Name:
Ventilator Management Refresher for Surgeons
Description:
Ventilator Management Refresher for Surgeons
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T00H46M33S
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Upload Date:
2022-02-28T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
DR. BINGHAM: Okay, everybody, welcome back to Behind the Knife. We have a special episode just covering the basics of vents management. We've been hearing from a lot of people out there that are getting concerns, rightfully so, with the COVID-19 pandemic that potentially we're going to have a lot of people out there managing vents that aren't used to managing vents. So we wanted to put together a quick refresher course for vent management for the non-intensivist.
DR. BINGHAM: I should say that this is something in our hospital that we're actively preparing for and one thing that we're doing is making little pocket guides, pocket cards that are laminated, that we're distributing to all our providers that have the basics of vent titration for different scenarios. And we're happy to share that with everybody out there with the understanding that, of course, there's going to be a lot of differences of opinion on how to manage a vent.
DR. BINGHAM: This is just the basics, so take it for what it's worth. Use it if you want to, don't use it if you don't want to. Don't send us a lot of angry tweets about how you disagree with our vent management. This is just a general for the non-intensivists. Also wanted to promote that for anybody out there that's interested, there's some excellent resources on the Society of Critical Care Medicine.
DR. BINGHAM: They have some complimentary refreshers for critical care management for non-intensivists, as well as some COVID-19 specific resources to help everybody get prepared. So we'll be posting a link to those resources in our show notes, so be sure to check that out. Today, to help us out, we have a man who really needs no introduction. He's been on the program multiple times, very popular, we have Dr. Matthew J. Martin.
DR. BINGHAM: He is the former trauma director at Madigan Army Medical Center and he's currently the associate director of trauma resource and professor of surgery at Scripps Mercy Hospital. Dr. Martin, thank you for being here with us on such short notice and we really appreciate your insights.
DR. MARTIN: Yeah, hey, thanks for having me. As I've said, it's hard to find time between not going to work or not going to meetings.
DR. BINGHAM: [chuckles] Well, I imagine, unfortunately I think we're all potentially going to be very busy here shortly, so it's good to have this downtime to get it rested up.
DR. MARTIN: Yeah. And let me add, I actually looked at the SCCM course for non-intensivists, the vent management one and it's actually excellent. So I'd recommend anybody who wants to brush up, just go and do that. It's a recorded PowerPoint presentation basically. And also there's going to be a COVID-19 specific addition to the Surviving Sepsis Campaign guidelines and the pre-publication print of that should be available, they said probably by this weekend, definitely by next week.
DR. MARTIN: So that's another great resource I would look out for.
DR. KNIERY: Take it as an addition to this, Patrick Georgia, a fellow at UT Houston, is putting together a fantastic video and it's going to go into a little more detail. So if you like visuals and you want a little more detail on all the ventilator modes, but it's simple enough for surgeons to understand, you should check out this video, it will be on our Behind the Knife YouTube page, we'll have it in our show notes and we'll be tweeting it out tomorrow.
DR. KNIERY: Okay and all these will be in the links on our show notes. And Jason, there's just one thing I disagreed with on your intro is that, if they do have any disagreements, I think they should direct them at Dr. Matthew Martin on Twitter.
DR. BINGHAM: [chuckles]
DR. KNIERY: I actually really enjoy seeing his arguments and debates on Twitter. So please send them to Dr. Martin.
DR. MARTIN: Yeah, they're going to have to take a number. [all doctors laugh] But actually that's a good point to start with as, like you said, there's a ton of different opinions on some of the fine points, but actually most people agree on the basics and I think that's really what we want to focus on today, is getting a good, basic approach to starting a patient on a ventilator and then, you know, making basic vent adjustments.
DR. MARTIN: And I think it's more important to highlight basic principles, even though technically when you dig down into the fine details, they may not be entirely correct, from what a high-level pulmonologist might understand, but I think it's more important people get the basic message, than we really rat around in the details too much.
DR. BINGHAM: Great. So let's just get started. So this is going to be down and dirty. We're not going to get into all the fine points of how to approach a COVID-19 patient as a lot of those treatments and the PPE and all that stuff is changing by the day. Hopefully we'll be able to put some information out there, but this is primarily going to be focused on ventilator management. So, Dr. Martin, let's say we have a COVID-19 patient, they're on that borderline of getting intubated they're becoming a little hypoxic.
DR. BINGHAM: How would you first-- I've heard a lot of different things in this coming week that we don't want to even bother with high flow or CPAP or anything because that's just going to spread the virus around the room. Have you heard anything like that and how would you approach that patient initially?
