Oxygen Delivery Devices

Oxygen Delivery Devices

By Ashly Liu

Supplemental oxygen can be used for patients, primarily to treat hypoxia. It is important to note that as medical practitioners, we prescribe oxygen to patients and consequently should understand the modes of delivery we can prescribe.

Oxygen Delivery Devices

Low Flow Nasal Prongs

• Percentage of oxygen delivered: 24-44% (variable performance device)
  • Conventionally, for every litre of oxygen supplied, FiO2 increases by 4%
  • I.e. for 1L/min, approximately FiO2 24% is delivered
• Flow rates: 0.5-6L/min

Simple Face Mask

• Percentage of oxygen delivered: 24-60% (variable performance device)
  • FiO2 depends on flow rates and patient’s work of breathing
• Flow rates: 5-10L/min
  • At lower flow rates below 5L/min, carbon dioxide may accumulate in the mask

Non-rebreather Mask

A non-rebreather has a one way valve between the reservoir bag and face mask, which prevents exhaled breath going into the reservoir, as well as a 2x one way valves on the exhalation ports from the face mask, which prevents room air entrainment. This maximises the oxygen concentration for the patient.

• Percentage of oxygen delivered: 40-90% 
  • This can vary depending on patient’s minute ventilation and the flow should be high enough to keep the reservoir bag inflated.
• Flow rates: 10-20L/min

Venturi mask

Venturi (air entrainment) masks are designed to deliver a precise level of FiO2, which may be required for patients with a dependence on a hypoxaemic respiratory drive. 

• Percentage of oxygen delivered: 24-70% (fixed performance devices)
  • Blue: 24% at 4L/min
  • White: 28% at 4L/min
  • Orange: 31% at 6L/min
  • Yellow: 35% at 8L/min
  • Red: 40% at 8L/min
  • Green: 60% at 12L/min
• Flow rates: 4-12L/min

High Flow Nasal Cannula

• Percentage of oxygen delivered: 21-100%
• Flow rates: 20-70L/min

CPAP/NIV

• Percentage of oxygen delivered: 21-100%
• Flow rates: 20-100L/min

Continuous Positive Airway Pressure (CPAP) devices apply constant pressure throughout the respiratory cycle via face mask or other interface to splint open the upper airway, increase lung volume, and increase intrathoracic pressure. 

Non-invasive ventilation (NIV) applies TWO levels of pressure during the respiratory cycle – a pressure during the inspiratory phase that is greater than the pressure applied during exhalation. This is effectively mechanical ventilation, and can unload the respiratory muscles and provide complete respiratory support.

Complications of over-oxygenation

Oxygen toxicity

Oxygen toxicity occurs when the partial pressure of O2 (PAO2) exceeds that which is breathed under normal conditions. Over time, with continuous exposure to supraphysiologic concentrations of O2, a state of hyperoxia develops. Under hyperoxic pathological conditions, a large influx of O2 species (ROS) are produced. 

Summary of oxygen delivery

References:

Batool. S, Garg. R, “Appropriate use of Oxygen Delivery Devices”. https://openanesthesiajournal.com/VOLUME/11/PAGE/35/FULLTEXT/ 

Michael Lipnick, MD, Cornelius Sendagire, MMed, Rich Kallet, MS, RRT, FAARC, Rich Branson, MS, RRT, Rebecca Silvers, BSN, MSN, DnP. Overview of oxygen delivery devices. OpenCriticalCare.org. Published on 28/02/2023. Accessed 12/06/2024. Available at OpenCriticalCare.org/encyclopedia/overview-of-oxygen-delivery-devices