Oxygen Therapy – Complete Nursing Notes

Oxygen Therapy is one of the most important supportive therapies used in nursing and clinical practice. Oxygen is administered when a patient is unable to maintain adequate oxygenation or has an increased demand for oxygen.

These notes cover the complete concept of oxygen therapy including indications, assessment, oxygen delivery devices, flow rates, FiO₂, administration procedure, nursing responsibilities, complications, safety precautions, emergency situations, documentation, FAQs and MCQs.

Quick Revision – Oxygen Therapy

Primary purpose: Improve tissue oxygenation and correct hypoxemia.
Oxygen is a drug: It should be administered according to clinical indication and prescription/protocol.
Most important assessment: Respiratory status + SpO₂ + overall clinical condition.
Common devices: Nasal cannula, simple face mask, Venturi mask, non-rebreather mask and high-flow nasal cannula.
Target SpO₂: Depends on the patient's condition and risk of hypercapnic respiratory failure.
General acute target: Often 94–98% in patients without a risk of hypercapnic respiratory failure.
Risk of hypercapnic respiratory failure: A commonly used target is 88–92% while further assessment is performed.
Major safety rule: Oxygen supports combustion; keep it away from flames, smoking and ignition sources.

Introduction
Definition of Oxygen Therapy
Objectives of Oxygen Therapy
Indications
Contraindications and Precautions
Oxygen Assessment Before Administration
Assessment Sequence in Different Clinical Situations
Oxygen Saturation and SpO₂
Target Oxygen Saturation
Oxygen Delivery Systems
Low-Flow Oxygen Devices
High-Flow Oxygen Devices
Oxygen Masks
Oxygen Flow Rates and Approximate FiO₂
Oxygen Administration Procedure
Nursing Responsibilities
Humidification
Oxygen Therapy in Special Situations
Complications of Oxygen Therapy
Oxygen Toxicity
CO₂ Retention
Oxygen Safety Precautions
Emergency Management
Documentation
Important Nursing Points
FAQs
10 MCQs for Practice
Answer Key

1. Introduction

Oxygen is essential for cellular metabolism and normal functioning of vital organs. When oxygen delivery to tissues becomes inadequate, the patient may develop hypoxemia and, if severe or prolonged, tissue hypoxia.

Oxygen therapy involves administering supplemental oxygen at a concentration greater than that present in room air. Room air contains approximately 21% oxygen. Supplemental oxygen can increase the amount of oxygen available for gas exchange and tissue delivery.

Oxygen therapy is not simply about giving the highest possible oxygen concentration. The goal is to provide the appropriate amount of oxygen required to achieve the desired clinical target while avoiding unnecessary exposure.

2. Definition of Oxygen Therapy

Oxygen therapy is the therapeutic administration of supplemental oxygen to a patient to prevent or correct inadequate oxygenation and maintain an appropriate oxygen saturation level.

3. Objectives of Oxygen Therapy

Correct or prevent hypoxemia.
Improve oxygen delivery to tissues.
Reduce symptoms associated with inadequate oxygenation.
Decrease the work of breathing in selected patients.
Support patients during acute respiratory illness.
Maintain an appropriate oxygen saturation target.
Support oxygenation during and after procedures when clinically indicated.
Provide respiratory support while the underlying cause is treated.

4. Indications of Oxygen Therapy

Oxygen may be indicated in patients with clinical or measured evidence of inadequate oxygenation.

Hypoxemia
Acute respiratory distress
Severe pneumonia
Acute pulmonary edema
Acute respiratory failure
Severe asthma with hypoxemia
Shock with inadequate oxygenation
Major trauma when hypoxemia is present or suspected
During certain procedures and recovery periods when clinically indicated
Cardiac arrest and resuscitation according to the resuscitation protocol
Carbon monoxide poisoning, where high-concentration oxygen may be required
Other conditions associated with inadequate oxygenation

5. Hypoxemia vs Hypoxia

Term	Meaning
Hypoxemia	Abnormally low oxygen level in arterial blood.
Hypoxia	Inadequate oxygen availability at the tissue level.

