Oxygen Delivery Devices

OBJECTIVES:

  • Understand differences in provided respiratory support between commonly used oxygen delivery devices


Oxygen Delivery Devices

Oxygenation is affected by inspired FiO2 and positive end expiratory pressure (or PEEP). Oxygen delivery devices used on acute care floors are largely limited to adjustments in FiO2. Non-invasive positive pressure ventilation (NIPPV), such as CPAP or Bilevel, provide PEEP to further support oxygenation (discussed in additional learning section).

In addition to PEEP and FiO2, oxygen flow rate (as compared to a patient’s inspiratory flow rate) can have an indirect effect on a patient’s oxygenation. It is important to recognize that the most commonly used oxygen devices on acute care floors (nasal cannula, simple face mask) deliver 100% FiO2 oxygen at an adjustable flow rate. This oxygen intermixes with ambient air (21% FiO2) which dilutes the oxygen to produce an “effective FiO2.” With respiratory distress, a patient’s inspiratory flow rate can range from 30 – 120 L/min which far exceeds the flow rate provided by some oxygen delivery devices.

Only more advanced oxygen delivery systems (Venturi mask, high flow nasal cannula) allow fine tune control over the delivered FiO2.


Nasal Cannula

Most common oxygen delivery device used on acute care floors. It is convenient and allows easy access to the face so the patient can easily talk and eat. It is most effective in nose breathing patients with mild hypoxia.


Oxymizer

A form of nasal cannula that contains a small external reservoir, which collects a small volume of 100% FiO2 oxygen that is delivered immediately upon inhalation. The reservoir and larger bore nasal prongs allow for more effective oxygen delivery (higher effective FiO2 per flow rate compared to nasal cannula).


Simple Face Mask 

Commonly used in patients who are mouth breathers or do not tolerate nasal cannula at higher flow rates.  However, the mask is less convenient than the nasal cannula and can be claustrophobic.


Venturi mask

The Venturi device delivers a consistent FiO2 at higher flow rates (achieved by intentionally entraining ambient air through the device). It can be useful if a patient has variable or higher work of breathing (and resultant increased inspiratory flow rate) or a consistent delivery of an exact FiO2 is desired.


Non-rebreather Mask (NRB)

This is a rescue method of oxygen delivery and can provide ~ 90% FiO2 at maximum flow rate of 15 L/min. A NRB additionally can be used to assess whether a patient will have a significant response to oxygen (e.g. presence of a large shunt).


High flow nasal cannula (HFNC)

HFNC is a newer form of oxygen delivery device that allows for delivery of high flow rates that can more closely match a patient’s inspiratory flow rate and high FiO2‘s. HFNC has been shown to not only improve oxygenation, but also to improves work of breathing and minute ventilation (VE). This is also the only form of delivery device that delivers a small amount of PEEP, though it is not readily measurable or adjustable.


Summary of oxygen delivery devices:

Why don’t we just use as much oxygen as possible? (~1-2 min) 


TAKE HOME POINTS: 


ADDITIONAL LEARNING:

Non-invasive Positive Pressure Ventilation (~ 10 minutes) 

What are the indications and contraindications for NIPPV? (~5 min) 

How does NIPPV improve outcomes in cardiogenic pulmonary edema? (~3 min)

Now you’re ready for some practice cases!


REFERENCES:

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