Hello, and welcome back. This week's APP webinar series will start with Dr. Michelle Kao, presenting Respiratory Management in Neuromuscular Disease. Dr. Kao is Clinical Associate Professor in the Division of Neuromuscular Medicine and Division of Sleep Medicine at the Stanford University School of Medicine. Please enjoy her wonderful talk. Hello, my name is Michelle Kao. I am a Clinical Associate Professor at Stanford University in the Division of Neuromuscular Medicine and the Division of Sleep Medicine, and my talk today will be on Respiratory Management of Neuromuscular Disease. Main objectives today include understand the pathophysiology of hypoventilation and progressive respiratory failure, recognize the symptoms of progressive respiratory insufficiency, review diagnostic testing for respiratory insufficiency, and develop the expertise with treatment using mechanical airway clearance and noninvasive ventilation. I have no conflicts of interest to disclose for this lecture. So the respiratory evaluation can, to start out with, the symptoms can be quite subtle with early disease onset, and it is often overlooked during the clinic evaluation. Respiratory insufficiency initially occurs during sleep, eventually progressing to daytime. The clinical evaluation therefore should include a detailed sleep history and the daytime symptoms, and bed partners, caregivers are great historians in this process. So in terms of respiratory involvement from sleep to daytime, there are four pathology. The first one is impaired pulmonary function, which involves the diaphragm. The second one is sleep disorder breathing, and this occurs during REM sleep, which is deep sleep, going on to non-REM sleep. This is evidenced by hypoventilation and hypoxemia. The third one is impaired cough due to abdominal muscle weakness, and this leads to adalectasis and subsequent pneumonia. And last is progressive respiratory insufficiency, and this manifests as a progressively elevated arterial carbon dioxide level, otherwise daytime hypoventilation. So in terms of the progression, I like this triangle because it really tells you the progression of disease starting with sleep. So initially, very early on in the disease process, there is abnormal gas exchange that occurs when you're doing sleep, and even doing REM sleep before it becomes a problem in non-REM sleep. And patients may have some sleep study disturbances if you were to put them through an overnight sleep study. And then after that, patients will develop sleep disturbances, such as frequent sleep disruption, difficulty sleeping, and so forth. And then as the disease progresses, you have evidence of abnormal daytime gas exchange. This is when patients start developing hypoventilation or CO2 retention during the daytime. And patients eventually will develop daytime symptoms, leading to acute respiratory failure. So in terms of the respiratory process, we talk about respiratory muscles that are involved in ventilation and airway clearance. In terms of ventilation, these are the inspiratory muscles, and this is active motion. So you have the diaphragm, which is the main muscle of breathing, and doing supine position or in supine position, this is the predominant muscle that's active, and then also the external intercostals. So passive breathing or passive ventilation are the expiratory muscles, and these are the internal intercostals and the abdominal muscles. In terms of airway clearance, so we break it down to cough. So the ability to cough is dependent on the inspiratory, expiratory, and glottic muscles, which are in the neck area. And then swallowing and airway protection also involve the glottic and bulbar muscles. So this is a really nice diagram because I think it really portrays what happens with patients who have neuromuscular respiratory weakness. So again, the three categories up here are the inspiratory muscle weakness, which is involved in breathing, the expiratory muscle weakness, which is involving cough, and then the bulbar muscle weakness. These are the neck muscles, the facial muscles, and this involves upper airway dysfunction. So inspiratory muscle weakness can lead to hyperventilation, both during sleep and during the daytime, leading to respiratory failure. Expiratory muscle weakness leads to cough dysfunction, inability to have effective airway clearance, which can lead to atelectasis pneumonia, and then the bulbar muscle weakness can cause upper airway dysfunction and obstruction, leading to sleep disordered breathing. So this is similar to something like sleep apnea, but you can appreciate that all these three muscle groups are intertwined and they all affect each other. So let's talk further about sleep and ventilation in these patients. So in normal sleep, someone without neuromuscular disease, this is the normal physiologic changes. So you have some reduced lung volume just by the fact that you're