As a nursing student, you might find all the different oxygen delivery systems confusing. But not anymore! In this post we’ll cover the main oxygen delivery systems you’ll see in your clinical rotations. Ready?

A Few Important Terms

Before we get into the different types of oxygen delivery systems, we need to go over a few key terms.

First of all, you will hear systems referred to as low-flow and high-flow. Low-flow systems (like the trusty nasal cannula) deliver oxygen at a rate that is less than the amount of air that the patient can inhale or exhale in one minute (called “minute ventilation.”) For reference, the minute ventilation of a healthy adult male at rest is about 6 L/minute. So, when we talk about low-flow systems, we talk about systems that deliver oxygen at a rate LESS than 6-ish liters per minute. Conversely, high-flow systems are going to deliver oxygen at a rate higher than the patient’s minute ventilation. Remember, this is not a hard-and-fast 6-liters per minute rule… it is RELATIVE to the patient’s own minute ventilation, which will change based on their physiologic status, activity and from person to person.

Next, you’ll need to understand that oxygen delivery is often talked about in two different ways: L/min (liters per minute) and FiO2 or “fraction of inspired oxygen” or, more simply “percent oxygen”. When we talk about “liters per minute” we are talking about how much oxygen flow is being instilled through the device. Note that there is  bit of variation based on the optimal flow rates and FiO2 delivery of these devices, which is due to multiple studies yielding results that vary to some degree. With that said, use these values as a general  guideline and you’ll be in the ballpark…and whenever you are in doubt, ask your facility or nursing school educator for guidance. Ready to get started? Let’s go!

Nasal Cannula

  • Description: nasal prongs that sit in the nares
  • Flow rate: 1 to 6 L/minute (so it’s a low-flow system!)
  • FiO2: 24 to 44%
  • Advantages: small, lightweight, can use while eating/drinking, comfortable
  • Disadvantages: can cause skin breakdown at nares and ears, can be drying (add humidification to prevent this)

Simple Face Mask

  • Description: standard face mask that covers the nose and mouth
  • Flow rate: 6 to 8 L/minute (borderline low-flow system, depending on how it’s used and the oxygen demands of the patient)
  • FiO2: 40 to 60%
  • Advantages: easy to use
  • Disadvantages: uncomfortable, claustrophobic for some, pt can’t eat or drink while wearing, dries the nares and may not fit well

Partial Rebreather

  • Description: face mask with reservoir bag and a two-way valve that allows SOME of the exhaled air to enter the reservoir bag. This air (which contains some oxygen)  is “reused” thereby increasing the amount of oxygen the patient receives
  • Flow rate: 6 to 10 L/minute
  • FiO2: 60 to 80%
  • Advantages: provides higher FiO2 than simple face mask
  • Disadvantages: uncomfortable, bulky due to reservoir bag, claustrophobic for some, pt can’t eat or drink while wearing, dries the nares and may not fit well

Salter Nasal Cannula

  • Description: A nasal cannula that can handle high-flow rates, so you also may hear it called a “high-flow” cannula, or simply a “salter”
  • Flow rate: up to 15L minute
  • FiO2: highly variable in the available studies; one study showed a mean of 69.8 to 80.6% FiO2. It’s definitely higher than a standard nasal cannula, but to get reliable FiO2 with a cannula, you’ll want to use a high-flow nasal cannula with a blender (see below!)
  • Advantages: patient can eat and drink, just as with any nasal cannula, can handle high-flow rates for patients with higher oxygen demands but don’t tolerate wearing a mask
  • Disadvantages: drying to the nares, so always use humidification , watch for skin breakdown at nares and ears

High Flow Nasal Cannula

  • Description: The HFNC is an oxygen-delivery system that includes an air/oxygen blender, humidifier, heater and nasal cannula to deliver precise and very high flow oxygen to your patient
  • Flow rate: up to 60L/minute
  • FiO2: 21 to 100%
  • Advantages: same as Salter with added benefit of providing higher flow rate and consistent FiO2 for patients with high oxygen demands
  • Disadvantages: expensive, not typically available for home use due to high flow rates


  • Description: looks like a simple face mask except it has big openings in it; its design directs oxygen toward the patient’s nose and mouth; the patient breaths this oxygen along with atmospheric oxygen through the openings…on exhale carbon dioxide is released into the air so there’s no need for valves or reservoirs like in a partial rebreather or non-rebreather.
  • Flow rate: 1 to 15 L/minute
  • FiO2: 24 to 90%
  • Advantages: comfortable, pt can drink with a straw due to the big openings in the mask, less claustrophobic than standard face masks, pt can speak more easily, less risk to rebreather CO2, less risk for aspiration of emesis
  • Disadvantages: not a lot…oxymasks are awesome and are what we use the most in my unit after the nasal cannula

Non Rebreather

  • Description: The non rebreather mask looks almost exactly like the partial rebreather, except it has two one-way valves; one of those valves prevents any exhaled air from entering the reservoir bag and the other valves prevents any room air from entering the mask while allowing CO2 to be exhaled out into the atmosphere
  • Flow rate: 10 to 15 L/min
  • FiO2: 60 to 90%
  • Advantages: A great choice when higher oxygen flow rates are needed
  • Disadvantages: bulky, cumbersome, can be claustrophobia-inducing for some patients; must watch reservoir bag closely to ensure it remains inflated at all times; impedes patient’s ability to communicate, eat and drink


  • Description: looks essentially like a face mask with the addition of color-coded adapters that direct a specific oxygen concentration to the patient; often used in persistent hypercarbia or moderate to severe hypoxemia
  • Flow rate: 2 to 15 L/min
  • FiO2: adapters deliver set amounts of FiO2 at 24 to 60%
  • Advantages: can delivery precise and dependable FiO2
  • Disadvantages: only goes up to 60% FIo2, so not for patients who have significantly high oxygen demands, bulky; impedes communication, eating and drinking

Bag Valve Mask

  • Description: also called a BVM, the bag valve mask is what you use when your patient is unable to breathe effectively without assistance; it consists of a face mask and reservoir bag that you position over the patient’s nose/mouth while forcing air into the lungs by squeezing the bag
  • Flow rate: 12 to 15 L/min
  • FiO2: 60 to 100%
  • Advantages: this is your go-to device in a respiratory emergency and should ALWAYS be at the ready; when you do your first head-to-toe assessment, make sure you know where the BVM is kept (in some units there is one per room, in med-surf units there might be one shared device located nearby…always always know where your BVM is and how to hook it up!
  • Disadvantages: requires an effective seal, provider fatigue, used for short-term ventilation only


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Hope that helps you breathe a little easier in clinicals!