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We’re gonna talk about the hierarchy of oxygen delivery. We’ve got a great cheatsheet about this, but we wanted to create a little video for you guys to help you understand the basics and the best ways to remember these things!
So let’s talk about the devices in order from least invasive to most invasive. When you’re administering oxygen to your patient you always want to start with the least invasive method and move to more invasive methods if they’re required. So it starts at Room Air – that’s essentially no device at all. Then you’ll see the devices get bigger and bigger as you advance. So we would move first to a nasal cannula, then a simple mask, then a venturi mask which allows us a bit more precise control. Then we’d move to a non-rebreather. At this point if you’re putting your patient on a non-rebreather it’s because they’re really struggling. You should at least have the Respiratory Therapist at bedside and you need to call the provider. Above that, we can do noninvasive ventilation like CPAP or BiPAP, and then we would move to invasive ventilation with an ET Tube or long term a tracheostomy. For trach’s we can use a trach collar or a T-piece as well as the mechanical ventilator to deliver oxygen.
So one of the most important things to know about the device you’re using is what kind of FiO2 you can get. FiO2 stands for Fraction of Inspired Oxygen. In other words – what percentage of the air they’re inhaling is oxygen? Well Room Air is 21% oxygen – the rest is hydrogen, nitrogen, and other gases. So our bodies can normally function on 21% oxygen. The cheatsheet will show you the exact numbers, but we want to show you a quick way to remember these. When we apply a nasal cannula, 1 liter per minute is 24% oxygen. Then, it goes up by 4% from there. So – 28%, 32%, 36%, etc. With a nasal cannula, we can’t go above 6 liters per minute – at that point the flow becomes so great within their nose that the oxygen just stirs up and comes right back out of their nose. Once you hit 6 liters per minute which is 44% FiO2 you would move up to a simple mask. With a simple mask, the FiO2 of 5 liters is the same as for a nasal cannula – 40%. So that makes it easier to remember. Then it goes up by 5-7 percent from there. So 6 liters would be about 45-50, 7 liters would be 50-55, and 8 would be about 60%. This allows us to get a higher FiO2 to the patient more easily than a nasal cannula.
Venturi masks are also used after nasal cannulas. The benefit of a venturi mask over a simple facemask is that it allows for a precise FiO2. There’s a colored attachment that goes on the mask. As you turn it, you can select the FiO2 you want and it will tell you what to set the flow meter on. So for example, 35% might say “6 lpm”. Make sure you are matching up what’s on the mask and what the flow meter is set on. Then from there we move up to a non-rebreather. It’s about 10% per lpm so 10 lpm is about 100%. We can’t get it exact because it sometimes pulls air in around the mask, but it’s pretty close. Now, yes you could put on a nonrebreather at 6 liters for 60% FiO2 BUT – like I said before if you’re headed to a non rebreather it’s because your patient is going downhill. Put it on, plug it in, and crank it to 10.
Now one thing to note here is that you do need an order for whatever device you’re using. You MAY change devices for the safety of your patient – but you need to immediately call the provider to get the order updated. Some facilities will have standing orders that allow Respiratory Therapists to advance devices as needed – so make sure you’re collaborating with them.
So let’s talk about the difference between CPAP and BiPAP. Both are forms of non-invasive ventilation done through a mask like the one in this picture. CPAP stands for Continuous Positive Airway Pressure – so it delivers positive pressure at one level throughout the whole breath cycle. This helps decrease work of breathing and open up alveoli. BiPAP stands for Bi-Level Positive Airway Pressure. So just by the name you know the main difference is that there are two levels instead of just one. There’s a level of pressure on inspiration called Inspiratory Positive Airway Pressure or IPAP. This helps to support the patient as they take a deep breath in to help decrease work of breathing and open the alveoli. Then Positive End Expiratory Pressure or PEEP is a minimum pressure that is left in the system after expiration. The goal of PEEP is to keep the alveoli expanded even after exhalation.
Now, after these two, we would move to invasive mechanical ventilation if needed. We’ll talk more about that in the Vent alarms lesson. For now, just know that that would be the next step.
So just to recap – we always start with the least invasive device and work our way up as the patient’s needs increase. Remember that your interventions have to match your orders so make sure you’re collaborating with your Respiratory Therapist and provider as your patient’s oxygen requirements are increasing. And finally, knowing where you are in terms of FiO2 and what the next device would be helps you to be prepared in advance should something go wrong. We want you guys to be on top of it and level-headed if your patient starts to go downhill.
Don’t forget to check out the cheat sheet attached to this lesson – you can even print it out and take it with you – or there’s a similar card in the Scrub Cheats that will fit right in your scrub pocket! Now, go out and be your best selves today, and, as always, happy nursing!