DR. MARTIN: Yeah and of course, part of that's going to depend on where are you, are you in an ER room that's open? Are you in a negative pressure room where you might have to worry less about aerosolization? What are your resources? So all of those are going to factor into it. And then again, there was the recent New England Journal publication that looked at this, that has shown that the virus can be aerosolized and it actually looks like it sticks around on surfaces for longer than we initially thought.
DR. MARTIN: So I think you need to take all those into consideration. But assuming we're at a relatively well-resourced U.S. medical center, then I think you would start with your basic obvious workup and diagnostic workup and your first thing should be testing them for coronavirus as well as testing them for the other common causes and ruling out influenza.
DR. MARTIN: But then initiating respiratory management, obviously you're going to start with supplemental oxygen and then your assessment of their oxygenation status. And I know I've seen some cautions about avoid high flow nasal cannula. There's really no good data though, to support that and I would actually probably go to high flow nasal cannula first, obviously with appropriate PPE and precautions.
DR. BINGHAM: Okay. Are you going to be quicker to intubate these patients over somebody else or are you going to try some CPAP, some BiPAP first?
DR. MARTIN: Yeah. So, I would take the same, kind of latter approach as I would to most patients with a couple of caveats. And this is all really evolving as we get some of the experience that comes in from Italy, from China, from Seattle, from other places that have been hard hit. It seems that these patients, their primary deficit is oxygenation and hypoxia. It doesn't appear to be usually a bad compliance issue like standard ARDS.
DR. MARTIN: It actually seems like it's acting more like a patient with pulmonary edema and most of the problem is from secretions and respiratory fluid. And really, I think a good basic approach is to think about treating them like a pulmonary edema patient. So supplemental oxygen, you want to avoid drowning them in fluid. And then I think CPAP is a great option because that will raise their mean airway pressure reliably.
DR. MARTIN: And I think the series we have so far have shown that you can prevent intubation in most of the patients just by doing those measures. So, I would do high flow nasal cannula, and then CPAP. There is some data that BiPAP is not a great option, There is some data that BiPAP is not a great option, and from similar viral outbreaks that actually outcomes were worse with BiPAP.
DR. MARTIN: So a patient that was failing those two, then I would go to intubation. And then I think, the final thing to say about intubation too, is depending on the scenario, as many people are advocating that as a form of source control in addition to a form of initiating pulmonary therapy with the thought being they're intubated now, you don't have to worry as much as long as the circuit is closed, about them aerosolizing and spreading.
DR. MARTIN: And I think if you have a real, a real problem with local contamination, you don't have negative pressure rooms, et cetera, that might be a place where you go to intubate early, also as a form of infection control.
DR. BINGHAM: Excellent. Okay, so take us through that process. So you have a patient that you've tried these non-invasive measures, but they're still hypoxic and now you've intubated. What would you go to for your initial vent settings?
DR. MARTIN: Yeah. And one final addition to that is the hallmark that people seem to be kicking around is this silent hypoxemia. And what they mean is the patients will generally look okay, and they'll have a significant degree of hypoxia that you might not have picked up on just by looking at the patient or examining them, meaning they tend not to get short of breath, not to have a lot of obvious respiratory difficulty, even with a significant degree of hypoxemia.
DR. MARTIN: And I think, again, that goes back to the pathophysiology we're dealing with that they're not getting non-compliant lungs like standard ARDS. So just be aware of that. They may not manifest the tachypnea or obvious respiratory distress that other patients would and they can be significantly hypoxemic. Okay. So, now you've intubated the patient and--
DR. BINGHAM: So wait. Before we get there, so that's a great point, so what would be your criteria then for intubation if they clinically look okay? Are you basing this off of your ABG? Are you basing this off of their oxygen saturations? What are you basing--
DR. MARTIN: I think, again, like in most ER settings, you're initially going to be basing off of oxygen saturations and if you aren't able to keep an oxygen saturation above 90%, that would be one criteria. And then if you have the capability to do a blood gas and guided by that, if you have a PO2 that you're unable to keep above, say 60, that would be another criteria to go ahead and intubate.
DR. BINGHAM: Okay.
DR. MARTIN: I don't think,
DR. MARTIN: and there's pretty good data on this, of trying to target a sat of 100 or 98 or higher, I think, as long as you're above 90 and you're not losing ground, you can forestall on intubation. But obviously if you're not meeting those goals or the patient is deteriorating, then that's the patient you would intubate then.
DR. BINGHAM: Great, okay. So, sorry to interrupt. So now we have the patient intubated, what's your initial approach?