falling asleep. And there's some reduced muscle tone, which is most pronounced during REM sleep. And the tidal volume heavily depends on the diaphragm. And this is most, again, most pronounced during REM sleep. There is a reduced chemosensitivity to hypercapnia and hypoxemia. What that means is that it takes a much higher level of CO2 to stimulate breathing and also takes a much lower level of oxygen in the blood to stimulate breathing. And then there's a reduced upper airway pharyngeal dilator activity. So the upper airway muscles also reduce in terms of their activity. And then there is some degree of... So what happens in sleep in neuromuscular patients is, so you have the normal physiology in sleep and then you add on the pathophysiology for these patients. So now, in addition to the above five changes, they have diaphragmatic weakness, they have increased respiratory load and increased work of breathing. They have changes in the central respiratory drive. And there's also changes that can lead to increase in upper airway obstruction. And some of these patients also have cardiomyopathy, which can also affect breathing during sleep. So you add all this, and then you have REM sleep, which is where sleep and breathing impairment is most pronounced. So you can imagine that these patients really, really have derangements in breathing during sleep and then REM sleep. So this is a nice cycle, and it really drives down the point of how sleep and breathing is greatly affected for these patients. So if you have a patient with neuromuscular respiratory weakness, you have an increase in respiratory load. What happens is that during REM sleep, there is lower levels of oxygen and higher levels of CO2 in the blood. This actually leads to more frequent cortical arousals. So an increase in arousals will lead to a reduction in total sleep time and a lower sleep efficiency, which will lead to daytime hypersomnolence and fatigue. So this chronic sleep deprivation or progressive sleep deprivation will lead to a rebound increase in REM sleep. And as I told you, REM sleep is when breathing is at its weakest. So if you have more REM sleep, you're going to have more hyperventilation. This leads to a compensatory bicarbonate retention, which further depresses the respiratory drive. And then eventually these patients develop severe nocturnal and daytime hyperventilation. So this is a cycle that repeats itself, and it's a cycle that we need to break. So this is a nice example of a sleep study. So let me just orient you. So the top bar is the CO2 level in green. The red is the SpO2 oxygen saturation, and then the black line is the heart rate. So you can appreciate here that doing the three areas here, the three different phases here, this is where REM sleep happens. Because the CO2 is somewhat within normal range, and then it just jumps up during this time here during sleep, and it goes back to normal, and it goes up again. So this is basically REM sleep. So during REM sleep, CO2 is markedly elevated with a corresponding drop in SpO2 or hypoxemia. And then this is consistent with someone doing sleep. You have about three or four REM episodes, and the longest one is in the second half of the night. So you know that this hypoventilation period is much longer, and there is significant desaturation. This is commonly seen if we were to put our patients through a sleep study. So let's talk about symptoms. So what do you want to look out for when you have these patients? So sleep symptoms are many, but these are the frequent ones. So you can ask for if these patients have frequent arousals or sleep disruption during the night. They may have snoring, they may have witness apneas by the bed partner, and they may have gasping and choking, which wakes them up from sleep. And orthopnea is pretty common. These patients, when they are supine, they get short of breath. Daytime symptoms, again, can be quite nonspecific, but they can point towards the fact that there is some respiratory impairment during sleep. So people, these patients, have morning headaches from the CO2 retention during the night. They have daytime fatigue, daytime sleepiness. They may have never napped before, and they started to nap, or they may nap already but have an increase in duration and frequency. They have a reduction in exercise capacity, and they may be just short of breath as well. And then there's some behavioral symptoms, right, because when sleep is poor, there's a lot of mood changes that come with it. So these patients have depression, anxiety, and so forth. In terms of testing, so these are the common tests that we do in the clinical setting. So spirometry is considered really a routine test for every single patient. And if there is a question of spirometry looking as if it's restrictive versus obstructive, then you would need a full pulmonary function test with lung volumes to verify further. The other