What are the methods for delivering supplemental oxygen to patients with hypoxemia?

Oxygen Delivery Methods for Hypoxemia

Primary Oxygen Delivery Devices

For patients with hypoxemia, oxygen should be delivered using the least invasive method that achieves the target saturation range: nasal cannula for low-flow needs, Venturi masks for precise FiO2 control, reservoir masks for high-concentration delivery, or high-flow nasal cannula for patients requiring higher flows with better tolerance. 1

Low-Flow Devices

Nasal Cannula (Standard)

• Delivers oxygen at 1-6 L/min, achieving FiO2 of approximately 24-44% 1, 2
• Mean delivered FiO2 ranges from 0.26-0.54 at flows of 1-6 L/min during rest 2
• Most appropriate for stable patients requiring modest oxygen supplementation 1
• FiO2 delivery varies significantly between patients and is affected by breathing pattern (mouth-open breathing achieves higher FiO2 than mouth-closed) 2
• Humidification is not routinely necessary at flows ≤4 L/min, as it does not significantly reduce patient complaints and adds unnecessary cost 3

Simple Face Mask

• Requires minimum flow of 5 L/min to prevent CO2 rebreathing 1
• Delivers FiO2 of approximately 35-50% 1
• Less comfortable than nasal cannula for prolonged use 4

Reservoir Masks (Non-Rebreather)

• Delivers high-concentration oxygen at flows of 10-15 L/min 1
• Can achieve FiO2 approaching 60-90% depending on fit and patient breathing pattern 1
• Should be used immediately for critically ill patients requiring high oxygen concentrations 1, 5

Controlled Oxygen Delivery Devices

Venturi Masks

• Provide precise, controlled FiO2 delivery (24%, 28%, 31%, 35%, 40%, 60%) 1, 5
• Essential for patients at risk of hypercapnic respiratory failure (COPD, neuromuscular disease, obesity hypoventilation, chest wall disorders) 1, 5, 6
• Recommended starting points: 24% Venturi mask at 2-3 L/min or 28% at 4 L/min for at-risk patients 5
• Air entrainment design ensures consistent FiO2 regardless of patient breathing pattern 1

High-Flow Devices

High-Flow Nasal Cannula (HFNC)

• Delivers heated, humidified oxygen at flows of 15-60 L/min for adults 4, 7
• Achieves mean FiO2 of 0.54-0.75 at flows of 6-15 L/min during rest 2
• Provides several physiologic benefits: washout of nasopharyngeal dead space, generation of low-level positive airway pressure (2-7 cm H2O), improved mucociliary function, and reduced work of breathing 4, 7
• Superior patient comfort and tolerance compared to standard oxygen masks 4, 7
• May reduce need for intubation in patients with hypoxemic acute respiratory failure 7
• Useful for preoxygenation before intubation and post-extubation support 7

Target Oxygen Saturations

Standard Target: 94-98%

• Appropriate for most acutely ill patients without risk of hypercapnia 1
• Includes patients with acute coronary syndromes (only if SpO2 <90%), stroke, pneumonia, and most medical emergencies 1

Restricted Target: 88-92%

• Mandatory for patients at risk of hypercapnic respiratory failure: moderate-to-severe COPD, severe obesity, neuromuscular disease, chest wall deformities, cystic fibrosis, bronchiectasis 1, 5, 6
• Critical safety point: Excessive oxygen (PaO2 >10.0 kPa) significantly increases risk of worsening respiratory acidosis in these patients 5
• High-concentration oxygen can cause hypercapnia within 15 minutes in acute COPD 5

Specialized Delivery Scenarios

During Procedures (Bronchoscopy, Endoscopy)

• Deliver oxygen at minimum 2 L/min via nasal cannula through one or both nostrils 1
• Target SpO2 >90% or correct falls >4% 1
• Continuous pulse oximetry is mandatory during sedation 1
• Routine oxygen administration is not recommended as it may delay recognition of respiratory depression 1

Acute Coronary Syndromes

• Administer supplemental oxygen only if SpO2 <90%, respiratory distress, or high-risk features of hypoxemia 1
• Routine oxygen in non-hypoxemic patients is not beneficial 1

Acute Stroke

• Administer oxygen to maintain SpO2 >94% 1
• Routine supplemental oxygen is not required in non-hypoxemic patients with mild-moderate strokes 1
• Use least invasive method: nasal cannula, Venturi mask, non-rebreather mask, or CPAP/BiPAP as needed 1

Sepsis

• Provide supplemental oxygen to maintain SpO2 approximately 88-90% (PaO2 ~60 mmHg) 1
• Use simple delivery systems (nasal cannula or face mask) if possible 1
• PEEP may be employed to reduce FiO2 below toxic thresholds (<0.60) in intubated patients 1

Critical Monitoring Requirements

All Patients Receiving Oxygen

• Pulse oximetry is mandatory and should be considered "the fifth vital sign" 1
• Record oxygen saturation, delivery device, and flow rate on monitoring charts 1
• Clinical assessment required if SpO2 falls ≥3% or below target range 1
• Adjust delivery device and flow rate to maintain target saturation 1

Patients at Risk of Hypercapnia

• Obtain arterial blood gases immediately for suspected hypercapnic respiratory failure 5, 6
• Repeat ABGs after 30-60 minutes of oxygen therapy or sooner if clinical deterioration 5, 6
• If respiratory acidosis (pH <7.35, PCO2 >6.0 kPa) persists >30 minutes despite standard therapy, initiate non-invasive ventilation 5, 6

Common Pitfalls to Avoid

• Never administer high-flow oxygen without monitoring in patients with COPD or other conditions predisposing to hypercapnia 5, 6
• Do not use oxygen-driven nebulizers in COPD exacerbations; use compressed air instead 5
• Never abruptly discontinue oxygen in hypercapnic patients, as this causes life-threatening rebound hypoxemia 5, 6
• Avoid routine humidification at low flows (≤4 L/min) as it provides no clinical benefit and increases costs 3
• Do not rely on oxygen therapy alone to treat breathlessness in non-hypoxemic patients, as oxygen has not been proven effective for dyspnea without hypoxemia 1