DR. MARTIN: Yeah. So, now the patient is intubated and I guess what I would say first is, and you mentioned it at the beginning is, each institution will have their own kind of preferred ventilator strategy, they'll obviously have their local brand of ventilators and what their standard modes are. And so the best thing you can do in preparation for something like this is go talk to your ICU teams and probably the best person to talk to would be your respiratory therapist and say, "Okay, what is our standard initial vent mode?
DR. MARTIN: And which ventilator do we have? And what are the common settings?" And so that's what I would say is get to know that at your own institution and you'll hear a lot of acronyms and abbreviations that mean the same thing and they're just different by the different vent brands, like, IMV or volume control or assist control and they may all mean the same thing, they're just different brands of ventilators.
DR. MARTIN: So now you've intubated the patient and really, I think your two first choices of a ventilation modality are, are you going to deliver a tidal volume by giving them a set volume, which would be a volume controlled mode? So you're going to set the exact number of cc's that you're going to instill into that patient's lungs to give them that breath, or are you going to do a pressure controlled mode, where what you're going to be primarily setting is a pressure and the machine's going to deliver enough volume to get you to that pressure.
DR. MARTIN: And I would say the simpler way for most people, because we think about breathing in terms of tidal volumes and not pressures, so for the non-intensivists, probably the safest and easiest is to start with a volume controlled modality. And I would say the most common volume controlled modality would usually be SIMV. So you would set a respiratory rate, you would set a tidal volume and then you would set the FiO2 or amount of oxygen you're giving them and then you would set the PEEP.
DR. MARTIN: And then the other big helper, I think now is the electronic medical record and whatever system you have, EPIC, et cetera, they usually now have predefined sets of orders for ventilator support, so a lot of times you can go through and just click boxes. But I'd say in most places, you would probably go to a volume controlled mode of ventilation first, like SIMV.
DR. BINGHAM: Now, would you lean towards a pressure controlled or a volume controlled based on their P/F ratio, would that affect your decision at all?
DR. MARTIN: The P/F ratio wouldn't affect my decision. The P/F ratio just tells you how bad their oxygenation is. And then it can also obviously let you categorize them. If their P/F ratio is less than 300 that meets ARDS criteria and that just lets you then categorize them into mild, moderate, or severe. The P/F ratio doesn't really give you any clues about whether you should go with volume control or pressure control as your initial modality.
DR. MARTIN: That decision really, I think, is a lot of that is institution and provider specific. And then there's some finer tuned factors, for example, if a patient has really bad lung compliance and you're really struggling with getting high pressures with a volume controlled mode, that's where you might switch over to a pressure controlled mode. But just based on the P/F no, and for, again, for the non-intensivist to keep things simple, I would just say, start off with a standard volume controlled mode, like SIMV, set your initial tidal volume and what I would also say is, just download the ARDSNet protocol, which tells you exactly how to initiate ventilation.
DR. MARTIN: And if you just follow that protocol, you're going to be good. And what that says is you start off at eight cc's per kilogram, and that's of predicted body weight, which you can look up the calculation for that if you don't have it and they're a normal body habitus person, you can start with their actual weight and then calculate their predicted, but you start off with eight cc's per kilogram.
DR. MARTIN: I would just start off with 100% FiO2. And your goal here is, you know, the patient's decompensating, you want to get control of their ventilation and then start worrying about titrating things, like FiO2, titrating that down. Just start them on full ventilator support. So an adequate tidal volume, eight cc's per kilogram, an adequate respiratory rate, which is usually anywhere from 15 to 20, start them off with a high FiO2 at 100%, get them intubated, get them on the ventilator, see what their saturations are.
DR. MARTIN: You can check a blood gas, I'd give him at least 30 minutes to equilibrate, check a blood gas and then you can start fine tuning things. Oh, and PEEP. Generally, you would start them off at a PEEP of five and then you would titrate that up as needed. And that's usually, again, based on if they still have low oxygen saturations or a low PO2, that's when you start titrating PEEP up.
DR. BINGHAM: Okay. So, a lot of information there. So you said you would start off with a tidal volume of eight. What is all this we hear about the ARDS and low tidal volume ventilation? When do we start thinking about that?
DR. MARTIN: Well, so that is the ARDSNet low tidal volume approach. You start them off at eight cc's per kilogram and your goal is to reduce them down to four to six cc's per kilogram or mLs per kilogram. So start them at eight and that'll usually, again, your goal initially is not to right away get them down to the lowest tidal volume possible, your goal initially is to oxygenate, ventilate, stabilize them, and then start adjusting the ventilator support, which hopefully will be decreasing the amount of ventilator support you're giving.
