Introduction
Oxygen (O₂) is a colorless, odorless, tasteless gas that constitutes approximately 21% of atmospheric air. As a medicinal product, it is classified as a drug and is essential for cellular metabolism and survival. Therapeutic oxygen is administered to correct or prevent hypoxemia in various clinical conditions. It remains one of the most fundamental and frequently administered medical therapies worldwide.
Mechanism of Action
Oxygen exerts its therapeutic effects through several mechanisms:
- Increases the oxygen concentration in inspired air, thereby raising alveolar oxygen tension
- Enhances oxygen diffusion across the alveolar-capillary membrane
- Increases arterial oxygen saturation (SaO₂) and arterial oxygen content (CaO₂)
- Improves oxygen delivery to tissues by increasing the oxygen dissolved in plasma and bound to hemoglobin
- Reduces work of breathing in certain pathological states by decreasing respiratory drive
Indications
FDA-approved indications include:
- Treatment of hypoxemia (SpO₂ < 88-90%)
- Prevention of hypoxemia during medical procedures
- Carbon monoxide poisoning
- Cluster headaches (high-flow oxygen)
- Decompression sickness
- Pulmonary hypertension
- Severe trauma and shock
Additional evidence-based uses:
- Acute respiratory failure
- Chronic obstructive pulmonary disease (COPD) exacerbations
- Myocardial infarction with hypoxemia
- Post-operative recovery
- Palliative care for dyspnea relief
Dosage and Administration
Routes of administration: Inhalation via nasal cannula, face mask, venturi mask, non-rebreather mask, or mechanical ventilation Standard dosing:- Mild hypoxemia: 1-4 L/min via nasal cannula (24-40% FiO₂)
- Moderate hypoxemia: 4-10 L/min via simple face mask (40-60% FiO₂)
- Severe hypoxemia: 10-15 L/min via non-rebreather mask (60-90% FiO₂)
- Mechanical ventilation: 21-100% FiO₂ as titrated
- COPD patients: Target SpO₂ 88-92% to avoid hypercapnia
- Neonates: Use lowest effective concentration to prevent retinopathy of prematurity
- Pregnancy: No dosage adjustment needed; maintain normal oxygenation
Pharmacokinetics
Absorption: Rapid diffusion across alveolar membranes following inhalation Distribution: Dissolves in plasma (0.003 mL O₂/dL/mmHg) and binds reversibly to hemoglobin (1.34 mL O₂/g Hb) Metabolism: Utilized in cellular respiration via cytochrome oxidase system; converted to water and carbon dioxide Elimination: Primarily exhaled as carbon dioxide; minor amounts excreted in water vaporContraindications
- Absolute: None in life-threatening hypoxemia
- Relative: Paraquat poisoning (may enhance toxicity)
- Fire hazard in presence of ignition sources
Warnings and Precautions
Boxed Warning: None Important precautions:- Oxygen toxicity with prolonged high concentrations (>50% for >24-48 hours)
- Retinopathy of prematurity in neonates
- Absorption atelectasis with high FiO₂
- Depression of ventilation in COPD patients with chronic hypercapnia
- Fire hazard: Oxygen supports combustion
- Equipment-related risks: Pressure injuries, nasal dryness, mucous membrane irritation
Drug Interactions
- Bleomycin: Enhanced pulmonary toxicity
- Amiodarone: Increased risk of pulmonary fibrosis
- Chemotherapeutic agents: Potential enhanced pulmonary toxicity
- Anesthetics: Fire hazard with flammable agents
Adverse Effects
Common (>10%):- Nasal dryness and irritation
- Mucous membrane drying
- Headache (with high concentrations)
- Oxygen toxicity (pulmonary and CNS effects)
- Retrolental fibroplasia in premature infants
- Absorption atelectasis
- Hypercapnia in COPD patients
- Fire/explosion hazard
Monitoring Parameters
- Continuous pulse oximetry (SpO₂)
- Arterial blood gases (pH, PaO₂, PaCO₂) in critical illness
- Respiratory rate and pattern
- Neurological status (for CNS oxygen toxicity)
- Signs of pulmonary toxicity in prolonged high-dose therapy
- Equipment function and delivery system
- Fire safety precautions
Patient Education
- Understand prescribed flow rate and delivery device
- Never adjust flow rate without medical supervision
- Keep oxygen equipment away from open flames and heat sources
- Do not smoke or allow smoking near oxygen equipment
- Recognize signs of inadequate oxygenation (shortness of breath, confusion)
- Proper equipment cleaning and maintenance
- Travel considerations: Portable oxygen systems, airline regulations
- Home safety: Oxygen storage, electrical safety
References
1. O'Driscoll BR, et al. BTS guideline for oxygen use in adults in healthcare and emergency settings. Thorax. 2017;72(Suppl 1):ii1-ii90. 2. Global Initiative for Chronic Obstructive Lung Disease. Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease. 2023 Report. 3. American Association for Respiratory Care. AARC Clinical Practice Guideline: Oxygen therapy for adults in the acute care facility. Respir Care. 2002;47(6):717-720. 4. Weinger MB, et al. Supplemental oxygen: ensuring its safe delivery. Anesthesiology. 2015;123(4):938-954. 5. FDA Drug Safety Communication: Important information on the safe use of oxygen therapy. 2017. 6. Martin DS, et al. Oxygen toxicity in man. N Engl J Med. 1970;283(27):1478-1484. 7. West JB. Respiratory Physiology: The Essentials. 10th ed. Philadelphia: Wolters Kluwer; 2016.