Timeframe for diving post covid +

[kinoons]

If Covid is causing damage that can lead to air trapping, like lung scarring, which it is in some people which does not seem to map perfectly to severity of illness, then by what mechanism would the scarring caused by Covid somehow not increase risk of air trapping when similar scarring caused by other things does? The physics involved don't care what induced the scarring, just if the scarring is trapping the air sufficiently to cause a problem.

Also, the more research is done on Covid, the more it's clear it's *not* an URI, it's a multi-system disease that happens to frequently produce URI symptoms in addition to the other things it's doing where the symptoms may be subclinical. Therefore comparing it to diseases that *are* limited to the upper respiratory system is not valid. That means that the safest behavior with Covid could be quite different from the safest behavior with other diseases even though the observable symptoms are very similar. (For that matter, we may well re-examine other diseases that were in the past thought to be inconsequential using approaches developed/honed with Covid and discover that our past practices were lacking and we *should* have been doing something different but we didn't know any better at the time. Like people keep saying "we didn't mask when the flu was going around!" as if that's proof we shouldn't mask for Covid when maybe it just means that we actually should have been masking for flu the whole time. Past behavior may have been wrong, you can't assume that just because it's what we were doing it's the correct thing to do.)

(And this is completely ignoring the potential for extended issues due to Covid infection, which we're realistically only at the very early stages of figuring out, since we have no practical Covid-related data since it hasn't been around long enough and our understanding of the role of infections in general in things like autoimmune diseases is also fairly 'young' as these things go. I'm not talking about long Covid but rather Covid-infection-induced issues like autoimmune diseases and the potential for things that turn up much later on in the way of post-Polio syndrome and Shingles and that sort of thing.)

I disagree with your fundamental premise that Covid is different than any other corona virus. I contend that the null hypothesis should be that the overwhelming majority of people who caught Covid will have an illness course and recover in a similar manner as all prior common corona virus strains. No prior corona virus strains (there are 4 common ones, known since the 1960s) have caused widespread autoimmune or other post viral syndromes like shingles. Therefor it is incumbent on those believing it may be possible to prove it. To this point I have not seen any evidence to support the hypothesis that Covid is different.

To the idea that lung scarring may cause air trapping - plausibility does not equate to reality. Medical science is littered with bioplausible theories that never actually worked or found true when applied to the human body. Again it’s up to those moving in the opposite direction of the null to prove it, not those supporting the established norms to prove them.

I’m all for looking at past practices and reevaluating them, but let’s remember that many past practices have evidence to support them. Taking your mask example, the reason we don’t universally mask is that it doesn’t work. Plenty of surgical masking studies in regards to influenza and work absenteeism have been performed prior to Covid. They all had the same conclusion; it doesn’t work. All of the well done surgical and cloth masking studies during Covid have also concluded community masking does not work.

I agree that we (the medical community) should always be trying to move our knowledge forward to offer the best outcomes for the largest number of people possible. I just contend that compelling evidence is needed when making recommendations on a population level.

 

[Dr Simon Mitchell]

Hello Kinoons,

I have been reading your criticism of the UCSD guidelines and your confident assertions about COVID-19, diving and appropriate levels of evidence with increasing concern.

I disagree with your fundamental premise that Covid is different than any other corona virus.

In the context of a discussion about return to diving this statement is incorrect. SARS-CoV-2 can produce a fatal pneumonitis. It can also cause significant lung changes including air trapping [1], even among patients with relatively minor symptoms [2]. The coronavirus that causes the common cold does not do these things; at least not without severe secondary complications, typically in extremely comorbid patients and only vanishingly rarely.

Air trapping lesions in the lung are a well-recognised risk factor for pulmonary barotrauma and arterial gas embolism in divers [3-5], and even in the context of very slow depressurisations in aircraft [6,7], or hyperbaric chambers [8-10]. These facts are not "plausibility" as you frame it, they are a proven realty of diving and hyperbaric medicine. You suggest that "it’s up to those moving in the opposite direction of the null to prove it, not those supporting the established norms to prove them". I put it to you that the "established norm" in this situation is that air trapping is a risk factor for pulmonary barotrauma and that if you want to claim that air trapping caused by SARS-CoV-2 is an exception, then it would be YOUR obligation to prove it.

