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RTL- Ep 73- Respiratory Support
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RTL- Ep 73- Respiratory Support
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2022-09-15T00:00:00.0000000
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Language: EN.
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[Dr. Smith] Welcome back to Run the List, a medical education podcast in partnership with McGraw Hill Medical. Our host are Dr. Navin Kumar, Dr. Walker Redd, Dr. Emily Gutowski, Dr. Joyce Zhou, and myself Blake Smith. As a quick disclaimer, this podcast is meant for informational and educational purposes only, and should not be understood as medical advice under any circumstances. [intro music] [intro music] [intro music] [Dr. Kumar] All right, welcome back everyone to another episode of Run the List.
Today, I am very excited to be joined by another great friend and star in the medical education, Dr. Morgan Soffler. In terms of background, she completed her residency, including a chief year in internal medicine at Yale-New Haven Medical Center. She then completed her fellowship in pulmonary and critical care in Mass General Hospital in Beth Israel Deaconess, where she is currently on faculty as a pulmonologist and intensive care specialist.
From a leadership standpoint, Dr. Soffler also serves as the associate fellowship program director at the Harvard Combined Program and is also an assistant professor at Harvard Medical School. And I can say from firsthand experience that Morgan is an amazing educator and we are so lucky to have her on the podcast today. [Dr. Soffler] Thanks so much for having me. [Dr. Kumar] We are so excited to have you, Morgan.
We're going to continue our mini series in critical care with an overview of respiratory support. Morgan, are you ready to Run the List? [Dr. Soffler] I have never been more ready. [Dr. Kumar] All right. So as always, we will start with a case and to do that, let's go back to the good old days when you were an intern and you're on overnight call and you get paged about a patient with hypoxia.
So you're hustling over to the patient room and you find your Sign-Out and identify the patient as a 55-year-old woman currently admitted on the medicine floor with presumed gallstone pancreatitis. She is on day two of hospitalization. When you get there, you see your patient is in acute distress with labored breathing. Her continuous O2 sat monitor reads 86% on room air, you ask for a full set of vital signs while preparing to examine the patient.
So the nurse gets the vital signs and tells you that her temperature is 99.0 degrees Fahrenheit, her heart rate is 114 beats per minute, her blood pressure is 146/80, she has a respiratory rate of 28 breaths per minute, and again, is satting 86% on room air, the nurse places the patient on 4 L of supplemental oxygen via nasal cannula and the O2 sat comes up a bit to 90%. All right. Let's pause here, Morgan.
Even before you start examining the patient, what information will you try to quickly obtain about the patient and their current hospitalization? [Dr. Soffler] Yeah, so walking in to this patient in the room, who seems to, by the sounds of it, sounds extremely distressed, of course, I'd want to be sure that the patient is stable. You provided some vital signs here, which thus far are reassuring.
And then start to hear a little bit about what's been going on for the patient immediately kind of before this event happened, kind of what's the context been? Has this been a problem that has started gradually? Has she been slowly starting to decrease her oxygen saturation over the course of the night or the past 24 hours? Or was this an acute event where she was, you know, all of a sudden?
So the timing for me tells me a lot, you know, acute events, I might think of things like pulmonary embolism, acute flash pulmonary edema, for example, pneumothorax are things that are acute, whereas something like a brewing pneumonia or brewing ARDS may be a little bit more insidious. I'd love to know more about the patient herself. So is she somebody who has a history of bad cardiac disease? Does she have heart failure or valvular disease?
Does she have underlying pulmonary disease? Is she somebody with chronic obstructive pulmonary disease, for example, and that would be important. The other piece, again, this sort of speaks to what was going on for the patient right before this happened is, you know, what was happening at the time that the patient started to become distressed, was she receiving a blood transfusion?
Should I be thinking of a transfusion reaction? Was she receiving IV fluids either during, or maybe, you know, in the proceeding hours before she became dyspneic, which again might make me think a little bit more about pulmonary edema. And so these are the sorts of questions. So sort of to summarize that, in a way I'd want to know, what's the timing, how long has this been going on?