common test is the respiratory muscle pressures, and this goes along with the spirometry. So this is the maximal inspiratory pressure, the maximal expiratory pressure, the SNF, and then the peak-off flow. So remember that early on, the MIP can be low in early disease with preserved FVC. So if you see this pattern, you might want to consider doing an upright and supine FVC, and usually a greater than 10% change in the two numbers is considered a positive sign that there is early respiratory muscle weakness. The rest of these studies are, I would say, a consideration. So a sleep study may be considered, especially if your PFTs are normal, but the patient has positive sleep symptoms. During the sleep study, you can add on CO2 markers. Some clinics have the ability to do this in the clinic setting, but this is routinely done in the sleep study. You can also do a quick check or a quick screening test with nocturnal pulse oximetry. So this is much easier to do than getting a sleep study. And then also you can do a turbulent gas or bicarbonate measurements. Now a turbulent gas is not easy to get, but you can do a basic chemistry panel and get your bicarb. And bicarb is a very good surrogate marker for elevated CO2. And then sometimes if you need other testing, such as a chest X-ray or a CT of the chest, and then for some people with associated cardiomyopathy, you might want to consider an echocardiogram as well. Let's go over the pulmonary function testing. So the vital capacity, or the forced vital capacity, this is a maximal capacity in a single breath. And it is the most widely available test and most widely used test for neuromuscular patients. It has established precedence in clinical trials. It is an assessment of diaphragmatic weakness. And again, like I mentioned, greater than 10% is considered a positive sign that there is evidence of weakness. If the FEC upright is normal, you can consider doing the upright and the supine and compare the two values. And it correlates with clinical endpoints, such as through the sort of breathing and respiratory insufficiency. The drawback is that it's a volitional test, meaning that it requires training of technicians and it is somewhat effort dependent. And it requires oversight of the raw data tracings for quality purposes. The other category, this is the maximal respiratory pressure and the maximal expiratory pressure. And this is the maximal output of muscles. The MIP can detect early diaphragmatic weakness prior to reduction in FBC. The MIP is one of those values that we say it's an early dipper, meaning early on in the disease, it dips very low and then it stays low. So it's not the best test to monitor for disease progression. This test is very effort dependent. So it does require oversight, again, of raw data for quality assurance. And it has a larger variability, test by test and then day to day. So this is just something that we, when we do spirometry, we also look at the flow volume curves because beyond the numbers, this gives us a better idea of what the process is. So this is an obstructive process. You can appreciate here in the X, this is the volume of air that your lungs can handle. This is the capacity. This is the flow on the Y axis. So for someone with obstructive process like COPD or asthma, expiratory is fine. So expiratory is going down. And then expiratory, they have this concavity. So obstructive process, these patients have difficulty exhaling air and there's air trapping. But there isn't a reduction in the air, in the volume of air. It's just that the air, the volume of air is trapped and the patients can't exhale. Versus restrictive process, you can appreciate here, I basically squished this flow volume loop. So now you can see that the total air, which is the area here is your volume. It's reduced, right? So that's reduction in tidal volume, but expiratory is fine. It's just these patients can't get the amount of air that they should be getting. That's a restrictive process. So what about a sleep study? I see a lot of people ordering sleep studies routinely for these patients. So in neuromuscular disease, remember that sleep disorder breathing is not equal obstructive sleep apnea. So a sleep disorder breathing is a big umbrella and it can be hypoventilation, hypoxemia, central sleep apnea, but definitely not obstructive sleep apnea. So I recommend a diagnostic sleep study when you suspect early nocturnal respiratory impairment, or just some patients may have isolated OSA. These are the patients who usually have symptoms, but during the day they are fine and their PFTs are normal. Remember that the PFTs is a daytime breathing test, or they may have daytime symptoms, but they have preserved PFTs as well. And then a titration study is when we have a patient on positive airway pressure or noninvasive ventilation already, but we do a sleep study with it to titrate the settings. This is rarely