DR. MARTIN: So I would start them at eight cc's per kilogram and then you can slowly reduce the tidal volume and they recommend at one cc per kilogram at intervals of at least two hours, until you get to four to six cc's per kilogram of predicted body weight.
DR. BINGHAM: Got it. And how about that FiO2 that you start off at 100%? How are you titrating that?
DR. MARTIN: Yeah, so again, it depends on your initial oxygenation response. And I would say most patients, including patients with coronavirus, usually you'll start them off on 100% FiO2, they'll respond immediately because you're giving them positive pressure ventilation with PEEP, which is really what they needed, and you're able to rapidly wean down their FiO2. So, I would start them at 100 and if their sats are 100, then I just start titrating the FiO2 down.
DR. MARTIN: And I think you can titrate it pretty quickly. And I usually titrate it, I would go from 100 to 80, immediately, and then I would keep titrating that down. You can titrate that down every 10 to 15 minutes by 10% until you get to whatever your desired goal is, which should be usually around an FiO2 of 30 to 40%.
DR. BINGHAM: Okay. And so let's say in this scenario, you do that, intubate a patient and you're able to titrate everything down appropriately and they're stable at this point. For the non-intensivist, how can they think about analgesia and sedation? What should they be using?
DR. MARTIN: So again, this will also vary by your center and whatever their protocols are. And the important thing, I think, is that you are using some predefined order sets. And the most important thing is you're using some kind of verified sedation scale that the nurses can titrate it by. And at our institution, it would usually be propofol for the initial sedation agent and then we would either add a PRN narcotic, or an intravenous drip, like a fentanyl drip for pain.
DR. MARTIN: Although for these patients it's really, again, for coronavirus patients, it would mostly be about sedation and you shouldn't need to add a whole lot of pain control on top of that. Other centers would use either a PRN, or a continuous drip benzodiazepine. And I think either of those is appropriate.
DR. BINGHAM: Okay. So now let's say that the patient's worsening, so you've had them on your minimal vent settings, but their oxygenation is worsening. What's your approach to changing these ventilator settings and increasing, decreasing the FiO2 first, increase the PEEP first, what do you do?
DR. MARTIN: Yeah, so, so I think now you've got them on the ventilator and you want to assess the results you're getting and see, do I have a problem? So it's either going to be patient's doing great, or I have some kind of problem. What type of problem is that? So the first thing you want to do is get them on the ventilator, assess their oxygenation, you want to get a blood gas at some point, usually within the first hour, and that will also help with the oxygenation, but it will give you the CO2, so you can assess the ventilation and see if you are ventilating okay, if you have a ventilation problem.
DR. MARTIN: And then the third thing, which again, you'll know immediately is, do I have a pressure problem? And that's where the vent will give you a pressure or the pressure they're hitting with every breath, you'll see it right on the screen, and that's called the peak inspiratory pressure. And your whole goal of this ventilation strategy is to avoid barotrauma, avoid ventilating them with pressures that are too high.
DR. MARTIN: And in general, that's when they start to get above 30, now they're in the pressure too high range and then you got to start thinking about, well, I need to make some adjustments to decrease that amount of pressure I'm causing in the lungs. On the ARDSNet protocol and a lot of the publications you'll read, they say to guide that by plateau pressure, and that can be confusing to non-intensivists because the number you're seeing on the ventilator with every breath, is a peak pressure.
DR. MARTIN: And the way you get a plateau pressure is, there's an inspiratory hold button and you push that. And what that does is it pauses them at the end of inspiration and then it gives time for the tidal volume to equilibrate throughout the lung. And what happens is your peak pressure will come down a little and level off and that number is your plateau pressure.
DR. MARTIN: And I think that's great to check that initially and just, you can see the relationship, it's usually just a little bit lower than your peak and make sure there's not a big gradient. After you've done that, if you've seen the relationship is pretty consistent, I just go by peak pressures, and if your peak pressure is less than 30, you know your plateau's less than 30 and it just makes it simpler to think about.
DR. MARTIN: So first thing I do is I then assess, do I have an oxygenation problem? Do I have a ventilation problem? Do I have a pressure problem? And then I would address each one of those. And the pressure problem is that's the one where you're lowering the tidal volume because you don't want to ventilate the patient at high pressures.