What was happening right before this event occurred, and who is my patient, more details about who she is and the other comorbidities that she might have that may predispose her to one problem over another. [Dr. Kumar] Nice, Morgan. All right, let me give you some of that information. So the patient was otherwise healthy before she presented with acute epigastric pain and was found to have a light pace of 1,200 with cholestatic liver enzymes and a right upper quadrant ultrasound showing cholelithiasis.
Again, she's on hospital day two at this point. So she was admitted with gallstone pancreatitis and thus far in her hospital course, she has received a total of 8 L of lactated ringers over the past 24 hours that is still currently infusing at 250 cc's per hour. She's receiving 2 mg of IV morphine every four hours for her pain and just received a dose a few hours ago.
And then when you look at her vital signs, in terms of the timeline of this O2 saturation issue, you see that her O2 sat has been steadily declining over the past four hours. So with all that information, Morgan, how do you start putting things together for this patient? [Dr. Soffler] Absolutely. So just by history, I can really start to- And the information that you've gathered about what's been going on for the patient, I could start to think about what my hypothesis might be and what my top differential diagnoses would be.
Of course, the exam and other data is going to be really crucial, but starting off, I think one of my primary concerns as it's common with patients with pancreatitis, would be volume overload. So patients with pancreatitis have really profound capillary leak, and they get a lot of significant pulmonary edema plus within the early stages of pancreatitis, of course, it's important to volume resuscitate these patients, but she's received a whole lot of fluid, it sounds like 8 L, so I would really be concerned that she has some ongoing pulmonary edema.
The timeline fits with that as well. Of course, I wouldn't want to anchor solely on pulmonary edema, I'd want to consider other potential etiologies. So things like infections in patients with pancreatitis are also common. So could there be some underlying pneumonia brewing? ARDS is another complication of pancreatitis which can occur with or without a pneumonia. And so could she be developing ARDS?
It's a little bit potentially early in her course, but certainly a possibility. Pulmonary embolism is also a consideration. Patients with pancreatitis are at increased risk for venous thromboembolization. And so I would want to be thinking about pulmonary embolism and certainly imaging, even a simple chest X-ray might help me prioritize those differentials right off of the bat and certainly the physical exam.
I want to note also, it sounds like she's been receiving a fair amount of narcotic, which is common in patients with pancreatitis that they do need that. I probably would put this pretty low on the differential in terms of, you know, could she be hypoventilating from receiving narcotics just by way that you described the patient, she's labored so she sounds more like a "can't-breathe" type of patient than a "won't breathe" type of patient, meaning she looks distressed.
Whereas patients who have hypoventilation from narcotics usually look calm and chill, they just won't breathe. not that they can't breathe. [Dr. Kumar] Yeah. That's great, wow. So that's a very nice differential. You're already thinking about it. I like how you're taking into consideration her history to think about risk factors for what will elevate one of your differential diagnoses over the other.
And then just kind of like looking at the patient, how the gestalt of just how she appears can help influence your differential as well. So, it's always great to have a differential mind even before you get to the exam, so it can inform the way you're looking for things on the physical exam. So let me tell you on exam, you again see a middle-aged woman in acute distress. She's leaning forward in her bed, her JVP is non-distended, but you do see her using her accessory muscles to help her breathe on the neck exam.
Then on cardiac exam, she's tachycardic, but regular, no extra sounds, and her lung fields are resonant to percussion bilaterally, but you do note coarse breath sounds throughout. So Morgan, where do you take it from there, with this extra information from the exam? [Dr. Soffler] Great, so I know that you all already discussed the approach to dyspnea earlier in an earlier episode, shout out to Jeremy Richards, who's another friend of mine and colleague.
So if it's all right, I'd like to list out the immediate diagnostic tests that I would be thinking to send in order to help, you know, reprioritize this differential diagnosis list. So already I alluded to the utility of chest X-ray. So we had listed on our differential diagnosis, pulmonary edema, infection, which we should expect to see something on chest X-ray, as opposed to something like a pulmonary embolism, where if this was an acute pulmonary embolism, we really should expect to see a clear chest X-ray or minimal findings on chest X-ray.