6. Oxygen Assessment Before Administration

Before starting oxygen therapy, the nurse should perform a systematic respiratory and clinical assessment.

A. Primary Assessment – ABCDE

A – Airway: Check whether the airway is patent. Look for obstruction, secretions, swelling, foreign body or abnormal airway sounds.
B – Breathing: Assess respiratory rate, rhythm, depth, effort, chest movement, breath sounds and signs of respiratory distress.
C – Circulation: Assess pulse, blood pressure, skin temperature, color, peripheral perfusion and capillary refill where appropriate.
D – Disability: Assess level of consciousness, mental status and neurological changes.
E – Exposure: Look for cyanosis, trauma, fever, edema, chest abnormalities and other relevant findings.

B. Detailed Respiratory Assessment

Respiratory rate
Respiratory rhythm
Respiratory depth
Work of breathing
Use of accessory muscles
Nasal flaring
Chest movement
Breath sounds
Cough and sputum
Ability to speak
Presence of cyanosis
Level of consciousness
SpO₂

7. Assessment Sequence in Different Clinical Situations

Important: The assessment sequence should be adapted to the patient's condition. In a life-threatening emergency, treat immediate threats first rather than delaying intervention for a complete routine assessment.

Stable Patient

Introduce yourself and identify the patient.
Assess general appearance.
Measure respiratory rate and SpO₂.
Assess respiratory effort and breath sounds.
Check pulse and blood pressure as clinically indicated.
Review relevant medical history.
Determine the prescribed oxygen target and device.
Administer oxygen if indicated.
Reassess response.
Document findings and intervention.

Patient in Acute Respiratory Distress

Immediate ABC assessment.
Assess airway patency.
Assess breathing and respiratory effort.
Check SpO₂ immediately if a reliable reading can be obtained without delaying emergency care.
Look for cyanosis, altered consciousness and inability to speak normally.
Provide oxygen according to emergency protocol and clinical target.
Call for urgent medical/critical-care assistance.
Prepare for escalation of respiratory support if required.
Continue frequent reassessment.

Unconscious Patient

Check responsiveness.
Assess airway immediately.
Assess breathing.
Check circulation.
Follow emergency/resuscitation protocol.
Administer oxygen and provide ventilatory support as indicated.
Continuously reassess the patient.

Cardiac Arrest

Cardiac arrest requires immediate activation of the emergency response system and high-quality CPR with appropriate airway and ventilation support according to the applicable resuscitation guideline.

Recognize cardiac arrest.
Call for help/activate emergency response.
Start high-quality CPR.
Use defibrillation when indicated.
Provide ventilation and oxygen according to the resuscitation protocol.
Continue monitoring and reassessment.

8. Oxygen Saturation – SpO₂

SpO₂ is the peripheral oxygen saturation estimated by a pulse oximeter. It provides a non-invasive indication of hemoglobin oxygen saturation.

Pulse oximetry should always be interpreted along with the patient's clinical condition. A pulse oximeter reading is not a substitute for clinical assessment or arterial blood gas analysis when blood gas information is required.

Factors Affecting Pulse Oximeter Accuracy

Poor peripheral perfusion
Cold extremities
Patient movement
Incorrect probe placement
Nail products or artificial nails in some circumstances
Low pulsatile flow
Ambient light interference
Some forms of dyshemoglobinemia

Nursing Tip: If the SpO₂ reading does not match the patient's clinical condition, reassess the patient, check probe placement and circulation, and consider whether another method of assessment is required.

9. Target Oxygen Saturation

Oxygen should be titrated to an appropriate target rather than automatically given at the highest possible concentration.

Patient Group	Common Target
Most acutely ill adults without risk of hypercapnic respiratory failure	Approximately 94–98%
Patients at risk of hypercapnic respiratory failure	Commonly 88–92% pending further assessment

Target ranges can vary according to the clinical condition, age, local protocol and clinician-directed treatment plan. Patients receiving long-term oxygen therapy may have individualized targets.

