Timeframe for diving post covid +

[Duke Dive Medicine]

So lets theorize a study that goes something like this...

Dive shop A located in a tropical dive location takes out four boatloads of 20 divers out each day. Two AM trips, two PM trips. Some divers may take both trips, but lets guess we're looking at 60-70 divers every day are heading out. They have made the decision that they want to dive and that they feel well enough to do so.

It is quite safe to say that 40%+ of folks in the US have had covid (that number is likely significantly higher, but its what the CDC is reporting). The CDC does acknowledge that 90%+ of kids have had covid. Think adults are really that far behind?

What was the SARS-CoV-2 seroprevalence among US adults during 2021 and 2022?

In a recent Morbidity and Mortality Weekly Report (MMWR), the United States Center for Disease Control and Prevention (U.S.-CDC) published the preliminary results of the National Health and Nutrition Examination Survey (NHANES) for August 2021–May 2022.

www.news-medical.net

COVID Data Tracker

CDC’s home for COVID-19 data. Visualizations, graphs, and data in one easy-to-use website.

covid.cdc.gov

so roughly 50% (or more) of the folks who have already self selected to go diving have had and recovered covid.

I would then postulate that it is acceptable to contact those divers a few days prior to their dive trip and attempt to enroll them in a study where the participants are randomized to dive as planned or the day prior to diving have an exam to establish their fitness for diving.

By definition the study would not be taking any participants who were initially planning to get an exam and exclude them from an exam. The dive trip is already planned. If the diver wanted an exam before the trip they would have arranged for one. (These divers who did receive an exam would be excluded from the study). This study would instead only be taking a population of divers who felt they did not need an exam prior to diving and potentially obtain one.

Even if you only got 4 or 5 folks a day to agree to be randomized it wouldn't take more than maybe a month at a few sites to obtain a few thousand participants. Follow them for several weeks and I'd bet you'd see a trend one way or another as far as the risk of covid and diving goes for those who were minimally ill and fully recovered. Dive injury rates prior to 2019 could be used as a control.

If a researcher came to your IRB with something like what I proposed above, you'd vote to not allow it?

My own WAG; 90%+ of the population has had and recovered from Covid. That means that 90%+ of divers have had and recovered from Covid. If there was some danger related to having recovered from Covid and subsequently scuba diving the community as a whole should have seen an increase in dive related illness/injuries. I am not aware of any such increase. However, I will admit that my location isn't a diving hotbed and I don't practice dive medicine for a living, so I likely wouldn't have heard of any changes in rate of injury.

Sounds like you're well on your way to a study proposal!

Best regards,
DDM

 

[hilljo88]

I considered giving the "thumbs up" to several posts in this thread but would instead like to express my appreciation to the several contributors for their thoughtful comments. The challenges of COVID to the general population, heightened by media and political posturing have made this kind of reasoned discussion too rare.

 

[kinoons]

Sounds like you're well on your way to a study proposal!

Best regards,
DDM

The question should be why has UCSD not ran such a study before making their proposal? Or, at the very least, concurrently when it became apparent that a set of recommendations were needed, but robust evidence was not available to make any.

The UCSD recommendations were published in May 2020. I don’t believe there is any recommendation from 2020, beyond hand washing, that has stood the test of time unaltered. UCSD has had nearly three years to run a study similar to what I proposed. It is a failure of academic medicine that in three years they have not generated better evidence than “this is our ‘educated’ best guess”.

Although, to be fair, UCSD in specific, and Covid in general, are not the only failures of academic medicine over the last two decades. It’s just one example of many.

 

[rob.mwpropane]

I can only give my real world experience. Absolutely not even a smidge of medical advice in this; I've had covid twice now.

Covid 12/04/21 - 1st dive after was 12/18/22 (so 2 weeks post). I mixed 40% as I felt it would help at least some. Coughed like crazy at times under water. Depth was all of 15'

Covid 12/13/22 - 1st dive after was 12/30/22 (so 3.5 weeks post). I dove air and didn't have any issues at all. Same exact place as 1st dive after covid, depth was all of 15'

I would not have done either one if it was to any depth, and maybe should not have done them at all. Just sharing my experience. I am in my later 30's. Both dives were done in full drysuit, doubles, etc. Water was in the upper 30's.

 

[Duke Dive Medicine]

The question should be why has UCSD not ran such a study before making their proposal? Or, at the very least, concurrently when it became apparent that a set of recommendations were needed, but robust evidence was not available to make any.

