Nancy A. Melville

June 11, 2013

INDIANAPOLIS, Indiana — Physicians are often asked to assess the health and fitness levels of baby boomers wanting to take on a challenge that involves vigorous physical activity before they "kick the bucket."

Dr. John Porcari

As part of a bucket-list symposium here at the American College of Sports Medicine 60th Annual Meeting, John Porcari, PhD, from the University of Wisconsin at La Crosse, outlined key criteria for those who show up with scuba diving on their list.

Hydrostatic pressure at a depth of only 33 feet is double what it is at sea level. If the water is colder than 70 °F, blood is forced into the body's core, increasing peripheral vasoconstriction and slowing the heart rate by 30% to 40%.

For a person who is fit and in good health, these effects should be manageable. However, for novice divers, even those who are fit, and their physicians, it can be easy to underestimate the true rigors involved in the dive itself and in the mechanics of getting in and out of the water, Dr. Porcari noted.

"Diving is hard work — you're wearing a wet suit, you have a weight belt on to keep you submerged," he explained. "You can be lugging about 75 pounds of gear and it can be a struggle to swim in the current and climb up the ladders to the boat."

Certification for scuba diving is often conducted in the calm of a swimming pool, he added, and some dives, such as those in calm, warm, shallow Caribbean waters, might mimic those benign conditions.

"The danger comes if you find yourself in a strong current or in wind or waves," Dr. Porcari said. "People often just don't realize how taxing it can be."

Some diving guidelines recommend a fitness level of at least 13 metabolic equivalents. That would restrict up to 85% of males and up to 95% of females older than 50 years from diving. Dr. Porcari suggested that 10 metabolic equivalents is more realistic.

Even if a person appears to be in good health, "the high cardiovascular and energy demands of diving can unmask underlying pathology," Dr. Porcari said.

Scuba diving can exacerbate some conditions and cause others to emerge, Dr. Porcari noted. For instance, blood pressure can rise under water, which could predispose a person to catastrophe.

Leading Cause of Death During Dive

The Divers Alert Network lists pre-existing disease or pathology as the leading cause of death during dives, followed by poor buoyancy control and rapid ascent or violent water movement.

However, if a condition such as hypertension, cardiovascular disease, or asthma is well managed, a fit person will not necessarily be prevented from diving, Dr. Porcari said.

The drugs used to control those conditions do not generally increase the risk of diving. Statins for elevated lipids, for example, should not pose a problem. Angiotensin-converting-enzyme inhibitors are the drug of choice for divers with hypertension. Although beta blockers are generally acceptable, caution should be used because they can reduce exercise capacity and reserve, Dr. Porcari explained.

Diuretics should be fine as long as the patient's hydration status is monitored.

 
The high cardiovascular and energy demands of diving can unmask underlying pathology.
 

About half of diving fatalities associated with health issues are caused by myocardial infarction, according to the Divers Alert Network. However, even a history of myocardial infarction, coronary artery bypass grafting, or percutaneous coronary intervention does not always preclude diving.

Key caveats are that diving should not be attempted for at least 6 to 12 months after the cardiovascular event, and the patient should be completely asymptomatic on a maximal graded exercise test, with no signs of residual ischemia or hemodynamic compromise, and no signs of heart failure, Dr. Porcari said.

Patients with artificial valves can generally dive, although there is a risk of bleeding from anticoagulation. Patients with regurgitant valves can dive safely, depending on the amount of regurgitation and the effect on exercise performance; however, diving is contraindicated for patients with stenotic valves.

Another contraindication for diving is patent foramen ovale, because of the risk for embolic complications related to the venous bubbles that occur in approximately 90% of divers. "Normally, these bubbles are filtered out by the lungs, but with patent foramen ovale, the bubbles can get shunted into the left side of the heart and get into the arterial circulation," Dr. Porcari explained.

Diving is also contraindicated for those with exercise-induced supraventricular tachycardia, atrial fibrillation, and ventricular tachycardia, he reported. However, occasional premature atrial contractions, premature junctional contractions, and isolated premature ventricular contractions should not be a problem for divers.

Diving is also contraindicated in patients with a pacemaker or implantable cardioverter defibrillator.

