COVID-19 patients seem to behave in a somewhat unique fashion, compared to other patients with ARDS. This isn’t based on high-level data, but it seems to be a theme emerging from a variety of centers (including my experience with one patient). Some salient points are:
- Low driving pressures are seen among ventilated patients. Thus, it appears that the compliance of the lung is fairly normal (unlike most traditional ARDS patients).
- “Silent Hypoxemia” — A normal lung compliance may cause patients to have a relatively low work of breathing prior to intubation (compared to the severity of their hypoxemia).
- Highly recruitable lungs – patients often have a good response to recruitment using either high levels of PEEP or APRV (n=1 for the latter).
- Favorable response to pronation – along with the typical CT scan findings of peripheral, basilar consolidation, this might be consistent with a significant contribution from basilar atelectasis.
So COVID-19 isn’t behaving like typical ARDS, implying that it might be best treated in a slightly different manner.
theory regarding underlying pathophysiology
Some patients might have progressive alveolar collapse, as shown above. Alveoli start collapsing, which distorts the lung architecture and promotes collapse of neighboring alveoli. If left unchecked, this may lead to progressive deterioration which eventually requires intubation.
Once patients are intubated, high levels of positive airway pressure recruit the collapsed alveoli. Thus, patients may revert from a requirement for 100% FiO2 to considerably lower oxygen requirements over a period of several hours.
best mode of noninvasive respiratory support?
The above model would suggest that COVID patients really need positive pressure more than anything else. For example, their work of breathing is often tolerable – so they may not need much mechanical support for the work of breathing (indeed, mechanical support could lead to injuriously large tidal volumes).
The best modality to provide lots of positive pressure is simply Continuous Positive Airway Pressure (CPAP). CPAP may not seem dramatic, but this modality actually provides the greatest amount of positive pressure to allow for the most powerful recruitment:
CPAP may have several advantages for COVID:
- CPAP provides the maximal amount of mean airway pressure without intubation.
- CPAP doesn’t augment tidal volumes, so this may promote a more lung-protective ventilation pattern.
- With the use of a closed system and viral filters, this may be reasonably safe regarding viral transmission (nothing with COVID-19 is 100% safe).
nuts and bolts: how CPAP might be used
- The pressure might be up-titrated as tolerated to a fairly high level (e.g. 15-18 cm). Using excessively high pressure could risk gastric insufflation and aspiration (Bouvet et al., 2014).
- The FiO2 could be titrated against patient saturation. A favorable response to CPAP would be reflected in lung recruitment and falling FiO2 requirements. Alternatively, rising FiO2 requirements would signal CPAP failure and a need to intubate.
- A helmet interface could be optimal, if available (to avoid mask seal problems).
- Monitoring:
- Mental status
- Oxygenation (FiO2 requirement, oxygen saturation)
- Ventilation efficacy (tidal volume & minute ventilation on the CPAP device, perhaps intermittent VBG/ABG as clinically warranted)
what is the role of CPAP in COVID-19?
This is really unknown. There are many strong opinions, but almost no data (especially COVID-19-specific data). Unfortunately, most available evidence with regard to “noninvasive ventilation,” tends to consist largely of BiPAP (rather than CPAP). Indeed, these two modalities are invariably lumped together (despite being quite different).
CPAP certainly isn’t the treatment of choice for all COVID-19 patients. However, it could potentially play a role in certain situations:
- A patient with worsening hypoxemia (e.g. requiring ~50-60% FiO2) who is in no distress and has no other organ failures.
- Patients whose preference is to not be intubated (DNR/DNI).
- Exhaustion of the supply of mechanical ventilators (there is a large supply of CPAP machines, which are often used for obstructive sleep apnea). Similarly, if CPAP could avert intubation in even only 20-40% of patients, this could help prevent running out of ventilators.
- Lack of a team present capable of intubating the patient (e.g. a small hospital without resources necessary for immediate intubation)
As with all forms of noninvasive ventilation, careful monitoring is the key to safety. This is particularly critical for patients with COVID-19, who may develop “silent hypoxemia” (causing them to look much better than they actually are).
- COVID-19 appears to cause an unusual form of hypoxemic respiratory failure, with profound hypoxemia but normal lung compliance. This might be due to diffuse atelectasis.
- CPAP could be a desirable mode of noninvasive support for these patients. CPAP is the modality which provides the most powerful lung recruitment (highest mean airway pressure). It also has the advantage of avoiding injuriously large tidal volumes.
- The optimal role of noninvasive support modes in COVID-19 is currently unknown. CPAP could be a rational selection for some patients with moderate hypoxemia and single-organ failure. As always, further evidence is needed.
going further
- Section on noninvasive ventilation in COVID-19 IBCC chapter.