10. Oxygen Delivery Systems

Oxygen delivery systems are broadly divided into low-flow and high-flow systems.

A. Nasal Cannula

A nasal cannula consists of two small prongs inserted into the nostrils and is commonly used for patients requiring low to moderate supplemental oxygen.

Typical adult flow: approximately 1–6 L/min.
Approximate FiO₂: around 24–44%, depending on flow and patient factors.
Comfortable and allows eating and talking.
Useful for stable patients requiring modest oxygen supplementation.

B. Simple Face Mask

Typical flow: approximately 5–10 L/min.
Provides variable oxygen concentration.
Should generally not be run below 5 L/min because of potential CO₂ rebreathing.
Useful when a patient requires more oxygen than a nasal cannula can provide.

C. Venturi Mask

A Venturi mask is a controlled-performance oxygen delivery device that can provide a more predictable oxygen concentration than a simple face mask.

Useful when a controlled FiO₂ is required.
Particularly useful in patients at risk of hypercapnic respiratory failure.
Different adapters provide different oxygen concentrations.
Always follow the flow rate specified for the selected adapter.

D. Non-Rebreather Mask

A non-rebreather mask can deliver a high concentration of oxygen when properly fitted and supplied with an adequate flow.

Typical flow: approximately 10–15 L/min.
Reservoir bag should remain appropriately inflated during inspiration.
Used for patients requiring high-concentration oxygen.
Commonly used in serious hypoxemia and certain emergencies.

E. High-Flow Nasal Cannula – HFNC

HFNC provides heated and humidified oxygen at high flow rates. It can provide a more controlled FiO₂ and some degree of positive airway pressure.

Can provide high flow rates in adults, commonly up to around 60 L/min depending on the device.
FiO₂ can be adjusted according to the device and clinical requirement.
Requires appropriate equipment and monitoring.
Useful in selected patients with acute hypoxemic respiratory failure.

11. Oxygen Devices – Quick Comparison

Device	Typical Flow	Approximate Oxygen	Important Point
Nasal Cannula	1–6 L/min	~24–44%	Comfortable, variable FiO₂
Simple Mask	5–10 L/min	Variable	Do not use below 5 L/min
Venturi Mask	Adapter-specific	Controlled	Useful for controlled FiO₂
Non-Rebreather	10–15 L/min	High concentration	Reservoir must function properly
HFNC	High flow	Adjustable	Heated and humidified

Note: Flow rates and delivered FiO₂ are approximate and vary according to device, patient breathing pattern, fit and manufacturer specifications.

12. Procedure for Oxygen Administration

Verify the oxygen order/prescription or applicable clinical protocol.
Identify the patient using appropriate identifiers.
Explain the procedure to the patient.
Perform hand hygiene.
Assess respiratory status and baseline SpO₂.
Select the appropriate oxygen delivery device.
Check the oxygen source and equipment.
Connect the tubing correctly.
Set the prescribed flow or FiO₂.
Apply the device correctly.
Ensure the patient is positioned appropriately, usually upright when tolerated.
Reassess respiratory rate, effort, SpO₂ and patient comfort.
Monitor for improvement or deterioration.
Adjust therapy only according to the prescribed target/protocol.
Document oxygen therapy and patient response.

13. Positioning During Oxygen Therapy

Positioning can significantly influence ventilation and respiratory comfort.

High Fowler's: Useful for many patients with respiratory distress.
Fowler's: May improve comfort and lung expansion.
Tripod position: Some patients with severe dyspnea may naturally adopt this position.
Maintain airway alignment and avoid unnecessary restriction of chest movement.

14. Nursing Responsibilities

Before Oxygen Therapy

Assess respiratory status.
Check SpO₂.
Assess level of consciousness.
Check vital signs.
Identify the clinical indication.
Review relevant history and risk of hypercapnic respiratory failure.
Select the appropriate device.
Check equipment functionality.

