14-May-15Najwa subuh- MSN in Pediatric1. 14-May-15Najwa subuh- MSN in Pediatric2 A pulse-oximeter is...

Apr 18, 2023 Najwa subuh- MSN in Pediatric 1


• A pulse-oximeter is a device that measures the amount of saturated hemoglobin in blood.

• An oximeter uses blood that has been removed from a patient and placed into a measuring cell where its oxygen content is accurately measured.


O2 SaturationO2 Saturation

- Oxygen capacity, maximum amount of collective oxygen that can be attached to hemoglobin & dissolved in plasma.

- Oxygen content, actual amount of oxygen that is carried in blood & can be different from oxygen capacity.


Oxygen capacity

• One gram of hemoglobin can carry a maximum 1.34ml of oxygen

• In a liter of blood there are 150gm of hemoglobin

• Approximately 10ml of oxygen dissolved in plasma


•In 1 Liter of blood oxygen capacity will be

150 X 1.34X 10= 211ml

If a person is carrying 211ml of oxygen per liter of blood his oxygen saturation will be 100%


Oxygen saturation (SO2)Oxygen saturation (SO2)

Oxygen saturation (SO2)Oxygen saturation (SO2)

oxygen content X100oxygen capacity


SpO2 and SaO2•There is different pulse-oximeter the terms SaO2 & SpO2 and often these are used interchangeably.

•SaO2 refers to the oxygen saturation of arterial blood as measured by a CO-oximeter and SpO2 refers to the oxygen saturation of arterial blood as measured by a pulse oximeter.


What can be learned by monitoring blood What can be learned by monitoring blood oxygen saturation?oxygen saturation?


• Oxygen saturation is an indicator of oxygen transport in the body, and indicates if sufficient oxygen is being supplied to the body, especially to the lungs.

• The pulse oximeter can also measure pulse rate. The volume of blood being pumped by the heart per minute is called the cardiac output.


What is the purpose of the pulse What is the purpose of the pulse oximeter?oximeter?

1. Determining the severity of a disease2. Blood gas analysis3. Deciding on hospitalization of patients with

chronic diseases when in acute phase4. Home oxygen therapy, prescribing oxygen, and

educating patients receiving home oxygen therapy

5. Assessment and risk management of respiratory rehabilitation & exercise therapy

6. Screening for sleep apnea syndrome


Why the difference?Why the difference?

•There is more than one form of hemoglobin. Typically we all have oxyhemoglobin, methemoglobin,

carboxyhemoglobin, sulfhemoglobin & carboxysulf hemoglobin. Admittedly

oxyhemoglobin predominates but the others, the so-called dysfunctional

hemoglobin's are always there.


Does the ratio of PaO2 to SpO2 always Does the ratio of PaO2 to SpO2 always remain the same?remain the same?

•The amount of oxygen dissolved in the blood is proportional to the partial pressure of oxygen. The amount of oxygen bound to hemoglobin will increase as the partial pressure of oxygen increases.

• In contrast, the amount of oxygen bound to hemoglobin does not increase in proportion to the partial pressure of oxygen.


• If the body temperature decreases and pH increases, the curve will shift to the left. If the temperature increases and pH decreases, the curve will shift to the right.

• In the following graph, the low pH curve shows that when PaO2 is 80mmHg (Torr), oxygen saturation is 80%.


How Does Pulse Oximetry Work?

• Pulse oximeter is medical devices that measure the pulse rate and the amount of oxygen saturation of the blood. More specifically, they measure the arterial oxygen saturation of the hemoglobin

• This process emits light from an oximeter and measures the transmission and absorption of the light by the hemoglobin in the blood.

• A microprocessor in the device uses this information to calculate your pulse and oxygen saturation. In order for the light to reach the blood, the oximeter is attached to a relatively translucent part of your body with good blood flow, such as your finger. This procedure is instantaneous, painless and noninvasive.


Oxygen Saturation• The goal of breathing and blood circulation is

to deliver oxygen to all areas of the body. Oxygen is carried in the blood by the protein hemoglobin, which chemically binds oxygen molecules to itself. Each molecule of hemoglobin is capable of carrying four molecules of oxygen.

• Oxygen saturation is the quantity of hemoglobin that is carrying oxygen versus the total amount of hemoglobin in the blood. Normal levels of oxygen saturation are 95- 100% depending on age.


• This means that 95-100% of all available hemoglobin in the blood should be carrying oxygen. Any reading <90% can lead to life-threatening complications.

• Certain factors can cause a decrease in oxygen saturation such as disease, aging, carbon monoxide poisoning and a traumatic injury.

• Low levels of oxygen saturation indicate that hypoxic (oxygen starved) and require medical treatment and supplemental oxygen.


• The percentage of oxygenated hemoglobin and deoxygenated hemoglobin is determined by measuring the ratio of infrared & red light detected by the pulse oximeter.

• The pulse oximeter emits red (R) and infrared (IR) LED light that passes through the body, receives data from a photo detector, and calculates the oxygen saturation by determining the ratio of the two waveforms.


What does a pulse oximeter What does a pulse oximeter measure?measure?

• 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.


Principles of modern pulse Principles of modern pulse oximetryoximetry

• Oxygen is carried in the bloodstream mainly bound to hemoglobin. One moleculeOne molecule of hemoglobin can carry up to four moleculesfour molecules of oxygen, which is then 100% saturated with oxygen.

• In addition, a very small quantity of oxygen is carried dissolved in the blood, which can become important if the hemoglobin levels are extremely low. The latter, however, isn't measured by pulse oximetry.


• The relationship between the arterial partial pressure of oxygen (PaO2) and the oxygen saturation is described by the hemoglobin-oxygen dissociation curve.

• The sigmoid shape of this curve facilitates unloading of oxygen in the peripheral tissues where the PaO2 is low and oxygen is required for respiration. The curve may be shifted to the left or right by various patient characteristics e.g. recent blood transfusion, pyrexia


What factors cause errors in the pulse What factors cause errors in the pulse oximeter?oximeter?

1. Abnormal hemoglobin2. Medical dyes3. Manicure and pedicure4. Major body motion5. Blood flow blocked due to pressure on arms

or fingers6. Peripheral circulatory failures7. Excessive ambient light (panel lamp,

fluorescent lamp, infrared heating lamp, direct sunlight, etc.)

8. Ambient electromagnetic waves9. Probe attached incorrectly


Alarms• If the Low Oxygen Saturation alarm sounds, check that the

patient is conscious if that is appropriate. Check the airway and make sure the patient is breathing adequately. Lift the chin or apply other airway maneuvers as appropriate. Give oxygen if necessary. Call for help.

• If the Pulse Not Detected alarm sounds, look for the displayed waveform on the pulse oximeter. Feel for a central pulse. If there is no pulse, call for help, start the procedures for Basic and Advanced Life Support. If there is a pulse, try repositioning the probe, or put the probe on a different digit.

• On most pulse oximeter, the alarm limits for oxygen saturation and pulse rate can be altered according to your needs. However, do not alter an alarm just to stop it sounding - it could be telling you something important!

14-May-15Najwa subuh- MSN in Pediatric1. 14-May-15Najwa subuh- MSN in Pediatric2 A pulse-oximeter is...

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