Kinoons,
My main objection to your posting in this thread is your nihilistic portrayal ("failure of academic medicine" "guesswork" etc) of a diving medicine community trying to do the right thing in a difficult situation. This has been laced with an authoritative voice (you imply you are a physician but give no detail) and (sorry to say) naive demands for a randomised trial to resolve this issue.
When the pandemic broke, it did not take long for evidence of serious and sometimes persistent lung changes to emerge. It became clear that this could occur in patients who had suffered relatively mild illnesses. One of these changes was air trapping which, as I have pointed out previously, is an indisputable established risk factor for pulmonary barotrauma. Under these circumstances, it is no surprise that months into the pandemic the early guidelines regarding return to diving (including those published by UCSD) were conservative.
Those guidelines have subsequently been modified to reflect the fact that (as you have observed) many divers have undoubtedly returned to diving after covid with few obvious problems so far. You have condemned this as "guesswork" and demanded a randomised trial to resolve the issue.
It is easy to be a triallist sitting at a keyboard. I don't know how many randomised controlled studies you have published, but in case it is none, then I can assure you it is not straight forward. The big problem in this case is power. We don't know the exact incidence of arterial gas embolism secondary to pulmonary barotrauma in 'normal diving', but in our recent review article [1] we cited several studies with over 3000 cases of DCI in which the authors believed about 6% were AGE and the rest DCS. There is reasonable evidence that the incidence of DCI in typical recreational diving is something in the vicinity of 1:10,000 dives [2]. If only 6.5% of 1:10,000 are AGE then the problem is obvious. You would need a massive study (100s of thousands of subjects) randomised to a medical assessment or not to show any difference in the incidence of AGE between a medical assessment vs a no medical assessment approach. On this thread you were proposing that a research team would contact all these people in a lead up to a dive trip and ask half of them to submit to a medical exam that they were not intending having. The rate of subjects declining such an imposition would be huge, not to mention the extra-ordinarily difficult logistics of such an undertaking. I hope you can appreciate that an experienced triallist (which I am) would find the virtual impossibility of your proposal somewhat ironic in the context of someone criticising the field for "a failure of academic medicine".
Kinoons, many of your points are valid. It is becoming clear that the risk is lower than originally feared. The community is responding to that by modifying its guidelines to be less conservative. There are still anxieties about air trapping lesions (eg reference 2 in my previous post), but these will be appropriately calibrated over time. For the record, I agree with you that the CXR recommendation for cat 1 cases in the UCSD guideline can be questioned. If you go back to their original paper they address the logic for this, but I'm still not sure I agree with it for the reasons you state. I also agree that other serious viral illnesses can provoke lung changes, but they did not break under pandemic conditions equivalent to SARS-CoV-2. Moreover, they probably are mostly dealt with in much the same way was UCSD advocates when seen by diving physicians. A diver coming to me for any pulmonary condition that put them in hospital on oxygen or in intensive care would get a fairly thorough work-up before I would endorse return to diving.
Finally, I want to be clear to others reading this thread that I agree with the liberalisation of the guidelines for return to diving. I am not advocating for more screening. It will probably be even less over time. I am simply defending the path the medical community has taken through this difficult situation.
Simon M
1. Mitchell SJ et al. Decompression illness. N Eng J Med 2022;386:1254-64
2. Hubbard M et al. Decompression illness and other injuries in a recreational dive charter operation. Diving Hyperb Med 2018;48:218-23
Dr. Mitchell,
Thank you again for the well presented post and discussion.
For the record I’ve been in healthcare for 25 years, first an EMT/Paramedic, then RN, and now as a Nurse Practitioner for 8 years certified in both emergency medicine and family medicine. All of my practice has been in emergency medicine.
I have not been on the team for any clinical research. All of my practice has been in the community, not at any academic centers.
I appericate the perspective that your research has provided on the potential injury rate associated with recreational diving. It does offer insight into why powering a RCT would require the involvement of a very large team of researchers over the entire world to get enough participants in a timely enough manner if the only concern was for AGE. Even if powering for all DCI several sites would be needed if the 10,000 dives per year average from the location used in your second reference is roughly standard for most dive operations.
This brings me back to the recommendations. I agree, as I stated before, that anyone requiring oxygen or hospital admission should have an evaluation prior to resuming diving.
However this may differ when talking about screening what are now presumably healthy individuals (what would be category 0.5 and 1 in the new recommendations or 1 in the old). Now that there is some insight into the rate of all DCI (roughly 1:10,000) and AGE (6% of 1:10,000), it can be argued that screening isn’t necessary at all.
It’s been noted that incidental findings on radiographs occur roughly 8% of the time. [1] As we discussed previously those incidental findings then rope a patient onto a whole world of healthcare evaluations and interventions that would have not otherwise ever happened if we never looked in the first place, sometimes at zero benefit to the patient (and by definition 100% harm) [2]
So how much harm are we causing by screening a “healthy” (fully recovered from either asymptomatic or minimally symptomatic Covid) population to prevent an occurance of AGE that is 6% of 1:10,000? Even if that rate was doubled by Covid, I think there is a discussion to be had.
I understand the concern that we did not have data early in Covid-19. I would still contend that the default expectation should have been that mild illness is very unlikely to cause a significant increase in DCI and AGE. Given the rarity of both instances any increase would easily be caught by active survelliance. Once this safety signal was realized (which does not appear to be the case) a discussion could be had as to what degree to increase screening and via what modalities (cxr vs ct chest).
Additionally, I would like to apologize for my blanket statement regarding academic medicine and research and its failings. While I stand by much of my criticism, such a strong and adversarial stance, in retrospect, is not appropriate in this instance.
1. Br J Radiol. 2010 Apr; 83(988): 276–289.
doi: 10.1259/bjr/98067945
2. Davenport, M. American Journal of Roentgenology: -. 10.2214/AJR.22.28926
