Hypercapnic Respiratory Failure from the Hospitalist Perspective: Recognition, Risk, and Perioperative Insights

Podcast Transcript

Dr. Raed Dweik, MD (00:01):

Hello and welcome to the Respiratory Exchange Podcast. I'm Raed Dweik, Chief of the Integrated Hospital Care Institute at Cleveland Clinic. This podcast series of short digestible episodes is intended for healthcare providers and covers topics related to respiratory health and disease in the areas of lung health, critical illness, sleep, infectious disease, and related disciplines. We will share with you information that will help you take better care of your patients. I hope you enjoy today's episode.

Dr. Dan Culver, DO (00:34):

Hello and welcome to this edition of Respiratory Exchange. I'm Dan Culver. I'm the Chair of Pulmonary Medicine here at Cleveland Clinic. I will be hosting this episode on hypercapnic respiratory failure from the hospitalist perspective. My guest today is Dr. Roop Kaw. Dr. Kaw is one of the expert hospitalists we have here who's jointly appointed in hospital medicine and also in anesthesia outcomes research. Roop, welcome.

Dr. Roop Kaw, MD (01:02):

Thank you, Dan. Delighted to be here.

Dr. Dan Culver, DO (01:06):

Hypercapnic respiratory failure is a big topic. And of course, as you know well, this is something that hospitalists are among the first people to encounter. And quite often, most of the management occurs by hospital medicine rather than in the ICU or other specialists. And so, I think it is really timely today that we talk about the full spectrum from outpatient assessment all the way into the acute management of hypercapnia in the hospital. I'm excited to hear your perspectives. Maybe we can start just a little bit with hypercapnia. We know what that is on a blood gas, but maybe you can define a little bit for me how you think about hypercapnia, especially these terms acute and chronic hypercapnia. And maybe also with that, how do you even recognize it? What makes you think, "Hey, I might be dealing with this problem"?

Dr. Roop Kaw, MD (02:01):

So, I will be purely talking from the point of view of a hospitalist, particularly the ones that work in the nighttime and may be encountering this situation for the first time. But I will also talk about the people that we get out of the MICU and SICU that have established diagnosis of hypercapnic respiratory failure. So generally speaking, most of the patients that I have seen, and I've been involved in this area for a while, come from the ICU, from the MICU as hypercapnic respiratory failure, and then it is our job to sort out what's the hypercapnia from, how much can we do inpatient and how can we arrange an outpatient workup?

Dr. Dan Culver, DO (02:45):

So, you're saying it's pretty unusual that somebody had not been known to have a problem with ventilation before you encounter them?

Dr. Roop Kaw, MD (02:56):

Well, it could be either way. We could get known patients of hypercapnic respiratory failure. At that point, we may not know whether they have obesity hypoventilation or what their hypercapnia is from, but we could also get people who are admitted with a third-party diagnosis like congestive heart failure or something else, and then they become hypercapnic. And if I jump to the second category where the diagnosis is not very apparent, the first call that typically comes is from a pulse ox drop, or sometimes from my mental status change.

Dr. Dan Culver, DO (03:31):

And those are both relatively late signs of respiratory failure.

Dr. Roop Kaw, MD (03:36):

Absolutely. Even the pulse ox drop is a delayed sign of hypercapnia, and the symptoms obviously by that time are already too late. So it's a challenging thing for my colleagues at the nighttime, because I may be not overstating this fact that in the non-critical care setting, even though most of our wards are very well monitored, in the non-critical care setting, it's really a challenge to figure out what the pulse ox drop is from or what the mental status change is from. Now, typically speaking, it depends on how quickly the hospitalist can land on the scene or whether they order the oxygen to be bumped up or whether they order the VBG, this is very variable in my eyes. So, I think that in terms of signs and symptoms, they're very subtle. Even if we talk about mental status change, by the time the patient goes from early mental status change to a complete stupor, there's a lot of time and zone to cover.

(04:52):

And again, it's a missed opportunity to diagnose this thing earlier, but a timely diagnosis can be made if we know what setting the patient came from and the settings would be like if we already have a patient coming from MICU and they were hypercapnic there, then it's a slam dunk. And the second setting would be if we have a patient that had a recent surgery and now is getting X amount or even higher doses of IV opioids, that's another... I'm talking about the common settings rather than all the settings. A third one I would like to mention, and this is to throw light on recent literature, and we actually have in this inaugural issue of CHEST, a paper that highlights, and this has been mentioned before, that highlights the association of heart failure with obesity hypoventilation, whether it's comorbid or whether it is completely secondary to the obesity hypoventilation. Either way, we highlighted there that about 60% patients can have associated heart failure, and the presence of heart failure alone can trigger the presentation of obesity hypoventilation and vice versa.