needed unless you feel that you cannot get the adjustments correct on the NIV device. Oh, and you suspect that patients may be suffering from respiratory events that can be triggered by the NIV device itself. But the bottom line is that you don't want to delay starting NIV waiting for a diagnostic sleep study, right? Because daytime respiratory function has much greater prognostic value than nocturnal measurements. So how do we treat neuromuscular respiratory weakness? So we treat it with the gold standard, which is non-invasive ventilation, NIV, because the fundamental problem with neuromuscular weakness is that there is progressive ventilatory insufficiency leading to hypoventilation and frank respiratory failure. So it's not that the lung parenchyma, the lung tissues are problems, the lungs are fine. It's the breathing muscles that are weak from the disease itself. Therefore, oxygen alone is ineffective because, again, the lung parenchyma, the lung tissue is fine. So giving oxygen can worsen hypoventilation because what happens is that you pretty much fool the brainstem, the respiratory control center, into thinking that there's enough oxygen so the patient doesn't have to breathe. So you decrease that ventilatory drive for hypoxia. So oxygen may increase because you're adding oxygen, but CO2 also increase. And the problem is that when you're measuring SpO2, it's a measurement of oxygen. So you might have a falsely reassuring high SpO2, but your CO2 is climbing up as well. So the other option is invasive ventilation by tracheostomy. This used to be very common, but now with the advances in non-invasive ventilation, this has gone sideways. And I think it's a rare decision for patients to elect tracheostomy. So therefore, NIV, as you know, is the treatment of choice because it has really improved how we can manage these patients. So the goals of respiratory intervention are one is to preserve lung function. We normalize oxygen, normalize carbon dioxide. We improve chest wall and lung development for the younger patients. Improve quality of life so we can facilitate care at home. We can decrease work of breathing and rest these muscles so the strength can be used elsewhere. We optimize sleep and then also help in breathing and coughing during illness. So that helps to reduce hospitalizations, ER visits, and prevents tracheostomy. So there are three main goals, right? So for nocturnal hyperventilation, isolated nocturnal CO2 retention, we still use non-invasive ventilatory support. And then for daytime hyperventilation, we still use this as well. And sometimes we go to invasive, such as tracheostomy, although that's more rare. And then for impairment with airway clearance, we use manual and mechanical cauphysis techniques. So let's talk about assistive ventilation and airway clearance. So for assistive ventilation, this is the gold standard, right? The non-invasive positive pressure ventilation. This improves gas exchange. It minimizes chest wall distortion for the younger patients. For the older patients, it released work of breathing. We use advanced modes of positive pressure modalities. This is not your CPAP and BiPAP. And then again, as I mentioned, oxygen alone should not be used for long-term support. For airway clearance, there's manual and mechanical. So for manual, this is oral suctioning. We can do chest physiotherapy. We can hydrate the airways to keep moist. And then for mechanical, I think the gold standard here is really the cauphysis. It's technically called mechanical in-exhalation. We can also use the ventilator for breast stacking. And both of these have added the advantage of lung volume recruitment and lung volume expansion beyond just airway clearance. So I just want to show you some of the common devices we use. Really no particular preference over the other. So for isolated sleep hyperventilation, we use this category called respiratory assist devices. So these are the advanced positive airway pressure or PAP devices with backup respiratory rates. And these are the modes that we use, that we would recommend. BiPAP-ST is with a backup rate modality. And the BiPAP-A VAPs and the VPAP-I VAPs. These are the advanced, most advanced modalities that guarantee a tighter volume for each breath. And these are the common devices here. For patients suffering from daytime hyperventilation or respiratory failure, we really go straight for the portable ventilators. These are the home ventilators. These are the common ones that are out there in the market currently. The Trilogy and EVO are by Philips. The Astral is by ResMed. The Voxen is a very specific multi-function ventilator by Ventex. These have the same modalities as the RADs and more. One of the advantages is that it has this mouthpiece, what we call SIP ventilation for daytime use. What is the criteria for getting these devices? So the initial coverage criteria is that you have to