And I should also mention ARDS would be something that we would expect to see blooming on chest X-ray with bilateral infiltrates. Similarly, the pattern of chest X-rays I just alluded to also would be helpful, or if I see a lobar consolidation, I might be thinking more of pneumonia, and if I'm thinking this bilateral infiltrates, I would be maybe thinking more along the lines of ARDS and/or cardiogenic or non-cardiogenic pulmonary edemas as the case with pancreatitis.
The other tool that's very useful if you have it available and you have some skill in using it is point-of-care ultrasound. So a bedside ultrasound of the patient to rule out some acute causes. So one could look for lung sliding to evaluate for pneumothorax, and then one could actually look at the lung parenchyma, so you can see B-lines in the case of alveolar infiltrate from fluid.
You could also use the ultrasound to look for effusion. So if they're, you know, again, to maybe support this idea of overall volume overload status. Those, I would say the chest X-ray and the point-of-care ultrasound are the quickest diagnostic tools that may help me decide what is acutely going on with the patient. Other things that are really important would be an EKG, so is this patient having an acute cardiac event or is there evidence of right heart strain, which might again lead me to consider a pulmonary embolism for example?
An arterial blood gas is less helpful necessarily for differentiating what's going on. So again, it doesn't sound like this patient is hypoventilating, an ABG would be able to tell us that, but the ABG will be helpful for helping us determine how severe the gas exchange defect is and what kind of care this patient might need moving forward. And then certainly basic lab data, right?
So a CBC, is there an acute drop in hemoglobin? Do we need to worry about alveolar hemorrhage for example, sending troponins and a BNP would be helpful. [Dr. Kumar] All right, Morgan. So we've sent all that testing off, but again, let's try to play this in real time for our listeners. You are waiting for those results to come back and while in the patient room, you note that her oxygen saturation is declining, it's now down to 88% on 4 L of oxygen.
As we introduced in this episode earlier, our focus today is on respiratory support. So what is your next step in this moment to support this patient's oxygenation? [Dr. Soffler] Yeah, so this patient is currently on nasal cannula and I would consider nasal cannula to not be the appropriate treatment for this patient at this very moment, right? It's clear she's not doing well.
Her breathing is labored. She has increased work of breathing and she's rapidly dropping her oxygen saturation on escalating nasal cannula. So I'd like to take a minute, I think it'd be helpful to talk about the difference between low flow nasal cannula versus a high flow nasal cannula, which has certainly really gained popularity in usage during the pandemic.
So low flow nasal cannula, I would say is a very appropriate device for patients who are not in respiratory distress and have oxygen deficit that is really easily supplemented with fairly minimal amounts of oxygen. So a low flow nasal cannula delivery device can supply- It supplies 100% FiO2, so you have no control over how much FiO2 you're supplying, it's 100%, and then you set the L/min flow, which typically goes up- The effective flows are really somewhere in the range of 6 L/min to 10 L/min, for a low flow nasal cannula device.
And the real limit to the low flow nasal cannula device is that L/min flow cap. So because you can only get, let's say, we'll call it 10 L/min of maximal flow, if you have a patient who's very dyspneic and is taking in really large breaths and has a big inspiratory flow rate, so maybe is breathing at 15 L/min, that means that only 10 L/min of that flow is 100% FiO2 and whatever L/min flow, that patient is entraining because they're so dyspneic, whatever excess L/min flow they have is entrainment of room air, which we know is only 21% FiO2.
So you essentially get this dilution of FiO2, depending on what the patient's work of breathing is. Now we don't routinely measure at the bedside a patient's work of breathing in L/min flow, but we can imagine that a patient who's really dyspneic and has a lot of work of breathing is exceeding 10 L/min of inspiratory flow. And so they're definitely entraining some room air. So that's one limit, is that we're really limited to how much FiO2 we can deliver with a low flow nasal cannula device.
