Pulse Oximeter Readings Normal Range

Pulse oximetry is a way to measure how much oxygen your blood is carrying. By using a small device called a pulse oximeter, your blood oxygen level can be checked without needing to be stuck with a needle.

The blood oxygen level measured with an oximeter is called your oxygen saturation level (abbreviated O2sat or SaO2).

This is a percentage of how much oxygen your blood is carrying compared to the maximum it is capable of carrying.

Normally, more than 89% of your red blood should be carrying oxygen.

How is oxygen transported in the blood?

Oxygen transport to the tissues is dependent on many factors

Oxygen is carried around the body attached to an iron-containing protein called haemoglobin, (Hb) contained in red blood cells. After oxygen is breathed into the lungs, it combines with the haemoglobin in red blood cells as they pass through the pulmonary capillaries. The heart pumps blood continuously around the body to deliver oxygen to the tissues.

There are five important things that must happen in order to deliver enough oxygen to the tissues:

• Oxygen must be breathed in (or inspired) from the air or anaesthesia circuit into the lungs.
• Oxygen must pass from the air spaces in the lung (called the alveoli) to the blood. This is called alveolar gas exchange.
• The blood must contain enough haemoglobin to carry sufficient oxygen to the tissues.
• The heart must be able to pump enough blood to the tissues to meet the patient’s oxygen requirements.
• The volume of blood in the circulation must be adequate to ensure oxygenated blood is distributed to all the tissues.

Pulse Oximeter Readings Normal Range

Maintaining the precise balance of oxygen-saturated blood is vital to your health. Most children and adults don’t need to monitor their blood oxygen level.

However, people with chronic health conditions may need to monitor their blood oxygen level. This includes asthma, heart disease, and chronic obstructive pulmonary disease.

In these cases, monitoring your blood oxygen level can help determine if treatments are working, or if they should be adjusted.

Pulse Oximeter Readings	Blood oxygen level (SpO2)
Normal	95 and 100 percent
Below normal	below 95 percent is considered low
Above normal	If your breathing is unassisted

A measurement of your blood oxygen is called your oxygen saturation level. In medical shorthand, you may hear it called a PaO2 when using a blood gas and an O2 sat (SpO2) when using a pulse oximeter.

These guidelines will help you understand what your result might mean:

Spo2 normal range

A normal ABG oxygen level for healthy lungs falls between 80 and 100 millimetres of mercury (mm Hg).

If a pulse oximeter measured your blood oxygen level (SpO2), a normal reading is typically between 95 and 100 per cent.

However, in COPD or other lung diseases, these ranges may not apply. Your doctor will let you know what’s normal for your specific condition. For example, it isn’t uncommon for people with severe COPD to maintain their pulse ox levels (SpO2) between 88 to 92 per cent trusted Source.

spo2 low

A below-normal blood oxygen level is called hypoxemia. Hypoxemia is often caused for concern. The lower the oxygen level, the more severe the hypoxemia. This can lead to complications in body tissue and organs.

Normally, a PaO2 reading below 80 mm Hg or a pulse oximeter (SpO2) below 95 per cent is considered low. It’s important to know what’s normal for you, especially if you have a chronic lung condition.

Oxygen transport in blood

How much oxygen can hemoglobin carry?

In a patient who is in good health:

• Each gram of haemoglobin combines with 1.34 ml of oxygen: Therefore, in blood with a normal haemoglobin concentration of 15g/dl, 100 ml of blood carries approximately 20 ml of oxygen combined with haemoglobin.
• In addition, a small quantity of oxygen is dissolved in the blood.
• The heart normally pumps approximately 5000 ml of blood per minute to the tissues in an average-sized adult.
• This delivers about 1000 ml of oxygen to the tissues per minute.

How is oxygen transported in the body?

The cells in the tissues extract oxygen from the blood for metabolism, normally around 250ml of oxygen per minute.

This means that if there is no oxygen being exchanged in the lung, there is only enough oxygen stored in the blood for around 3 minutes (only 75% of the oxygen carried by the haemoglobin is available to the tissues).

Safe oxygen levels for humans

Breathing 100% oxygen prior to induction of anaesthesia increases the oxygen stores in the lungs. If a patient stops breathing and is not ventilated, the amount of oxygen in the lungs will rapidly diminish.

If the patient has been given 100% oxygen to breathe for several minutes prior to induction of anaesthesia, the increased oxygen reservoir will supply much-needed oxygen, adding potentially life-saving minutes.

Low hemoglobin symptoms

Anaemic patients have lower levels of haemoglobin and are therefore unable to carry as much oxygen in the blood.

At a haemoglobin concentration of less than 6g/dl, delivery of oxygen to the tissues may become too low to meet the metabolic demands.

Patients who suffer major blood loss during surgery and become acutely anaemic should be given 100% oxygen to breathe.

This will increase the amount of dissolved oxygen in the blood and will improve tissue oxygen delivery by a small amount. A blood transfusion may be life-saving.

What is oxygen saturation?

Red blood cells contain haemoglobin. One molecule of haemoglobin can carry up to four molecules of oxygen after which it is described as “saturated” with oxygen. If all the binding sites on the haemoglobin molecule are carrying oxygen, the haemoglobin is said to have a saturation of 100%.

Most of the haemoglobin in the blood combines with oxygen as it passes through the lungs.

A healthy individual with normal lungs, breathing air at sea level, will have an arterial oxygen saturation of 95%– 100%.

Blood oxygen saturation levels at altitude

Extremes of altitude will affect these numbers. Venous blood that is collected from the tissues contains less oxygen and normally has a saturation of around 75%.

Arterial blood looks bright red whilst venous blood looks dark red. The difference in colour is due to the difference in haemoglobin saturation.

When patients are well saturated, their tongues and lips appear pink in colour; when they are desaturated, they appear blue. This is called cyanosis.

It can be difficult to see cyanosis clinically, particularly in a dark-skinned patient. You may not notice this sign until the oxygen saturation is less than 90%. Detecting cyanosis is even more difficult in a poorly lit operating theatre.

Cyanosis is only visible when the deoxygenated haemoglobin concentration is greater than 5 g/dl. A severely anaemic patient may not appear cyanosed even when extremely hypoxic as there is very little haemoglobin circulating through the tissues.

During anaesthesia, the oxygen saturation should always be 95 – 100%. If the oxygen saturation is 94% or lower, the patient is hypoxic and needs to be treated quickly. A saturation of less than 90% is a clinical emergency.

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