Oxygen Therapy
Key Points
- SpO2 normal: 95–100% in healthy adults; 88–92% target for COPD patients (hypoxic drive)
- LTOT indication in COPD: Resting SpO2 88% or lower in stable condition supports long-term oxygen therapy referral
- Early hypoxia signs: Anxiety, restlessness, confusion — late signs: cyanosis, decreased LOC
- Escalation thresholds: In adults without chronic low baseline, new SpO2 below 92% warrants provider notification; below 88% indicates severe hypoxia requiring urgent intervention per policy
- Nasal cannula: 1–6 L/min → 24–44% FiO2 (4% increase per L/min); most common device
- Non-rebreather mask: 10–15 L/min → 60–80% FiO2; reservoir bag must never fully deflate
- Venturi mask: COPD indication — delivers precise FiO2 (24–60%); avoid high O2 in COPD
- Oxygen safety: Not flammable itself but accelerates combustion — no open flames, petroleum products
Oxygenation Concepts
Pulse Oximetry (SpO2)
SpO2 estimates hemoglobin oxygen saturation noninvasively via light absorption through tissue. Each hemoglobin molecule can bind up to four oxygen molecules, and pulse oximetry indirectly estimates this saturation from optical signal changes. Finger-probe pulse oximetry is used across settings, from home checks to continuous hospital monitoring in high-acuity units.
Normal values:
- Healthy adults near sea level: commonly in the mid-to-high 90s (often about 94-98% in many references)
- COPD/chronic respiratory conditions: 88–92% (some chronic retainers/emphysema contexts may be managed near 88–90% per order and policy)
- Long-term oxygen therapy (LTOT) consideration in stable COPD: SpO2 ≤88% at rest
- At higher altitude, baseline SpO2 may be lower than sea-level expectations and should be interpreted in clinical context.
Inaccuracies — SpO2 requires clinical judgment alongside the reading:
| Cause | Effect | Intervention |
|---|---|---|
| Motion artifact | False readings | Ensure patient still; use earlobe/forehead probe |
| Poor peripheral perfusion | Low reading | Warm extremity; use forehead/earlobe probe |
| Nail polish | Inaccurate reading | Remove polish before probe placement |
| Carbon monoxide poisoning | Falsely HIGH reading | ABG required for accurate assessment |
| Severe anemia | Normal SpO2 despite inadequate O2 | ABG — SaO2 can be normal with low hemoglobin |
Arterial Blood Gas (ABG)
More accurate than SpO2 — not affected by hemoglobin levels. Drawn from radial artery.
| ABG Component | Normal Range |
|---|---|
| pH | 7.35–7.45 |
| PaO2 (partial pressure of oxygen) | 80–100 mmHg |
| PaCO2 (partial pressure of CO2) | 35–45 mmHg |
| HCO3 (bicarbonate) | 22–26 mEq/L |
| SaO2 (calculated O2 saturation) | 95–100% |
See respiratory-acidosis and fluid-electrolyte-regulation-by-organs for acid-base interpretation.
Hypoxia vs. Hypercapnia
Hypoxia — reduced tissue oxygenation:
- Early signs: Anxiety, restlessness, confusion, tachycardia, tachypnea
- Late signs: Cyanosis (lips and oral mucosa), decreased LOC, decreased SpO2
- Chronic sign: Clubbing of fingertips (gradual enlargement)
Hypercapnia — elevated PaCO2 (>45 mmHg):
- Causes: Hypoventilation, ventilation-perfusion mismatch
- Signs: Tachycardia, dyspnea, flushed skin, confusion, headache, dizziness
- Early presentation may include somnolence with reduced respiratory depth/rate even when SpO2 appears near baseline
- Leads to respiratory acidosis (pH drops as CO2 accumulates)
- Management: Treat underlying cause; BiPAP support; intubation if severe
Oxygen Delivery Devices
| Device | Flow Rate | FiO2 | Best Use |
|---|---|---|---|
| Nasal cannula | 1–6 L/min | 24–44% | Low-moderate O2; COPD long-term; allows eating/talking |
| Simple face mask | 6–10 L/min | 28–50% | Moderate O2 needs; never below 6 L/min (CO2 rebreathing) |
| Non-rebreather mask | 10–15 L/min | 60–80% | High-acuity; spontaneously breathing patients needing high O2 |
| Partial rebreather mask | 10–15 L/min | 35–50% | Allows some exhaled air mixing |
| Venturi mask | Varies by adaptor | 24–60% (precise) | COPD — controlled FiO2 to avoid O2-induced hypercapnia |
| High-flow nasal cannula | Up to 60 L/min | Up to 100% | Critical care; heated/humidified; set up by respiratory therapist |
Nasal Cannula
- Most common oxygen device; appropriate for stable patients
- 4% FiO2 increase per L/min (1 L/min = 24%, 6 L/min = 44%)
- Add humidification for hospitalized patients receiving >4 L/min or long-term therapy
- Limitations: Ineffective for mouth breathers; nasal polyps; deviated septum
- Skin breakdown risk: Nares and over ears — apply padding per agency policy
- Petroleum-based lubricant is contraindicated (fire risk with oxygen)
Non-Rebreather Mask
- One-way valves direct exhaled CO2 out through exhalation ports; patient inhales only from reservoir bag
- Reservoir bag must remain inflated — complete deflation indicates system failure requiring immediate intervention
- Delivers highest noninvasive O2 concentration; use for patients in significant respiratory distress
Venturi Mask
- Specific adaptors set precise FiO2 regardless of flow meter reading — consult respiratory therapist before adjusting
- Preferred for COPD to prevent suppressing hypoxic respiratory drive
- Flow rate does not correspond directly to FiO2 — use adaptor-specific guidelines
Nursing Assessment
Before Initiating Oxygen Therapy:
- Obtain brief focused respiratory history (home O2, CPAP/BiPAP use, COPD/asthma history)
- Assess airway patency, respiratory rate, lung sounds, SpO2, cyanosis
- Treat dyspnea as a subjective symptom; severe breathlessness can be present even when respiratory rate or SpO2 appears less abnormal.
