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REVIEW OF OVERALL FUNCTION (updated at prototype review 10/20/08) It is important to understand that the Freediver's Recovery Vest (FRV) will NOT prevent freediver blackout (FB), nor is it designed to prevent FB. FB occurs when the level of oxygen in the brain decreases below the level necessary to support consciousness. (For a more complete description of FB see : http://www.freedive.net/SWB/vest1_lo_rez.pdf.) Only good diving practices, fitness and good judgment will prevent FB. FB may occur under the water during any phase of the freedive and it may also occur on the surface immediately after ascent. The FRV is designed to deliver the freediver, who has exceeded his self-set parameters, to the surface in a face-up position where recovery and rescue attempts will be more successful than if he had sunk to the bottom, which is where most victims of FB are found. It is important to understand that even if the victim (we'll call him that now) reaches the surface, there may well be serious consequences, for example continued airway obstruction due to laryngospasm (the vocal cords have slammed shut, shutting of any airway exchange), aspiration, and continued apnea due to sever hypoxia and cardiac arrest. Therefore, the diver returned to the surface may still suffer airway compromise and require immediate intervention from a rescuer to provide rescue breathing and eventually, the basics of CPR in order to avoid permanent injury or death. As with any product, there are limitations and warnings regarding it use. To use the FRV the diver sets both the maximum time, and separately, the maximum depth when he wants the vest mechanism to deploy and send him face-up toward the surface. In other words, the user sets the maximum time he wants to be underwater. Upon exceeding this maximal time, the vest will deploy its flotation bladder. Similarly, the diver will set the depth at which he wants the vest to inflate. As long as the diver’s profile remains within these settings, and the diver deactivates the vest on the surface in time, the vest remains inactive. The FRV is composed of four major components, the wrist unit, the back-mounted activation unit, the Swipe pad and the flotation vest. Using the wrist unit, the freediver sets the dive parameters and monitors the progress of his dive. The activation unit contains the electronic chips that also monitor the dive and activate two redundant valves, which release air from the integrated compressed air tank into the inflation bladder. It is retained within a pouch, which is connected to the inflation bladder and the waist belt. The flotation vest covers the activation unit and houses the inflation bladder—it’s streamlined and contains release snaps for donning and Velcro the streamline the inflation bladder. The external surface of the flotation vest is built from a durable material similar to that used in inflatable boats. It lies flat against the diver’s body and when it fills, air pressure forces out several layers of folded pleats, which provide for expansion. The pleats are brightly colored to signify to others that the vest has deployed, and extra pressure released through the over-pressure valve activates a whistle. Ironically, a significant number of freedivers who suffer FB do so at the surface, after the otherwise successful completion of a freedive. When the vest, using it’s electronic sensors, determines that the diver has reached the surface, it will then accept a disarming signal from the diver. Unless the vest is effectively disarmed by the diver at the surface (it will not accept disarming anywhere in the water column other than the surface), it will deploy when the time limit set by the diver is reached. Because it is possible for the diver who has recently surfaced to be confused or only partially aware and conscious, the diver may forget to deactivate. We expect that a significant number of freedivers will be surprised by vest inflation while on the surface due to their decreased—and unacknowledged—level of awareness, which caused them to fail to voluntarily disarm the device. While the freediver might initially interpret the vest deployment as a nuisance, it should be clear that this is a warning that he was perilously close to complete FB. The vest deployed because the maximal time was reached and the vest was not deactivated. Inflation in this instance should be a clear signal that the diver should alter his dive practices and/or receive further training. Upon surfacing, the diver must wait 10 seconds before the unit will accept a disarm swipe (The diver swipes his magnetized wrist band by the chest pad sensor equipped with a light that acknowledges receipt of a successful swipe.) He then has 5 seconds to successfully swipe his arm by the sensors in the chest pad. Even if the diver successfully disarms the vest after 10 seconds, he still may suffer surface blackout and he may also begin to sink back under the water. Therefore, after receiving a successful first swipe, the unit will reset another 20-second timer after which another swipe is required. In the circumstance of unconscious descent, the vest is designed to deploy within 15 seconds after surfacing or after the diver exceeds 10 feet deep. (These time and depth parameters are subject to change during the prototype testing phase.) After the first swipe, the diver who is alert and in no danger of SB, may override the need for the second swipe by pressing a series of 3 buttons on the wrist unit A deployed vest can be made ready for reuse by repacking the flotation bladder into the over-garment pouches and by recharging the integrated compressed-air cylinder, which supplies the air to fill the inflation bladder. The maximal service depth, with a fully charged air cylinder is 120 feet. The cylinder can be filled at a dive shop, but more conveniently for the freediver, directly from a standard 3,000 psi scuba tank. Should the charging scuba tank hold less than 3,000 psi, it will not provide protection at 120 feet, but it will calculate a more shallow depth where there may be sufficient pressure to provide adequate inflation. The electronics and sensors contained in the activation unit will measure the air pressure in the air cylinder and then will calculate the maximal dive depth that the freediver may set—up to 120 feet. In addition, the electronics constantly poll the inflation air cylinder and inform the user if there is inadequate compressed air to inflate the bladder at the diver’s selected depth. The wrist unit will monitor the elapsed time and depth of the dive and supply the water temperature. When the user approaches 10 feet of his maximum depth a warning buzzer will sound. When the user approaches the last 10 seconds of his dive, a numerical countdown preceding inflation will start. Freedivers may re-set the next dive’s parameters on the surface. The user may also use the large monitor to review his last 4,900 dives in graphical format. The diver may also annotate special dives for review later, for example when a record fish was taken or the dive was otherwise memorable. The user may also command inflation of the vest at any time by pressing a 3-button sequence on the wrist unit. The inflation unit in addition to providing the basic function of inflation of the flotation bladder, the electronics provides for the following:
The swipe pad, which appears at the diver’s mid-chest on the right lapel contains 3 electronic components: 1. magnetic sensors that detect a diver’s swipe. 2. An Infra-red transmitter/receiver for communication with the wrist unit. 3. A 3-color LED that directs light signals directly toward the diver who can view them at the bottom of their field-of-view from their mask. |
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Copyright 2008 Oceanic Safety Systems LLC |
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