Pulmonary Oedema incident

[TSandM]

A couple of interesting abstracts. The rise in PAP in cold water is pretty striking. The other finding I thought was interesting was the decrease in minute ventilation during hyperoxia. I've seen it stated before that at least some divers are prone to CO2 retention, and I've seen various theories as to why, including increased work of breathing and restrictive clothing and equipment. This certainly suggests that purely breathing an elevated ppO2 is enough to do it.

 

[Ayisha]

Given how little is known, and the relative rarity of diving-related pulmonary edema, I wonder if there is any utility in using a resource like Scubaboard, which links divers from around the world and harnesses the power of the world wide web, of creating a Pulmonary Edema Reports Page (or whatever you want to call it) where cases and accounts can be reported by divers. Collating cases into a single repository concentrates the events and allows common features and risk factors to become recognized. This kind of thing is done routinely for rare diseases and conditions. As it is, these accounts get scattered on various threads and forums....

This sounds very useful, especially if you were to create it as a series of questions/sections for divers to answer in order to keep the reporting uniform. For example, Type of dive; depth/temperature/length of dive; any known health issues; fitness level; any prescribed or over-the-counter medications; type of equipment; equipment/exposure protection issues; over- or under-hydration; when breathing difficulty began; symptoms/signs; when breathing difficulty resolved; follow-up medical care; follow-up medical advice, etc.

Having sections will keep the info organized, easy to read and more manageable...

 

[Duke Dive Medicine]

This sounds very useful, especially if you were to create it as a series of questions/sections for divers to answer in order to keep the reporting uniform. For example, Type of dive; depth/temperature/length of dive; any known health issues; fitness level; any prescribed or over-the-counter medications; type of equipment; equipment/exposure protection issues; over- or under-hydration; when breathing difficulty began; symptoms/signs; when breathing difficulty resolved; follow-up medical care; follow-up medical advice, etc.

Having sections will keep the info organized, easy to read and more manageable...

This is being worked on right now.

 

[retendokid]

We're starting to do that here at Duke. IPE is getting a lot more online visibility in the triathlete community, and through threads like this one, the diving community. Pete and Howard do a fantastic job of search engine optimization so that often when a diving-related topic is searched, Scubaboard threads are at or near the top of the list. When a diver comes here with questions about pulmonary edema, someone typically refers him/her to us if we don't pick it up right away. Dr. Moon's research assistant has recently established a Scubaboard user name, DukeIPE, and has an alert set up for new internet postings on immersion pulmonary edema.

Dr. Moon and his team have already published several papers on the subject: Risk factors for immersion pulmonary edema: h... [J Appl Physiol. 2011] - PubMed - NCBI, Effects of hyperoxia on ventilation and pulmo... [J Appl Physiol. 2010] - PubMed - NCBI, Effects of head and body cooling on hemodynam... [J Appl Physiol. 2009] - PubMed - NCBI. They continue to actively research IPE and are transitioning to a couple of new studies: one that looks at overhydration as a risk factor, and another that is looking at mitral valve regurgitation.

Awesome, sounds like there is a mechanism for collecting and analyzing these accounts. And even better to see research capable of assessing risk factors.

I'm still very intrigued by the idea of analyzing volume shifts specifically associated with wearing wetsuits, and wonder if it isn't an underappreciated component. There are a variety of ways to analyze circulating volumes- PACs, Echo, and radio-isotope labeled albumin tracers, and some newer techniques for looking at intrathoracic volumes....might be fun to look at 1mm vs 3mm vs 5mm vs 7mm suits and the impact they play alone shifting volumes around.

 

[bowlofpetunias]

Fascinating... thanks for the links!

 

[Ayisha]

Dr Smith, do you think that volume shift happens with everyone wearing any type of wetsuit, or only if the wetsuit is very/too tight?

 

[Duke Dive Medicine]

I think it's very reasonable that an ill-fitting wetsuit could be a factor. I'm not sure that a wetsuit that fits a diver properly would cause any significant fluid shift but it may be worth investigating.

 

[retendokid]

I think it's very reasonable that an ill-fitting wetsuit could be a factor. I'm not sure that a wetsuit that fits a diver properly would cause any significant fluid shift but it may be worth investigating.

The short answer is, we don't know how much fluid shifting is caused by wetsuits. But my guess is that proper fitting suits, thinner than 3 mm, may not make much of a difference, but thicker suits and ill fitting suits, as mentioned above, may be a real factor. As somebody who daily watches blood pressure changes from volume redistribution simply by changing the position of the body (supine to trendelenberg-head down), I can tell you that the body's fluid compartments are far more dynamic than most people suspect. Similarly, think about how much fluid can collect in your lower extremities while flying from a reduction in air pressure and recumbent positioning. Last time we flew overseas, my wife's legs looked like she had elephantiasis, and she has no cardiovascular disease whatsoever. As I mentioned in my post, simply from water immersion, something on the order of 3/4 of a liter rapidly is shunted from the periphery, and that is just immersion at sea level. But if you think about standing in a pool of water, you don't really feel much of a "squeeze" all over your body, certainly nothing like wearing a thick wetsuit. When you combine a heavier, tighter wetsuit, and cold water immersion, and several atmospheres of pressure, there must be a significant volume forced from the interstitial tissues back into the venous and lymphatic systems and redirected to the core. I'm pretty sure these mechanisms exist, but the bigger question is who and why are some individuals affected by this common process and others remain immune. And does the volume redistribution play a significant role in this?

 

[Duke Dive Medicine]

I think we have to be careful when comparing hemodynamic changes in anesthetized surgical patients to those in divers.

Pressure is equally distributed in the body. Once an individual is immersed, the ambient pressure at which the immersion occurs has little bearing on fluid redistribution, e.g. the immersion-related fluid redistribution at 2 ATA will be essentially the same as that at 6 ATA.

Can you elaborate on how ambient pressure is a factor in dependent edema while flying?

Best,
DDM

 

[InTheDrink]

I may be missing the point here but has anyone ever measured BP before and after putting a wetsuit on (let's say a well fitting one)?

---------- Post added December 19th, 2012 at 08:28 PM ----------

Just so I'm clear: I have various theories about pulmonary edema now I've been part of it and read quite a few case studies. But I'm not a doctor and don't have the insight you guys do. On the flip side, having had it, I've probably got some other insights into what might be sliding scale factors.