Indications for Oxygen Therapy 

Oxygen therapy is the administration of supplemental oxygen to treat or prevent hypoxemia. It is considered a drug and should be prescribed with appropriate indications, dosage, and target saturations. 

1. Primary Indication: Hypoxemia 

– PaO₂ < 8KPa (60 mmHg) on arterial blood gas 
– SpO₂ < 92% on pulse oximetry 

2. Acute Clinical Conditions 

Respiratory causes: 
– Acute exacerbation of COPD 
– Severe asthma 
– Pneumonia 
– ARDS 
– Pulmonary edema 
– Pulmonary embolism 

Cardiac causes: 
– Acute heart failure 
– Myocardial infarction with hypoxemia 
– Cardiogenic shock 

3. Chronic Conditions 

– COPD with chronic respiratory failure 
– Interstitial lung disease 
– Pulmonary hypertension 
– Advanced heart failure 

Long-term oxygen therapy (LTOT) in COPD: 
– PaO₂ ≤ 7.3KPa (55 mmHg) 
– PaO₂ 7.5-7.9KPa (56–59 mmHg) with cor pulmonale or polycythemia 

4. Perioperative and Procedural Use 

– During anesthesia 
– Postoperative period 
– Sedation-related hypoventilation 

5. Special Situations 
– Carbon monoxide poisoning (100% oxygen) 
– Smoke inhalation 
– Cluster headaches 
– Neonatal respiratory distress 
– High-altitude illness 

6. Potential Complications of Oxygen Therapy 
– Oxygen toxicity (pulmonary and CNS) 
– Carbon dioxide retention (especially in COPD patients) 
– Absorption atelectasis 
– Dryness of airways and mucosal irritation 
– Retinopathy of prematurity (in neonates) 
– Fire hazard (oxygen supports combustion) 

7. Oxygen Toxicity 
Oxygen toxicity occurs due to prolonged exposure to high concentrations of oxygen, leading to excessive production of reactive oxygen species and cellular damage. 

A. Pulmonary Oxygen Toxicity 
Seen with FiO₂ > 60% for more than 24–48 hours. 
Signs and symptoms: 
– Substernal chest pain 
– Dry cough 
– Dyspnea 
– Decreased lung compliance 
– Worsening hypoxemia 
– Features resembling ARDS in severe cases 

B. Central Nervous System (CNS) Oxygen Toxicity 
Occurs with very high oxygen pressures (e.g., hyperbaric oxygen). 
Signs and symptoms: 
– Nausea and vomiting 
– Dizziness 
– Visual disturbances (tunnel vision) 
– Muscle twitching 
– Seizures (classic feature) 

Clinical Notes 
– Target SpO₂ in most patients: 94–98% 
– Target SpO₂ in COPD patients: 88–92% 
– Oxygen therapy should be regularly reviewed and titrated to the lowest effective dose 
– Monitor patients using pulse oximetry and arterial blood gases when indicated