PFO - Diving with more conservatism, specifically CCR

[davehicks]

Thanks for the replies everyone.


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.

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.

I just want to show you this chart of a recent dive on CCR I made to 76 feet.

At a PPO2 of 1.26 at 76 feed the partial pressure of the Nitrogen is 2.02. This about the same as it would be on 32% nitrox on OC. While you will take up less overall nitrogen in the shallows with a higher CCR setpoint, once you are at depth it is really not different than diving Air or Nitrox. You can ride out a lot of time in the shallows at a high PPO2 to wait out your SurfGF and drop it <30% which might help.

 

[Duke Dive Medicine]

Thanks for the replies everyone.


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.

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.

The general malaise that you've described is hard to differentiate, but given the context, may be related to subclinical DCS brought on by decompression stress. Your recent pain-only DCS event lends some support to this. Again, PFO is not associated with these types of symptoms. Good call ruling out CO, though if you did have some sort of breathing gas contamination, your symptoms would more likely appear at depth rather than after surfacing. It seems like you are leaning toward reducing your decompression stress, which I think is a good path forward if you're able to continue diving.

The ear symptoms are another thing. What you're describing sounds more like repeated barotrauma as opposed to infection or DCS. The facial nerve runs right by the middle ear and, depending on your anatomy, could be affected by pressure changes in the middle ear. Also depending on your anatomy, the nerves that innervate the eye muscles could be affected if your sinuses are involved.

It is extremely unlikely that using high concentrations of oxygen while exercising will have any effect. You're better off using your time and financial resources seeking out a competent ENT physician who can thoroughly assess you (i.e. beyond just looking in your external ear canal) before diving again. You may need radiographic imaging of the head to check for inflammation in your mucous membranes (possibly related to the infection you mentioned) and anatomic anomalies that could explain your facial and eye twitching. I'd also recommend finding a trained, experienced diving physician who can evaluate you and maybe offer some advice on mitigating your risk of DCS. DAN Asia-Pacific may be able to point you at some providers.

Best regards,
DDM

 

[RVBldr]

Not a PFO per my Seattle hyperbaric/cardiology/pulmonary team, but closely related. I've really adjusted my conversancy quite a bit, downgraded my Upper GF, always take a minimum of 5 minute safety stop, slow the surfacing from 6m, I'll get on the higher set-point earlier and leave it longer, but really watch my SfGf, stay on the loop after a deeper dive, and limit straining/exertion after dive. All common tech practices, but I follow a lot closer these days.

 

[Imla]

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.

This would be a misread of what I intended to write. My bad for not specifying.
I will do my best to ascend from depth to first decompression stop as fast as reasonable. (IE, some local wrecks, the ascent is on a line and the first part of the ascent can just as nicely be done pointing the DPV to the sky.) Usually, 1m/min is applied from 6m depth. In extreme cases (Deep cave dive in Plura 100ish m with two descents/ascents) we have applied "20up". IE 1m/min from 20 meters. This was however because the cave lends itself to do this.
I will adhere to GF low of 40 and a GF high of 80, finish my deco at 6m usually and the add another "6up".
I have no issues ascending while scootering up to first point of offgassing. Using 1m/min for the entirety of the dive would only result in unnecessary ongasing and resulting increase in decompression.

 

[Scuba-Lad]

I just want to show you this chart of a recent dive on CCR I made to 76 feet.

At a PPO2 of 1.26 at 76 feed the partial pressure of the Nitrogen is 2.02. This about the same as it would be on 32% nitrox on OC. While you will take up less overall nitrogen in the shallows with a higher CCR setpoint, once you are at depth it is really not different than diving Air or Nitrox. You can ride out a lot of time in the shallows at a high PPO2 to wait out your SurfGF and drop it <30% which might help.

