Alert Diver is the dive industry’s leading publication. Featuring DAN’s core content of dive safety, research, education and medical information, each issue is a must-read reference, archived and shared by passionate scuba enthusiasts. In addition, Alert Diver showcases fascinating dive destinations and marine environmental topics through images from the world’s greatest underwater photographers and stories from the most experienced and eloquent dive journalists in the business.
RESEARCH, EDUCATION & MEDICINE FROM THE MEDICAL LINE An important consideration relative to the device is the pressure rating. These particular devices are often rated only to an ambient pressure of 2 atmospheres absolute (33 feet of seawater). Medtronic, one manufacturer, states that exceeding this pressure could lead to degradation of the system. Furthermore, exceeding the recommended maximum pressure could lead to changes in the way the device works or cause it to fail, which would require surgical removal and reimplantation. People with neurostimulators can determine the pressure rating of their system by reviewing in the literature provided to them the sections that address sports and other activities. They can also get information by calling the toll-free number on the device identification card and providing the serial number. Another consideration that shouldn’t be overlooked is the underlying reason for the device. That condition must be evaluated with respect to any potential problems with diving. — Scott Smith, EMT-P Q: I am 48 years old and have moderate hypertension. I was diagnosed with pulmonary stenosis, which was surgically corrected. The pulmonary valve, however, is allowing some blood to leak, permitting backflow. Is this a disqualifier for scuba diving? What short-term and long-term risks are involved in diving with this medical issue? A: Whether or not a medical condition disqualifies a person from diving depends on several factors, including the severity of disease and the presence of associated medical conditions. The diver must undergo a thorough evaluation by a doctor, and fitness to dive must be considered on a case-by-case basis. The general comments here are intended to provide background on pulmonary valve insufficiency and some of the associated cardiac issues that influence decisions regarding fitness to dive. Deoxygenated blood returning from the body enters the heart before making its way to the lungs for reoxygenation. Pulmonary valve insufficiency may result in the backward flow of blood (regurgitation) into the right ventricle of the heart. Minimal or mild pulmonary insufficiency is common in many people with otherwise healthy hearts and rarely requires medical intervention. Although mild pulmonary insufficiency may not manifest with symptoms, individuals with a more severe condition may experience fatigue, shortness of breath (especially during physical exertion), exercise intolerance, fainting, palpitations or chest pain. Backflow may result from a number of medical conditions, including congenital malformation, pulmonary hypertension and pulmonary stenosis. Pulmonary stenosis, a narrowing between the right ventricle and pulmonary artery, results in an obstruction in the flow of oxygen-poor blood from the heart to the lungs. Even after being corrected, pulmonary insufficiency may still be present. Whether or not regurgitation disqualifies someone from diving depends on the severity of regurgitation, the existence of underlying myocardial disease 58 | FALL 2016
ISTOCKPHOTO.COM and especially the health and function of the right ventricle. Factors such as age and chronic hypertension can result in thickening of the ventricle walls (hypertrophy) and loss of cardiac elasticity that reduce the heart’s ability to adapt to physiologic stress. Various factors — including immersion, exercise and cold water — shift fluid from the body’s periphery to the core and increase cardiac workload. If the muscle of the right ventricle is compromised in some way, the heart may not be able to handle these diving-associated fluid shifts. If the leak is mild enough that symptoms are not apparent and the right ventricle is of normal size and function, it is likely that diving can be done safely. Valvular incompetence can result in increased right ventricular stress and result in hypertrophy (independent from systemic elevations in blood pressure). How the heart muscle responds to this overload depends on the severity of the condition and how long it has been present. Chronic overload can result in hypertrophy, which reduces cardiac efficiency and requires increased blood flow to the heart muscle itself. During physiologically stressful states such as immersion, exercise and extreme temperatures, the heart may not be able to meet the demands of cardiac muscle. Hypertrophic disease also increases the risk of irregular heartbeats (arrhythmia), which may lead to heart failure or unstable heart rhythms. Hypertrophic ventricles are also less able to accommodate significant fluid shifts. Valve repair can require lifelong anticoagulant therapy, although this is more common with the aortic and mitral valves. Although the use of anticoagulants alone is not necessarily an absolute disqualifier from recreational diving, it should factor into an overall decision about one’s medical fitness to dive. It is important to seek medical evaluation prior to diving, and it would be prudent to consult a cardiologist, who may order a cardiovascular stress test or other testing to determine cardiac function and your ability to perform at the higher levels of activity needed for diving. If you have additional questions, call the DAN Medical Information Line at +1-919-684-2948. AD — Payal Razdan, MPH, EMT, and Nicholas Bird, M.D., MMM DIVING AS IT SHOULD BE! Experience the best diving the Turks & Caicos Islands have to offer. 1-800-234-7768 www.diveprovo.com ALERTDIVER.COM | 59
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