"Patients with type 1 diabetes should have been on insulin for at least a year and with type 2 on hypoglycemic agents for at least 3 months," Dr. Porcari said.

Divers should have had no hypoglycemic episodes for at least a year prior to the dive, be regular exercisers, and have no history of underlying pathology.

Blood glucose should be checked 60 minutes, 30 minutes, and immediately before a dive.

Asthma is another concern, but patients whose condition is under control and who have normal pulmonary function tests at rest and after maximal exertion should be able to safely dive, Dr. Porcari said.

Epilepsy and other seizure disorders are among the strongest contraindications for diving. "With any condition where an individual is at risk of losing consciousness, diving is contraindicated," he said.

Diving Contraindications and Precautions

Neurologic contraindication
Epilepsy
Other seizure disorder
Any risk for loss of consciousness
Cardiac contraindications
Pacemaker or implantable cardioverter defibrillator
Atrial fibrillation
Exercise-induced supraventricular tachycardia
Ventricular tachycardia
Patent foramen ovale
Stenotic valve
Cardiovascular event (e.g., myocardial infarction, percutaneous coronary intervention, or coronary artery bypass grafting) within the previous 6 to 12 months
Cardiac precautions
Risk of bleeding from anticoagulation related to an artificial valve
Other precautions
Diabetes with hypoglycemic episode in the previous year
Poorly controlled asthma

 

Dr. Porcari proposed general guidelines for prudently assessing patient risk. He said that no more than 1 major coronary risk factor indicates low risk; 2 or more risk factors with no signs or symptoms of cardiovascular, pulmonary, or metabolic disease indicates moderate risk; and known cardiovascular, pulmonary, or metabolic disease indicates high risk.

"Because diving is considered vigorous activity, a physical exam and maximal graded exercise test should be required for all moderate- and high-risk individuals," he explained.

According to a Divers Alert Network report, more than 75% of fatalities from 2002 to 2004 involved divers who were overweight or obese, Dr. Porcari noted. However, obesity without any other comorbidities does not necessarily place a diver at risk, he said.

"A physician should look at the whole constellation of risk factors and make the decision. If the patient is overweight, that's not likely going to be the only factor in suggesting that they shouldn't dive," Dr. Porcari explained.

Dr. Lindell Weaver

Diving medicine expert Lindell Weaver, MD, medical director and division chief of hyperbaric medicine at LDS Hospital, Salt Lake City, Utah, said that he agrees that obesity is not always a contraindication for diving.

He described a diver with a body mass index of about 35 kg/m² who made a dive to the Andrea Doria shipwreck in treacherous waters off the coast of Nantucket, Massachusetts.

"That is probably the hardest dive to make in North America," said Dr. Weaver. Because of its extreme depth (240 feet) and heavy current (typically running at 4 to 6 knots), the dive has been dubbed "the Mount Everest of wreck diving."

"It really shows that the issue isn't necessarily obesity, it's conditioning."

That being said, obese divers are often not nearly as well conditioned and can experience a range of issues, including dive gear that does not fit properly and reduced functional residual lung capacity, he said.

The motivation to make a dive can be a great opportunity to get a patient to a healthier body mass index. "The interesting thing about divers is they really want to do it; it's a serious passion," Dr. Weaver said. Why not use that passion to encourage a patient to lose weight, get fit, and become a safer diver.

Mental Health

Panic, another well-known cause of diving injuries and fatalities, prompts many to ascend too quickly and develop decompression sickness, noted Dr. Weaver. Therefore, a patient's mental state should be considered, in addition to physical state, before diving. This involves screening for anxiety or panic disorders and getting a sense of the person's cognitive function.

One hard-hitting approach to underscore the importance of being prepared on all levels before a dive and being alert during the dive can be to remind patients that they might not be the only ones to suffer the consequences of the lack of preparation, Dr. Weaver explained.

"I remind patients that if they get into trouble, the people around them are going to help. In doing so, they will probably also get into trouble and they could die too. This drives home the message that there is a ripple effect involving the people around you."

Dr. Weaver is the Southwest regional coordinator for Divers Alert Network. Dr. Porcari as disclosed no relevant financial relationships.

American College of Sports Medicine (ACSM) 60th Annual Meeting. Presented June 1, 2013.

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