Your advocacy of an RCT to answer the relevant question ignores both the virtual impossibility of adequately powering such a study (among many other methodologic difficulties) and the fact that few such questions in public health are answered with RCTs. Much of the relevant evidence is observational, and although you give them little credit for it, the diving medicine community has not been ignoring the emerging observational evidence in relation to COVID and diving. Although I believe (based on my above commentary) that the diving medicine community was entirely justified in taking a conservative stance on investigation prior to return to diving early in the pandemic, here is where our opinions converge somewhat.

Most would now agree with your claim that "the overwhelming majority of people who caught Covid will have an illness course and recover in a similar manner as all prior common corona virus strains". Moreover, despite concerns about the finding of air trapping lesions in mild COVID sufferers, there is now evidence that some changes resolve in many cases [2], and there is increasing experience with apparently 'safe' return to diving by such 'patients'; mostly undocumented, but occasionally documented [11]. That is why the UCSD guidelines have evolved from moderately conservative [12] to considerably less so [13], and why organisations like the UK DMAC have progressively 'liberalised' their return to diving guidelines to where they are now [14]. Nevertheless, anxiety remains about air trapping in mildly affected COVID-19 sufferers. Over time the observational evidence base will evolve, and there will be more certainty.

I won't get into your commentary about masks. It is not my area of expertise, but one doesn't have to look far through listings of papers in highly credible journals to find that your claim that all studies suggest they don't work is nonsense.

Simon M

1. Cho JL, et al. Quantitative chest CT assessment of small airways disease in post-acute SARS-CoV-2 infection. Radiology 2022;304:185-92

2. Mirasoglu B, et al. Post COVID-19 fitness to dive assessment findings in occupational and recreational
divers. Diving Hyperb Med 2022;52(1):35-43

3. Goffinet CM, and Simpson G. Cerebral arterial gas embolism in a scuba diver with a primary lung bulla. Diving Hyperb Med. 2019;49:141−4.

4. Toklu AS, Erelel M, Arslan A. Pneumomediastinum or lung damage in breath-hold divers from different mechanisms: a report of three cases. Diving Hyperb Med. 2013;43:232–5. PMID: 24510331.

5. Tetzlaff K, et al. Risk factors for pulmonary barotrauma in divers. Chest. 1997;112:654–9.

6. Closon M, et al. Air embolism during an aircraft fl ight in a passenger with a pulmonary cyst: a favorable outcome with hyperbaric therapy. Anesthesiology 2004;101:539–42.

7. Edwardson M, et al. Cerebral air embolism resulting in fatal stroke in an airplane passenger with a pulmonary bronchogenic cyst. Neurocrit Care 2009; 10: 218 – 21.

8. Cable GG, et al. Pulmonary cyst and cerebral arterial gas embolism in a hypobaric chamber: a case report. Aviat Space Environ Med 2000;71:172–6.

9. Wolf HK, et al. Barotrauma and air embolism in hyperbaric oxygen therapy . Am J Forensic Med Pathol 1990;11:149–53.

10. Rivalland G, et al. Pulmonary barotrauma and cerebral arterial gas embolism during hyperbaric oxygen therapy. Aviat Space Environ Med 2010;81:888-90.

11. Smart D. Validation of very mild COVID-19 illness criteria to guide successful return to occupational diving. Diving Hyperb Med 2022;52(3):222-3

12. Sadler C, et al. Diving after SARS-CoV-2 (COVID-19) infection: Fitness to dive assessment and medical guidance. Diving Hyperb Med. 2020;50:278–87.

13. Sadler C, et al. Diving after COVID-19: an update to fitness to dive assessment and medical guidance. Diving Hyperb Med. 2022;52: 66–7.

14. https://www.dmac-diving.org/guidance/DMAC33.pdf

 

[WeRtheOcean]

No prior corona virus strains (there are 4 common ones, known since the 1960s) have caused widespread autoimmune or other post viral syndromes like shingles. Therefor it is incumbent on those believing it may be possible to prove it.

It is important to cut through the hysteria. People's beliefs about COVID, and the vaccine, often seem to be based more on their preexisting worldviews than on their understanding of facts and evidence.