DR. MARTIN: So for example, if you've come down to 6 cc's per kilogram on your tidal volumes and you're still hitting pressures, peak pressures or plateaus that are above 30, that's when you might continue to decrease down to four cc's per kilogram. But if you've come down to 6 cc's per kilogram and your peak pressures are 20, then I wouldn't decrease them any further because your pressures are fine.
DR. MARTIN: In fact there is some data that decreasing tidal volumes in patients who have great compliance actually worsens outcomes. So that's where that little fine tuning of the tidal volume comes in. And you don't have to be crazy about getting them down to four cc's per kilogram, no matter what. Now if you're ventilating them with pressures that are in a reasonable range, especially 20 to 25, then you're good.
DR. MARTIN: Don't mess around with that, go on next and look at do I have an oxygenation or a ventilation problem?
DR. BINGHAM: Now when you decrease that, let's say you're having a pressure problem and you decrease your tidal volume, do you reflexively increase your respiratory rate in order to maintain that same minute ventilation or do you kind of see where they settle out?
DR. MARTIN: Yeah, you see where they settle out and that's where the concept of permissive hypercapnia comes in. So, one of the general principles of ICU care to avoid So, one of the general principles of ICU care to avoid is trying to make them look exactly like a normal non-critically ill person. And we've probably hurt a lot of patients doing that, like with the strict glycemic control, trying to get sugars down to 80-110 range, we probably hurt a lot of patients with that, trying to make their blood gas look exactly normal.
DR. MARTIN: That's not something you need to focus on. So what we know is, we can let the CO2 rise, which will happen if we're ventilating with low tidal volumes and low respiratory rates, we can let the PCO2 rise, having a high PCO2 doesn't hurt at all, unless it causes your pH to get significantly low and where that harm point is, is probably about a pH of 7.2. So I'd say as long as the pH is in the 7.25 or above range, we accept a high CO2, we accept that we're underventilating them, and as long as the pH is 7.25 or above, then we don't make changes just to make that blood gas number look better and make ourselves feel better, because it has no benefit to the patient.
DR. MARTIN: So, what I would say is, I would not change the respiratory rate reflexively, I would see what my blood gas is doing and look at my pH and my PCO2.
DR. BINGHAM: Okay. What about an oxygenation problem then? Okay? So how do we address that?
DR. MARTIN: Yeah, so, an oxygenation problem. Again, first thing I would look at are the pressures, and am I having a pressure problem? And then if not and it's a pure oxygenation problem, the standard ARDSNet approach is, you know, how do you make oxygenation better. Right? You either increase the FiO2 or you can start increasing the PEEP or the third option is change them to a different mode that you think will oxygenate them better.
DR. MARTIN: And the ARDSNet approach in most cases would be you then start to titrate the PEEP up. And your whole goal there is to see if they're PEEP responsive. So you start bringing their PEEP up, so you start off at a PEEP of five, let's say, you know, I would go to eight and from there go to 10. And again, download the ARDSNet protocol, there's a PEEP, they call it, a PEEP ladder.
DR. MARTIN: There's actually two different scales, there's a low PEEP titration ladder and a high PEEP titration ladder. And it seems, especially for coronavirus, again, thinking about this almost like a pulmonary edema patient, that they do better with a higher PEEP ladder. So I would use the higher PEEP ladder of the ARDSNet protocol, which basically has you titrate up the PEEP based on how much FiO2 they're requiring, and it starts at a PEEP of five and you can titrate it all the way up to a PEEP of 24, again, for a patient who's requiring 100% FiO2.
DR. MARTIN: So I would start titrating their PEEP up but what you don't want to do is just keep turning that PEEP number up and you're not seeing any improvement. So you want to see if they're PEEP responsive or not. And so you follow the oxygen saturation and you can also follow intermittent blood gases and see if your PiO2 is getting better with those PEEP increases.
DR. MARTIN: And if it is, then you just titrate them up to an optimal PEEP. If it's not, you know, you've done a couple PEEP adjustments and it's not doing anything, or you're getting worse, that's now where you have to start thinking about, do I need to change to a different mode of ventilation or do something else to improve their oxygenation?
DR. BINGHAM: What are you getting at there, something else?
DR. MARTIN: Well then we get into what are the adjuncts we can do for these patients and in what order? And I'd say really, your three main options are, do I give them a paralytic? Do I prone them, flip them over and place them in prone position? Do I go to a different ventilator modality? And I'd say probably the most common one is APRV, which we can talk about a little bit. And then the final, kind of the big gun would be, do I need to go to something as drastic as ECMO for the patient, who's failing all of those?