- History of COPD → consider Venturi mask (controlled FiO2)
- Nonemergency: typically begin nasal cannula at 1–2 L/min and titrate
- Verify oxygen prescription unless emergent rescue care is required
- Titrate to the ordered saturation goal for that patient (for example, maintain SpO2 above 90% when specified in standing orders).
- Document baseline respiratory rate, heart rate, blood pressure, and oxygen saturation before titration
During and After Administration:
- Reassess SpO2 within minutes of initiation — if no improvement, escalate intervention
- In adults without chronic low baseline, treat new SpO2 below 92% as escalation trigger; SpO2 below 88% indicates severe hypoxia requiring urgent response per policy
- Reassess respiratory rate, dyspnea severity, and SpO2 during the first minutes of ambulation or exertion because hypoxemia may be activity-induced.
- During dyspnea-focused reassessment, include speech tolerance (sentences/phrases/words), anxiety level, chest-pain screening, and aggravating/relieving factors.
- If exertional SpO2 falls below the ordered target, titrate oxygen within active orders/protocol and document flow changes with distance and tolerance response.
- Monitor skin integrity at pressure points: nasal cannula — nares and over ears; face masks — chin and cheeks
- Monitor for signs of worsening — if deteriorating, activate rapid response
- For COPD patients: monitor for CO2 retention if high FiO2 delivered — ABG may be ordered
- Notify provider promptly when the ordered oxygen range fails to maintain target saturation during activity or respiratory distress worsens.
- Confirm flow meter remains at ordered dose and humidification is applied when indicated to reduce mucosal drying
- Ensure oxygen continuity during transport and evaluate tolerance after each transfer
- If tolerated, switch from mask to nasal cannula during meals to support intake while maintaining oxygenation
- Evaluate and document therapy effectiveness using objective trends (vitals, SpO2, respiratory effort) and symptom response
Special Populations:
- Children: Age-appropriate equipment sizes; tape tubing to face if needed; pulse oximeter on palm/foot for infants
- Older adults: Ensure extension tubing reaches bathroom; coil excess tubing to prevent falls; assist with ambulation
Safety Precautions
Oxygen Safety
Oxygen is not itself flammable but significantly accelerates combustion of other materials.
- No open flames, smoking, or lit candles in room
- No petroleum-based lubricants near oxygen equipment
- Keep tanks secured upright; ensure adequate supply before transport
- Post “Oxygen in Use” signs per agency policy
Patient Education
- Inhale through nose with slow, deep breaths; exhale through mouth
- Nasal cannula can remain in place during eating and talking
- Report any sensation of worsening shortness of breath immediately
- Do not adjust flow rate without healthcare provider approval
- Home oxygen users: no smoking; keep equipment away from heat sources
- Extension tubing for home use — ask for assistance when ambulating to prevent falls
Related Concepts
- respiratory-system — Anatomy of the respiratory system
- respiratory-failure — Indications for escalating oxygen therapy
- respiratory-acidosis — Hypercapnia and CO2 retention
- asthma-action-plan-and-exacerbation-management — Acute exacerbation oxygen management
- bronchodilators — Concurrent bronchodilator therapy
- evidence-based-respiratory-care — Respiratory care protocols
- prioritizing-early-deterioration-cues-in-fluid-electrolyte-care — Recognizing respiratory deterioration
Self-Check
- A patient with COPD has an SpO2 of 93%. The nurse increases the nasal cannula from 2 L/min to 6 L/min. What concern does this raise, and what device would be more appropriate?
- A patient on a non-rebreather mask is noted to have a completely deflated reservoir bag. What does this indicate and what is the priority nursing action?
- A nurse checks a patient’s SpO2 after initiating oxygen and finds the reading is 99%, but the patient is confused and flushed. What condition might explain the discrepancy between SpO2 and the patient’s symptoms?