Dr. Dan Culver, DO (06:07):

So bidirectional. So what you're saying is when you get sign out a patient who came out of the ICU recently, a patient who had surgery recently, who's on opiates possibly, or maybe not, maybe it's abdominal surgery, something like that, or somebody who has heart failure or risks for heart failure, automatically you're more sensitized to think about hypercapnia as a change for the status of that patient. Are there other situations or risk factors that really get your radar going?

Dr. Roop Kaw, MD (06:40):

Absolutely. I only talked about the most common so that there's a general level of awareness to the least common denominator but this is a situation that's more dependent on what setting the patient came from, but there are like this patient with neuromuscular disease, for example, a lot of patients on the neurologic floors, and that's another big one. And then there are other sorts of hypoventilation states from other medications rather than just the opioids. So broadly speaking, those are the major categories. Yeah.

Dr. Dan Culver, DO (07:15):

And you highlighted really the drop of a pulse oximeter, assuming there's even pulse ox being monitored and mental status changes, which of course at night is probably assessed less often and can be confused with other things like delirium. Are there some other signs or symptoms that also people should be aware about that should lead them to think about hypercapnia?

Dr. Roop Kaw, MD (07:41):

I think there could be more severe form of neurologic signs. For example, a patient could basically become [inaudible 00:07:51] or even have a seizure at times when it comes to symptoms, but then if we're trying to catch the process early, if we have a setting where we can have other forms of monitors, which as opposed to pulse ox can pick it a little earlier, for example, end-tidal CO2, which is not generally routinely available on the surgical or medical floors, we can capture hypercapnia at an earlier clip.

Dr. Dan Culver, DO (08:21):

So really awareness is the first diagnostic tool in your toolkit.

Dr. Roop Kaw, MD (08:26):

Yes.

Dr. Dan Culver, DO (08:26):

You mentioned also VBG, and I just wonder in your experience, what's your threshold for obtaining a VBG in a patient when there's a change? And do you always use that as opposed to ABG nowadays? So, tell me a little bit about how that tool works.

Dr. Roop Kaw, MD (08:45):

I think there's a personal component to it and there's a practical component to it. The personal part is that I was actually one of the members of the American Thoracic Society Guideline Committee in 2019 that wrote the guidelines for diagnosis and management of obesity hypoventilation syndrome. So in that document, we had a preference for using an arterial blood gas in the right suspected patient, but I think that as clinical practice goes, especially after the time we've had COVID, people have gotten good at using VBG in the correct situations, ordering it in the correct situations, and it's also very practical and an easier test and has absolutely minimal complications. So, the limitation we have, I think with the VBG is on the hypoxia side, is in the PAO2 side rather than the PaCO2 side. But flipping back to the ATS document, I think it hasn't been officially recognized that we can use a VBG for the diagnosis of-

Dr. Dan Culver, DO (10:01):

So surprisingly enough, the guidelines are not keeping up with clinical practice. We've never heard that story before, have we?

Dr. Roop Kaw, MD (10:07):

We're all very familiar with that.

Dr. Dan Culver, DO (10:13):

So, I agree. It seems like VBG is a much more easily accessible test and people have become comfortable making the small titrations in their understanding about the expected values and also assessing oxygenation separately. I also think with assessing oxygenation, which brings in the issue of skin color and some of the issues around pigmentation for pulse oximetry. I presume that you work through that as you're thinking about a change in status for your patient.

Dr. Roop Kaw, MD (10:46):

Yes. There's a lot of recent data also about quote, unquote "accuracy" or "practicality" of pulse ox in people with darker skin, but the use of pulse ox will stay as long as the limitations are very well understood. But I think that I would make a broader statement is that if we only rely on pulse ox, we're for the most part only trying to diagnose hypoxia and not necessarily where the hypoxia came from, unless we investigate it further. And it's not prime time for end-tidal CO2 monitoring on the regular floors, yet with improvements in technology, we may get to that point.

Dr. Dan Culver, DO (11:43):

That, or maybe transcutaneous capnography is another one.

Dr. Roop Kaw, MD (11:47):

Yes.

Dr. Dan Culver, DO (11:49):

So, can I paint a scenario for you?

Dr. Roop Kaw, MD (11:52):

Absolutely.

Dr. Dan Culver, DO (11:53):

I suppose this is a common one. An obese patient with a history of diastolic dysfunction, a smoking history, maybe they carry a chart diagnosis of COPD, and now you're called to see the patient on a medical floor for some changes or some respiratory symptoms. How do you think about acute and chronic components in that patient and what are the practical steps you go through to sort out what's happening to the patient as you think about the possibility of hypercapnia?

