5.pulse oximeter

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Pulse Oximeter Definition: -

The pulse Oximeter is a photoelectric instrument for

measuring oxygen saturation of blood.


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Purpose:

A pulse Oximeter measures the amount of oxygen present in blood by

registering pulsations within an arteriolar bed (an area between arteries

and capillaries).

It is a noninvasive method widely used in hospitals on newborns,persons with pulmonary disorders, and individuals undergoing

pulmonary and cardiac procedures.

Oxygen levels can be estimated during exercise , surgery, or other

medical procedures, or while a person is asleep.


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Description: -

The Oximeter consists of a light-emitting diode (LED), a photodetectorprobe containing a permanent or disposable sensor.

The device works by emitting beams of red and infrared light that are

passed through a pulsating arteriolar bed.

Sensors detect the amount of light absorbed by oxyhemoglobin and

deoxyhemoglobin in the red blood cells.

The ratio of red to infrared light measured by the photodetectorindicates the amount of oxygen present in the blood.

The sensor is attached to the body over the arteriolar area in the ear,

the fingertip, the big toe, or across the bridge of the nose.


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Advantages of Pulse Oximetry


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measures a patient's arterial saturation of oxygen (SaO2) in

seconds; measurements obtained from arterial blood gases

(ABG) can take several minutes to acquire and are usually drawn

by a respiratory therapist, transported to the blood gas lab,measured and finally reported back to the doctor. The information

from an ABG analysis provides for more information than just the

oxygen level and is essential in emergencies, but oximetry is

equally important to ensure the patient does not suffer the effects

of hypoxia unnecessarily.

Speed


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ABG measurements, though exact, require blood drawn from an artery,

which can lead to complications ranging from hematoma to laceration of

the artery. Pulse oximetry is performed on a fingertip and measures

through the nail bed.As long as the oximeter is used properly and iscalibrated regularly, it is easy to use and usually reliable. Good

peripheral circulation in the patient's extremities is critical to obtaining

accurate readings and most oximeters on the market incorporate a

perfusion gauge, usually in LED bar lights, that shows the strength of

the patient's peripheral circulation.When a strong pulse is not present inthe hands or feet, readings can be made with a special adhesive probe

placed on the patient's earlobe or even the bridge of the nose.

Non-Invasive and Reliable


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Limitations in Usinga Pulse Oximeter


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Carbon Monoxide

Carbon monoxide molecules can attach to the patient's hemoglobinreplacing oxygen molecules.A pulse oximeter cannot distinguish the

differences and the reading will show the total saturation level of oxygen

and carbon monoxide. If 15% of hemoglobin has carbon monoxide and

80% has oxygen, the reading would be 95%.

This can be dangerous.

A pulse oximeter should not be used on people with smoke inhalation,

carbon monoxide poisoning, and heavy cigarette smoking.

Hemoglobin Deficiency (Anemia)

Low quantity of hemoglobin may affect the result. The normal values for

a person is 11 - 18 g/dl.


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Blood Volume Deficiency

Conditions, such as hypovolemia, hypotension, and hypothermia, may

have adequate oxygen saturation, but low oxygen carrying capacity.

Due to the reduction in blood flow, the sensor may not be able to pick

up adequately the pulsatile waveform resulting in no signal or loss of

accuracy. Taking measurement on sick patients with cold hands can bechallenging.

Irregular Signals

Irregular signals can post problems for a pulse oximeter. The problemsignals can be caused by irregular heart beats or by patient's

movements. If this is the problem, one can tell by looking at the SpO2

waveform which is available on some pulse oximeters.


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External Interference

Exposure to strong external light while taking measurement may

result in inaccurate readings. Shield the sensors from bright

lights. Strong electro-magnetic fields may also affect readings.

Fingernail Polish and Pressed on Nails

Nail polish and pressed-on nails may interfere with readings.

Remove them.


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Skin Pigmentation

Dark skin pigmentation can give over-estimated SpO2 readings when itis below 80%. Find a place where the skin color is lighter.

Intravenous Dyes

Intravenous dyes can cause inaccurate readings.

Methaemoglobin

Methaemoglobin is a form of hemoglobin that does not carry oxygen.

It is normal to have 1-2% of hemoglobin in this form.A high level of

methaemoglobin would cause a pulse oximeter to have a reading of

around 85% regardless of the actual oxygen saturation level. The

higher percentage of methaemoglobin can be genetic or caused by

exposure to certain chemicals and medications.


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5.pulse oximeter