Tuesday, September 22, 2020

Me and my PFO


I have been diving since 1996 and have been working and diving in the industry since then. I have done underwater photography and video; some basic free diving and love wreck diving. I qualified as a PADI Open water diver in early 1996. The water was cold, the visibility was bad, but I loved every minute of it.

Having a low breathing rate, I was prone to headaches post diving which I always put this down to skip breathing. At this time, I had a breathing rate of approximately 5-8 breaths per minute. I also used to get headaches regularly on the surface, and felt that post-diving headaches were not unusual.

Not being the fittest person in the world, with back, knee and pelvis problems I was often pulling muscles and getting bruises, from knocking myself about pre or post dive; which meant to have muscular pain post diving appeared justifiable.

As quite a young adult, I did not have the best diet or fluid consumption in the world. I was always looking for a ‘chocolate fix’, fizzy drinks and fast energy foods. However, I would always eat a good meal post diving.

In 1998 my diving became more diverse and in 1999 I completed PADI Master Scuba Diver qualification and Basic EANx course.

At this stage, a large percentage of my diving was at an inland site with the majority of the dives conducted at 7-9mtrs for 20-40 minutes. Which, as far as decompression theory suggested, made the amount of nitrogen loading almost negligible.

On deeper dives I ensured I had a long surface interval between dives, however I always felt worse after a second / third dive and put it down to increased energy used on the previous dive and dehydration.

In early 1999, I completed my IANTD Advanced Nitrox Course, which was a real turn in the tables for me. I thought the content about foods and there effects on diving were unbelievable, so very quickly my eating habits began to change, and my fluid consumption increased dramatically. I was now eating boxes of sandwiches, drinking at least 1 litre of weak orange juice and the occasional chocolate bar, or fruit before diving. My gas mixes were chosen for optimum decompression benefits and the result was that I felt much better after dives.

However, things were to take a dramatic turn for me during one weekend of diver training, even though it would not become apparent for several hours after I returned home from diving.

Day One

It was a rather chilly day at my local dive site. I was helping a novice with some skills, and it was his first time in open water in a dry suit. We were doing a little bit of bobbing up and down as he got to grips with his buoyancy. Max depth of 7 meters for 20-25 minutes.

After an hour surface interval, we were back in the water again. Another skills dive for my student, for a total dive time of 20-25 minutes and max depth of again of 7 meters.

As ‘usual’, I experienced a headache post dive, but had no aches or muscular pain. The water temperature was around 5-6 degrees Celsius. Both dives were conducted using a 36% EANx mix.

Day Two

After a long walk, carrying a twinset, from the car park to the water’s edge (about half a mile), we began the days diving activities.

First dive was to 25mtrs with a total dive time of about 25 minutes, including a safety stop at 6m.

After a 1½-hour surface interval, the group decided to take a short surface swim to the buoy marking the artificial wreck. The dive time was approximately 25 minutes, with a pause at 10 meters to correct a problem with the ascent line, followed by a direct ascent to the surface.

We did not complete our planned safety stop, since some of the group were running low on air. However, the ascent rate was well within acceptable limits as well as the dive being conducted within table decompression limits. We then took a leisurely swim back to the key side.

Again, post-dive I experienced a headache and attributed this to my normal post-dive experience. The dives were also conducted using EANx, this time a 34% mix.

About 45 minutes post diving, I had to carry my twinset back to the car park. As I was walking, I felt as though I had pulled the muscle around my knee, but I dismissed this as an old surgery site when I was a child. I was driven home by a friend, and slept the entire journey, ate and went to bed.

The next morning I woke up with a bad headache but I was already running late for university so I packed my things and left. My knee was still sore but it still felt as though it was due to muscular pain. I continued on my normal day and felt better for drinking copious amounts of fluid. That evening, I had a warm shower and came out with a heat rash on my right shoulder; I immediately phoned my diving insurers who deal with hyperbaric treatment. They said it sounded like I had pulled some muscles and that I had a rash from my hot shower, so try and sleep on it, but if it got any worse I should contact them again.

