Understanding Ventilator Settings (Nursing)

by Rhonda Lawes, PhD, RN

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    00:00 This portion of our video series is going to talk specifically about oxygen.

    00:05 So, this isn't a really quick review of what you likely have already been introduced to in our other series.

    00:11 But I want to show you the difference in how you start supporting oxygen until what happens when they end up on a ventilator.

    00:17 Now there are multiple oxygen delivery devices, right.

    00:21 They can offer different flows and concentrations of oxygen.

    00:25 FiO2, is a fraction of inspired oxygen.

    00:29 So we're going to titrate these based on the patient's experiences and the orders that you have.

    00:34 So let's take them out the things that do not include invasively sticking a tube into your patient.

    00:40 Room Air is 21%.

    00:43 I just taught this in my patho class the other day, and they were guessing 85, 90. And really, it's 21%.

    00:52 This air that you're breathing right now is 21%.

    00:56 When we put oxygen onto you in any format, we're going to increase the percentage the fraction inspired oxygen that you're breathing.

    01:05 So let's take a look at the nasal cannula.

    01:07 If you've been in a hospital, you've likely seen somebody on a nasal cannula.

    01:11 That flow per minute, if you get it between two and six, the fraction of inspired oxygen is 25 to 40.

    01:18 What's room air? 21. You got it.

    01:21 Simple facemask. Well, that flow is going to be between six and 10 of oxygen. And when we say flow, that's the number of liters. You have a little meter on the wall and you adjust it by a down and you see a small black ball move up and down.

    01:34 That black ball will be in the middle of six or 10.

    01:37 That means that's the number of liters of oxygen the patient is receiving.

    01:42 That FiO2 is 35 to 50%. Remember 21? Nasal cannula 2 to 6, 25 to 40.

    01:50 Simple facemask 35 to 50.

    01:53 So depending on how many liters of oxygen the patient is on, you'll see there's an overlap between the simple face mask and nasal cannula.

    02:01 Now, venturi mask different type of mask.

    02:03 Look,FiO2 is 24 to 60.

    02:06 If you have a non rebreather that's 80 to 90.

    02:09 And if you have a high flow nasal cannula, look at what the FiO2 is.

    02:14 Whoa, yeah, that is a supercharged version of a nasal cannula.

    02:20 But please remember that all of these five examples, they don't push air into your patient.

    02:27 So your patient has to be able to inspire on their own.

    02:32 So that's when we use these different five types.

    02:35 The goal is not to intubate a patient unless we absolutely have to.

    02:39 But here's a review of the different types of oxygen delivery methods we use, how many liters they run at and what the FiO2 is.

    02:48 And this is what we would utilize before a ventilator.

    02:52 Now, let's look at what happens when we put a patient on a ventilator as far as FiO2.

    02:58 So, we've already looked at what the level of oxygen that can be delivered with a nasal cannula and all the other masks.

    03:05 But remember, the patient has to be able to breathe in on their own in order for those to work.

    03:10 Because you might have been thinking, why would you not just keep somebody on that high powered nasal cannula if he can get up to 100%? If they can't breathe in on their own, or can't support or protect their airway that's not effective.

    03:22 Remember, as you increase the FiO2, you're going to increase the amount of oxygen in their blood.

    03:28 As you decrease the amount of FiO2, you're going to lower oxygenation.

    03:32 So it's this dance that we play based on what your patient needs, and how we can try and wean them off that FiO2 We want it to go down and down and down till we can pull them excavate them from the ventilator.

    03:46 So that is the fraction inspirative oxygen with a patient who is on a ventilator.

    03:51 Let's talk about lung volumes.

    03:53 Now if you look at the graph that we have for you there, you see that along the bottom, the horizontal axis is time along the top is lung capacity.

    04:04 And we measure lung capacity in milliliters.

    04:06 So you see as the patient is breathing in, you'll see that it's about 500. And then they breathe out, it's down with a tiniest bit still left in there, And then up and then down, up and down, up and down.

    04:19 That's what we call the tidal volume.

    04:22 Now the tidal volume on this drawing would be about 500.

    04:26 We've got lots of formulas for you to calculate what would be the appropriate tidal volume to plug into the ventilator.

    04:32 But this is what they mean when they say tidal volume.

    04:35 That is that upper limit of how much air is filling up the lungs at the top of the breath.

    04:41 Up to this point, we've talked about two types of ventilator settings.

    04:44 The first one was FiO2. The second one was tidal volume.

    04:50 That's the volume of air that's being blown into the patient lungs.

    04:54 The third one is respiratory rate.

    04:57 Now if we increase the respiratory rate, this will increase ventilation, but it will decrease the CO2 level.

    05:03 If we decrease it, it will likely increase the CO2 level.

    05:08 So, respiratory rate is usually set somewhere between 12 or 22 a minute, unless they're on a very specialized ventilator, or a tiny human, baby, neonatal kind of client.

    05:19 They're going to have rates way different.

    05:22 This is for an average adult client.

    05:24 It'll be set between 12 and 22.

    05:27 So know that if the rate is too high for the patient.

    05:29 Their CO2 level will be too low.

    05:31 If it's too slow for the patient's needs, their CO2 level will be higher. Just like happens in my own body.

    05:40 If I'm hyperventilating, I'm blowing off CO2, my CO2 level will go down.

    05:45 If I'm sedated, and I'm not breathing very much my CO2 level is going to be retained or higher.

    05:53 Now, flow rate is another one.

    05:55 The maximum flow, the ventilator will deliver, and a set tidal volume in liters per minute.

    06:00 Okay, so flow rate is the maximum flow. Makes sense.

    06:06 So flow rate, the maximum flow, that the ventilator will deliver the volume that's been set in the machine.