DR. MARTIN: And I'd say that's the usual stepwise approach. And there's a little bit of disagreement about which order those things should be done in. And that will also depend on your unit and your local capabilities. So some places would go to proning as the next intervention. And for example, in Italy, there's been some videos of their ICU's and you'll see all the patients are on their stomach and they're proning everybody and proning them early.
DR. MARTIN: Other places would go to a paralytic first, then probably go to proning. Other places would probably switch them over to APRV first and then go to proning and paralytic. And then the ECMO question, I think we can, I don't think we need to get into that, because that's really, a non-intensivist will not be getting into the ECMO issue, but for anybody whose center is getting prepped to deal with this, I think you need to also have that as part of your plan of what if we have a patient who needs ECMO.
DR. MARTIN: You know, do we do ECMO, do we have an ECMO center available and what's our process going to be for that?
DR. BINGHAM: Yeah, I would hope if you're getting to these adjuncts, the paralytics, the proning, the APRV and certainly ECMO, if you're a non-intensivist, hopefully at this point you have a little bit of intensivist assistance, but let's play worst case scenario out there. We're not going to have enough Rotobeds for everybody. So for the non-intensivists out there, or even, how do you explain to your nurses what's the idea behind proning and what's a good kind of practical guide to how often do you need to be flipping them, what can you do when we're doing this in the hallway?
DR. MARTIN: Yeah. And what I would say and especially for the non-intensivist, I'm actually a big fan of give them a dose of paralytic, give them one dose of a relatively short acting paralytic and just see what that does, especially for the patient who's desatting and they're trying to figure out what to do next. And you'll see a significant number of patients that you do that and their oxygenation improves and some of their issue was vent dyssynchrony and not only does that improve them, but it buys you time to think about, okay, what am I going to do next?
DR. MARTIN: So, I would use that as something to do very early, especially by the non-experienced intensivist or person who's filling in. Give them a dose of vecuronium or rocuronium, see how they respond and then you can start thinking about, okay, do I need to prone them? Should I switch them to a different mode of ventilator? Proning, I think would be a next go-to.
DR. MARTIN: This I think would also depend on your local resources, and if you're in a unit and you have one or two coronavirus patients, and you have a bunch of personnel and you can prone them pretty safely, you might do that. If you are in a unit that's full of coronavirus patients, and you're one to three, one nurse for every two to three patients, you may not be able to safely prone all those patients.
DR. MARTIN: So that might be somewhere where you just say, we're going to go to paralytic, we're going to go to a different mode, like APRV and proning will be a last resort. So proning, there's been a couple of studies that have shown a benefit. It does appear to be particularly beneficial again, in coronavirus respiratory failure and I think that just gets to part of the issue of it's a patchy consolidation ventilation/perfusion mismatch it's a patchy consolidation ventilation/perfusion mismatch that tends to accumulate posteriorly.
DR. MARTIN: And so proning them helps you improve their ventilation/perfusion match. So they seem to respond very well to proning. So you either have the RotoProne or similar bed that can do the proning for you, I would say a lot of places now don't have that. So that's something where you really should create a protocol of how you do that upfront. And if you're at a place that hasn't done that a lot, I'd say, talk to your OR teams, because your anesthetist and your OR nurses prone patients all the time for procedures and they can tell you their protocol for doing it.
DR. MARTIN: Obviously, the important thing is that you have the patient padded, so everything is protected and they don't get any pressure injuries. And then two, all their tubes and lines are protected when you are flipping them to prone and back from prone, because it's very easy to pull lines, it's very easy to inadvertently extubate a patient doing this.
DR. MARTIN: And it takes usually at least four to five people to safely prone a patient if you're doing it manually. The data generally shows that you don't want to do short proning periods. I remember before the PROSEVA trial came out, we would prone patients for two to four hours and be flipping them. Generally, you want to prone them for at least 12 to 16 hours. So you prone them 12 to 16 hours and then put them back to supine and then you keep doing those cycles.
DR. MARTIN: I think the important thing is you want to be assessing them as you're doing that, is the proning doing anything for me and when can I stop proning? And the best way to do that, I found, is you just make a P/F ratio chart. So what's their P/F ratio supine, you prone them, what's their P/F ratio doing when you prone them.
DR. MARTIN: And in almost all cases, that'll go up and it'll go up significantly. And then you keep doing that every time you flip them back and forth. And what you'll generally find is the P/F ratio will improve when you prone them, but that improvement will get smaller and smaller. And then you'll get to the point where you're not getting any further P/F improvement by flipping them prone.
