Oxygen Therapy: Indications & Patient Management

Instructor: Jennifer Pettigrew

Jennifer has a master's degree in nursing and been a clinical instructor for BSN students.

In this lesson, we'll discuss what causes someone to need supplemental oxygen, devices that can be used to deliver oxygen and how to monitor patients receiving oxygen therapy.

Out of Thin Air

Most people know we need to breathe oxygen to survive, but did you know that the air you're breathing now is made up of a mixture of gases that are mostly NOT oxygen? In fact room air, the air surrounding us that we breathe in, is only 20.9% O2 (oxygen). Health care providers refer to this percentage as the FiO2, or fraction of inspired oxygen.

When Does A Patient Need Oxygen Therapy?

Oxygen therapy (delivery of oxygen at a higher concentration than room air (at a higher FiO2)) is used to treat hypoxia, which is a condition of very low concentration of oxygen in the tissue. Hypoxia is caused by hypoxemia a condition of low oxygen in the blood. This makes sense because if there isn't enough oxygen in the blood, the blood can't deliver enough oxygen to the body tissues as it circulates.

A pulse oximeter is used to estimate oxygen saturation

Oxygenation is usually measured using:

  • Pulse oximeter (most common) measures estimated oxygen saturation or SpO2 using a sensor applied to the skin. These sensors can be intermittent or continuous and this test is non-invasive.
  • ABG or arterial blood gas (most accurate) tested by drawing blood from a patient's artery and testing it using laboratory equipment to determine the level of O2 in arterial blood). This is painful and intermittent.

Regardless of how the level of O2 in someone's blood is determined, a low level of O2 is the main reason for delivery of oxygen therapy to a patient.

Symptoms of hypoxia include:

  • shortness of breath
  • anxiety or agitation (may progress to somnolence if not treated)
  • fast heart rate & increased blood pressure (may progress to low heart rate and low blood pressure if not treated)
  • paleness (may progress to cyanosis (blue tinge to tissue) if not treated)
  • headaches (may progress to confusion, blurred vision, loss of muscle coordination and eventually coma if not treated)

Potential causes of hypoxia include:

  • Neurological causes: any brainstem damage or neurologic disease that affects the body's ability to appropriately regulate breathing.
  • Cardiovascular: anemia (or low hemoglobin; hemoglobin is the part of blood that carries oxygen to tissues), heart problems (diseases that weakens the heart (heart attack, congestive heart failure, heart rhythm problems etc) which can affect the ability of the body to circulate oxygenated blood).
  • Toxins: cyanide poisoning, carbon monoxide poisoning, medications (including narcotics) that depress respiratory drive
  • Lung diseases: asthma, COPD, bronchitis, pneumonia, trauma etc

The long-term solution is to figure out why the patient is experiencing hypoxemia and/or hypoxia and reverse the cause. In the meantime, however, oxygen can be administered in higher concentrations to support the patient.

Oxygen Delivery Devices and Patient Management

Oxygen delivery devices can be divided into two categories. The first group listed below has one basic job: they deliver oxygen, but they don't do anything else to assist with breathing. They are used for patients who can breathe on their own but who aren't getting enough oxygen for any number of reasons.

Oxygen via nasal cannula can be used by patients in settings other than the hospital

Patients who can't adequately perform the work of breathing, either due to neurological or musculoskeletal issues, an airway obstruction or something else may require assistance with the physical act of breathing. This can take the form of using air pressure to make breathing easier (non-invasive), or inserting a tube into the airway and attaching it to a machine (ventilator) that will take over the act of breathing for the patient, as well as delivering oxygen (invasive).

Here you can see the reservoir bag below the non-rebreather mask as this patient receives high flow oxygen

Devices That Only Deliver Oxygen

Name Liters/Percentage FiO2 Indications and Management
nasal cannula 2-6 L/ 24%-50% FiO2 Used for patients with minor hypoxia or increased work of breathing and patients who won't tolerate a mask.
simple face mask 5-10 L/ 35%-60% FiO2 High-flow oxygen required to prevent rebreathing of CO2, which occurs when a patient breaths in CO2 that they just exhaled. The patient still breathes large percentage of room air (up to 75%) through holes in the side of the mask.
non-rebreather 6-15L/ 60%-80% FiO2 or more Do not administer fewer than 6L/min due to the risk of rebreathing CO2. A valve closes during expiration to keep expired air from entering reservoir bag. Additional valves on the side of the mask open during exhalation but close during inhalation to prevent breathing of room air. Do not allow reservoir bag to deflate due to the risk of rebreathing CO2.
Venturi mask 10L/ 21%-100% FiO2 Used to deliver precise concentrations of oxygen in critically ill patients or patients with COPD (due to low CO2 build-up).

Devices for Patients Requiring Ventilation Assistance

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