During Oxygen Therapy

Monitor SpO₂.
Observe respiratory rate and effort.
Monitor breath sounds.
Observe mental status.
Check skin and mucous membranes.
Monitor for dryness and irritation.
Ensure correct device positioning.
Maintain prescribed oxygen flow or FiO₂.
Maintain oxygen safety precautions.

After Oxygen Therapy

Reassess oxygenation.
Compare with baseline findings.
Assess whether symptoms have improved.
Monitor for complications.
Continue or wean oxygen according to clinical target and prescription/protocol.
Document the intervention and response.

15. Humidification

Supplemental oxygen can contribute to dryness of the nasal and upper airway mucosa. Humidification may be appropriate in selected situations, particularly with higher flows or prolonged therapy, depending on the device and institutional protocol.

Use sterile or appropriately prepared water according to institutional policy.
Maintain the humidification system correctly.
Prevent contamination.
Monitor for condensation and equipment problems.
Do not routinely add humidification when it is not clinically indicated.

16. Oxygen Therapy in Special Situations

COPD / Risk of Hypercapnic Respiratory Failure

Some patients with COPD or other conditions are at risk of carbon dioxide retention. Oxygen should not be withheld when hypoxemia is present, but it should generally be controlled and titrated to the prescribed target, commonly 88–92% while further assessment is undertaken in patients at risk of hypercapnic respiratory failure.

Blood gas analysis may be required to assess PaO₂, PaCO₂ and acid-base status.

Pneumonia

Assess respiratory effort and oxygen saturation.
Administer oxygen according to clinical need and target.
Monitor respiratory deterioration.
Encourage appropriate positioning.
Monitor temperature, secretions and overall clinical condition.

Asthma

Assess respiratory distress.
Monitor SpO₂ and work of breathing.
Administer oxygen when clinically indicated.
Administer prescribed bronchodilators and other emergency treatments.
Watch for exhaustion and impending respiratory failure.

Carbon Monoxide Poisoning

Carbon monoxide poisoning is a special situation because standard pulse oximetry can be misleading. A patient may have significant carbon monoxide exposure despite an apparently acceptable SpO₂ reading. High-concentration oxygen is commonly used while urgent medical assessment is undertaken.

17. Complications of Oxygen Therapy

Nasal and oral dryness
Nasal irritation
Skin irritation or pressure injury from devices
Fire hazard
Oxygen toxicity with prolonged exposure to high concentrations
Absorption atelectasis in certain circumstances
Potential worsening of hypercapnia in susceptible patients when oxygen is excessive
Discomfort and anxiety associated with masks
Inadequate oxygen delivery due to equipment malfunction

18. Oxygen Toxicity

Oxygen toxicity refers to injury associated with exposure to excessive oxygen concentrations, particularly when high concentrations are administered for prolonged periods.

Possible Manifestations

Chest discomfort
Cough
Difficulty breathing
Substernal discomfort
Changes associated with pulmonary injury in severe cases

Oxygen should therefore be titrated to the appropriate clinical target whenever possible.

19. CO₂ Retention and Excess Oxygen

In susceptible patients, particularly some individuals with chronic hypercapnic respiratory disease, uncontrolled high-concentration oxygen may contribute to worsening hypercapnia.

Therefore, oxygen therapy should be carefully controlled and monitored rather than routinely administered at maximum concentration.

Important Nursing Point: Do not assume that every patient with COPD should receive exactly the same oxygen therapy. Assess the individual patient, follow the prescribed target and local protocol, and escalate care when the patient's condition deteriorates.

20. Oxygen Safety Precautions

Oxygen itself is not flammable, but it strongly supports combustion. Therefore, oxygen administration requires strict fire-safety precautions.

No smoking near oxygen equipment.
Keep oxygen away from flames and ignition sources.
Do not use oil or petroleum-based products around oxygen equipment unless specifically approved.
Keep electrical equipment in safe working condition.
Secure oxygen cylinders properly.
Do not allow cylinders to fall or roll.
Keep oxygen tubing free from kinks.
Check for leaks and equipment malfunction.
Ensure adequate ventilation where required.
Follow hospital oxygen-storage policies.