have documentation and a diagnosis of neuromuscular disease or severe thoracic cage abnormalities such as kyphoscoliosis. The second criteria is that you have to have one of this right here. So either your arterial blood gas has to be greater than 45 while awake or the oxygen saturation has to be less than 88 for at least five continuous minutes and a two hour recording. Or for the patients with neuromuscular disease, you need to have either the MIP less than negative, less than 60 centimeters of water pressure or the FVC that is less than 50% predicted. And then you have to have this attestation in your documentation that COPD and also OSA here, which is not mentioned here, but OSA is included, do not contribute significantly to the patient's pulmonary limitations. So if you meet these three criteria, then you get your coverage. And so I have this 45, 50, 60 rule to make it easy to remember. 45 is your ABG, 50 is your FVC, and that negative 60 actually is the MIP. So one of these three needs to be met for a neuromuscular patient. So remember that sleep study is not a part of this coverage criteria. It is not required to get your NIV device. So a ventilator on the other hand is actually not, so it follows the same guideline as the previous slide, except that Medicare specifically says that for neuromuscular disease, the choice of a ventilator versus an advanced bilevel PAP device, it's actually based on the specifics of each individual patient's medical condition. And this, if you can document this appropriately, the ventilator would be granted. So in a nutshell, I think a lot of people ask me, well, how do I qualify for NIV, right? So for the respiratory assist device, again, just to summarize, you need to have a diagnosis of neuromuscular disease. You need to meet one criteria of these parameters, either one, FVC, MIP, CO2, or the overnight pulse oximetry less than 88%. You need to document that COPD and OSA are not contributing to the patient's pulmonary limitation. And then there is this caveat here, is that when you get a RAD device, there is a 90-day compliance policy with all insurances, which means that the patient has to use it for a certain amount of hours for so many days, and also a face-to-face follow-up with the provider who's documenting the treatment benefits. Without those two criteria met, the patient, the insurance will stop treatment for these devices. For the ventilator, the treating physician's documentation is really the key, right? You have to detail the symptoms, why the ventilator is superior to the respiratory assist device. Of course, you have to have pretty impaired PFTs, severe symptoms, and that you document that the patient will benefit from daytime use of non-invasive ventilation, level of disability such as patient's wheelchair bound, and that the patient's life will be threatened without a portal ventilator. So I also get this question a lot, which device and mode do I choose for my patients? So I would say that the mode and the setting depends on the severity of disease. So in early stage, when FEC is relatively preserved, or if there's isolated sleep disorder breathing, I usually go for the respiratory assist device with a backup rate. I always start with low pressures with an IPAP of 9 and an EPAP of 5 and a backup rate of 12 to get patients acclimated to the device. So if I have a patient with advanced or rapidly progressive chronic respiratory failure, then I go straight for the ventilator, and I also add the daytime use of the ventilator. Just quickly here, what is bi-level ST, right, the backup rate? So remember a fixed bi-level delivers an IPAP, which is the instatory pressure, and then an EPAP, which is the expiratory pressure, and the variable is tidal volume, right, so it doesn't guarantee a tidal volume. It gives you a fixed amount of pressure. So versus the AVAPs or the volume-assured pressure support mode, these are really advanced bi-level PAP devices, and what the difference between this one and the backup rate device is that it targets a tidal volume per breath. So for example here, here's a patient's tidal volume, patient's breathing, breathing, and this is the target volume that you want the patient to get with each breath. Well, this is the EPAP. Let's say it's set at 5. The IPAP main, let's say, is set at 10, and the IPAP max set at 30. So the device here recognizes that the patient isn't meeting the goal tidal volume, so it's going to march up on the IPAP pressure, right, and then once the patient over-achieves the tidal volume, then it's going to back down again, and it'll keep doing this until it can maintain the patient at goal. So it does this very well within the course, within about an hour or two of falling asleep. So this, just so you have these slides and you can just read this, if you're looking at, you know, what are the initial settings for bi-level ST, what are the settings for the