Dr. Roop Kaw, MD (12:25):

I typically tell my associates and residents is that if you have ordered a VBG and you typically see that the pH is within the normal range, but the CO2 is varying and going up, and basically you're dealing more or less with a chronic hypercapnic situation, and that's usually the common situation that we see is, so the presence of PH and pH accuracy on VBG is pretty good. And granted that even within those situations, when the PaCO2 goes up, you can still have all the range of symptoms, but obviously, as we said earlier, that would be a later stage in hypercapnia.

Dr. Dan Culver, DO (13:10):

So, a thing that people always talk about in those situations is concern or fear about supplemental oxygen. And I wonder what your approach is to that and whether your thinking has evolved over the course of the years you've been doing this as new research has come out.

Dr. Roop Kaw, MD (13:29):

Yes. And I'm glad, I appreciate you asking me this question. The supplemental oxygen is, first of all, oxygen use is very liberal thankfully at lower concentrations in the hospital. It can be used for things as trivial as comfort and as much as maintaining oxygenation. And the important fact, which I think you're trying for me to highlight is that when you are on supplemental oxygen, it will hamper the detection of hypercapnia. And that's an essential fact that after that, the use of pulse ox, if you were to depend on the desaturation driven by hypercapnia, you lost that signal already.

Dr. Dan Culver, DO (14:19):

Sure. And then there's this whole question about suppressing respiratory drive, that is a concept that perhaps just won't quite go to bed.

Dr. Roop Kaw, MD (14:29):

Yes, I think the data on this is, it's an open-ended stream, but the concerns for causing worsening CO2 retention in certain situations, certain subset of patients is actually real, if not across the board. And especially obese patients, higher BMI, possible obesity hypoventilation, and higher concentrations of oxygen. That will make it happen for sure.

Dr. Dan Culver, DO (15:02):

So, when you think about the patient that I was laying out, obese patient with diastolic dysfunction and some COPD history, and then you layer in a history of sleep apnea, does that change your thinking at all? Does it change your management approach at all? How does sleep apnea play into this, especially if you're a nocturnist?

Dr. Roop Kaw, MD (15:26):

Yeah. One of the common things that I feel doesn't get enough light is that many people who are admitted for a completely different diagnosis and are desaturating in a benign way, and this we see... And not being a nocturnist, but when we come next morning, we're told about these desaturation episodes, these are people who would be doing that at home. It's just that we started monitoring them for the first time. So that's like, and not to say that those desaturations are harmless, but we know what they're coming from. I think that one has to have a radar for desaturations that come from hypercapnia, which I think the most important step for that is the clinical circumstance the patient is coming from, an ICU patient, a known obesity hypoventilation patient, a neuromuscular disease patient, a post-op patient. Since my area of research is mostly perioperative, and that's how I landed into this, I can't begin to overemphasize how many times we make the diagnosis of obesity hypoventilation syndrome in a total post-op situation. It's one of the leading channels of picking this diagnosis, in my opinion.

Dr. Dan Culver, DO (16:53):

Well, it's like an obesity hypoventilation stress test.

Dr. Roop Kaw, MD (16:56):

Yes.

Dr. Dan Culver, DO (16:57):

We're going to unmask it by bringing you in and doing surgery and getting your equilibrium off kilter.

Dr. Roop Kaw, MD (17:03):

Totally. You're putting the patient through the tunnel and here it is, and they didn't have this diagnosis before. We published this in CHEST in 2016, and we used clarity here to select patients who had sleep apnea at one point, blood gastrin at one point, and surgery at another point, and we created the database and clarity, and this was then called Exploris, which became a spinoff company for data eventually. But in that study, majority of our patients never had a diagnosis of obesity hypoventilation syndrome before they had any surgery.

Dr. Dan Culver, DO (17:42):

I think it's very underdiagnosed. My experience is that patients get mislabeled with a lot of other causes for respiratory insufficiency when really obesity hypoventilation is a major problem. So, I'm glad that you're emphasizing the recognition of it. I think we can all be more sensitized to it. I want to just pivot for a second. I do want to get to your issues around perioperative management and evaluation, but maybe if we just come back to our case scenario for a moment first, and I wonder if you can describe your approach to thinking about the setting of care. After you identify some decompensated acute on chronic hypercapnia, when do patients need to go to the ICU? When do you need to think about something like NIV? How do you approach those decisions?