And the other piece of that too, is let's say we talked about sending off an ABG for this patient. We would check an ABG which is helpful to know exactly kind of what her oxygenation status is in the moment, but if we actually want to go forward and calculate something like a PF ratio, so looking at the arterial- The relationship between the arterial oxygenation status compared to how much supplementation they're giving, remember we don't really know what the FiO2 is because we don't know how much room air this patient is in entraining.
And so a nasal cannula is really kind of limited that way, and we know that low flow nasal cannula does not offset work of breathing at all. [Dr. Kumar] That was perfect. Wow. So thank you so much for that discussion. So a lot of reasons why using low flow nasal cannula has significant limitations in a patient like ours in this case. significant limitations in a patient like ours in this case. It's funny, right? Because oftentimes we'll just dial up the leaders on the nasal cannula, and think we're doing something, but now thanks to your nice explanation there, we realize that we're not actually delivering the FiO2 that we're hoping for in addressing the underlying issues for the patient. So sure enough, let's say we did increase the nasal cannula to 10 L and again, the patient does remain hypoxic at 89% which makes sense, given everything you just explained to us.
So what's next Morgan, what's your framework for thinking about escalating the respiratory support for this hypoxic patient? [Dr. Soffler] Absolutely. So I mean, it is totally appropriate in the moment you need to just get the patient's oxygen level at a safe place. So in the moment, totally okay to reach for the non-rebreather, as a bridging therapy I would say to some therapy that's going to help offset the work of breathing.
And so the two therapies that I think would be really important to consider again, okay, put the patient on non-rebreather, get the sat up, but remember, we haven't addressed the work of breathing, thinking about the therapies BiPAP and high flow nasal cannula as really the predominant options in this case. And really my decision tree to think- The branch, I should say, in my decision tree to consider either high flow nasal cannula or BiPAP is number one, do I think this patient is hypercarbic at all?
So are they a COPD patient? Do they have a chronically elevated CO2 level? Do I think they're hypoventilating for some reason? If I think that there's any hint of that, then I would really consider BiPAP therapy. The other grade 1A recommendation for BiPAP therapy is for patients who have cardiogenic pulmonary edema. And the reason for this is because, well, I should pause to actually explain what we set with BiPAP but when we set BiPAP remember we said, this really does help with work of breathing it's because we set two pressures, we set an inspiratory pressure, which helps augment the tidal volume, it helps give inspiratory pressure support to the patient, so that's pretty intuitive.
We also set what we call an EPAP or an expiratory pressure, and that is a pressure that exists even as the patient exhales. And that's a helpful pressure because it increases the intrathoracic pressure, which then decreases the venous return, which can help offset issues with an acute pulmonary edema. And then there's also some thought that that increase in intrathoracic pressure can help kind of push out some of that fluid from the alveoli, which may be particularly pertinent for our patient who has a lot of capillary leak and pancreatitis.
So I would highly consider BiPAP for this patient because we are pretty concerned that there may be some ongoing pulmonary edema. The alternative treatment, which I also think would be a reasonable consideration is high flow nasal cannula. I think of high flow nasal cannula for patients who truly have pure hypoxic respiratory failure, which we don't quite know yet if this patient is in the camp of, because we don't have the results of our ABG as of yet, but presuming that she's predominantly hypoxic, this would be inappropriate therapy and high flow nasal cannula, as opposed to low flow nasal cannula has a number of benefits.
Number one, as the name implies, they are high flows. So as opposed to that cap of 10 L/min flow, you can go up to 70 L/min of flow. And so you can overcome really any inspiratory flow that the patient has to deliver an exact amount of FiO2, because they won't be entraining any room air. And also with those high flow rates, we actually deliver a modest amount of PEEP. So that's very helpful, again, providing that kind of end expiratory pressure to help offload the work of breathing and all the turbulent flow created by that high flow nasal cannula actually washes out the dead space of the non-conducting upper airways.