EVAPs, you can just follow these guidelines here. What about CPAP? Well, CPAP is appropriate for OSA only, especially if the respiratory parameters, like PFTs, are preserved. It should never be used when PFTs are normal, and one thing to know is that if the patient does have OSA, well, the bi-level devices and these advanced models all treat OSA, so that's not the issue. And just so you know, these devices are quite technologically advanced, and it really helps in the COVID-19 era, because these devices basically have remote monitoring, so I can log into a secure cloud program and monitor the patient's usage and output. So it definitely does capture a lot of ventilation data, a lot of ventilation data, from pressure, to volume, to flow, to minute ventilation, leak. It also has the ability to integrate CO2 monitoring and SpO2, so it's quite impressive. I want to say one thing, one slide about mask fitting. So mask fitting makes all the difference in terms of effective NIV use. So mask options are, there are four of them, pillow style, nasal style, and oral nasal, which is a full face, and this is total full face that we really don't use. Mouth leak is very common, right? So patients have mouth leak if they have chronic nasal obstruction, obesity, aging, and male. These are risk factors for mouth leak, but you can see here that this was a clinical practice guideline from the American Thoracic Society that was recently published, and nasal masks are much more comfortable. There are many, many advantages of nasal masks. There is the risk of mouth leak, but even with the mouth leak, the nasal masks are more tolerated. The full face masks, yes, have better control of mouth leak, but there's a lot more disadvantages here. So I always go for the nasal mask first, and I really do the full face mask if the patient cannot tolerate nasal or pillows mask. So these are some of the mask interface. There are many out there, so just to give you kind of a prototype of what they look like, these are the pillows, these cones that go in the nose. This is a full face. As long as it covers the nose and the mouth, it's considered a full face mask, and the nasal mask just covers the nose. So a few slides on airway clearance, so let's just switch gears. So what is airway clearance? So the benefit of airway clearance is that it has lung volume expansion capability. Of course, it improves strength of respiratory secretions, and it can prevent infection and definitely prevents tracheostomy. When do we initiate airway clearance, right? So we measure peak cough flow, and the cutoff is that if it's less than 270 liters per minute, it's time to initiate airway clearance. You can also consider the FBC in initiating airway clearance, and usually when the peak cough flow is less than 160 liters per minute, this is impending respiratory failure, and these patients are at high risk for tracheostomy. So cough assist wise, there are several ways to do cough assist. You can do it manually with breast stacking. So we can use this, what we call the Ambu bag, and we can just breast stack. And by breast stacking, you inflate your lungs to the point where you have an increase in respiratory pressure, which helps bring out the secretions. And then the mechanical in-exhalator, that's your cough assist device, which is, this is one of the common ones here. And then also you can use the patient's ventilator, and if you put it in a specific mode, which is volume cycle, you could also breast stack. So what happens is that you just basically give the patient, you know, breath by breath by breath, a volume of air, and to the point where the patient's lung capacity is filled up, and then you have the patients just naturally cough it up. So it's kind of like the breast stacking manually, but in this case, using the ventilator to breast stack. So this is my summary slide. So hyperventilation starts early during sleep and progresses to daytime respiratory failure. The FVC is used to monitor disease progression. FVC, MIP, arterial CO2, and overnight pulse oximetry are used to qualify patients for non-invasive ventilation. NIV includes bi-level PAP devices to portal ventilators, and these are advanced modes of respiration. Remember that CPAP is contraindicated in neuromuscular disease, unless there is really just isolated sleep apnea, which is very, very rare. A sleep study is usually not indicated for NIV initiation, again, unless you are suspecting very early on isolated nocturnal respiratory impairments. And then technological advances have made NIV really the first-line therapy for respiratory insufficiency, along with the use of mechanical cough assist therapy. Thank you. Hi, everyone. Thanks for listening. If you have any questions, I'm happy to answer them. What are the three main types of respiratory impairments that we can think of? One of the questions on the chat format was about the AVAPS