger and measures the transmission of light through tissues Measures the amount of oxygen in arterial blood There is a large difference between red light absorbed by haemoglobin compared to oxyhaemoglobin Used to measure the oxygen saturation of the blood in patients undergoing any procedure that requires anaesthesia or sedation or those whose breathing or circulation is abnormal

PULSE OXIMETER and CONDITIONS WHERE IT IS USED The pulse oximeter is a non – invasive technique which measures the concentration of oxygen in the body. The device is either attached to the finger or ear lobe of the patient, which measures oxygen saturation with haemoglobin and pulse rate. The oximeter works in the following way: a light source passes through the blood. Different amounts of light are absorbed depending on the degree of saturation of oxygen to haemoglobin. A processor then calculates the light absorption rate and converts this to saturation of haemoglobin.

Oximeters are used in many hospital situations even though they do not measure carbon dioxide levels. They are used as monitoring units during anaesthesia. They are very efficient because they can be used during surgery or after surgery to monitor oxygen saturation, pulse rate and blood flow. Oximeters can be used in the success of ventilation procedures, to see if the administration of oxygen is successful for the patient. Oximeters can also be used in intensive care units or after surgery to monitor unconscious patients and to notify nurses/doctors of any changes in oxygen levels. Therefore, oximeters are an efficient monitoring system for oxygen, pulse and blood flow levels.

The Conditions It Is Used Technology How it Works The Conditions It Is Used Arterial blood gas (ABG) analysis Measures O2 and CO2 Uses electrochemical methods Measures partial pressure (or the concentration) of O2 and CO2 in the blood Measures saturation of oxygen (which is the amount of oxygen combined to haemoglobin compared to the maximum) Measures levels of bicarbonate and pH (which show CO2 levels) This analysis evaluates how effectively the lungs are delivering oxygen and removing carbon dioxide Used when there are signs of dangerously low oxygen or high carbon dioxide levels Helps for diagnosing as well as monitoring patients Helpful for monitoring patients under anaesthesia, in intensive care, in accident or emergency facilities and for premature babies Eg, a patient in a coma can have their blood gases regularly monitored

BLOOD GAS ANALYSER and CONDITIONS WHERE IT IS USED Invasive technique. (Goes inside the body) Takes small samples of arterial blood. The analyser measures the oxygen using two electrodes. Oxygen diffuses through a membrane between the two electrodes. This produces a small electric current. This current is proportional to the amount of oxygen. e.g. certain values equal certain amounts of oxygen.

Carbon dioxide levels are also measured by placing the blood specimen in one chamber and the other chamber a hydrogen electrode. Dissolved carbon dioxide diffuses into the hydrogen ion chamber. The pH is then measured. The hydrogen ion concentration is proportional to carbon dioxide levels. E.G. certain values equal certain amounts of carbon dioxide. Alternatively instead of taking a blood sample an arterial probe, which is inserted into the body, may take these measurements. Blood gas analysers are commonly used in intensive care units especially baby care units and labour wards. This is due to the fact that slight changes in carbon dioxide levels can affect the development of newly born babies. Excess carbon dioxide and poor oxygen saturation levels can have detrimental affects on the child. The analyser is used as a measuring tool to ensure the patient is looked after and if oxygen/carbon dioxide levels change a nurse/doctor can take necessary action to return oxygen/carbon dioxide levels to their optimum values.