Day Three

The next morning I went to my GP who said he could not find any problems, but suggested I gave them a ring back. The insurance company put me in touch with a hyperbaric Doctor who suggested that I go and see them – better to be safe than sorry!

The Assessment for DCS

I was transported to the hyperbaric chamber where the doctor and his team were excellent. After a review of my diving and medical history, I had a number of neurological assessments, which revealed I had a Type I and II DCS. My reflexes were out in my feet; I had spinal damage, which was causing knee, hip, back and shoulder/neck problems and a swollen lymph gland. The headache was also considered a neurological symptom.

The Treatment for DCS

I was put in the chamber for US navy table 6 treatment, which is designed to remove any remaining bubbles. This was unlikely in my case due to the time elapsed since I had surfaced, during this time the bubbles would have dissipated, but the damage that was left was realistically what they were treating.

The treatment lasted approximately six hrs in the chamber, pressurised to 21mtrs, whilst breathing pure oxygen for 10-20 minute cycles followed by air breaks, for 2 hours of the treatment. After which, a variation of cycles of oxygen exposure.

After this treatment and once out of the chamber, I was reassessed. I still had some residual damage, which was treated the following day. The next treatment was US navy table 5 and in total, I would be recompressed four times.

At this stage, I discussed my future with the hyperbaric doctor; he and I discussed my diving profiles and he said that I had attained DCS on the first of my two days diving. The “staggered tooth” profile, was the first cause of the DCS, also water temperature was an issue. Day two I had aggravated the problem, my first profile was fine, but again water temperature was a major issue. For dive two, even though I had stayed within my ascent rates having not completed a safety stop was not good.

Nevertheless, I had done similar, if not worse, profiles than this in my diving life and would never have considered it as DCS. Then came a jaw opener…

He said that I was the worst case of DCS he had ever seen, and it was probably because every dive I had done, I had a bend to some degree or another. Also, even though most of my symptoms were neurological, I had not drawn attention to it.

Now I really understood it. My entire diving life I have been living in denial, every post dive symptom I had had, was a DCS symptom. The hyperbaric doctor suggested I never dive again and arranged to reassess me after 4 weeks. We discussed why I might have developed DCS on a 7meter dive, and our thoughts led to Patent Foramen Ovale (PFO).

In the mean time, I went to see a Private Hyperbaric Doctor and discussed my diving practices and needs. I explained to him that stopping diving was not an option, it was my job, my life and all I had ever done for years. We discussed my medical history and I asked him that as I was a premature and ill baby, could I have a PFO? That seemed entirely possible and I had to consider getting tested which I did at a private clinic in London.

Testing for PFO

The doctor inserted an intravenous needle attached to a device that produced an agitated saline solution (bubbles), which passed into the venous blood. Once the solution was released into the blood stream, I had to conduct the Valsalva manoeuvre (used commonly by divers to relieve pressure in the inner ear). This increased pressure on one side of the heart, once released this would cause a pressure change and create a shunt and allow the bubbles to move across the heart. This would verify that a hole was present.

After a couple of attempts, a clear shunt of bubbles was visible on the ultra sound. Finally a confirmation of my PFO!

What is a PFO?

Patent Foramen Ovale, otherwise known as a PFO. Is where the Arterial Septum does not completely close after birth. Approximately one in three people have a PFO, but the size is the main issue in diving related injuries. The ‘flap’ lies between the left and right atria. Increasing pressure on one side of the heart can cause the flap to open, thus causing a shunt of blood across the heart. This shunting causes blood to travel from the venous side of the heart in to the arterial and by passes the lungs.

A ‘shunt’ (shown with green arrows) can be caused from many different things. Any activity, which can increase the pressure on the heart, standing up, straining to use the toilet, climbing a ladder, sneezing, coughing and many other things, may also cause a change in pressure on the heart.

In the case of a diver, de-oxygenated blood returning to the heart, which contains dissolved nitrogen, can be shunted from the right atrium to the left atrium.