Plenty of surgical masking studies in regards to influenza and work absenteeism have been performed prior to Covid. They all had the same conclusion; it doesn’t work. All of the well done surgical and cloth masking studies during Covid have also concluded community masking does not work.

You know, when I added this to my multiquote, I did so to agree with you; but then I saw this:

one doesn't have to look far through listings of papers in highly credible journals to find that your claim that all studies suggest they don't work is nonsense.

The thing it is, it isn't just your word against Dr Mitchell's. Dr Mitchell went to the additional effort of citing his sources, as if he was going to submit his post for peer review.

As much as I would love for the maskers to have been wrong (sensory issues due to autism mean that anything on the lower half of my face is torment; I shave dry because I can't stand facial hair or shave gel), and as much as I would love for the masks to become a historical memory like the miasma theory of yellow fever, I am not prepared to believe that the CDC and the WHO are unaware of evidence.

 

[MacDuyver]

how's your lung capacity?
I got COVID a couple weeks ago, and I'm feeling like I'm running a 5k still.

I'm dying to get back in the water, and at the same time I'm not wanting to create issues for a dive buddy

 

[kinoons]

https://assets.publishing.service.g...Masks_and_Respirators_Science_Review.pdfHello Kinoons,

I have been reading your criticism of the UCSD guidelines and your confident assertions about COVID-19, diving and appropriate levels of evidence with increasing concern.



In the context of a discussion about return to diving this statement is incorrect. SARS-CoV-2 can produce a fatal pneumonitis. It can also cause significant lung changes including air trapping [1], even among patients with relatively minor symptoms [2]. The coronavirus that causes the common cold does not do these things; at least not without severe secondary complications, typically in extremely comorbid patients and only vanishingly rarely

<snip > for character limit

I won't get into your commentary about masks. It is not my area of expertise, but one doesn't have to look far through listings of papers in highly credible journals to find that your claim that all studies suggest they don't work is nonsense.

Simon M

<snip> for character limit

Dr. Mitchell,

Thank you for the well researched and cited post. I know the kind of time and effort that goes into such an endeavor.

To your first cite - regarding patients who are continuing to experience symptoms from Covid-19 may have air trapping or some degree of lower airway disease; this is not exclusive to Covid-19. As noted in a review of small airway disease workshop in 2011 multiple different viral infections can cause air trapping post infection, Sars-CoV-2 is not unique in this aspect. [1] Additionally, the patient group of the study you reference is those who continue to be symptomatic post covid-19 infection and not part of the group in which I take UCSD to task for over their recommendations.

The second cite is interesting, but I am unable to find the whole text of the article online. The abstract certainly suggests that roughly 30% of divers who have had Covid-19 have evidence of continued lung disease post illness. I would like to see the article in its entirety. Missing from the abstract is what portion of those divers were symptomatic at all, severely ill, or continue to be symptomatic during the post infection phase. Furthermore this study was published in March of 2022. I would assume the patient population was screened during 2021. It has been well established that subsequent variants of Covid-19 are less virulent now in 2023 than in 2021.

As to the potential for barotrauma associated with diving and lung damage - I agree that a risk has been demonstrated previously. What has not been adequately demonstrated to my satisfaction is that asymptomatic or minimally symptomatic infection and subsequent recovery from Sars-CoV-2 has such an extreme potential to cause injury as to recommend screening. As I referenced above, many different infections and diseases have the potential to cause air trapping within the lungs, yet until Covid-19 no one (to my knowledge) was recommending a fitness to dive exam post a mild case of influenza or other viral illness and subsequent recovery.

To drive this point home, H7N9 and H1N1 influenza was also demonstrated to cause long term lung injury in patients who were admitted to the hospital. [11] [12]. Yet I don't recall anyone clamoring to screen anyone who had a mild infection for lung disease. Is it possible that the rate of lung disease with mild Covid-19 is similar to prior viral illness, but we've never looked in the past like we are now?

