Oxygen Therapy: Nasal Cannula or Oxygen Mask (Ambulatory) - CE/NCPD

The content in Clinical Skills is evidence based and intended to be a guide to clinical practice. Always follow your organization’s practice.

ALERT

Oxygen is considered a medication and requires a practitioner’s order; administer it cautiously and observe the patient closely for adverse reactions.

Use caution in the presence of oxygen. Oxygen is a fire hazard because it lowers the temperature at which materials catch fire in the presence of an ignition source, such as a spark or heat from a light source.

Respiratory depression can develop in a very small percentage of patients who are chronically hypercapnic when breathing moderate to high oxygen concentrations.^{undefined#ref1">1}

OVERVIEW

The goal of oxygen therapy is to maintain adequate levels of oxygen to manage suspected or confirmed hypoxemia. Signs and symptoms of hypoxia include restlessness, anxiety, disorientation, confusion, and fatigue (Box 1).

Two types of oxygen delivery systems are high flow and low flow. Selection of the type of oxygen therapy is based on the patient’s need, the severity of hypoxemia, and the disease process. A prescription is required for oxygen therapy. The prescription should include the oxygen-delivery device, the flow rate, and the amount of oxygen to deliver.²

The target peripheral oxygen saturation (SpO₂) for most acutely ill patients is 94% to 98%.¹ Patients with chronic obstructive pulmonary disease should have a target of 85% to 92%.¹

Devices that deliver oxygen therapy include a nasal cannula, various types of face masks, and oxygen tents and hoods (Table 1).

A nasal cannula is a simple, effective, comfortable device for delivering low-flow oxygen (Figure 1).¹ It consists of two prongs protruding from the center of a disposable tube and inserted into the nostrils. The nasal cannula allows breathing through the mouth or nose, is available for all age groups, and is adequate for short- or long-term use. Compared with other oxygen delivery systems, a nasal cannula does not produce a feeling of claustrophobia, but it may not be suitable for mouth breathers. Cannulas are inexpensive, disposable, and easily accepted by most patients.

Approximate FIO₂ is estimated by the flow rate. The delivered oxygen percentage varies, depending on the rate and depth of the patient’s breathing.¹ When cannulas are used at high-flow rates, the patient’s airway mucosa may dry. A humidifier filled with sterile water should be used to help prevent drying of the nasal and oral mucous membranes if the flow rate is greater than 4 L/min.¹

A simple face mask is for short-term, low-flow oxygen therapy (Figure 2).¹ A clear plastic mask is placed on the patient’s face and secured with an elastic strap. The body of the mask stores oxygen between the patient’s breaths. Side port openings located on either side of the mask allow room air to mix with delivered oxygen and allow exhaled air to escape. The percentage of delivered oxygen varies, depending on the rate and depth of the patient’s breathing.¹ Using a simple mask with a flow rate less than 5 L/min causes the mask volume to act as dead space and causes carbon dioxide rebreathing.³ Some patients find a face mask uncomfortable, and it must be removed for eating.

A partial rebreather mask is a face mask with a reservoir bag that delivers moderate to high concentrations of oxygen (Figure 3A).¹ Frequent inspection of the reservoir bag is required to ensure that it remains inflated; if it is deflated, exhaled air collects in it, which results in the patient rebreathing large amounts of exhaled carbon dioxide. Side port openings on either side of the mask vent exhaled air on expiration and allow room air to enter the mask on inspiration. The delivered oxygen percentage varies, depending on the rate and depth of the patient’s breathing.¹

A non-rebreather mask is a face mask with a reservoir bag that delivers high concentrations of oxygen (Figure 3B).¹ A one-way inspiratory valve sits on top of the reservoir bag, and a one-way expiratory valve covers one of the side ports on the mask. During inhalation the expiratory valve over the side port closes, preventing air from entering the mask while the inspiratory valve on top of the reservoir bag opens, providing oxygen to the patient. During exhalation, the expiratory valve opens allowing exhaled air to vent out of the mask while the inspiratory valve closes preventing exhaled air from entering the reservoir bag. The open exhalation port is a safety feature designed to allow air to enter the mask if the oxygen source fails. However, this feature can result in dilution of the inspired oxygen. The delivered oxygen percentage varies, depending on the rate and depth of the patient’s breathing.¹

A Venturi mask is a cone-shaped device with entrainment ports of various sizes at its base (Figure 4).¹ The entrainment ports can be adjusted to deliver various oxygen concentrations. This mask is useful because it delivers high-flow oxygen and a more precise concentration of oxygen to the patient.

