Thanks for the replies everyone.
Just so it's out there, PFO is associated with severe, sudden-onset neurological DCS, inner ear DCS, and cutis marmorata. The hissing could conceivably be attributable to inner ear DCS but it sounds like you and your providers are leaning more toward another mechanism. At what point in your dives did the hissing start, and did it resolve with hyperbaric oxygen treatment? You mentioned that you don't get marbling/cutis. Have you ever had severe neurological DCS symptoms?
Best regards,
DDM
I had also considered that the symptoms of PFO were usually reported either on ascent, or very shortly after surfacing. I'm also aware that it's not an exact science, so I'm keeping an open mind in that regards.
Usually, I'm fine on the dive, but I start to feel unwell about 2-3 hours after surfacing. The best way to describe the unwell feeling as that it is like I've been breathing car exhaust fumes or something. I'd suspected this was down to bad / contaminated tanks at first, however for the last 6 months or so, I've been renting / filling my tanks from a local reputable technical dive shop, and I test every tank I dive with the CO tester (ensuring it reads 0). My regulators are also clean after inspection (and actually only have about 50 dives on them too).
At one point, after continuing to dive despite feeling unwell, although only to depths of about 8m (26ft), the hissing got pretty loud and I developed minor muscle twitching on the right side of my face and minor vision wobble on the same side. The vision wobble would clear up after a few days of stopping diving, but the hissing would persist for much longer. I think the facial stuff could possibly be described as Hemifacial spasms, and I did have an issue with an ear infection about 12 months ago which initially went undiagnosed, but was later confirmed when I showed photos retrospectively to another ENT doc (after I had decided to try decongestants / corticosteroid treatment). Over the past 6 months, multiple ENT docs have looked into my ear canal and explained they can't see any issues. It's possible the original infection might have progressed to inner ear - I've not been diagnosed with anything however.
As I write this post, I'm at 2 weeks post Table 5 chamber ride (which was to clear up Type 1 DCS joint / MSK pain). The hissing has just yesterday, reduced to a point where I can only just hear it. I'm undecided if the chamber rides help with this. It seems to fluctuate somewhat and I've noticed stress can sometimes make it a little worse, or sometimes if I wake up in the night it can be pretty loud. Right now I'm about to try some "exercise with oxygen" therapy, as it's reported to have good results with regards to general healing. Note that I am convinced this is not the same as Tinnitus, I'm familiar with that sound / sensation. I've noticed it maybe once a year or so for most of my life, for about 10 seconds and then it stops. That can be defined as ringing and it certainly feels like it originates further out in the ear.
A potential plan this time round is to wait until the hissing completely clears before diving (In the past it didn't really clear up, despite waiting 6-8 weeks), regardless of if the hyperbaric doc clears me to dive in my evaluation visit in 2 weeks time from now. Then, I may opt to try a CCR dive with my local instructor again, this time with a high setpoint - and closely note how I feel afterwards over the coming days, without any other diving. My instructor also has the Odive system (which we forgot to use last time I did the "try CCR") so I'm also hoping this might give me some insight into my physiology. If I still have problems with this dive, I will probably give up. I'm also still waiting for opinions on the severity of my PFO, and if I would need to carry out TEE (mine was TTE) or if the videos I have from the TTE are a good enough indication of severity.
Not sure I recognize those cases. Assume I am "the other diver". I dive both OC and CCR, and didn't cross to CCR because of skin-bends, I mostly crossed because of deeper wrecks and sick of being cold. I also usually dive 40/80.
However... tricks to minimise gas tissue tension. Slow shallow ascent speed (IE NEVER more than 1m/min), well hydrated with the use of a pee-valve, focus on retaining normal body temperature and use of heated undergarments if available, avoid physical strain immediately after (decompression) dives, avoid valsalva on ascent.
I do firmly believe that a slow shallow ascent rate is the single most beneficial change I made to my diving.
With regards to the ascent speed, I just want to make sure I understand correctly. Over the entire dive - you would never exceed 1m / min? Although this seems to be contrary to the current decompression thinking (fairly quick ascents at deeper depths but progressively slower the shallower you get) - I had also considered applying the 1m / min rule to the entire dive. I'm certainly at 1m/min from 6m depth, but for depths below about 10m, I've only been sticking within about 4-8m per minute. If this turns out to help, I may speak to Shearwater and ask them about implementing a custom ascent speed alert.
