Pulse Oximetry

PULSE OXIMETRY

DEFINITION: • Pulse oximetry is a non invasive method allowing the

monitoring of the oxygenation of a patients haemoglobinPULSE OXIMETER DEFINITION:• A pulse oximeter is a medical device that indirectly

monitors the oxygen saturation of a patient's blood (as opposed to measuring oxygen saturation directly through a blood sample) and changes in blood volume in the skin, producing a photoplethysmograph.

Plethysmographic trace (Pleth)

• Pulse oximeters often show the pulsatile change in absorbance in a graphical form. This is called the "plethysmographic trace” or more conveniently, as "Pleth".

How does a Pulse Oximeter Work?

• The measurements are obtained by simply shining two wavelengths of light (1 is a visible red beam, the other an invisible infrared beam) at e.g. the fingertip.

TYPES-OF Pulse Oximeters

Desktop Finger/mobile

Desktop

Finger/mobile

Pulse Oximeters may be used in patients:

Undergoing surgical procedure under general anesthesia

Undergoing surgical procedure under conscious sedation

Pulse Oximeters may be used in patients:

Emergency situations like loss of consciousness, trauma etc.

After surgery during the recovery phase

• In the ICU, Pulse Oximetry is used extensively on mechanically ventilated patients

Pulse Oximeters may be used in patients:

• Pulse Oximeters are routinely used in certain hospital wards and in casualty departments for immediate assessment of patients

Pulse Oximeter reading may not be accurate

Venous congestion (partial obstruction of the veins) of an arm or leg

Reduced peripheral pulsatile blood flow

Bright overhead lights, such as in an operating theatre

Shivering or significant, repeated movement of the sensor

Pulse Oximeter reading may not be accurate:

• Pulse oximetry struggles to distinguish between different forms of hemoglobin, such as carboxy-hemoglobin

• Nail varnish may cause falsely low readings with most pulse Oximeters, especially those colored blue or black

The following won’t affect the Pulse Oximeter reading:

Anemia Jaundice

But what is a "normal" reading?

• A fit, healthy person should have an oxygen saturation level between 95% & 99%. Results lower than this, and especially below 90% may be caused by problems including lung diseases, such as COPD, breathing difficulties, cigarette smoking or circulatory problems such as excessive bleeding or blood vessel problems.

What happens to the pulse Oximeter reading of a patient immediately after a cardiac arrest?

• The pulse would be lost (causing the alarm to sound) and the saturations will decrease