View attachment 773265

Thanks for the dive log. I had also carried out some dive planning regarding the rebreather and could see that descending below a certain depth (dependant on setpoint) would result in a higher PPN2 than for example a 32% Nitrox mix. Hopefully I can try the rebreather again with the added conservatism approach and see if it makes a difference, especially with a higher set point. This won't necessarily be a permanent fix, but hopefully could see me through until a better method for PFO closure becomes widely available (radio frequency for example). I'm into underwater videography and most of the stuff I film is less than 15m (50ft) anyway. Not much natural light any deeper than that around these waters.

The general malaise that you've described is hard to differentiate, but given the context, may be related to subclinical DCS brought on by decompression stress. Your recent pain-only DCS event lends some support to this. Again, PFO is not associated with these types of symptoms. Good call ruling out CO, though if you did have some sort of breathing gas contamination, your symptoms would more likely appear at depth rather than after surfacing. It seems like you are leaning toward reducing your decompression stress, which I think is a good path forward if you're able to continue diving.

The ear symptoms are another thing. What you're describing sounds more like repeated barotrauma as opposed to infection or DCS. The facial nerve runs right by the middle ear and, depending on your anatomy, could be affected by pressure changes in the middle ear. Also depending on your anatomy, the nerves that innervate the eye muscles could be affected if your sinuses are involved.

It is extremely unlikely that using high concentrations of oxygen while exercising will have any effect. You're better off using your time and financial resources seeking out a competent ENT physician who can thoroughly assess you (i.e. beyond just looking in your external ear canal) before diving again. You may need radiographic imaging of the head to check for inflammation in your mucous membranes (possibly related to the infection you mentioned) and anatomic anomalies that could explain your facial and eye twitching. I'd also recommend finding a trained, experienced diving physician who can evaluate you and maybe offer some advice on mitigating your risk of DCS. DAN Asia-Pacific may be able to point you at some providers.

Best regards,
DDM

My choices are limited for diving doctors here in Indonesia (of which I already consulted with previously as part of my DCS hits). However, I'd be interested in hearing from an experienced cardiologist as to the severity of my PFO. I have the report and videos of the ultrasound scans. The report doesn't say much to my eye other than "Hyperkinetic interatrial septum. shunt is not feasibly seen. Bubble test with and without valsalva maneuverer was done, there were few bubbles crossing RA to LA at rest and more than 20 bubbles crossing RA to LA during valsava manoeuvre. Negative bubble effects was difficult to evaluate. No chiari network is seen".

The videos might provide more insight to a cardiologist however.

Not a PFO per my Seattle hyperbaric/cardiology/pulmonary team, but closely related. I've really adjusted my conversancy quite a bit, downgraded my Upper GF, always take a minimum of 5 minute safety stop, slow the surfacing from 6m, I'll get on the higher set-point earlier and leave it longer, but really watch my SfGf, stay on the loop after a deeper dive, and limit straining/exertion after dive. All common tech practices, but I follow a lot closer these days.

Those are also my plans, to follow the tech practices closely and in addition, stay on the loop after surfacing for some time breathing pure O2.

This would be a misread of what I intended to write. My bad for not specifying.
I will do my best to ascend from depth to first decompression stop as fast as reasonable. (IE, some local wrecks, the ascent is on a line and the first part of the ascent can just as nicely be done pointing the DPV to the sky.) Usually, 1m/min is applied from 6m depth. In extreme cases (Deep cave dive in Plura 100ish m with two descents/ascents) we have applied "20up". IE 1m/min from 20 meters. This was however because the cave lends itself to do this.
I will adhere to GF low of 40 and a GF high of 80, finish my deco at 6m usually and the add another "6up".
I have no issues ascending while scootering up to first point of offgassing. Using 1m/min for the entirety of the dive would only result in unnecessary ongasing and resulting increase in decompression.

Ah sorry, I understand now. It had crossed my mind that this was a little strange to allow the slower tissues to still be on-gassing by limiting ascent to 1m/min for the entire dive, as you pointed out. Now I see that I'd just mis-understood

 

[Dr. Doug Ebersole]

Thanks, Pete. I'm in Lakeland, Florida at Watson Clinic.