- IBCC chapter on noninvasive respiratory support.
Opening Image: Nathan Dumlao via Upsplash.
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Interesting reading, I have learned some new things which can help my patients in the close future.
I thought of CPAP because I have my own machine gathering dust in the corner. I’m really glad that someone with credentials is suggesting it.
To mitigate room contaminants sucked into the CPAP and delivered to patient’s lungs an N95 mask ‘strapped’ to a CPAP so intake is covered by mask will drastically lower PM2.5, as measured on my AQI meter. Am assuming it will also lower other harmful particles especially since N95 is touted as protective re Covid. And If no N95 available a piece cut from a roll of 3M Filtrete material may work using duct tape to tape it over the small air intake on a NIV (CPAP, etc)
The only concern i have about this is the fact that exhalation may be hindered and CO2 might build up. Not sure about how much this may increase patient’s respiratory rate to compensate. If they have normal lung pathology otherwise and are not retainers, it may not be an issue. I wish there was a filter that could be placed into the mask between the exh valve and the mask.
“I wish there was a filter that could be placed into the mask between the exhale valve and the mask”. Good point about wanting to limit what is exhaled out of patient into the room. I believe a piece cut from a roll of 3M Filtrete material may also work in this case, using duct tape to tape it over the small air OUTtake on a NIV (CPAP, etc).. Then, use a ($150) handheld AQI meter set on PM2.5 to measure PM2.5 exiting mask versus what is in the room to get an idea of how well it works, and… Read more »
https://imgur.com/v87t7YK
Two inline viral filters, extra exhalation port and a non vented mask
SO our in our ED the current protocol is to not use CPAP and go directly to intubation for any COVID-19 or suspected patient. We are not to use CPAP do to concern about our safety. So how is the safety of the staff maintained with a patient on CPAP?
A lot of hospitals in Denmark use Pulmodyne CPAP, and we found a connector that fits the system, so we now can place a filter between the mask and the exhale valve. The company also has a filter that fits. Maybe you could do that with other CPAP systems?
We also first hold the mask tight over the patients face before plug-in/turn on the system.
Hi Marie,
Could you share some information on your set up- Whether it is a picture, or description of specific parts. This is quite intriguing.
Is your mask then “non-vented” and all exhaled air exits through the filter then valve?
How are patients tolerating this? I can imagine they have a greater exhalation resistance perhaps?
My hospital is using a circuit like this
https://imgur.com/v87t7YK
The machine has its standard air inlet filter, and we’re adding two other viral filters and using non vented masks
1. use an anti-viral filter before the PEEP valve (https://bit.ly/3aXdo11)
2. use a helmet with a high-flow CPAP system (>45 L/min) that has no leaks compared to the mask
Hi Josh thanks for your deep insight. I want to share with you our experience with > 900 COVID19 PNAs. more than 30% need an FiO2 > 50%. Among them, we observed that those who cannot reach 90% of peripheral saturation with a reservoir mask at 15 L/min respond better to Helmet CPAP than to HFNC, since PEEP application determines alveolar recruitment and prompt oxygenation increase. The risk with CPAP use is to delay intubation or perpetuate the patient-SILI occurring with patient respiratory efforts. The advantage is to treat patients immediately with symptom relief and improved oxygenation without admitting patients… Read more »
Hi Josh, a question about the relative contraindication of CPAP because of the risk of aerosolizing viral particles. If aerosolized particles are the issue, would it be possible to place something over the CPAP mask and expiration filter to physically limit the particles’ velocity? If you could imagine a hood placed over the mask that had many small tubes coming out of it, they would slow the velocity of the partilces compared to the velocity that they would escape a CPAP filter. That formula flow rate = area of tube X velocity comes to mind. Reduce the velocity enough, and… Read more »
Aerosol tents, often used for infants, could help contain aerosolized particles, over the patients upper body as a solution although off label. There are many quality PAP providers at relatively low costs that could easily be readily procured as a life saving measure. Also BILEVEL PAP with back up rates may be solution as well.
I wonder if the exhaled air could be directed into the stream of a steam vaporizer or passed through a closed vessel on a heat source, like a pot of hot water. Should be able to heat the exhaled air stream to a temperature that would kill a virus without creating much backflow resistance
I think that idea is ingenious, but I would worry that the increased tempature would spread into the patients lungs??? I personaly would just disconnect the circuit from the CPAP machine before placing or removing the mask from the patient, thus ensuring no or minimal high flow air is escaping around an unvented mask. In my experience as an RRT a good portion of patients almost always move and adjust thier mask creating leaks up to 100 LPM. This could be the only option in the event we have no ventilators left. We need to figure out these problems before… Read more »
https://www.columbiamissourian.com/news/covid19/er-physician-hopes-homemade-chambers-help-protect-against-covid/article_d845eed4-7049-11ea-ba25-9321dc335b28.html
Is there any place for Home CPAP for Covid positive patients with minor symptoms who are not admitted?