It is your belief that an RCT to evaluate if a return to diving exam is required would be impossible due to power issues - If that is the case, if you would need to recruit tens of thousands of people to demonstrate the risk of diving post Covid-19 is higher than the normal background rate of risk associated with diving, does this not demonstrate that the risk cannot be that great? This isn't like testing a new varicela vaccine in 2022 when rates are exceedingly low. Over the last three years damn near everyone had Covid-19. Data from the CDC shows Nucleocapsid antibody seroprevalence is well over 90% in many studies. [2] The patient population is virtually everyone. All that needs to be done is the legwork.

My issue with observational data is that it is often wrong. [10] RCTs are the gold standard for a reason. While it is fair to use observational data to form an hypothesis, the end result of that observation should be a well designed and executed RCT, or clustered RCT for population level interventions. Early in the pandemic UCSD made a recommendation, but never then took the second step to try and generate credible data. Unfortunately this has been common over the last several years (which I will address in a few paragraphs). In the cases of uncertainty, the goal should be the vigorous pursuit of additional data via research, not let us wait and see.

This leads us to the updated recommendations and the creation of category 0.5 between 0 and 1. [3] The only evidence that can support the change in the recommendations is the multitude of patients who are diving and not getting ill, as I cannot find any additional research to support the change (and your second cite would seem to contradict this). I am curious at the continued recommendation (or the initial recommendation) for a 2V CXR at category one. It is my understanding that the sensitivity of a 2v CXR is not very good for the majority of lung associated diseases, to include Covid-19. [4] If there is genuine concern that even mild illness could cause something as significant as barotrauma why depend on an inferior 2v CXR vs a CT of the chest? Or is the correct conclusion that for even mild lower resp. symptoms no screening is necessary, like was done in the past for influenza?

As to masks, I disagree that the evidence primarily published by the CDC in MMWR demonstrates effectiveness on a community level. Prior to Covid-19 community masking to prevent influenza like illness had very little supportive evidence. [13] During covid-19 any RCTs ran for cloth masking failed. Surgical masking has exceedingly small benefits. [5] In Spain and Finland population level interventions were made at specific ages, allowing for analysis of rate of infection, and mask wear made no difference. [6] [7]

It is important to cut through the hysteria. People's beliefs about COVID, and the vaccine, often seem to be based more on their preexisting worldviews than on their understanding of facts and evidence.

You know, when I added this to my multiquote, I did so to agree with you; but then I saw this:

The thing it is, it isn't just your word against Dr Mitchell's. Dr Mitchell went to the additional effort of citing his sources, as if he was going to submit his post for peer review.

As much as I would love for the maskers to have been wrong (sensory issues due to autism mean that anything on the lower half of my face is torment; I shave dry because I can't stand facial hair or shave gel), and as much as I would love for the masks to become a historical memory like the miasma theory of yellow fever, I am not prepared to believe that the CDC and the WHO are unaware of evidence.

It has been noted that the CDC has on more than one occasion cherry picked data to support which intervention on Covid-19 was felt appropriate at the time to include masks, vaccinations for children, over inflating the risk of Covid-19 to kids, claiming Covid-19 increases the risk of diabetes in kids, ignoring myocarditis associated with vaccination, paxlovid recommendations regardless of vaccination status, and others. [8] [9] I did specifically state that well done studies have not shown a benefit. I do not lend any strength to wildly confounded observational studies.

 

[kinoons]

References for the above - ran into the 10,000 character limit

1. Pierre-Régis Burgel, et al. Small airways diseases, excluding asthma and COPD: an overview
European Respiratory Review Jun 2013, 22 (128) 131-147; DOI: 10.1183/09059180.00001313

2. Covid-19 SeroHub. COVID-19 SeroHub

3. Sadler C, et al. Diving after COVID-19: an update to fitness to dive assessment and medical guidance. Diving Hyperb Med. 2022;52: 66–7.

4. Stephanie S, et al. Determinants of Chest Radiography Sensitivity for COVID-19: A Multi-Institutional Study in the United States. Radiology: Cardiothoracic Imaging 2021; 2(5):e200337 • https://doi.org/10.1148/ryct.2020200337

5. Liu, I. Prasad, V. Darrow, J. How Effective Are Cloth Face Masks? https://www.cato.org/regulation/winter-2021/2022/how-effective-are-cloth-face-masks

6. Coma, E. et al. Unravelling the role of the mandatory use of face covering masks for the control of SARS-CoV-2 in schools: a quasi-experimental study nested in a population-based cohort in Catalonia (Spain). Archives of Disease in Childhood 2023;108:131-136.