    06:12 So, if I have on a ventilator, and it's been set with a tidal volume of 500 milliliters flow rate is just how fast that air is going to be delivered up to that 500 milliliters.

    06:24 Now, you can increase it, but you might also have a possible increase in ventilation effect it can be lowered. But what do you think's going to happen? If I increase the flow rate, what do you think the impact would be on the CO2? If I increase it, it could likely decrease the CO2.

    06:43 What if I lower it? Well, that would do just the opposite, it could increase the CaO2.

    06:50 Let's look at the very end of the line in your respiratory system.

    06:54 So this is an alveoli. Should look kind of familiar.

    06:58 You see that it's a round shaped and it's also kind of damp in there, right? So I've got the alveoli, the round shape, and then those are the capillaries.

    07:07 Now, the alveoli is one cell thick, the capillaries are one cell thick.

    07:11 And that's because there is a gas exchanged.

    07:14 Now we need it moist in there, but look at where the water is.

    07:18 Now, you knew if you took, you dipped your fingers in water and you flung it at a tabletop, that water would beat up, right? It would pull together because that's what water does.

    07:29 The tension of the water it's pulling together, that's what water naturally does. We call that surface tension.

    07:36 So if the water was just left to do what it would normally do, it would cause alveoli to collapse.

    07:43 Because that blue ring you see in this alveoli would pull the alveoli together. It would collapse.

    07:50 Luckily, we have a cool thing in our body called surfactant.

    07:52 And that makes sure it doesn't happen.

    07:55 But this is why if someone doesn't have adequate surfactant, Their alveoli like don't stay open and intact.

    08:01 And then we have really poor gas exchange.

    08:04 Alveoli need to be open, intact, and round in order for CO2 and O2 to be exchanged in the lungs.

    08:11 So without that surfactant that's what would cause you alveolar collapse.

    08:16 So let me give you an example of what that looks like.

    08:19 Now we've got a close up of that alveolar wall.

    08:21 Now the surfactant molecules, see them? You've got the little head and the two legs, they kind of push themselves in between the water molecules.

    08:30 Why this is good as it breaks up that tension? So that's why the water behaves itself and spreads out instead of globbing all together in the middle, causing the alveoli to collapse. Why do you care? Makes a huge difference in how a patient can ventilate.

    08:45 So look at that little surfactant.

    08:48 It's got that round circle on one side, which is hydrophilic.

    08:52 That means it loves philo. It loves water.

    08:56 That's why it's squirms right in there.

    08:58 Then it's got a hydrophobic.

    09:00 It hates or think of it as afraid of water, and it floats out in the alveoli.

    09:06 This is why everyone needs adequate amounts of surfactant to make sure that water that tension is broken up.

    09:14 So it stays all around the alveoli instead of dragging everything into the middle and causing collapse.

    09:22 Another setting is Positive end-expiratory pressure PEEP is what you most often hear call I don't rarely hear someone call what is the Positive end-expiratory pressure setting? They'll call it PEEP.

    09:34 The reason I talk to you about surfactant just now is because this is kind of a manufactured way of trying to get around that.

    09:41 If the patient doesn't have adequate surfactant, there's a lot of inflammation going into the lungs.

    09:46 This is what we can do, PEEP. Positive end-expiratory pressure.

    09:51 So this is what helps keep those air sacs.

    09:54 The alveoli from collapsing on themselves.

    09:56 We just keep a constant. That's what it is, a constant low pressure.

    10:01 Positive end-expiratory pressure to help keep those alveoli open.

    10:07 Now, there comes some challenges with that.

    10:09 This is what keeps the alveoli open, and allows them to be able to exchange CO2 and O2.

    10:15 But as we increase it, there's increased risk of what can happen.

    10:19 So we know that PEEP, Positive end-expiratory pressure is the pressure that stays in the distal airways, right, the alveoli weighed down at the bottom.

    10:28 So at the end of their expiration, they still have pressure in there.

    10:31 So there alveoli, don't collapse or deflate.

    10:35 And you can increase it, if you're having trouble with oxygenation.

    10:39 but please know that that comes with risks.

    10:41 Depends on how friable or fragile the patient's lungs are.

    10:45 If we have to keep going up and up and up on PEEP, we can cause damage or barotrauma damage.

    10:51 So you want to make sure that you balance that PEEP that we know we're gonna get some benefit from it.

    10:56 And we have minimized as much as we can the risk that's going to actually happen to the tissue.

    11:02 So if positive and pressure can actually harm the patient like it can cause trauma to the alveoli. Why would we use it? Well, because it's necessary sometimes and without it that patient's alveoli would collapse.

    11:15 So who makes that decision? We'll choose you're going to be a pulmonologist and the respiratory therapy and communication with you looking at all kinds of responses and testing.

    11:24 So it's done with great care.

    11:27 But you have that discussion with your healthcare professional, talk to them about what they're trying to manage this with what they're trying to get from the PEEP? And just be aware to watch for those pressure alarms when someone's on PEEP.

    About the Lecture

    The lecture Understanding Ventilator Settings (Nursing) by Rhonda Lawes, PhD, RN is from the course Mechanical Ventilation (Nursing).

    Included Quiz Questions

    1. 21%
    2. 5%
    3. 78%
    4. 56%
    1. High-flow nasal cannula
    2. Venturi mask
    3. Non-breather
    4. Simple face mask
    1. Tidal volume
    2. Flow rate
    3. Respiratory rate
    4. FiO2
    1. Increasing the respiratory rate
    2. Increasing the FiO2
    3. Decreasing the tidal volume
    4. Decrease the flow rate
    1. The client without adequate surfactant.
    2. The client undergoing routine surgery.
    3. The client with paralysis.
    4. The client with an upper airway obstruction.

    Author of lecture Understanding Ventilator Settings (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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