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AD 2016 Q4

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.


DIVE SLATE PATENT FORAMEN OVALE AND FITNESS TO DIVE DIVE INTO THE BLUE With our world renowned dive crew; explore wrecks, reefs and marine life. Tel: (242) 373-1244 Freeport, Grand Bahama Near The Port Lucaya Marketplace unexso @unexsobahamas by venous blood bypass the pulmonary filter, enter arterial circulation and block blood flow in terminal vessels (embolism), which results in ischemic injury of tissue downstream of the obstruction. The most common form of embolism is caused by blood clots from peripheral veins passing through the PFO and causing a stroke. Paradoxical embolism may occur in divers with a PFO if the RLS occurs postdive when a lot of venous gas emboli (VGE) are present. Paradoxical embolism caused by VGE may manifest with symptoms of neurological (spinal, cerebral and vestibular) or cutaneous decompression sickness (DCS). The overall incidence of DCS in recreational divers is two to four per 10,000 dives, and the incidence of neurological DCS is less than one per 10,000 dives. In the presence of a PFO, however, the incidence of neurological DCS increases fourfold. While the average DCS risk for divers with a PFO seems low, for some individuals the risk may be greater than overall statistics predict. The main question regarding PFOs and diving is how to identify individuals who are likely at an increased risk of DCS and how to mitigate that risk. The workshop’s consensus guidelines provide some answers. WHO SHOULD BE TESTED FOR A PFO? The consensus maintains that no routine screening for PFOs in all divers is necessary. It recommends, however, that divers with a history of more than one episode of DCS with cerebral, spinal, vestibulocochlear or cutaneous manifestations should be tested for a PFO. On the other hand, divers with mild (other than cutaneous) DCS need not be tested. HOW TO TEST FOR A PFO Experts well practiced in the procedures should conduct the test. The most appropriate testing method is transthoracic echocardiogram (TTE) with “Divers should always remember that the main factor causing DCS is the dive exposure itself — the depth, time and ascent rate. With a significant exposure, anybody is at risk of DCS. Most people who get DCS do not have a PFO.” 26 | FALL 2016

ubble contrast and a provocative maneuver such as a Valsalva or sniffing. Other methods are suboptimal. INTERPRETATION OF FINDINGS A spontaneous shunt is a passage of contrast bubbles from the right atrium to the left atrium without a provocative maneuver. This is considered to very likely represent an increased risk for DCS in cases when dives result in a lot of VGE. A large provoked shunt means that a lot of VGE are passing through after a Valsalva maneuver or sniffing. It is likely to open with any kind of straining and is recognized as a risk factor for the previously listed forms of DCS. The presence of smaller shunts is associated with lower risk that should be evaluated on a case-bycase basis. It is important to note that the detection of a PFO in divers who suffered an episode of DCS is not proof that the PFO caused that specific episode of DCS. RISK MITIGATION Divers with a diagnosed PFO that’s likely to be associated with increased risk of DCS should consult a dive physician and consider options that best suit their needs and diving styles with a solid understanding of the risks and benefits of each option. The options are as follows: 1. Stop diving. 2. Dive more conservatively to reduce occurrence of VGE, and do not strain after diving to avoid opening the PFO and provoking RLS. 3. Close the PFO. Conservative diving includes strategies to reduce the risk of significant venous bubbles postdive and of shunting bubbles through the PFO. Since there is significant variability in VGE occurrence among divers and in the same diver over time, discuss options with a dive medicine expert before making any decision. For more details about conservative diving, see Diving. The closure of a PFO may reduce the risk of DCS, but it is not a guarantee that DCS will not occur in the future. Deep and long dives may cause DCS without VGE passing to the arterial side. Even in the absence of a PFO, VGE may pass to the arterial side through shunts within the lungs that tend to open with exercise, hypoxia and beta adrenergic stimulation and close with hyperemia. RETURN TO DIVING AFTER A PFO CLOSURE Diving should not be resumed before full closure is confirmed with another contrast echocardiogram at least three months after the closure. Divers should not return to diving as long as there is a need to take potent antiplatelet medications. If the test at three months or more after closure shows complete closure and the diver is prescribed only aspirin or nothing for clotting prevention, diving can be resumed. Divers should always remember that the main factor causing DCS is the dive exposure itself — the depth, time and ascent rate. With a significant exposure, anybody is at risk of DCS. Most people who get DCS do not have a PFO. Divers with a complete closure of PFO may avoid DCS episodes that they may have had in the past, but if they engage in extreme diving, their risk of DCS will be commensurate. AD MOALBOAL Magic Islands Dive Resort 10 Boat Dives Breakfast Daily • Free WiFi from $991 ANDA BOHOL Magic Oceans Dive Resort 10 Boat Dives Breakfast Daily • Free WiFi from $1,057 PUERTO GALERA El Galleon Dive Resort Up to 4 Boat Dives Daily • Free WiFi from $914 LIVEABOARD Atlantis Azores Up to 5 Dives Daily All Meals • Local Beer + Wine from $3,495 PUERTO GALERA Atlantis Dive Resort Puerto Galera Up to 5 Dives Daily All Meals • Free WiFi from $1,528 DUMAGUETE Atmosphere Resort & Spa 10 Boat Dives • Breakfast Daily from $1,358 800-328-2288 All packages include 7 nights, airport transfers to hotels (excludes Atlantis Azores), taxes and service charges. Rates are per person, double occupancy as noted and subject to availability and standard terms and condition. Valid for varying dates. CSOT#2111993-40 • WSOT#603254369 • FSOT#38781 Beth Watson ALERTDIVER.COM | 27