modality. The question was that, my understanding is that AVAPS is not ideal for its ideal setting due to the ramping up to meet tidal volume. Is this correct? So AVAPS, or volume-assured pressure support modalities, are actually, the advantage of the AVAPS modality is that it can meet the tidal volume with each breath that the patient takes. That is the advantage over a regular bi-level PAP device. The bi-level PAP devices are set pressure, so the volume is actually the variable, and you can't guarantee a volume. Whereas the VAPS mode, you can guarantee that volume. The way it does that is that it uses varying pressure support to get that volume that the patient needs. So when you look at the VAPS download, you need to look at the average inspiratory pressure that the patient's needing, and then you want to adjust your IPAP minimum or your pressure support minimum, depending on which device you use to meet that need. So for example, if your EPAP is at 4, and your IPAP or pressure support min is at 8, and your IPAP or pressure support max is at 20, and the patient is getting an inspiratory or average pressure of around 12, you don't want to keep that IPAP min or that pressure support min at 8. You want to bring it up to 12 to match the patient's needs. So I hope that makes more sense. Now, AVAPS is obviously proprietary to Philips, but the ResMed version is called Intelligent Volume Assured Pressure Support, or IVAPS, and it can also do a VAPS modality as well. One thing I also wanted to say is that you all may have heard, as of Monday, Philips made a recall nationally on all their PAP devices and their ventilators, with the exception of the DreamStation 2, which is a CPAP device, which is not going to be relevant to our patient population, as well as the new EVO ventilator, EVO. So as of now, we are not, we should not be prescribing, you know, Philips devices. So just so you know, moving forward as of this week. If you have any questions, please just type it in the chat box and then I'm happy to answer as well. There was another question on respiratory training in neuromuscular disease. So one of the attendees mentioned that she works in an academic setting and it is very difficult to get local pulmonologists to manage respiratory care for neuromuscular patients. I find that to be very true. Unfortunately, I think it is really a national problem. I will say that in the more recent years, there is a lot of push for pulmonologists to understand and be educated on noninvasive ventilation in general for neuromuscular patients, as well as other conditions like COPD and other chronic respiratory failure syndromes. So a lot of us are really trying to push this educational lead at more of an international national level with our societies, such as American Thoracic Society, ATS, or American College of Chest Physicians, which is chest. But I understand your point. It is very hard to find a local pulmonologist who would feel comfortable taking care of these patients. One good thing, though, is that there is telemedicine now in telehealth. So if you have a pulmonologist even just within your city or your state who does manage these patients, it is possible to take care of these patients remotely. I do a lot of telemedicine for my patients. So I don't necessarily need to see them in person. So that may help if you are short of a local pulmonologist. Another question is, do you find it advantageous to continue to test PFTs and spirometry once NIV ventilation is initiated? So I do. And the reason why is because the spirometry, especially the FVC, is really an indicator of disease progression, right? So beyond just for qualifying for noninvasive ventilation for treatment, it is really helpful for the neurologist and for us to see the progression of disease and be able to provide recommendations and support as the disease progress, right? So it is really important to continue the FVC as long as you can. Obviously, when the patient's FVC is about 20% predicted, I think at that point, most patients are already on NIV 24 hours a day or are leading to going towards a tracheostomy. And at that point, it's probably not necessary to do anymore. But I think until then, it is really important to continue that monitoring. And also, I think it helps your NIV management as well, right? So if you are starting out with a patient on a bi-level PAP device and the FVC drops below 50% and the patient is experiencing daytime shortness of breath, you're going to want to go to a ventilator. So I think in that case, it is important to monitor FVC for disease progression as well. Dr. Cao, thank you so much for your time. We really appreciate it. Sure. Thank you. Yes, wonderful afternoon. Thank you very much.

respiratory management

neuromuscular disease

pathophysiology

hypoventilation

progressive respiratory failure

diagnostic testing

mechanical airway clearance

noninvasive ventilation