21. Emergency Management of Severe Hypoxemia

Think: ABCDE

Assess airway.
Assess breathing.
Check oxygen saturation when feasible.
Provide appropriate oxygen according to emergency protocol.
Call for urgent medical assistance.
Monitor vital signs continuously or frequently as appropriate.
Prepare for escalation to HFNC, non-invasive ventilation or invasive ventilation when clinically indicated.
Identify and treat the underlying cause.

22. Signs of Worsening Respiratory Status

Increasing respiratory rate
Increasing work of breathing
Use of accessory muscles
Unable to speak comfortably
Cyanosis
Falling SpO₂ despite oxygen therapy
Confusion or altered consciousness
Extreme fatigue
Silent chest in severe asthma
Hemodynamic instability
Exhaustion

These findings may indicate deterioration and require urgent reassessment and escalation of care.

23. Documentation of Oxygen Therapy

The nurse should document relevant information such as:

Date and time.
Reason/indication for oxygen.
Baseline SpO₂.
Oxygen delivery device.
Flow rate or FiO₂.
Patient's respiratory assessment.
Oxygen saturation after intervention.
Patient's response.
Adverse effects or complications.
Escalation or changes in treatment.
Communication with the medical/critical-care team when appropriate.

24. Important Nursing Points for Exams

Oxygen is considered a medication/therapeutic intervention.
Room air contains approximately 21% oxygen.
Always assess the patient before and after oxygen administration.
SpO₂ should be interpreted along with clinical assessment.
Simple face masks should generally not be used below 5 L/min.
Venturi masks are useful when a controlled oxygen concentration is required.
Non-rebreather masks are used when high-concentration oxygen is required.
HFNC provides heated and humidified high-flow oxygen.
Patients at risk of hypercapnic respiratory failure commonly have a target of 88–92% pending further assessment.
Many other acutely ill patients have a target around 94–98% when they are not at risk of hypercapnic respiratory failure.
Oxygen supports combustion.
Smoking must be prohibited around oxygen.
High oxygen concentrations for prolonged periods may cause oxygen toxicity.
Do not ignore a deteriorating patient just because the SpO₂ number appears acceptable.
The underlying cause of hypoxemia must always be investigated and treated.

25. Easy Memory Trick – Oxygen Therapy

ASSESS → SELECT → ADMINISTER → MONITOR → REASSESS → DOCUMENT

ASSESS: ABCDE + SpO₂ + respiratory status.
SELECT: Choose appropriate device.
ADMINISTER: Give prescribed oxygen.
MONITOR: SpO₂, breathing and patient response.
REASSESS: Determine effectiveness.
DOCUMENT: Record therapy and response.

26. Frequently Asked Questions – Oxygen Therapy

Q1. What is the main purpose of oxygen therapy?

The main purpose is to correct or prevent inadequate oxygenation and maintain an appropriate oxygen saturation target.

Q2. How much oxygen is present in room air?

Room air contains approximately 21% oxygen.

Q3. What is SpO₂?

SpO₂ is the peripheral oxygen saturation estimated using a pulse oximeter.

Q4. What is the usual target SpO₂ for many acutely ill patients without hypercapnic risk?

A commonly used target is approximately 94–98%.

Q5. What is the common target for patients at risk of hypercapnic respiratory failure?

A commonly used target is 88–92% while further clinical and blood-gas assessment is undertaken.

Q6. Which device provides a controlled oxygen concentration?

The Venturi mask is commonly used when a controlled oxygen concentration is required.

Q7. Why should a simple face mask not usually be used below 5 L/min?

Low flow through a simple mask can increase the risk of rebreathing exhaled carbon dioxide.

Q8. Which oxygen device provides a high concentration of oxygen in emergencies?

A properly functioning non-rebreather mask can provide a high concentration of oxygen when supplied with an adequate flow.

Q9. Is oxygen flammable?

Oxygen is not itself a fuel, but it strongly supports combustion. Therefore, flames, smoking and ignition sources must be kept away from oxygen.

Q10. Can oxygen toxicity occur?