SUPPLIES

See Supplies tab at the top of the page.

EDUCATION

• Give developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, preferred learning style, and overall neurologic and psychosocial state.
• Provide the patient with an explanation of the equipment and the procedure.
• If oxygen therapy will continue after discharge, teach the patient the importance of and rationale for oxygen therapy as well as the safety precautions for oxygen use.
  • Explain to the patient that oxygen increases the risk of combustion and that activities that increase the risk of a fire (such as smoking or open flames) or activities that could create sparks are not allowed.
  • Explain to the patient that all electrical equipment near an oxygen source must be properly grounded to prevent electrical sparks, which can lead to a serious fire.
  • Ensure that the patient has oxygen tanks or an oxygen concentrator at home.
  • Encourage the patient to drink plenty of fluids to help prevent drying of the mucosa unless contraindicated.
• Explain how to use the oxygen delivery device, how to contact the supplier of medical equipment, and when to contact the practitioner.
• Ensure that a referral for home oxygen is in place so that the patient has continuity of care and a decreased risk of hypoxia.
• Inform the patient that any oxygen delivery device may irritate the skin and instruct the patient to inspect the skin frequently and to report any changes in appearance.
• Encourage questions and answer them as they arise.

PROCEDURE

1. Determine if the patient has health literacy needs or requires tools or assistance to effectively communicate. Be sure these needs can be met without compromising safety.
2. Review the patient’s previous experience and knowledge of oxygen therapy and understanding of the care to be provided.
3. Evaluate the patient’s respiratory status, including the symmetry of chest wall expansion, respiratory rate and depth, sputum production, and breath sounds.
4. Evaluate the patient for signs and symptoms of hypoxia (Box 1).
5. Observe the patient for behavioral changes (e.g., apprehension, anxiety), decreased level of consciousness (LOC), or light-headedness.
6. Evaluate the patient’s airway patency. If secretions are present, encourage the patient to cough and expectorate mucus (as needed).
7. Evaluate the patient’s vital signs and the SpO₂ value.
8. Inspect the condition of the patient’s skin around the nose and ears.
9. Set up the oxygen delivery system.
   1. Attach the oxygen flowmeter to the oxygen source (Figure 5).

      Verify that the flowmeter is connected to oxygen, not air or another gas. Connecting the flowmeter to a gas other than oxygen can have fatal consequences.

   2. Attach the humidifier to the oxygen flowmeter, if needed.

      Rationale: Humidity prevents drying of nasal and oral mucous membranes and airway secretions. Humidification should be used if the liter flow rate is greater than 4 L/min.¹

   3. Attach the oxygen delivery device (i.e., cannula, mask) via the oxygen tubing to the humidifier or directly to the oxygen flowmeter via the flowmeter adaptor.
   4. Adjust the oxygen flowmeter to the prescribed flow rate (Figure 5).
10. Position the oxygen delivery device on the patient’s face and adjust the elastic headband (or behind-ear loops and under-chin lanyard of the cannula) to achieve a comfortably snug fit. Maintain sufficient slack on the oxygen tubing.

    Rationale: The patient is more likely to keep the device in place if it fits comfortably.

    1. Nasal cannula: Ensure proper positioning of the cannula tips in the patient’s nares. If the cannula tips are curved, ensure that they point downward² (Figure 1).

       Rationale: Ensuring proper positioning of the cannula tips directs oxygen flow into patient’s upper respiratory tract. Looping the cannula around the patient’s ears reduces pressure on the nares.

