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Pulmonary Embolism and Blood Thinners

 

By Dr. David Sawatzky

In DIVER September 2002 I talked about blood thinners and diving, a discussion about deep venous thrombosis (DVT) and the requirement for people diagnosed with a DVT to be on a blood thinner for several months afterwards.  To be clear, ‘blood thinners’ do not actually thin the blood.  They interfere with the clotting mechanisms so that the blood clots less easily than normal.  This is a mixed blessing. Blood must clot whenever we cut ourselves or damage the blood vessels in any way. The bottom line is that you should not dive while taking a blood thinner because of the increased risk of bleeding.  After you are off the blood thinner it should be safe to return to diving.

A short while ago I received a call from a diving instructor who’d been diagnosed with a pulmonary embolism (PE) last summer and who’d then taken blood thinners for six months and was now off them.  He wanted to know if it was safe to return to diving.  In this column I’ll review pulmonary embolism and the concerns of diving afterwards.

PE Common

Pulmonary embolism is relatively common (one per 1,000 people per year in the USA) and is the second most common cause of sudden death, after cardiac problems.  It’s the third most common cause of death in hospitalized patients (approximately 650,000 cases annually in the USA) and is present in 60 per cent of people who died while in hospital (the diagnosis was not made prior to death in many cases).  If someone dies ‘unexpectedly’ while in hospital, massive PE is seen on 80 per cent of the autopsies.

Pulmonary embolism is 50 per cent more common in blacks than whites and 50 per cent more common in whites than in Asians, Pacific Islanders and American Indians.  Before age 50 PE is slightly more common in women and after age 50 PE is slightly more common in men.  PE is more common in people who sit a lot, and it may account for 15 per cent of postoperative deaths, especially after leg amputations, hip, pelvic, and spinal surgery.

Pulmonary embolism is not a disease but a complication of thrombosis, or blood clotting, in veins in some other part of the body, most commonly the deep veins of the legs (DVT).  What happens typically is that blood clots in the leg veins and a piece or pieces of the clot break off and are carried to the right side of the heart where they’re pumped into the arteries feeding the lungs.  Depending on their size, the clots can get stuck and block some of these arteries.

Approximately 10 per cent of people who develop PE die in the first hour as a result of massive clots.  Untreated, approximately 30 per cent of people who are diagnosed with PE die, usually from recurrent clots.  If they are treated with anticoagulants, the mortality drops to less than five per cent.  Less than five per cent of patients have another PE while on treatment, but 30 per cent of them will have another PE in the ensuing decade.

Historically PE was diagnosed by scanning the lungs after injecting a radioactive substance. Greatly reduced blood flow, or none at all, to part of the lung would show as an area of reduced radioactivity on the scan.  In treated patients with PE, 36 per cent of lung scans returned to normal in five days, 52 per cent had resolved by two weeks and 73 per cent had resolved within three months.  But this is a relatively crude test that detects only fairly large defects.  The preferred test now is contrast enhanced high resolution CT of the lungs.

The classic presentation of pulmonary embolism, “abrupt onset of pleuritic chest pain, shortness of breath, and hypoxia,” is rarely seen.  Rather, patients typically experience vague, nagging symptoms that are very difficult to diagnose.   Studies of people who died from pulmonary embolism show that at autopsy most of them had nonspecific symptoms for a few weeks before they died and 40 per cent of them had actually seen a physician about these symptoms, but PE had not been diagnosed.

One study showed shortness of breath (73 per cent), pleuritic chest pain (66 per cent), cough (37 per cent) and coughing blood (13 per cent) as the most common symptoms in PE.  Other presenting symptoms include seizures, syncope, abdominal pain, fever, productive cough, wheezing, decreasing level of consciousness, new onset atrial fibrillation, flank pain and delirium in elderly patients.  It should be obvious that most patients who present with these symptoms will not have PE.

PE Risk Factors

The following risk factors have been identified for PE.  Travel of four hours or more in the past month, surgery within the last three months, malignancy (especially lung cancer), history of thrombophlebitis, trauma to the legs or pelvis during the previous three months, smoking, central venous instrumentation within the past three months, stroke, paresis, or paralysis, prior pulmonary embolism, heart failure and chronic obstructive pulmonary disease.  Another study had a list of risk factors twice as long!

Pulmonary embolism generally occurs in one of these three ways:

  • The blood vessel linings are damaged and clots form
  • The blood flow changes so that blood either sits still and clots, or blood flow becomes turbulent and damages the endothelium
  • In blood that’s abnormally likely to clot due to multiple genetic abnormalities.

The bottom line is that PE is relatively common, often undiagnosed, and can occur in many different settings.

As a result of this challenge, a scoring system has been developed to quantify the risk of a person having a PE. The accompanying Table indicates the greatest risk is having a DVT and no other probable diagnosis. Next is a rapid heart rate, immobilization, history of DVT, coughing blood and cancer.  Even with this tool, many cases of PE will not be diagnosed.

When a blood clot or clots block part of the circulation to the lungs, several things can happen.  If the obstruction is very large, the backpressure on the right side of the heart can cause problems or death.  The lungs will have increased alveolar dead space and there can be hypoxemia and hyperventilation.  If the obstruction is smaller there may not be too many signs or symptoms.  Fortunately, pulmonary ‘infarction’ is uncommon because the lungs have two circulations and when one is blocked the second will keep the lung tissue alive until the first blockage resolves.

Normally the clots resolve within a few weeks of the person starting treatment and the lungs heal.  Unfortunately, sometimes the clots do not resolve and/or significant scarring can result.  In addition, some people continue to generate clots in the veins and continue to shower the lungs with emboli.