7. Juutinen, A. Sarvikivi, E. Päivi Laukkanen-Nevala, P. Helve, O. Use of face masks did not impact COVID-19 incidence among 10–12-year-olds in Finland. MedRxiv 2022.04.04.22272833; doi: Use of face masks did not impact COVID-19 incidence among 10–12-year-olds in Finland

8. Prasad, V. How the CDC Abandoned Science. How the CDC Abandoned Science (2022)

9. Milijkovic, M. Prasad, V. Paxlovid, A Regulatory Gamble. The American Journal of Medicine. DOI:Redirecting

10. Prasad V, Cifu A. Medical reversal: why we must raise the bar before adopting new technologies. Yale J Biol Med. 2011 Dec;84(4):471-8. PMID: 22180684; PMCID: PMC3238324.

11. Chen, J., Wu, J., Hao, S. et al. Long term outcomes in survivors of epidemic Influenza A (H7N9) virus infection. Sci Rep 7, 17275 (2017). Long term outcomes in survivors of epidemic Influenza A (H7N9) virus infection - Scientific Reports

12. Singh V, Sharma BB, Patel V. Pulmonary sequelae in a patient recovered from swine flu. Lung India. 2012 Jul;29(3):277-9. doi: 10.4103/0970-2113.99118. PMID: 22919170; PMCID: PMC3424870.

13. PH-HPER-ID&BP 10200. The Use of Facemasks and Respirators during an Influenza Pandemic: Scientific Evidence Base Review (2014). https://assets.publishing.service.g...6198/Masks_and_Respirators_Science_Review.pdf

 

[Centrals]

I had not read anything about infection with Wuhan virus on diving.
I have made two diving trips since my only infection and did not notice my gas consumption has gone down. Some of my buddies also had gone diving and I did not hear anything except how great it was to be able to dive/travel again.

BTW, none of us had been hospitalized because of infection.

 

[Lorenzoid]

It sounds like it might be prudent to get screened after any respiratory infection before returning to diving. Maybe Covid has been the wake-up call, and prudent divers would have been doing this all along had we only known there could be such longer-term effects.

 

[kinoons]

It sounds like it might be prudent to get screened after any respiratory infection before returning to diving. Maybe Covid has been the wake-up call, and prudent divers would have been doing this all along had we only known there could be such longer-term effects.

Perhaps - one of the things I’m trying to get a feel for is how common barotrauma was before Covid. I don’t practice dive medicine in specific, and my practice location does not see a lot of divers in general, so I don’t have a good feeling for the rate of injury pre-Covid. My gut is that on a per dive basis it is very low as likely thousands (tens of thousands?) of people dive worldwide every day.

The big rub about screening is the time and cost, as well as possible unintended outcomes of trying to make a healthy person “healthier”. Having the rate of injury would give some needed perspective.

 

[Nick_Radov]

It sounds like it might be prudent to get screened after any respiratory infection before returning to diving. Maybe Covid has been the wake-up call, and prudent divers would have been doing this all along had we only known there could be such longer-term effects.

That is simply unrealistic. The average person gets a couple of upper respiratory infections (colds) every year. Many of those infections are asymptomatic or paucisymptomatic (including with SARS-CoV-2) so divers don't even necessarily know when they have been infected.
We already have a shortage of primary care physicians. Most of them aren't familiar with diving medicine or set up to perform a full range of respiratory function tests and imaging studies. Those procedures would typically not be covered by insurance since they aren't considered medically necessary.
Realistically any standard return-to-diving protocol will need to be calibrated to symptom severity. The NIH guidelines for COVID-19 define a clinical spectrum and I would think the same levels could be extended more generally to any respiratory infection. There could be an escalating set of return-to-diving protocols recommended at the moderate / severe / critical levels (although anyone who gets critically ill from COVID-19 would have likely already been medically unfit to dive anyway).

Clinical Spectrum | COVID-19 Treatment Guidelines

Learn how SARS-CoV-2 infection is categorized by severity of illness.

www.covid19treatmentguidelines.nih.gov