In Hospital could one CPAP/BiPAP be split for 2 or 4 patients?
I’d be wary of using CPAP for care in the home as it could mask declining condition unless a trained person was present to monitor closely.
I also don’t think the machines would be powerful enough to split to multiple patients. Standard Dreamstation machine can deliver a max of 20cmH2O, but patients are needing 15-18cmH2O of pressure.
I have wondered the same thing. Could early cpap in the mildly affected help.orevent progression to ards? Have considered buying a home unit as I am 50. Who knows?
I’m one week into an infection likely aquired at work and I have a sleep doc in the family. 2 days ago he got me a CPAP and this machine is magic. I feel essentially normal only after a few hours at 10cm and the effect last for about half a day and when cough and sob return, it’s much milder. I only need a few hours a day. I think home treatment during the first week has real promise although concerns about aerosolization, masking worsening primary lung infection exist. My n of 1 fully approves. Demographics: I’m less then… Read more »
Dave , I’m very happy to hear your personal account of using home CPAP. . I’m on home quarantine without symptoms and don’t have any experience with home CPAP but since tens of thousands use it , it can be that complicated. It seems that there may be a place for this is the pathway of treating non-admitted patients with Covid symptoms. Positives are maybe a few less days on a Vent and less hospital aquired secondary infections.. Maybe patients could also have a home Pulse Ox and regular phone checkups by RT. What do have to lose it you… Read more »
Scott, if you give it a go, let us know your experience. I ordered a unit last week fully anticipating becoming infected at some point.
Brian , I think I’m in the clear at this point but have been thinking about alternatives to just sending Covid patients home who don’t meet admission criteria such as younger patients and those without comorbidities who have mild SOB and decent Sats. . Also if they have a place at home where they can isolate and use their CPAP and no one else gets exposed . I agree with you that the minute I found out I was positive, I would order the home CPAP .. I hope Dave is OK and continues to post his progress. Also would… Read more »
So I’ve continued to get better and am able to use the machine less frequently. I think the application you described above would be an excellent basis for a study or potentially even admitted patients with risk factors to progress. Obviously you would need to control aerosols in the inpatient setting although my hospital is considering it in high flow negative pressure rooms
Glad you’re feeling better, Scott. Keep on trucking!
Dave, thanks for the testimonial. I think this is a modality that merits further investigation.
CPAP can be split effectively (with respect to uniform positive pressures across two patients) in a double lung model that we used to simulate two patients. We looked at this with Philips Respironics v60s (they haven’t paid me a dime, that is simply what we have available in our hospital)
What about CPAP through a dual limb system? Why we can not use this system?
Why we can not use CPAP through a dual limb system? What is the reason to not use that system?
Prone Position Pre-Ventilator: Pulmonary Consult Needed! I’ve come across literature* indicating that prone positioning is an underutilized complement to ventilator therapy, and may also work prophylactically for not-yet-severe cases. This could reduce the need for intubation and reduce demand on ventilators and ICUs. I mention this because makers around the world are now also working on open-source ventilator designs, but the technical challenges and iatrogenic risks are worrisome. I’m wondering whether a prone position, non-invasive air pressure apparatus (like a CPAP or just pure oxygen feed source). Note that merely providing 30% more air pressure provides 30% more oxygen.) This… Read more »
Oh my god, a return of the circle beds? I do wonder if some of the bad hospital outcomes are due to delays in using mechanical assistance because of low resource availability. This leads to waiting till they crash instead of preventing it beforehand. This is no criticism, whatsoever, of the providers, rather a reflection of the dire straits of resources due to poor planning and an incompetent federal leadership that is not sending resources to states appropriately, rather by whim and grievance.,
“not sending resources…appropriately” I was surprised and impressed hearing yesterday’s briefing…Find in Page “jared” at
Dear All We have created a power face shield. It is based on Latimer flow, Standard filtering and the use of copper mesh and vortex airflow. This is for medical workers and the general population. Combining all 3 principles standards testing results this SHOULD stop all viruses and bacteria entering the airflow and the airflow inhibits contact from the exterior. There set up so phase 1 unites you can build at home right now. Phase 2 will be Kits and phase 3 will be manufacture. Techknodlage is in 3 forms from now to add to the existing systems with UV… Read more »
ch 19th, 2020 at 19:51:06
This quote is taken from an online discussion about home building a CPAP ventilator…. i am curios what you thoughts may be on this…
“After some additional research I’m finding that neither a CPAP nor a BIPAP is sufficient to blow off CO2 (pCO2)- in fact, in some cases these devices will do more harm than good. So the question remains: in Covid-19 patients with severe respiratory distress, what is the failure mode- low SPO2 or high pCO2?”