Yes. Prolonged exposure to excessive oxygen concentrations can cause oxygen-related tissue injury.

Q11. Can a patient have serious respiratory deterioration with a normal SpO₂?

Yes. SpO₂ is only one part of assessment. Respiratory effort, mental status, circulation, ventilation and the underlying disease must also be considered.

Q12. What should a nurse do if SpO₂ suddenly falls?

Immediately reassess the patient and airway, check the oxygen device and probe, assess breathing, increase support according to the applicable emergency protocol/target, and seek urgent medical assistance when clinically indicated.

27. Oxygen Therapy – 10 MCQs for Practice

Try to answer all questions before checking the answer key.

1. What is the approximate concentration of oxygen in room air?

A. 10%

B. 21%

C. 35%

D. 50%

2. Which oxygen device is commonly used when a controlled FiO₂ is required?

A. Simple face mask

B. Nasal cannula

C. Venturi mask

D. Oxygen hood

3. What is the usual minimum flow recommended for a simple face mask?

A. 1 L/min

B. 2 L/min

C. 3 L/min

D. 5 L/min

4. Which device can provide high-concentration oxygen during an emergency?

A. Non-rebreather mask

B. Nasal cannula

C. Simple nasal catheter

D. Venturi mask at low concentration

5. What is a commonly used target SpO₂ for patients at risk of hypercapnic respiratory failure?

A. 70–75%

B. 80–85%

C. 88–92%

D. 99–100%

6. Which of the following is an important oxygen safety precaution?

A. Encourage smoking near the oxygen cylinder

B. Keep oxygen near an open flame

C. Keep oxygen away from ignition sources

D. Apply petroleum products around the oxygen equipment

7. Which assessment should be performed first in a severely deteriorating patient?

A. Dietary history

B. ABC assessment

C. Sleep history

D. Family history

8. Which device provides heated and humidified high-flow oxygen?

A. HFNC

B. Simple mask

C. Nasal cannula at 1 L/min

D. Non-rebreather mask

9. Which factor can interfere with pulse oximeter accuracy?

A. Poor peripheral perfusion

B. Correct probe placement

C. Normal circulation

D. Patient remaining still

10. What is the correct sequence in oxygen therapy?

A. Document → assess → administer → monitor

B. Assess → select → administer → monitor → reassess → document

C. Administer → document → assess → select

D. Monitor → administer → assess → document

28. Answer Key

B – 21%
C – Venturi mask
D – 5 L/min
A – Non-rebreather mask
C – 88–92%
C – Keep oxygen away from ignition sources
B – ABC assessment
A – HFNC
A – Poor peripheral perfusion
B – Assess → Select → Administer → Monitor → Reassess → Document

Final Revision – One Minute Before Exam

Oxygen Therapy = Assess + Appropriate Device + Correct Target + Continuous Monitoring + Safety.

Room air = approximately 21% oxygen.
Nasal cannula = low-flow oxygen.
Simple mask = generally 5–10 L/min.
Venturi mask = controlled FiO₂.
Non-rebreather = high-concentration oxygen.
HFNC = heated and humidified high-flow oxygen.
Many acutely ill patients without hypercapnic risk = target around 94–98%.
Risk of hypercapnic respiratory failure = commonly 88–92% pending further assessment.
Always reassess after oxygen administration.
Oxygen supports combustion — maintain strict fire safety.

Keep Learning. Keep Practicing. Keep Improving.

These Oxygen Therapy Notes are useful for B.Sc Nursing, GNM, ANM, NORCET, NCLEX-RN and other nursing competitive examinations.

Share these notes with your nursing friends and classmates.

Knowledge + Practice = Safe Patient Care ❤️

Educational Disclaimer: This article is intended for nursing education and examination preparation. Oxygen therapy should be administered according to the patient's clinical condition, authorized prescription or institutional protocol, and applicable professional guidelines. Device specifications and target ranges may vary according to patient condition, equipment and local policy.

Nursing Foundation - Oxygen Therapy Nursing Notes: Complete Guide, Devices, Flow Rates & MCQs