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Hey everybody. This is Jon with NURSING.com. Today I just want to talk about a couple of the different methods of oxygen delivery systems that we have available for our patients.
There will be a chart available for this at https://nursing.com/cheat-sheets/. So basically when a patient comes in and is in need of oxygen delivery, we have a choice about how invasive we want to be with that delivery and how much oxygen a patient is going to need.
Delivery needs and everything is going to depend on the patient condition, how acidotic they may be if they’re COPD, and various other things that could determine the amount of oxygen that that patient might need. But today we’re just going to talk about the different kinds of oxygen delivery systems and just kind of the basics behind that.
So the patient comes in and is in need of oxygen. The least invasive method of oxygen delivery is going to be the basic nasal cannula. Now, the nasal cannula is going to deliver just a very minimal amount more of FiO2 than basic atmospheric air. So we know that FiO2 in the basic atmospheric air, if you go outside today, the FiO2 is going to be about 23 percent.
Now if you give a patient a nasal cannula at one liter per minute, they’re going to get about 24 percent oxygen. Give them the two liters and they’re going to get about 28 percent.
Now with the nasal cannula, you can go all the way up to about six liters per minute and you wouldn’t want to go much above that just for damage to the nasal airways and everything. At six liters per minute, they’re going to get about 44 percent FiO2.
So really at one liter per minute, they’re starting at 24 percent and it goes up kind of four percent per liter and the most you want to give a patient on nasal cannula is six liters per minute.
After nasal cannula, the next option for a patient would be a simple face mask and all the simple face mask does, it really kind of just covers the nose and the mouth and you can start – if you have a patient who needs five liters per minute, that would be a good time to start the simple face mask.
You can go up to eight liters per minute with a simple face mask. With that, at eight liters per minute, they’re going to get about 60 percent FiO2. So the patient really just isn’t cutting it on a simple face mask.
There are kind of two options here. You’ve got a non-rebreather mask or a venturi mask. With a non-rebreather mask, it’s a face mask that is the one that has the bag at the end as well. What the non-rebreather does differently from the simple face mask is it prevents the patient from breathing in some of that expired CO2. So this would help the patient who’s really just not SAT-ing well despite being on a simple face mask.
So if they’re really just not SATs well even though they’re on a simple face mask, you would – you could throw them a non-rebreather, prevent them from taking any of that expired CO2 and you would start that at about six liters per minute. That would be 60percent FiO2. You can go all the way up to 10 liters per minute and at 10 liters per minute they’re going to be getting close to 100 percent.
So from there, you can do a venturi mask and the venturi mask is a simple face mask but it also has – on the oxygen delivery port, you also have a dial that allows you to provide a set rate of FiO2. So you can definitely get very precise FiO2 using the venturi mask.
So it’s kind of just a simple face mask and coming off on the oxygen delivery portion. You can dial in a very precise set rate of FiO2.
Now there are a couple of non-invasive – from there, so the patient still just isn’t doing well. You’re most likely going to need some positive pressure ventilation.
The patient is awake and doing decently well. You have a couple of options for non-invasive positive pressure ventilation. So what positive pressure does is if they’re just really not able to get that air into the lungs and to oxygenate themselves, you can add pressure to the ventilation.
What this is going to do is it’s going to kind of force those alveoli open and in some ways keep the alveoli open on expiration as well. So if you are not wanting to intubate or trach the patient, then you have a couple of options for non-invasive pressure, positive pressure ventilation.
There are two options with that. There’s CPAP and BIPAP. So what CPAP does is it provides positive pressure during spontaneous press. So as the patient takes spontaneous press on their own, it’s going to provide just a small amount of positive pressure to make sure that they’re getting the alveoli open.
So with BIPAP, it’s biphasic, positive pressure. So inspiration and expiration, it’s going to provide them with positive pressure. So it’s going to provide that little bit of peep to make sure that they keep those alveoli open.
Now if neither of these are working, there are non-invasive methods. You can go to invasive methods for mechanical – to ventilate the patient. You have a couple of different options with that. There are many options. The two that we’re going to discuss are basically SIMV and assist-control.
So if your patient just really – despite all these other efforts or the patient – so really the number one criteria for if your patient needs to be mechanically ventilated is if the physician and if you as the nurse assess that the patient needs to be mechanically ventilated.
If they’re not protecting their airway, if they’re somnolent, if they have a drastic acid-base imbalance, then these are all reasons to mechanically ventilate the patient.
So you have a couple of different settings. So mechanical ventilation just means that you are providing airway assistance inside the airway and there are many different modes. We’re going to discuss SIMV and assist control.
So with SIMV ventilation, you have a preset title volume and rate. But between the ventilator and the patient, there’s a circuit that either allows the patient to take their own breaths and expire – or prevents them from kind of taking their own breaths.
With SIMV, the circuit remains open between mandatory breaths, so the patient can take additional breaths on their own. When the patient takes spontaneous breaths, it triggers the ventilator to not deliver one of its required – one of its. So the patient’s tidal volume varies with those. So, basically, anytime the patient takes a spontaneous breath, the ventilator is not going to deliver a breath and the patient can – and due to that, the ventilator will not deliver its tidal volume.
So this is usually recommended for patients who – as a weaning method for patients who are maybe trying to get off the ventilator or for patients who are doing a little bit better respiratory-wise, because it allows patients to kind of take their own breath.
So a lot of times what we do on our floor for example is we will start patients on a rate of about 12 on SIMV and as we see that they’re breathing over the vent or that they’re taking more breaths than the required breaths, then we will start to decrease the rate and it kind of allows the patient to take breaths on their own and manage their own tidal volumes, which is the amount of volume that they’re bringing in, the amount of volume that they’re bringing out.
If the patient is doing well with that, then we assume that we can start thinking about weaning from the ventilator. So above that, kind of is the assist control method.
So there’s – with the assist control, you have a preset tidal volume and rate and inspiratory effort is required to assist with spontaneous breaths. So if the patient does take a spontaneous breath, it’s going to deliver a set tidal volume no matter what.
So rather than allowing them to kind of determine their own tidal volumes, we’re pushing a specific amount of air in every time. It’s going to be at that set rate. So it’s not going to say, “OK, well, you’re breathing on your own. I’m not going to deliver a breath.” It’s going to set that rate no matter what.
So whether they’re taking breaths on their own or not, we’re going to push our set amount of tidal volume. We don’t want to keep our patients on a ventilator for too long. This kind depends on the physician. Some physicians don’t want to keep the patient on for more than a couple of days. Others will go for two weeks, sometimes more.
From mechanical ventilation, from being intubated, what can happen next is that a patient can get trached.