So we get rid of some of that dead space, some of that CO2 to just make sure that all of the airways are just filled with whatever that FiO2 is that you decided that you would like to deliver to the patient. And so high flow nasal cannula has absolutely been shown in patients with hypoxic respiratory failure to not only improve oxygenation, but to also decrease the work of breathing.
So I think that either of these options for this patient would be appropriate. I probably would lean a little bit more to the BiPAP because of our concern for pulmonary edema. And BiPAP also tends to be a little bit faster to get onto the patient, the setup is a little bit smoother. [Dr. Kumar] All right, excellent. So sure enough, you know, in the acute moment you do find it 100% non-rebreather on the floor.
And so you do have the patient start on that treatment, but sure enough, just as you discussed nicely, there are issues with that compared to the other options of high flow nasal cannula or BiPAP and her O2 sat again, falls to around 88%, even after that 100% non-rebreather, so beyond just looking at the O2 sat, you are looking at your patient, she's becoming more fatigued, short of breath, X-ray, they're taking their time, they're on their way.
You were able to get the ABG so that was a success, but you're waiting for the results to pop up in your EHR. And so things are going, you know, kind of going downhill right now, you have her on 100% non-rebreather, it doesn't really seem to be supporting her. How are you thinking about the stability of this patient and what do you want to happen in short order? [Dr. Soffler] Yeah. So I agree this sounds like a really sick patient who probably is too sick to stay on a medical floor.
So again, we are talking about interventions like BiPAP and high flow nasal cannula, particularly for the indications of respiratory failure. And so these are great options and hopefully she'll respond, but if she doesn't respond and she's not improving, or her work of breathing becomes even worse or she becomes hemodynamically unstable, then we really have to think about augmenting her support probably to intubation for mechanical ventilation.
And certainly, all of this is best done in the intensive care unit. So I would favor moving this patient to the intensive care unit, and really what I tell my residents is that I'm always like, most worried about patients who are on BiPAP or high flow nasal cannula, because I kind of consider it a trial period, right? We're not out of the woods, we don't say, "Yep, we have them on definitive therapy.
Now we just have to give it time and see what happens." Absolutely not, these patients require frequent check-ins, very close monitoring because if they're not improving or they're worsening then it really is time to think about intubation for mechanical ventilation. [Dr. Kumar] Got it, Morgan. That's great. You know, so much of the early trainee years are really trying to identify in your patients those who are critically ill versus not ill, and I think you really nicely outlined the reasons why this patient is critically ill and needs to be escalated to the ICU.
So fortunately, the ICU does have an available bed and the patient's urgently being transferred. You are able to have respiratory start BiPAP on this patient en route to the ICU and we will pick up this case in our next episode. So today, we covered a lot of material. Let's go ahead and pause and Morgan, we always finish with three pearls from each of our RTL episodes.
Can you provide our three pearls from today, please? [Dr. Soffler] Absolutely, I'd be happy to. So pearl number one, I want to emphasize the importance of the bedside exam as a crucial part of yours assessment for patients who have of course, any complaint, but particularly hypoxia and pay particular attention to their work of breathing, because that's going to help you both with your differential diagnosis and thinking about what sort of support the patient might benefit from.
My second pearl is that for non-invasive options for respiratory failure, one can consider high flow nasal cannula or BiPAP with a preference for BiPAP in patients who have hypercarbic respiratory failure or respiratory failure from COPD or CHF, which are grade 1A recommendations for the use of BiPAP. And then my third pearl would be that to consider a broad differential diagnosis for patients who develop acute respiratory distress and that a crucial part of their workup includes chest X-ray, a cardiac evaluation and consideration of point-of-care ultrasound if you have that available to you.
[Dr. Kumar] Amazing. Thank you so much, Morgan. I promise I will finally get you those ABG results in our next episode. I feel like you were asking for it at each little junction of this case, I will get that to you. Thank you to our learners for joining us. We will see you next time, where again we'll pick up this case as this patient arrives in the ICU. [outro music] [outro music]