    2. Simple face mask: Ensure that the mask is over the patient’s mouth and nose, forming a seal (Figure 2).
    3. Partial rebreather mask: Ensure that the mask is over the patient’s mouth and nose, forming a tight seal. Ensure that the oxygen flow is high enough to maintain the reservoir bag partially inflated (Figure 3A).
    4. Non-rebreather mask: Ensure that the mask is over the patient’s mouth and nose, forming a tight seal. Ensure that both one-way valves at the side ports are in place to maintain a full non-rebreather system. Ensure that the oxygen flow is high enough to maintain the reservoir bag partially inflated (Figure 3B).
    5. Venturi mask: Ensure that the mask is over the patient’s mouth and nose, forming a tight seal and that the appropriate FIO₂ setting has been selected (Figure 4).

       Rationale: A tight seal reduces carbon dioxide retention.

11. Verify that the oxygen delivery device is functioning properly.

    Rationale: Verification ensures patency of the delivery device and accuracy of prescribed oxygen flow rate.

12. Observe the patient’s vital signs and SpO₂ level when making changes in oxygen therapy.

    Rationale: Changes in oxygen therapy should be based on the patient’s SpO₂ levels.

EXPECTED OUTCOMES

• The signs and symptoms of hypoxia are reduced or eliminated.
• The patient’s vital signs remain stable.
• The patient experiences a decrease in work of breathing.
• The patient tolerates the oxygen delivery device without difficulty.
• The oxygen delivery device fits properly.
• The patient had no facial irritation or skin breakdown from the oxygen delivery device.
• The patient’s SpO₂ values return to target levels.

UNEXPECTED OUTCOMES

• The signs and symptoms of hypoxia are not reduced or eliminated.
• The patient experiences drying of nasal and upper airway mucosa.
• The patient’s vital signs become unstable.
• The patient repeatedly removes the oxygen delivery device.
• The oxygen delivery device is improperly fitting or uncomfortable.
• The patient experiences facial irritation and skin breakdown.
• The patient’s SpO₂ values do not return to target levels.

DOCUMENTATION

• Patient’s tolerance of oxygen therapy and device
• Evaluation of respiratory status or symptoms
• Method of oxygen delivery and flow rate
• Vital signs and SpO₂ level
• Education
• Unexpected outcomes and related interventions

PEDIATRIC CONSIDERATIONS

• Some infants and small children are able to tolerate a nasal cannula. The prongs are secured with tape or strips of transparent dressing over the child’s cheek.
• Typically, infants receive oxygen therapy via an oxygen hood or tent. The hood is placed over the infant’s head (sometimes including the shoulders, if a small infant) with sufficient room between the curve of the hood and the infant’s neck to allow carbon dioxide to escape. The oxygen tent is placed over the infant’s upper body and rests on the sides of the examination table.
• Family members’ presence provides comfort and reassurance to the child and helps decrease anxiety and labored breathing.

OLDER ADULT CONSIDERATIONS

• Because older adults have fragile skin and mucous membranes, adequate hydration and skin care are important.
• The skin should be checked for signs of irritation or breakdown. Padding the skin may be necessary to prevent pressure injuries.

REFERENCES

1. Heuer, A.J., Lombardo, G. (2025). Chapter 42: Medical gas therapy. In J.K. Stoller and others (Eds.), Egan’s fundamentals of respiratory care (13th ed., pp. 900-929). St. Louis: Elsevier.
2. Perry, A.G. (2025). Chapter 23: Oxygen therapy. In A.G. Perry and others (Eds.), Clinical nursing skills and techniques (11th ed., pp. 718-752). St. Louis: Elsevier.
3. Piraino, T. and others. (2022). AARC clinical practice guideline: Management of adult patients with oxygen in the acute care setting. Respiratory Care, 67(1), 115-128. doi:10.4187/respcare.09294

Clinical Review: Genevieve L. Hackney, MSN, RN

Published: January 2025