The Nation's First Private Veterinary Neurology Hospital
Specializing in Canine and Feline Neurology and Neurosurgery

pulse oximeter

Purpose:  Instrument used to measure the arterial oxygen saturation of hemoglobin and pulse rate.  Oxygen saturation is the average amount of oxygen bound to each hemoblobin molecule.  Each erythrocyte (red blood cell) contains millions of hemoglobin molecules and one molecule of hemoglobin can carry up to 4 molecules of oxygen (which is then 100% saturated with oxygen).  This is an indicator of how well the cardio-respiratory system is working together to get oxygen delivered to all parts of the body.  

How Works:  Shines two different wavelengths of light (red and infrared) through a thin piece of tissue, e.g. tongue.  The absorption of light at the different wavelengths by hemoglobin differs depending on the degree of oxygenation of hemoglobin.  The percentage saturation is given as a digital readout together with an audible signal varying in pitch depending on oxygen saturation.  The light signal following transmission through the tissues has a pulsatile component, resulting from the expansion and contraction of the arterial blood vessels with each heartbeat.  This can be distinguished by the microprocessor from the non-pulsatile component resulting from venous, capillary and tissue light absorption.  Where flow is sluggish (e.g. hypovolemia or vasoconstriction) the pulse oximeter may be unable to function.

Example of Uses:  Detect hypoxia before a patient becomes clinically cyanotic.