DR. MARTIN: And that's usually where you can say, "Okay, I've maxed out my proning and now I can just keep them supine."
DR. BINGHAM: Okay, great, so moving on from there. So I think the only thing of those adjuncts we haven't really touched on is APRV, and we already said we're not going to get into ECMO. But for APRV, let's touch on this a little bit. Can you maybe give us a little APRV for dummies? What are the settings, and if you're going to this mode of ventilation, what do you need to be thinking about and how do you approach it?
DR. MARTIN: Yeah. And this is where we might get the angry tweets.
DR. BINGHAM: [chuckles]
DR. MARTIN: There's a lot of debate about APRV and about when you should go to it. I'd say, in general, you'll find there's a significant percentage of patients who will respond great to APRV and then there's a smaller percentage that just won't respond to APRV. But you will find that it can be a great adjunct for patients who you're having a lot of problems with oxygenation.
DR. MARTIN: And again, at least the early reports from the coronavirus experience are that patients have had a good response to APRV. And a lot of the recommendations I've seen are to actually go to APRV earlier, rather than later in these patients. But even a lot of intensivists get a little confused about APRV if they haven't used it a lot. And so I imagine for the non-intensivist, it can be relatively confusing.
DR. MARTIN: And there's a bunch of different ways of thinking about it. And I think, I think the way I've come to think about it, that communicates it the best is, that communicates it the best is, especially for surgeons, it's like incentive spirometry. So, if you think about all of your patients on the ward who are getting incentive spirometry, right? There's a pretty predictable cycle they go through and also, if you think about how incentive spirometry works.
DR. MARTIN: So what happens, you go into that post-op patient and they're post-op day one and they get handed the incentive spirometer and the first thing is they don't understand what to do with it, right? So that's say, the non-ICU physician who doesn't know what APRV is and what do they usually do? They usually start trying to blow into it--
DR. BINGHAM: Yep.
DR. MARTIN: Rather than inhale. Okay, so then you explain it to them that you want them to inhale, and then they'll inhale and they'll kind of do normal breaths. So, inhale quickly, exhale, inhale quickly and they'll get the little ball inside to quickly spike up to whatever tidal volume, then come down. And then you explain to them, "No, I want you to do continuous inhalation and I want you to keep it" and you'll raise your arrow to whatever level you want them to keep that ball at, right?
DR. MARTIN: And you'll tell them inhale as long as you can and keep the ball at that level. And then, when they've reached their maximum time they could possibly inhale, they'll do a short exhale, and then you want them to inhale again, and you tell them, whatever, do that 10 times an hour. That's almost what you're trying to do with, or what you are doing with APRV, is you're having that patient do these very long inhalations to try and keep the lungs open and maximize your recruitment.
DR. MARTIN: And then you're giving them very short periods where they exhale and then go right back into a long inhalation period. And what that does is, again, that optimizes your ventilation/perfusion match, it recruits alveoli that were previously collapsed. So, imagine again, your incentive spirometry patient, if now you just had a machine that you put in their mouth that did that for them, that long inhalation, short exhalation, long inhalation, so they didn't have to do any work.
DR. MARTIN: But they still want to breathe on their own while that machine is doing that. So if you imagine this machine also lets them take spontaneous breaths whenever they want throughout that inhalation-exhalation cycle, that's APRV, that's what you're doing. So, the machine is giving them a long inspiration to a certain pressure that you set and then a short exhalation, long inhalation, but they can do tidal breathing anytime they want throughout that process which makes it comfortable for a patient because otherwise that's very uncomfortable, if you think about it, if somebody was forcing you to do that, and patients can do the incentive spirometry for 10 breaths but they couldn't do that all hour, because it's not that comfortable.
DR. MARTIN: So, adding that ability for them to breathe spontaneously. So again, if we think about the incentive spirometer, when you raise that, when you raise the arrow to tell them, "Here's where I want you to raise the ball to." And we talk about APRV settings, we talk about setting a P high and a P low. So raising that arrow to tell them, "Well, here's the pressure volume I want you to hit", that's your P high.
DR. MARTIN: So you set a P high number and that's the amount the machine is going to instill air into their lungs until they hit that pressure and then it's going to hold them in that pressure for a long inhalation and that's your T high. So now you've said, for example, I want you to get them to an airway pressure of 30 and hold that for five seconds. So you've set a P high of 30, a T high of five seconds.
DR. MARTIN: Now you're going to set a time that you let them exhale. And remember, you want them to give them a very short time to exhale because you just want them to exhale enough that they get some ventilation, but then go right back up. So generally your T high is going to be less than a second and it's usually you start them anywhere from 0.5 to 0.8. We'll usually just start at 0.5 and that's your T low. And then there's another setting for P low, which is the low pressure you get them to.