Dr. Roop Kaw, MD (18:35):

So again, we can layer it out into acute versus chronic situations. If it's an acute situation and patient hasn't had it and is on the floor for another diagnosis, and it's already too late in terms of mental status change, or the VBG just looks too bad, unless the patient is... It also depends on where the patient physically is. Some floors are very attuned to initiation of positive airway pressure, and others basically don't even allow you to have the patient there. So essentially, if it's an acute situation, the chances of patient landing up in escalation of care is basically going to be high probability. If it's a situation where you have chronic COPD or a known hypercapnic from OHS, you could basically start using NIV on the floor if that is a possibility and watch the patient closely and probably also have MICU on the backup and see if things can be handled that way.

Dr. Dan Culver, DO (19:47):

You need a lot of respiratory therapy support, of course, to do that.

Dr. Roop Kaw, MD (19:50):

Absolutely. And we have phenomenal respiratory therapists and I can't also... I want to thank all of our respiratory therapists and also say this that over the entire course of my training, I learned so many things from our respiratory therapists, which I did not know at that time, and it's still true till today.

Dr. Dan Culver, DO (20:09):

Yeah, they're great partners, that's for sure. That's for sure. I'm just curious in your experience, sometimes we try different things and how often do you really see a real home run from things like furosemide or naloxone or other kinds of medical maneuvers to get out of a sticky situation with an acute component of hypercapnia? Is that very effective very often?

Dr. Roop Kaw, MD (20:37):

Naloxone definitely is when used in the right setting. I don't think there is a lot that can be said about that. The furosemide, I would say a lot of that is my clinical bias. I am also a believer in the fact that just like hypercapnia, just like it's harder to pick hypercapnia in the earlier phases, it's probably even more hard to pick hypervolemia, especially intravascular hypervolemia at an earlier clip, especially in an obese patient where the physical examination practically becomes useless. Also recognizing that one third of patients with diastolic heart failure may not necessarily have signs of extravascular volume overload and they still are in exacerbation.

(21:26):

So, using that knowledge base, and every clinician has a a trigger or a knee-jerk reflex, I'm very excited to start people on high dose diuresis. In the right setting, knowing that this is a patient with known heart failure, or maybe it wasn't picked and you suspect that it is, what I can't say for sure is that, and I'm probably in future, like to be part of a study where we could prove this, that starting diuresis at the right time may essentially help us in mitigating some of the after effects of hypercapnia in a acute situation in a chronically hypercapnic patient.

Dr. Dan Culver, DO (22:14):

That makes sense. I think-

Dr. Roop Kaw, MD (22:16):

I'm not sure what your question was.

Dr. Dan Culver, DO (22:19):

Yeah. And you're pointing out that waiting for an echo or a BNP to come back is not always necessarily the right move. Sometimes using clinical judgment and treating based on your suspicion might be appropriate.

Dr. Roop Kaw, MD (22:34):

And if you're working in the daytime and you have a POCUS available, you could just see some signs of volume overload there and just get started. But whether there's an exact correlation and diuresing very aggressively, very quickly, and that mitigating the possibility of hypercapnic events happening down the road, it remains to be established at a broader level, but I think that when you end up in that situation, we actually had... I was talking about this study that we published in the March issue of CHEST. We wanted to look at the effect of NIV in people who have OHS and heart failure, comorbid or secondary to it, versus people who don't have. I wanted to see how much does that get us? But this was from the NIS database, which has its own obvious limitations, but has a large number of patients, hospitalized patients all across the US.

Dr. Dan Culver, DO (23:32):

And that's national inpatient sample.

Dr. Roop Kaw, MD (23:33):

Yes, national inpatient sample. I think what we were limited by is that the overall use of NIV was in the range of 20% to 25%. So, it doesn't give us the right idea about... So, it would be a negative study that NIV did not benefit people with comorbid heart failure compared to the ones who didn't have heart failure but had OHS. So, what I'm trying to get at is that we also don't have the tools in an acute care setting of treating a person with volume overload and hypercapnia at the same time. It's all supportive at the moment, but these things like high dose diuresis or the NIV in the right setting could prove to be beneficial in the acute care setting.

Dr. Dan Culver, DO (24:25):

Yeah. I suppose dissecting out each intervention individually is challenging.

Dr. Roop Kaw, MD (24:30):

Yes.

Dr. Dan Culver, DO (24:31):

I want to just, in the last couple of minutes we have, I want to pivot for a couple minutes and talk about perioperative assessment risks for hypercapnia, postoperative identification, and then what's changed in the evaluation and management in that situation?