The UCSD recommendations were published in May 2020. I don’t believe there is any recommendation from 2020, beyond hand washing, that has stood the test of time unaltered. UCSD has had nearly three years to run a study similar to what I proposed. It is a failure of academic medicine that in three years they have not generated better evidence than “this is our ‘educated’ best guess”.

Although, to be fair, UCSD in specific, and Covid in general, are not the only failures of academic medicine over the last two decades. It’s just one example of many.

I would not call this a failure of academic medicine and I'm surprised to hear you continue to name it that, and to continue to equate "expert opinion" with "guessing". The two are not equivalent. The ACLS algorithms that you probably use regularly are based on a mixture of evidence, some of which is still expert opinion. Nevertheless, it's the best we have, so that's what we do. My guess is that you also probably depart from those algorithms from time to time, and justify that departure based on your own expert opinion which may or may not be grounded in clinical evidence. I would not call that guessing and I hope you would not either.

I also wonder if you fully appreciate the idea (and the practicalities) of evolution of evidence. COVID was (and still is, to a certain extent) a novel disease. Treatments had to be developed and tested, and all of the effects that it has that are completely different than the more commonplace respiratory illnesses are still under investigation. UCSD derived their recommendations from what was known anecdotally at the time, which was that even mild cases of COVID can result in lung damage that causes air trapping. That has not changed. And, air trapping in a diver can be fatal. Again, it's a low-probability occurrence that has high consequences. I bet you can name a few of those related to your specialty. Thus the recommendation, albeit overly conservative in your opinion, that people who have had even mild cases of COVID have a simple chest x-ray series and spirometry to rule out air trapping. It's not even proscriptive, it's a recommendation. Is that really so objectionable? As I said before, I do hope that retrospective data are gathered that will allow the diving medical community to continually re-evaluate those recommendations. Maybe some day we'll learn that the risk is low enough that that particular recommendation can be eliminated. A loose analog might be PFO. We know that it statistically increases the probability of DCS, yet we don't recommend routinely screening divers for it because we know, through examination of evidence, that roughly a third of the population has one and that the correlation between PFO and DCS is loose. But, admittedly there's a paradox there in that if a diver (who has a roughly 30% statistical chance of having a PFO) comes to us with a case of DCS that appears to be related to shunted bubbles, we'll test for PFO and if there is one, we'll assume that the PFO had something to do with the DCS. Do we know? No, but the mechanism is there so that's what we go with. More expert opinion.

All that said, the practicalities of the study you're suggesting would be cumbersome at best and I doubt there's a busy academic researcher who would take that on, with the possible exception of DAN, who stay pretty busy with their current research. Much easier to gather retrospective data. I wouldn't be surprised, a few years down the road, to see a paper on divers with occult air trapping post-mild COVID.

Best regards,
DDM

 

[Germie]

In March 2022, I had a sore throat, nothing more than that. I ate the day before very hot, so I was thinking that was causing the sore throat. I was further completely fit. I did 2 decompression dives that day and after turning back home, I did a free selftest (we got 2 from our government for free, 1 was used in coke). That was positive. So did I had covid? I never know, but I was not ill, only a sore throat. Diving was no problem, I absolutely had no feeling of influenza or a cold. I was not ill. I was fit. I only had a positive test after the dives, but I will never know if I had a normal cold or was attacted by a coronavirus. For me it was even not te be called a cold or something. I was less. No fever, nothing. It was that I had 1 free selftest, otherwise I even did not test, it was just about being curious. But a selftest is not so trustfull, so you still never know. Since then I haven't had any cold or illness. Now people here around get influenza, colds caused by other viruses and the RS virus.
If you are ill, you wait with diving till you are fit again, that is normal in my eyes.

 

[kinoons]

I would not call this a failure of academic medicine and I'm surprised to hear you continue to name it that, and to continue to equate "expert opinion" with "guessing". The two are not equivalent. The ACLS algorithms that you probably use regularly are based on a mixture of evidence, some of which is still expert opinion. Nevertheless, it's the best we have, so that's what we do. My guess is that you also probably depart from those algorithms from time to time, and justify that departure based on your own expert opinion which may or may not be grounded in clinical evidence. I would not call that guessing and I hope you would not either.

