Oxygen Delivery Devices

Introduction to Oxygen Therapy

• The British Thoracic Society recommends that oxygen delivery devices fall into three main categories: low-flow variable performance systems, fixed performance systems, and high-flow/reservoir systems, each with specific clinical indications based on the patient's oxygen requirements and risk of hypercapnia 1, 2

Low-Flow Variable Performance Devices

• The American Thoracic Society suggests that nasal cannulae should be the first-choice delivery device for most patients requiring supplemental oxygen due to superior patient comfort and tolerance, particularly for prolonged use 3
• Each liter per minute of oxygen flow adds approximately 3-4% to inspired oxygen concentration, though actual delivery varies significantly between patients (24-35% at 2 L/min) 3, 4, 5
• Flow rates typically range from 0.5-6 L/min, with higher rates causing upper airway discomfort 1, 2
• The American College of Physicians recommends that nasal cannulae are preferred for medium-concentration oxygen therapy targeting saturations of 94-98% in patients without hypercapnic risk 6, 7

Fixed Performance Devices

• The European Respiratory Society recommends that Venturi masks are the preferred device when precise oxygen control is essential, particularly in patients with hypercapnic respiratory failure or COPD 1, 3, 6
• Venturi masks deliver accurate fixed concentrations of 24%, 28%, 31%, 35%, 40%, and 60% oxygen when used with specified flow rates 1, 6
• The British Thoracic Society suggests that Venturi masks are specifically indicated for patients requiring controlled oxygen with target saturations of 88-92% 1, 2

High-Flow and Reservoir Systems

• The American Thoracic Society recommends that non-rebreather/reservoir masks deliver oxygen concentrations between 60-90% at flow rates of 15 L/min, making them suitable for critically ill patients requiring high-concentration oxygen 6
• The Society of Critical Care Medicine suggests that high-flow humidified nasal oxygen should be considered as a potentially superior alternative to reservoir masks in acute respiratory failure without hypercapnia 1

Specialized Delivery Systems

• The American College of Cardiology recommends that CPAP with entrained oxygen (targeting 94-98% saturation) should be considered for cardiogenic pulmonary oedema not responding to standard treatment 1
• The European Society of Cardiology suggests that patients with sleep-disordered breathing on home CPAP should continue therapy perioperatively, with oxygen entrained to achieve 88-92% if needed 1

Humidification Considerations

• The American Thoracic Society recommends that humidification is not required for low-flow oxygen or short-term high-flow oxygen use 1
• The British Thoracic Society suggests that humidification should be considered for patients requiring high-flow oxygen systems for >24 hours or those with upper airway discomfort 1
• The Infectious Diseases Society of America recommends that bubble bottles should never be used due to infection risk without clinical benefit 1, 8

Clinical Decision Algorithm

• For patients without hypercapnic risk, the American Thoracic Society recommends starting with nasal cannulae at 2-6 L/min for medium oxygen needs (SpO2 target 94-98%) 7
• For patients with hypercapnic risk, the European Respiratory Society recommends using Venturi mask at 24% or 28% (SpO2 target 88-92%) 1, 2, 6

Critical Pitfalls to Avoid

• The American Thoracic Society warns that never using simple face masks below 5 L/min causes dangerous CO2 rebreathing 6
• The Society of Critical Care Medicine suggests that mask effectiveness is greatly reduced if not properly positioned and sealed 6
• The American College of Physicians recommends avoiding high-flow oxygen in patients at risk of hypercapnic respiratory failure without controlled delivery systems 1, 6

Nasal Cannula Replacement Guidelines

Equipment Maintenance Principles

• The British Thoracic Society recommends that nasal cannulae do not require routine scheduled replacement and should only be changed when visibly soiled, damaged, or malfunctioning 9

When to Replace Nasal Cannulae

• Nasal cannulae should be replaced when there is visible contamination with secretions, blood, or other bodily fluids 9
• Nasal cannulae should be replaced when there is physical damage, including kinks, cracks, or tears in the tubing that could affect oxygen delivery 9
• Nasal cannulae should be replaced when there is malfunction, such as blocked prongs or compromised connections 9
• Nasal cannulae should be replaced between different patients as standard infection control practice 9

Clinical Context Considerations

Standard Oxygen Therapy (1-6 L/min)

• Nasal cannulae used for conventional oxygen therapy can remain in place for the duration of hospitalization unless the above replacement criteria are met 9
• The British Thoracic Society emphasizes proper connection verification rather than scheduled replacement 9

High-Flow Nasal Cannula (HFNC)

• HFNC systems (30-70 L/min) incorporate heated humidification, which may lead to moisture accumulation in tubing 10, 11
• Replace HFNC circuits when water accumulation impairs function or creates infection risk 10, 11

Infection Control Perspective

• There is no evidence that routine time-based replacement of nasal cannulae reduces infection rates 9

Common Pitfalls to Avoid

• Do not replace nasal cannulae on arbitrary schedules (e.g., daily, every shift) as this wastes resources without clinical benefit 9
• Do not confuse nasal cannula replacement with oxygen tubing verification - ensure proper connections at both wall outlet and patient interface 9
• Do not use damaged or kinked tubing even if recently placed, as this compromises oxygen delivery 9

Practical Algorithm

• For standard nasal cannula (1-6 L/min), inspect daily during routine care and replace only if visibly soiled, damaged, or causing patient discomfort 9, 10
• For high-flow nasal cannula (HFNC), monitor for water accumulation in circuit and replace when moisture impairs function or follow manufacturer guidelines (typically 7 days maximum) 9, 10, 11
• Always replace nasal cannulae between different patients and verify connections are secure at both ends 9