Dr. Roop Kaw, MD (24:52):

Thanks again for asking me this question. That's where the crux of my research basically lies over the years. So, I would say first of all, and this is from the angle of having been involved in anesthesia research, the American Society of Anesthesiology, they issue documents every two to three years, which are based on litigation data. They call it closed claim analysis and they looked at... And this is when there was a controversy about how bad OSA and OHS can be in the perioperative setting, is it really a big issue or not? Because if you look at garden variety OSA, people being operated, most people just happen to be fine.

(25:36):

Partly because the anesthesiologists are aware, half the times they do the right things anyway, but in the closed claim analysis, which basically had two major outcomes, death and neurologic morbidity from respiratory compromise, the data showed that in the first 24 hours after surgery, most of these events happen within the first 24 hours, at least half the events happen within two hours of the nurse having seen the patient by the bedside. And 15% happened within less than five minutes of nurse having seen the patient by the bedside. And there are these situations, what we call as the 'dead in bed', which is obviously not the most common thing, but my point being that there are these either apneic episodes or dramatic rise in the CO2, which causes the lights-out desaturation and people decompensate and have bad outcomes like neurologic compromise.

(26:38):

 So, ASA closed claim was the first one basically to motivate us to figure out this thing, like look into this. Then the Society of Anesthesia and Sleep Medicine that I'm a part of basically issued guidelines after that, after doing a lot of studies. This is a group of dedicated chest physicians and anesthesiologists. It's a very small society, but very smart people and they should guideline and they said, if you're trying to do an electro non-cardiac surgery on a sleep apnea patient, generally everything is fine as long as you're aware that the patient has sleep apnea or it has been measured by some tool like the STOP-Bang or whichever screening tool that you use is fine. However, you should step back if the patient has sleep apnea and clinical hypoventilation, you should step back if they have sleep apnea and pulmonary hypertension, and you should step back if the patient has sleep apnea and hypoxia of non-cardiopulmonary cause.

Dr. Dan Culver, DO (27:49):

So those would be indications for more careful preoperative assessment and perioperative management in those settings.

Dr. Roop Kaw, MD (27:55):

And I have incorporated this into my practice, and I do cancel those surgeries and then we put them through formal assessment, first make the diagnosis of how severe the sleep apnea is, what the gas shows, and whether this surgery can be done outpatient versus inpatient. And even if it's done inpatient, whether this patient, the surgery can be done under the auspices of a general anesthesiologist or a cardiovascular anesthesiologist, assuming if the patient is PH, which was also undiagnosed. So that would be the shortest version of like pre-op screening, I would say, in the severe forms of sleep apnea, which have OHS or hypercapnia respiratory failure or associated pulmonary hypertension.

Dr. Dan Culver, DO (28:45):

So, this sounds like a nice advance. This is getting past the identification of obesity, hypoventilation, and hypercapnia postoperatively in the hospital from mental status changes. This is really much more preventive, and I think it accords with our notion of first, do no harm. So, congratulations on that research and those guidelines. I think those are important advances. I want to thank you for being here. It's obvious that you've thought deeply about these topics. Maybe to wrap this up, I could just ask you as a closing thought, you've been doing this now for several decades. What is the biggest thing you've seen change over the course of your time doing this in the management, identification, risk assessment of hypercapnia?

Dr. Roop Kaw, MD (29:40):

I think the biggest change has been that sleep apnea, and you have to go by how far back I've been involved in this. I do remember the times when some anesthesiologists would actually say, "Well, it's been blown out of the water." Nobody says that now. So maybe garden-variety sleep apnea we don't worry about, but embedded are the cases of severe sleep apnea and then the worst case is the obesity hypoventilation syndrome. So, sleep apnea is recognized, routinely screened. You don't need a polysomnography before surgery, so that's a major way we have come along. I think the obesity hypoventilation syndrome awareness, particularly amongst primary care, internal medicine, hospital medicine is arising, but I think that has to come to the next level because we are still under-diagnosing in a big way and we have to bridge that gap.

Dr. Dan Culver, DO (30:43):

Well, thank you for the work you're doing to help lead in this space and to raise awareness. And it's been really a pleasure talking to you today. Thank you very much for being with us.

Dr. Roop Kaw, MD (30:53):

Thank you for the opportunity. And I also would like to thank our audience, and I hope that they find this conversation useful. I hope I can also inspire some younger minds to look further into these questions.

Dr. Dan Culver, DO (31:06):

I think like much in medicine, the more you know, the more questions arise. So, thank you everybody for joining us today and we look forward to seeing you at the next episode of The Respiratory Exchange.

Dr. Raed Dweik, MD (31:18):

Thank you for listening to this episode of the Respiratory Exchange Podcast. You can find additional podcast episodes on our website, clevelandclinic.org/podcasts or wherever you get your podcasts.