I also wonder if you fully appreciate the idea (and the practicalities) of evolution of evidence. COVID was (and still is, to a certain extent) a novel disease. Treatments had to be developed and tested, and all of the effects that it has that are completely different than the more commonplace respiratory illnesses are still under investigation. UCSD derived their recommendations from what was known anecdotally at the time, which was that even mild cases of COVID can result in lung damage that causes air trapping. That has not changed. And, air trapping in a diver can be fatal. Again, it's a low-probability occurrence that has high consequences. I bet you can name a few of those related to your specialty. Thus the recommendation, albeit overly conservative in your opinion, that people who have had even mild cases of COVID have a simple chest x-ray series and spirometry to rule out air trapping. It's not even proscriptive, it's a recommendation. Is that really so objectionable? As I said before, I do hope that retrospective data are gathered that will allow the diving medical community to continually re-evaluate those recommendations. Maybe some day we'll learn that the risk is low enough that that particular recommendation can be eliminated. A loose analog might be PFO. We know that it statistically increases the probability of DCS, yet we don't recommend routinely screening divers for it because we know, through examination of evidence, that roughly a third of the population has one and that the correlation between PFO and DCS is loose. But, admittedly there's a paradox there in that if a diver (who has a roughly 30% statistical chance of having a PFO) comes to us with a case of DCS that appears to be related to shunted bubbles, we'll test for PFO and if there is one, we'll assume that the PFO had something to do with the DCS. Do we know? No, but the mechanism is there so that's what we go with. More expert opinion.

All that said, the practicalities of the study you're suggesting would be cumbersome at best and I doubt there's a busy academic researcher who would take that on, with the possible exception of DAN, who stay pretty busy with their current research. Much easier to gather retrospective data. I wouldn't be surprised, a few years down the road, to see a paper on divers with occult air trapping post-mild COVID.

Best regards,
DDM

Sorry for the delay in reply, its been a busy few days.

Since you brought up ACLS, lets look at how ACLS has evolved over time. I certainly have seen ACLS change in my 20+ years of resuscitation practice.

I'll link to a very nice presentation by Dr. Ehmann who at the time was an associate professor at Hopkins. In short the initial ACLS recommendations were 100% expert opinion or consensus. These recommendations included .

The guidelines recommend early intubation but mouth to mouth-or-mouth-to-nose is “unequivocally superior to all manual methods,” and a compression rate of 60 is preferred.

How about the decision to routinely use Epi in V-fib arrest (1974)?

To be clear, what I have just told you is that the original ACLS recommendation for using epinephrine in cardiac arrest was based on the outcome of an experiment (1968) with 15 dogs, 87% of whom were dead or comatose after treatment with epi. The ACLS recommendation for epinephrine in cardiac arrest, based on this experiment, established epi as the standard of care for half a century.

How about defibrillation (1974 and 1986)?

The recommendation for shock strength is based on two reviews from One author writes, “The appropriate electrical shock strength for trans-chest defibrillation is controversial. As in most controversies, there are data to support both positions, but there are not enough data to resolve the issue. Studies to determine the best shock strength are in progress, and may settle this issue later. Meanwhile, practicing physicians need guidelines for using defibrillators now." This goes to show that these guidelines were not only NOT evidence-based; they were KNOWINGLY not evidence-based. It's really kind of amazing.

Focusing on electricity, though there was no evidence published to support the 3 stacked shocks recommendation, the initial defibrillation charge recommendation was changed from a range to 200J after – for the first time – a well-designed prospective randomized trial for ACLS care. Dr. Weaver in Seattle published a study in NEJM of 249 patients with VF who were shocked with 320J on even days of the week & 175J on odd days. They were tracked for number of shocks needed to defibrillate, post-shock rhythm & overall survival. There was no difference in outcomes so the recommendation was for the lower strength.

It would appear that nearly zero of the expert opinions related to ACLS when first started have survived the test of time. Unfortunately it took many decades to undo those expert opinions.

I can list many other "expert opinions" that have subsequently been reversed once research was performed. AAP's recommendation for peanut avoidance to lessen allergies is one I listed. Hell, Dr. Prasad has written a book on the premise of ending medical reversal, when treatment courses are selected for the population as a whole on little or poor evidence. The simple fact is expert opinion in medicine is often wrong. This is also why retrospective evidence is only considered slightly better than expert opinion; This level of research is also frequently not supported when someone actually runs the RCT. I'm disappointed in your acceptance of this level of evidence.

Dr. Prasad has also proven that RCTs with real endpoints (overall death) can often be completed more quickly than non-randomized studies, or studies with surrogate endpoints.

