Oxygen Delivery Devices - Amplified

Quick Reference

Device Summary

Venturi Colour Codes

Device Selection

Low-Flow Devices

These devices don't meet the patient's full inspiratory demand. The patient draws in room air around the device, diluting the oxygen. The actual FiO2 depends on the patient's breathing pattern.

Nasal Prongs: Most comfortable option. Patient can eat, drink, and talk. Each L/min adds roughly 4% to FiO2 (so 2L/min ≈ 28%, 4L/min ≈ 36%). Above 4L/min, nasal drying becomes uncomfortable - add humidification or switch to mask.

Hudson (Simple) Mask: Higher FiO2 than prongs alone. Must keep flow ≥5L/min to flush exhaled CO2 from the mask - otherwise the patient rebreathes their own CO2.

Non-Rebreather Mask (NRB): For sick patients needing high FiO2. One-way valves prevent room air entering. The reservoir bag must stay inflated - if it collapses during inspiration, flow is too low. Set to 10-15 L/min.

High-Flow / Fixed FiO2 Devices

Venturi Mask: Uses the Venturi effect to entrain a fixed ratio of room air, delivering a precise FiO2 regardless of breathing pattern. Essential for CO2 retainers where you need tight control. Match the flow rate to the colour-coded adaptor.

High-Flow Nasal Cannula (HFNC): Delivers heated, humidified oxygen at very high flows (30-60 L/min). The high flow meets inspiratory demand, reducing room air dilution and providing a small PEEP effect. Used in hypoxic respiratory failure, particularly COVID pneumonia and acute pulmonary oedema.

Prep

Check flow meter reading (equator of ball)

Read the flow at the middle (equator) of the ball float, not the top or bottom. Ensure the ball moves freely in the tube. On Inhalo portable cylinders, you must first crack the grey seal to open the master valve before the flow meter will work.

Check tubing connections

Trace the oxygen tubing from the wall/cylinder to the patient. Look for kinks, disconnections, or wrong ports. Green = oxygen (not air, which is yellow/white). Loose connections are a common cause of "oxygen not working."

Execute

Select appropriate device

Match the device to the patient's oxygen requirement and clinical situation:

• Mild hypoxia, stable: nasal prongs 2-4 L/min
• Moderate hypoxia: Hudson mask 6-10 L/min
• Severe hypoxia, acutely unwell: non-rebreather 15 L/min
• CO2 retainer (COPD): Venturi at 24-28% initially
• Respiratory failure, high work of breathing: consider HFNC

Set flow rate

Turn the flow meter to the appropriate rate for your chosen device. The ball should float steadily in the tube. For NRB, always use 10-15 L/min. For Venturi, match the flow to the coloured adaptor instructions.

Apply to patient

Position the device correctly:

• Nasal prongs: prongs curve into nostrils, tubing over ears
• Masks: cover nose and mouth, tighten straps for seal without pressure injury
• NRB: ensure reservoir is inflated before placing on patient

Check reservoir bag inflates (NRB)

For non-rebreather masks, watch the reservoir bag during expiration - it should inflate fully. If it collapses during inspiration, oxygen flow is insufficient. Turn up the flow until the bag stays inflated throughout the respiratory cycle.

Finish

Document FiO2 and SpO2

Record: device used, flow rate (L/min), approximate FiO2, and patient's SpO2 at that setting. This allows others to assess the patient's oxygen requirement - a patient on 2L prongs at 98% is very different from one on 15L NRB at 92%.

Reassess in 15-30 min

Oxygen requirements change. Check back to ensure the patient is stable on the current therapy. If SpO2 is falling or work of breathing is increasing, escalate therapy or call for help.

Special Populations

CO2 Retainers

Patients with chronic hypercapnia (usually COPD) have lost their CO2 drive and breathe based on hypoxic drive. Giving high-flow oxygen removes this stimulus and they may hypoventilate, causing dangerous hypercapnia.

• Target SpO2 88-92% (not 94-98%)
• Use Venturi mask for precise FiO2 delivery
• Start at 24-28% and titrate carefully
• Monitor for drowsiness (sign of CO2 narcosis)

Carbon Monoxide Poisoning

CO binds haemoglobin with 200x affinity of O2, displacing oxygen. SpO2 reads falsely normal because the oximeter can't distinguish COHb from O2Hb.

• Give 100% oxygen regardless of SpO2
• Use non-rebreather at 15 L/min
• Consider hyperbaric oxygen for: loss of consciousness, pregnancy, COHb >25%, cardiac involvement