A Pulse Oximeter

This article is therefore intended for the occasional user of pulse oximetry. * Pulse oximeters. Measure the arterial oxygen saturation of haemoglobin. The technology involved is complicated but there are two basic physical principles. First, the absorption of light at two different wavelengths by hemoglobin differs depending on the degree of oxygenation of hemoglobin. Second, the light signal following transmission through the tissues has a pulsatile component, resulting from the changing volume of arterial blood with each pulse beat. This can be distinguished by the microprocessor from the non-pulsatile component resulting from venous, capillary and tissue light absorption. Function of a Pulse Oximeter * The function of a pulse oximeter is affected by many variables, including: ambient light; shivering; abnormal hemoglobins; pulse rate and rhythm; vasoconstriction and cardiac function. A pulse oximeter gives no indication of a patients ventilation, only of their oxygenation, and thus can give a false sense of security if supplemental oxygen is being given. In addition, there may be a delay between the occurrence of a potentially hypoxic event such as respiratory obstruction and a pulse oximeter detecting low oxygen saturation. However, oximetry is a useful non-invasive monitor of a patients cardio-respiratory system, which has undoubtedly improved patient safety in many circumstances.   Pulse Oximeter as part of an anesthetic machine * A portable desktop unit * A finger/mobile pulse Oximeter Indications COPD disease pulse oximetry is useful in stable patients with severe and in patients with worsening symptoms or other signs of an acute exacerbation, as a tool for patients to use at home to assist with their management * Asthma pulse oximetry complements peak flow meters in assessing the severity of asthma attacks/exacerbations and response to a treatment. * Acute respiratory infection pulse oximetry is useful in evaluating the severity of the illness and, in conjunction with other criteria, determining whether and how to refer pa tients for further treatment. What does a Pulse Oximeter Give? Nursing Responsibilities * Pulse oximetry offers an easy and non-invasive measurement of oxygen saturation, but has limitations and practice considerations that every nurse should be aware of. * Oxygen saturation (SpO2) is a measurement of the percentage of hemoglobin molecules carrying a full load of oxygen. Oxygenated hemoglobin (HbO2) absorbs more infrared light than red light, while deoxygenated hemoglobin (Hb) absorbs more red light. By comparing the relative amounts of different light absorbed, the oxygen saturation (SpO2) can be determined. However, there are some possible causes of erroneous readings: †¢Ã‚  Motion artifact: Movement (shivering or tremors) or improper fit of the sensor can cause erroneously low readings. †¢Ã‚  Hypotension (due to cardiac arrhythmias, blood loss or peripheral vascular disease) and peripheral vasoconstriction (caused by hypothermia, smoking or sickle cell disease) can alter readings. Smoke inhalation or carbon monoxide poisoning can cause high levels of arboxyhemoglobin and also skew pulse oximetry readings.   Response delay: A technical limitation that requires additional time to detect hypoxemia (SpO2  less than 90 percent). The length of delay can be affected by poor sensor site perfusion and vasoactive drugs. * Sensors are sized according to weight and it is important to select the correct size to avoid reading errors.