Is CO2.buildup a major issue in Covid-19 patient? How does CPAP affect this?
Three ways to filter cpap exhalation I tested today with trash bag lung
We used CPAP for compasionate use on a COVID patient who was not going to go to ICU/get intubated. The pt felt better with it, at least. Just kept in Neg Pressure room. I think there is some role for this, especially given no-cpr/DNR/DNI rather aggressively.
Curious what the EMCRIT gods think about the theory that COVID infection is somewhat akin to a hemoglobinopathy, destroying ability to collect O2 and release CO2 due to virus destroying heme molecule function. This leads me to theorize regarding treatment along the lines of malaria treatment and curious about aerosolized atovaquone treatment, along the same lines. Any research studies pending with bundled CPAP proned, quinine/hydroxychloroquine plus aerosolized atovaquone and IV vitamin C?
Hi Josh,
Very much appreciate updating use of CPAP in COVID-19. You also mentioned prone positioning which is often very difficult to do for obvious reasons. I have used right and left decubitus positions often successfully especially if infiltrates are dominantly unilateral in improving oxygenation. This can be done much more easily both in mechanically ventilated and patients on CPAP or simply on mask / hi flo O2.. Remember NEJM editorial in 1981 by Al Fishman MD titled “DOWN WITH THE GOOD LUNG”
There seem to be many renowned physicians suggesting PEEP as low as possible because these patients have very compliant lungs. They state we need to offer the most gentle vent approach to just buy time and let things heal.
This is in stark contrast to what many others are suggesting with very high peep.
Can you comment?
Dear All, I’m of a similar mind. None of us have thankfully got COVID-19, yet, however, I am anticipating that sometime between now and herd immunity or vaccination one or all of us will get it. So as a precaution we have a few N96’s when out, and use a UV lamp for their sterilization. At home we’ve identified an isolation area with an O2 pulse meter, BP cuff, IR thermometer and Obs chart to capture and track readings, and a nebulizer, O2 concentrator and CPAP, which I hope will be useful when we have to isolate and manage the… Read more »
The methods for preventing coronavirus in China are worth learning: in daily life, wear a mask, wash your hands frequently, disinfect, and wear gloves to carry out some activities. Recently, I found a website for buying epidemic prevention products https://us.9020.com/category/Health/. The products in it are of good quality, affordable and fast delivery.
Hope it will help you.
Interesting article,
Have you considered upper airway oedema being a cause of breathing difficulty? Explains why CPAP works so effectively in these patients. We’re also considering in our unit whether we’re diagnosing latent OSA in some patients; a combination of OSA and airway oedema causing the perfect storm seen in COVID patients. We’re setting up a clinical trial monitoring AHI in patients requiring oxygen therapy as well as those who don’t; interested to see whether we can predict those that would benefit from CPAP using overnight oximetry.
Your thoughts would be appreciated
Did anyone try to use sound or ultrasound to check really fast lung elasticity?
You saved myself and my wife’s lives. We had silent hypoxia from covid19 and when I saw our skin color changing and wondered why I was fairing better than my wife I suspected it was my Cpap use (because every morning I was briefly better.) I happened on this site while looking into it. Veterans affairs didn’t want me to come in unless I was critical, it was at the beginning of the crisis. We used my Cpap machine to support our breathing and slowly recovered without needing hospitalization or vent. God bless you. Roughest 30 days of our lives.… Read more »
Wanted to share my experience. I had a positive covid patient the last three days i worked. Patient was a 30 y/o latino female approximately 135kg. Patient was admitted to SD unit and transferred to icu for increasing O2 requirements. When i picked up the patient she was on HFNC 58L 67% FiO2 RR 40-50 with sats anywhere from low 80s to 90s. Patient was febrile, sinus rhythm 80-90, no B/p issues, interactions were appropriate was using phone ect. Discussed care with doctor. Patient ABG drawn and found to have a PaO2 of 44% (suspect venous per physician note at… Read more »
In our hospital we are trending more to CPAP for our Covid patients . Most have good compliance and Bipap will routinely over ventilate these patients with large tidal volumes , even with a small PSV . CPAP provides greater MAP and patients are better synchronized with the machine as compared to Bipap .