Estimation of Study Time Reduction Using Surrogate End Points Rather Than Overall Survival in Oncology Clinical Trials - PubMed

From the findings of this study, an estimated 11 months appeared to be needed (ie, approximately 12% longer in the drug development cycle) to assess the OS benefit of a cancer drug. This study's findings suggest that this must be weighed against the downside of increased uncertainty of clinical...

pubmed.ncbi.nlm.nih.gov

I take issue with these recommendations and guidelines because they have consequences. It wouldn't take a lot of imagination to see insurance companies denying medical claims for divers who are not screened based on UCSD's recommendations if they are injured after diving post covid, for example. Now that UCSD's recommendations are in the wild, how long will they persist before someone develops the evidence to support or disprove them? ACLS took decades. There is also the cost and risks associated with the recommended screening, as I eluded to before.

I also wonder how effective they may be. For example, how sensitive is a CXR at detecting pathology that may be associated with air trapping? Does a CXR effectively exclude this possibility? If the concern is truly founded (which we don't even know) does a CXR actually reduce this risk? As far as I can tell no one knows. Has any of this been studied?

You bring up the in the moment clinical decision making associated with ACLS. In truth we do not vary from the recommendations very often. When we do its via discussion about the specific patient we have in front of us and that pt's specific circumstances. The art vs the science of medicine if you will. This is vastly different than making recommendations for a population as a whole, like UCSD is.


Dr. Ehmann's presentation

ACLS: Apocryphal Conclusions Lacking Substantiation - ppt download

Disclosures None But before we get to those cases, I have no conflicts of interest to disclose

slideplayer.com

 

[Duke Dive Medicine]

Sorry for the delay in reply, its been a busy few days.

Since you brought up ACLS, lets look at how ACLS has evolved over time. I certainly have seen ACLS change in my 20+ years of resuscitation practice.

I'll link to a very nice presentation by Dr. Ehmann who at the time was an associate professor at Hopkins. In short the initial ACLS recommendations were 100% expert opinion or consensus. These recommendations included .


How about the decision to routinely use Epi in V-fib arrest (1974)?


How about defibrillation (1974 and 1986)?




It would appear that nearly zero of the expert opinions related to ACLS when first started have survived the test of time. Unfortunately it took many decades to undo those expert opinions.

I can list many other "expert opinions" that have subsequently been reversed once research was performed. AAP's recommendation for peanut avoidance to lessen allergies is one I listed. Hell, Dr. Prasad has written a book on the premise of ending medical reversal, when treatment courses are selected for the population as a whole on little or poor evidence. The simple fact is expert opinion in medicine is often wrong. This is also why retrospective evidence is only considered slightly better than expert opinion; This level of research is also frequently not supported when someone actually runs the RCT. I'm disappointed in your acceptance of this level of evidence.

Dr. Prasad has also proven that RCTs with real endpoints (overall death) can often be completed more quickly than non-randomized studies, or studies with surrogate endpoints.

Estimation of Study Time Reduction Using Surrogate End Points Rather Than Overall Survival in Oncology Clinical Trials - PubMed

From the findings of this study, an estimated 11 months appeared to be needed (ie, approximately 12% longer in the drug development cycle) to assess the OS benefit of a cancer drug. This study's findings suggest that this must be weighed against the downside of increased uncertainty of clinical...

pubmed.ncbi.nlm.nih.gov

I take issue with these recommendations and guidelines because they have consequences. It wouldn't take a lot of imagination to see insurance companies denying medical claims for divers who are not screened based on UCSD's recommendations if they are injured after diving post covid, for example. Now that UCSD's recommendations are in the wild, how long will they persist before someone develops the evidence to support or disprove them? ACLS took decades. There is also the cost and risks associated with the recommended screening, as I eluded to before.

I also wonder how effective they may be. For example, how sensitive is a CXR at detecting pathology that may be associated with air trapping? Does a CXR effectively exclude this possibility? If the concern is truly founded (which we don't even know) does a CXR actually reduce this risk? As far as I can tell no one knows. Has any of this been studied?

You bring up the in the moment clinical decision making associated with ACLS. In truth we do not vary from the recommendations very often. When we do its via discussion about the specific patient we have in front of us and that pt's specific circumstances. The art vs the science of medicine if you will. This is vastly different than making recommendations for a population as a whole, like UCSD is.


Dr. Ehmann's presentation

ACLS: Apocryphal Conclusions Lacking Substantiation - ppt download

Disclosures None But before we get to those cases, I have no conflicts of interest to disclose

slideplayer.com

No need to apologize, especially if you're taking care of patients.

