I don’t know about anyone else out there, but I learned minimal amounts of information regarding all of the different devices respiratory therapists use when we have a patient who needs oxygen support. Perhaps this is something I should have looked up sooner, but my guess is that it wasn’t a priority for boards so I ignored it unfortunately.
The other night I got a page that a patient on my list had O2 saturations in the mid 80’s on 31% 6L Venturi mask. My literal response was: What in the world is this and what do I do about it? Literally. Hello?! I’m a licensed PA shouldn’t I know this? I should tell you that before I was a PA I was a mental health therapist and that was my patient care experience–so my time in a hospital was well–nil.
Side Note: there has been a lot of talk on AAPA Huddle whether people with my background are prepared for PA school and to practice hospital medicine and whether programs should tighten their accepted health care hour experience–perhaps more on this on another day. Interesting thought.
Let’s be real, there is only so much time to cover vital information during didactic year. And I’m pretty sure my main thought during clinical year was “Dear baby Jesus please let me pass the PANCE”. This was just not one of those things we covered extensively–and if we did I totally zoned out (if we are being honest we all do it at some point). So, I talked with the other PA’s that were working with me, we printed out some information for me to read and I started watching you tube videos.
The purpose of this post is to examine the most common types of oxygen delivery systems, a basic understanding of how they work and a general understanding of when to utilize each of them. I’ll also provide pictures, because I don’t know about you but I had no idea what half this stuff looked like.
Before I go into descriptions of each type of oxygen delivery, a reminder as to what the FiO2 is, because it’s important to understanding oxygen delivery methods. Different devices are able to deliver different FiO2. Thus, have varying effects on oxygenation.
- FiO2: Fraction of inspired O2 being measured in space. Naturally occurring in the atmosphere, you and I walk around breathing 21% FiO2. So, when we place patients on supplemental oxygen, they are all requiring a higher FiO2 to maintain adequate oxygenation. We can supplement patients all the way up to 100% FiO2.
- The chart below is a summary of the devices I go on to describe, and the ability to effect FiO2. I provided this information under each of the separate devices, but I realize that some people might like the condensed information (table found in the online ACLS manual).
I think most of you know what nasal cannula is, but I will go through a
brief description. Nasal cannula is a low flow delivery system, the regular good old tubing that has an opening for each nostril. Generally speaking, NC is able to deliver anywhere from 21-40% FiO2 and is typically not run higher than 5L. If you patient is at 5L and not reaching saturation goal, they probably need a higher level of oxygen delivery. In order to use nasal cannula the patient has to be spontaneously breathing on their own because how well NC works is influenced by breath rate, tidal volume and whatever the underlying pathophysiology. It’s also not a bad idea to humidify oxygen as it can dry out the nares. A simple rule of thumb that I found by reading many articles and web sites is that for every liter/min of oxygen that you add you increase the FiO2 by 4%, starting with 1L. So, it would look at follows:
- 1L = 24% FiO2
- 2L= 28% FiO2
- 3L= 32% FiO2
- 4L= 36% FiO2
- 5L= 40% FiO2
- 6L= 44% FiO2
Simple Face Mask
Not used commonly in a hospital setting, typically only when patients are not tolerating standard nasal cannula. It is a low flow delivery system and cannot accurately deliver a specific FiO2. The FiO2 thought to be maintained through simple face mask is 40-60% at 5-20L/min. A minimum of 5L is absolutely required because. Anything less than this and the CO2 will not be removed from the mask. The simple mask also requires a patient who is breathing on their own and is influenced by respiratory rate and tidal volume. Mostly used in a hospital setting when a patient is not tolerating nasal cannula due to irritation of the nares or epistaxis..
The Venturi mask is considered a high flow oxygen device that has the ability to deliver various settings of FiO2 based on the attachment utilized. So, that normal 21% FiO2 that we consume in the atmosphere– patients who require additional assistance getting proper oxygenation require a higher FiO2. The various attachments which are pictured, provide the ability to deliver varying percentages of oxygen. It sounds confusing— so it’s like this there is 100% oxygen being delivered to the patient via the special tubing and varying jet adapter devices that allow a certain amount of atmosphere air to mix with the atmosphere air–altering the FiO2 the individual is receiving. The Venturi mask provides the most precise oxygen delivery. The one downside, the potential for respiratory depression in patients with COPD when oxygen concentrations are high (>50%).