The PFO merely allows nitrogen rich blood to transfer from one side of the heart to the other, this is not to say that a diver absorbs any more nitrogen due to having a PFO, but by by-passing the lungs, which act as a filter for inert gas, nitrogen bubbles may travel to other parts of the body including the brain.

Treatment of the PFO

Now I had a confirmed PFO. The next step would be to meet with a surgeon to see if surgery was viable and arrange a trans-oesophageal echocardiogram to confirm the size of the hole.

After a four-month wait, I had an appointment with a cardiologist, who discussed the benefits and possible complications of the procedure and was able to answer my questions that I had. He also made me aware that there was a waiting list of 6 months for the operation.

About a week later, after being on 48 hour call out for the procedure, I had a trans-oesophageal echo cardiogram. This was the least comfortable experience I have ever had. An ultrasound device, which you have to swallow and which felt like a large garden hose, is placed in the oesophagus behind the heart. The procedure with the intravenous saline was repeated and I was instructed to bear down, as though you were going to the toilet. This reveals a clear image of bubbles passing from one side of the heart to the other, although it is not possible to see, at this stage, the size of the hole.

Six months after first seeing the cardiologist I was on the ward preparing for the operation.

I did not know until the day of my operation, that a sizable PFO can be heard as a murmur on a stethoscope. A murmur sounds rather like a “whoosh”, rather than a regular “dub-lub, dub-lub” of a normal heartbeat. It is not always heard and may be inconsistent in its appearance. Bear in mind, that it was a cardiologist that was with me at the time, and they have a ‘keen’ ear for the sound of a heart and its defects. However, it is more than likely that a GP will not always diagnose this.

I met the anaesthetist who explained the risks and things that were unlikely to happen in the operation. In the theatre, there were four screens, which would display the images that the surgeon would use to guide him.

The procedure involves feeding a sheath and a keyhole surgery device from the femoral vein up to the heart, the cardio-seal (the device used to seal the hole) is inserted and its position is confirmed using a Trans-oesophageal ultrasound. Once in place, the key hole surgery equipment is removed from the veins and sheath remains in place in the vein, which is then removed after a review by medical staff and all is going well. This was removed after a four-hour wait and the medical staff were happy to do so.

I was discharged the next day after I had confirmation that the device was in place, this was done by taking an ultrasound of my heart. On which I could see an image of the hole which is now filled with the device which spans over a total area of 25mm, filling the hole and is supported around the rest of the cardiac tissue.

Following my discharge I was prescribed anti-coagulants to thin the blood and aid in preventing platelets from forming on the device. This allowed it to become integrated within the cardiac tissue.

The future

It takes approximately one month for the device to be embedded in place, and a further 5 months before it is entirely integrated to the heart and surrounded by cardiac tissue. Medical personnel suggested that I do not dive for at least the first month, but I had been given a depth limit of 6mtrs after that time.

My first dive was a very interesting experience. After about 30 minutes of getting cold, I decided it was time to head for the surface to see what my post dive symptoms were going to be like. I had a short ladder climb ahead of me but could not wait to get back on board the boat to see how I felt.

I sat on board the boat thinking for about 5 minuets, trying to decide if I had a headache or not. My head was clear, no aches, no pains, nothing!

Before I had my first experience of decompression sickness, I was just due to finish my IANTD technical nitrox course, with dates for my trimix and cave course in mind. Having friends who were planning for the Britannic in 2003, I thought I had plenty of time to get my dives in and get my skills up, to be out with them. However, it will be at least a year before I get myself up to that level again.

With thanks to Hyperbaric Medicine Unit for the use of their images.


  1. Thanks for sharing.
    I know this post is old, but I think it’s important to note that it’s not surprising that the whole incident started with the 7m training dive.
    A rapid ascent is much more dangerous when going from shallow to surface than, say, from 40m to 30m. From 7m to the surface there is a 1.7 to 1 bar difference which is a 40% change in pressure. From 40m to 30m the difference is from 5 to 4 bar which is a 20% change, half the amount of the 7m-to-surface ascent, even though in the second case you are actually ascending 10m instead of 7m!
    That’s why shallow-to-surface dives are to avoid, even if just for training, PFO or not.


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