DR. MARTIN: And this is easy, just don't worry about this, just leave it at zero. Don't mess with the P low, don't even think about it. Just leave it at zero. The numbers you want to focus on are setting the P high, which again, is the red arrow on the incentive spirometer. Here's what I want you to hit in terms of tidal volume or pressure, how long I want you to hold it, that long inhalation and then this short period I'm going to give you for exhalation.
DR. MARTIN: And those are your APRV settings. And what that does is it gives you a very long period at a high mean airway pressure that helps maximally recruit alveoli and improve your oxygenation. [Dr. Gupta] Dr. Martin, can you go over some of the alarms, basic alarms that we see at the bedside and how we can troubleshoot a ventilator?
DR. MARTIN: Yeah, I'd say, again, probably the most important alarm is high pressure. And if you're getting high pressure alarm, that's where you need to look at your tidal volumes, that's where I would. You're getting a high pressure alarm because your peak pressure is exceeding whatever limit you set. I would check a plateau pressure and see if those are correlating or if you have a huge difference between them and that can indicate some kind of obstruction in the tubing.
DR. MARTIN: And then you want to look at the patient, because probably the most common cause of those alarms actually isn't that you're having a compliance problem, it's usually that the patient is not synchronizing with the vent and they're fighting the vent. And again, that's where, if you run into that problem and their stats are coming down, their oxygen [unintelligible], that's where I would give them a dose of a short acting paralytic, see if they respond to that.
DR. MARTIN: And then work on fixing that issue that's causing the alarm. One of the good things about the coronavirus is, again, the majority of the patients who need mechanical ventilation don't appear to have a significant compliance problem. So, we're not running into a lot of problems where we just, we can't ventilate them at reasonable pressures, like some other ARDS patients. That they generally have good compliance, it's kind of become a hallmark of the disease.
DR. MCCLELLAN: So that brings one question then, just for the non-intensivists, why are they dying?
DR. MARTIN: Yeah, that's a good question. And most of the deaths, the cause does appear to be hypoxemia. We don't have a lot of detailed information about exactly why they're dying and why they're so refractory to this. I mean, we know the high risk populations, patients with underlying lung disease, older patients, but exactly why they're dying and why they're having such a different reaction to the virus, we still don't fully understand which is really an interesting question because there's a lot of these viral syndromes where kids will actually do worse and this is one where kids clearly do much better.
DR. MARTIN: There was another, I think it was a New England Journal paper, just showing that there there's now multiple different subtypes of what we're calling COVID-19 or this coronavirus and they probably interact differently with the patient. But that's the next question to be asked. But it doesn't seem like they're dying from diffuse multiorgan failure, it seems that it's primarily a respiratory issue.
DR. MARTIN: And again, this also is going to be, what rescue modalities do you have? So, some place where they're not hit very hard and they have resource and they can go to ECMO, they're seeing very low death rates from this. Places where they're having, like in Italy, where they're overwhelmed with patients and they're having to make decisions about not even intubating and offering patients ventilation, that's where you're seeing the higher case fatality ratios.
DR. MARTIN: And again, that's primarily in the older patients or patients with other comorbid diseases and especially pulmonary comorbidities. So, part of that is a resource issue. And again, if you can go to ECMO, you can probably salvage almost all these patients, at least from an oxygenation standpoint.
DR. BINGHAM: Well, excellent as always Dr. Martin, we can't thank you enough. I know it was short notice, but it's a very important topic. And I think that this was absolutely wonderful and it's going to be very helpful for a lot of people out there who rightfully so have some increased anxiety that they may be a little bit out of their comfort zone managing some of these patients. I think, something that you touched on throughout your talk was just have a plan, know your local resources and make sure that the system and you and your colleagues are prepared.
DR. BINGHAM: Once again, we're going to put some links to the show notes to some resources that can help people out there. Scientific American Surgeon has some excellent, basic and advanced ventilator management chapters as well as a recent chapter on COVID-19, Society of Critical Care Medicine, that we'll put a link to in our show notes, it has some free resources for critical care refreshers for non-intensivists and COVID-19 resources.
DR. BINGHAM: And again, Dr. Martin, that was an excellent crash course on ventilator management and I hope everybody out there has enjoyed it. Thank you for being with us today.
DR. MARTIN: Yeah, thanks for having me on. [narrator] Until next time, dominate the day. [upbeat outro music]