Home . The Importance of Pulse Oximetry

The Importance of Pulse Oximetry

Pulse oximetry is a method of monitoring a patientís cardio-respiratory status. Pulse oximetry tests are now a standard part of preoperative monitoring which gives the operator a non-invasive look at the cardio-respiratory status. Itís been successfully used in intensive care, the recovery room and during anesthesia; they have been introduced in other areas of medicine as well.

What does it measure?
The Criticare Pulse Oximetry measures the oxygen saturation of hemoglobin in arterial blood which is a measure of the average amount of oxygen bound to each hemoglobin molecule. The percentage saturation is given as a digital readout together with an audible signal varying in pitch depending on the oxygen saturation. It also measures the pulse rate in beats per minute, averaged over 5 to 20 seconds.

Why use a pulse oximeter?
Pulse oximeters may be used in a variety of situations but are of particular value for monitoring oxygenation and pulse rates throughout anesthesia. They are also widely used during the recovery phase. The oxygen saturation should always be above 95%. In patients with long standing respiratory disease, or those with cyanotic congenital heart disease, readings may be lower and reflect the severity of the underlying disease.

In intensive care pulse oximetry tests are used extensively during mechanical ventilation and frequently detect problems with oxygenation before they are noticed clinically. They are used as a guide for weaning from ventilation and also to help assess whether a patient's oxygen therapy is adequate.

How does the device work?
The Criticare 503DX Pulse Oximetry consists of a probe attached to a patient's finger or ear lobe which is linked to a computerized unit. The unit displays the percentage of Hb saturated with oxygen together with an audible signal for each pulse beat, a calculated heart rate and in some models, a graphical display of the blood flow past the probe. Audible alarms which can be programmed by the user are provided.

Within the probe are two light emitting diodes (LED's), one in the visible red spectrum and the other in the infrared spectrum. The beams of light pass through the tissues to a photo detector. During passage through the tissues, some light is absorbed by blood and soft tissues depending on the concentration of hemoglobin. The amount of light absorption at each light frequency depends on the degree of oxygenation of hemoglobin within the tissues.

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