High flow delivery system, that also requires a spontaneously breathing patient. Settings here are 8-10L/min and greater than 40%FiO2 requirement of your patient. The non-rebreather mask as pictured, has a one way valve that inputs high FiO2 when the patient inhales. When patient exhales there are two ports on the side where CO2 escapes. All of the exhaled air in this situation escapes. I did read that there are 3 one way valves and you can maximize the percent of oxygen your patient receives if all 3 are closed; however, because of legal purposes one of them always has to be open. The bag attached acts as an oxygen reservoir, and should never become collapsed at any point to ensure possibility of 100% O2 delivery. These can be uncomfortable so they are not appropriate for long-term care of hypoxemia; however, they are appropriate to utilize in the acute care setting.
Tracheostomies are performed for a variety of reasons. These obviously, do not require a spontaneously breathing patient. Individuals receive a tracheostomies for reasons such as obstruction, long-term ventilation requirement, weaning patient off vent, respiratory muscle paralysis (ALS). It is exactly what it sounds like, a catheter a few inches long inserted directly into the wind pipe. There are all different types of trach tubes–which is beyond the point of this post. Know that trach cuffs with fenestrations are what allow patients to be able to speak with a tracheostomy. Most of what I have seen of patients who are trached, are those who are in critical condition, came in because of a trauma, being weaned off the ventilator, or have had obstruction due to esophageal cancer. From my reading I have learned that it is easier to wean a patient off the vent with a trach as opposed to an ETT. Disclaimer: I know next to nothing about how to wean a patient off a vent. Perhaps that is a discussion for another day.
NIPPV: Non-Invasive positive pressure ventilation
Although one could argue whether this fits in the “oxygen delivery method” section I didn’t think it could hurt to add a word or two about CPAP and BiPAP. NIPPV refers to methods of assisting patients to properly oxygenate without intubation or trach (which would obviously be considered “invasive”).
Continuous Positive Airway Pressure (CPAP)
Most commonly used in our patients with obstructive sleep apnea (OSA). In order to use CPAP the patient must spontaneously breathe on their own. It is typically used when someone is hypoxic despite other less invasive measures (ie nasal cannula, mouth pieces for OSA). Patients with OSA often require CPAP because of their body habitus and anatomy, they have a difficult time getting their breath past a collapsed upper airway. The pressure that is continually delivered to the patient to help keep the alveoli in the lungs “popped” open to optimize the lungs surface area for ventilation. There are various settings to CPAP machines in order to maintain appropriate O2 saturations. Settings range between 5-20cm H2O pressure. Pressure put into airway keeps tongue forward and therefore airway = open.
Bi-level Positive Airway Pressure (BiPAP)
Used in a variety of settings, delivers inhale and exhale pressure, meaning there is a generated inspiratory as well as expiratory airway pressures (IPAP and EPAP respectively). Also used for COPD, ALS, CHF and Acute Respiratory failure. Unlike CPAP you have the choice of two level settings for IPAP and EPAP. Patient takes breath in: delivers IPAP. Patient exhales: exhales against positive pressure–with bipap the airways don’t completely collapse so CO2 can be pushed out more effectively. To improve ventilation (meaning if you have high CO2) IPAP needs increased. If oxygenation is low, increase EPAP. Again, these are just basics that I have come across through my research for this post. The goal here for patients is to have an appropriate tidal volume and oxygen saturation.
I hope this was helpful to others out there who were in the same situation. This is by no means comprehensive coverage. There are other options out there and there is so much more related information I could have covered–but it would have been a snow ball effect that never ended. Below are a list of resources I consulted to help my post!
Resources Helped to create this post:
ALCS Provider Manual
- I believe it was the same manual you first get when you become ACLS certified. Found a copy online and sifted through.
- This is an endless site of information on anything related to what respiratory therapists do! I absolutely loved what they had going on!
- The same old UpToDate I’ve talked about before that mostly everyone knows about. Super expensive if your institution doesn’t pay for it but an awesome resource.
- The first time I’ve used their channel but love, love, loved it! The “surviving your ICU rotation” playlist looks awesome, definitely getting added to my resources page!