Diving Considerations

So what is the significance of pulmonary embolism for diving?  If you have a PE, you must be treated with blood thinners, usually for six months.  This will dramatically reduce your risk of dying from the PE and/or having a recurrent PE during this time period.

While you are taking blood thinners you should not dive.  Diving is an activity where the risk of trauma is quite high and a person taking blood thinners who suffers trauma has a significant risk of a massive bleed.  Although the risk is very low, some forms of Decompression Sickness involve bleeding, especially into the spinal cord.  If a diver has this happen and they are taking blood thinners, the bleeding will be much worse and the outcome severe.  It is also probable that bleeding is more likely to occur in a diver on blood thinners who experiences ‘decompression stress’, even if he or she is not ‘bent’.

But what about a diver who has a PE, is treated with blood thinners for six months without problem, and is then off the blood thinners and is doing great.  Can they return to diving?

There are several considerations.  After PE many people have permanent changes to the right side of the heart, presumably from the backpressure created by the PE.  Everyone should have a cardiac workup.  Their ability to return to diving will depend on their exercise capacity and any heart abnormalities that are detected.

A significant number of people will have permanent changes in their lungs after PE.  Full pulmonary function tests and high resolution CT should detect most significant changes but small areas of abnormality will not be detected.  High resolution CT with contrast is a more sensitive test but the increased risk and cost is probably not justified.  The advisability of the person returning to diving will depend on what is found.

If the cardiac workup and the lung studies are completely normal there are still some concerns.  Small areas of damage may not be detected.  In arterial gas embolism the area of damage in the lungs is often as small as the tip of your little finger and in many cases the area of damage cannot even be found on autopsy.  Never forget that arterial gas embolism (AGE) and pulmonary barotrauma are shallow water problems.

In addition, 30 per cent of people who have had a PE will have a second one within 10 years.  If that happens, they will need to be on blood thinners for the rest of their lives.  Finally, the recurrent PE may be asymptomatic, but still put the person at risk of AGE.  Anyone diving after a PE will almost certainly have an elevated risk of problems.

Points

Clinically suspected deep vein thrombosis (DVT)

3

Alternative diagnosis less likely than PE

3

Rapid heart rate

1.5

Immobilization within past 4 weeks

1.5

History of DVT

1.5

Hemoptysis

1

Malignancy

1

Total score of greater than 6 indicates a high probability of PE, a score between 2 and 6 moderate probability and a score below 2 low probability.

 

 

 

 

 

 

 

 

 

 

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3 Responses to “Pulmonary Embolism and Blood Thinners”

  1. Chris Menjou
    17/12/2012 at 10:43 am #

    I appreciate the article as this issue is not well covered.

    However, and with all due respect, I think the absolute conclusion “While you are taking blood thinners you should not dive” is neither supported by the science nor responsible without any information as to a particular diver’s circumstances. If trauma risk were a sufficient basis alone for participation in a particular activity, there would be scant few activities available to those of us on thinners. We may need to make adjustments (i.e., I would not go on the Galapagos Aggressor again and be 24 hours from land), but the risk of trauma alone is not a contraindication for diving.

    As for DCS bleed complications, is there any scientific study showing a statistical significance between thinners and DCS-bleed complications? What is the increased risk? 5%? 10%? .001%? My UCLA hematologist explained this to me early on but, noting the rarity and my DCS free history, supported my diving.

    For the record, I was cleared by a leading hyperbaric doc here in L.A. to dive on thinners (as well as a UCLA thrombophilia specialist), following a consultation, history and PFO test. In addition, I race triathlons, including Ironman, ocean swim, trail run, zip line, paddle, snowboard – all of which I am sure would be absolutely contraindicated if trauma risk alone was enough to bar participation.

    Of course, as with most medications, one should consider whether diving is appropriate on thinners. But a blanket statement that one should not dive without taking other factors into account – prior DCS hits and profiles? INR range? INR stability? Self testing? Age? Reason for thinners? ability/willingness to dive conservatively? EANx? – is unwarranted. Rather, it is a question that each diver should consult with his or her physician, with referral to a hyperbaric and/or thrombophelia expert as appropriate, and make their own decision

    My fear is that the next diver that thrombolizes with Factor V and performs the inevitable google search will run across an opinion by an M.D. that they will never dive again. When, in reality, they can live a normal life and do those activities that bring them joy, and not have to live wrapped in bubble wrap.

    Just one anticoagulated diver’s opinion

    • zig smigaj
      01/04/2013 at 4:13 am #

      I agree with Chris Menjou on that each individual should consult a hyperbarics doc before deciding to quit diving after being told to do so by their physician. I would slump into depression if I was told I could never dive again…. I would have to take up some other risky sport just to compensate, such as skydiving or playing piano in a brothel.

  2. Amy
    03/06/2013 at 6:52 am #

    I moved to Englewood FL…Gulf of Mexico. Paradise. I enrolled in a Scuba Certification class last week, something I’ve wanted to do my whole life. I was diagnosed with PE three days later. I was very disappointed when the ER doctor told me that i would not being diving next week…I was so excited to start. My primary care physician said it would be at least 6 months before I could dive…but he did not say I would never be able to. Im only 42 and otherwise healthy…as far as I know. My Doc said as long as all goes well with treatment of my PE I should be able to dive by the end of the year no matter if I’m blood thinners or not. It will be a long 6 months but worth the wait. I could have had a very different outcome if I wouldn’t have gotten diagnosed when I did:)

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