Re ACLS, you have nicely articulated my point that evidence evolves. We're not doing stacked shocks any more, and we're now giving epi early on in asystole and PEA. That doesn't completely invalidate what we did before. One of the first things I did as a brand new nurse was convert a patient out of witnessed Torsades with a precordial thump (disclosure: I just did what my preceptor told me to do), which was passe then. Interesting how it's not completely so now. And, as I've said, the post-COVID fitness-to-dive recommendations may/probably will evolve over time, and that's ok. It's how clinical evidence works. That fact does not invalidate current expert opinion. Low level of evidence, yes, but nevertheless an opinion by people with enough training and experience to render one worthy of serious consideration. The idea that experts shouldn't render opinions unless they have RCTs to support them essentially invalidates an entire level of clinical evidence. I don't know about you, but I don't have the credentials to do that

Your point about expert opinion being weaponized in litigation is well taken. I've seen it happen too, and it's hard to defend against. But, if you are in a position to clear post-COVID divers, you consider the expert opinion and you make a clinical judgement that goes against it based on your professional evaluation of a patient in front of you, and a reasonable individual in a similar position, with similar training and experience, would have done the same, I will personally stand up and defend you.

Best regards,
DDM

 

[kinoons]

No need to apologize, especially if you're taking care of patients.

Re ACLS, you have nicely articulated my point that evidence evolves. We're not doing stacked shocks any more, and we're now giving epi early on in asystole and PEA. That doesn't completely invalidate what we did before. One of the first things I did as a brand new nurse was convert a patient out of witnessed Torsades with a precordial thump (disclosure: I just did what my preceptor told me to do), which was passe then. Interesting how it's not completely so now. And, as I've said, the post-COVID fitness-to-dive recommendations may/probably will evolve over time, and that's ok. It's how clinical evidence works. That fact does not invalidate current expert opinion. Low level of evidence, yes, but nevertheless an opinion by people with enough training and experience to render one worthy of serious consideration. The idea that experts shouldn't render opinions unless they have RCTs to support them essentially invalidates an entire level of clinical evidence. I don't know about you, but I don't have the credentials to do that

Your point about expert opinion being weaponized in litigation is well taken. I've seen it happen too, and it's hard to defend against. But, if you are in a position to clear post-COVID divers, you consider the expert opinion and you make a clinical judgement that goes against it based on your professional evaluation of a patient in front of you, and a reasonable individual in a similar position, with similar training and experience, would have done the same, I will personally stand up and defend you.

Best regards,
DDM

I think we’re likely closer together on all of this than we are far apart. To boil my point down.

I would argue the evolution of ACLS over the last 40+ years is the reason that RCTs should be the standard for guideline settings and changing practice. In the 1950-90s the push for evidence based medicine was not like it is now, and the practice at that time shows it.

Sometimes there is a need for a “global” recommendation from experts immediately regarding a clinical problem and stronger evidence isn’t available. Much of Covid has been that way.

Other times experts want to offer guidance on an topic that no one is clamoring for an answer to, again without evidence to support their opinion. (AAP and peanuts)

In one case the recommendations must come out, some guidance is better than none. In the other it is reasonable to not offer any guidance until research is generated.

My big rub with UCSDs recommendations isn’t that they were made, it’s that they’re waiting for evidence to be generated instead of doing it.

It’s okay to offer an expert opinion when no evidence is available. However once an organization makes that recommendation it is imperative that same organization runs the studies (I would argue for RCTs in all instances) to support or disprove that recommendation. The fact that we’re nearly 3 years post publication of the recommendations with virtually no additional insight to the validity of the recommendations is very disconcerting.

 

[Duke Dive Medicine]

I think we’re likely closer together on all of this than we are far apart. To boil my point down.

I would argue the evolution of ACLS over the last 40+ years is the reason that RCTs should be the standard for guideline settings and changing practice. In the 1950-90s the push for evidence based medicine was not like it is now, and the practice at that time shows it.

Sometimes there is a need for a “global” recommendation from experts immediately regarding a clinical problem and stronger evidence isn’t available. Much of Covid has been that way.

Other times experts want to offer guidance on an topic that no one is clamoring for an answer to, again without evidence to support their opinion. (AAP and peanuts)

In one case the recommendations must come out, some guidance is better than none. In the other it is reasonable to not offer any guidance until research is generated.

My big rub with UCSDs recommendations isn’t that they were made, it’s that they’re waiting for evidence to be generated instead of doing it.

It’s okay to offer an expert opinion when no evidence is available. However once an organization makes that recommendation it is imperative that same organization runs the studies (I would argue for RCTs in all instances) to support or disprove that recommendation. The fact that we’re nearly 3 years post publication of the recommendations with virtually no additional insight to the validity of the recommendations is very disconcerting.

Probably so, and I definitely concur that we shouldn't stop at "expert opinion" and have that be the sole guidance.

Best regards,
DDM