that is obvious to the diver or examiner Weakness or paralysis of limbs that is obvious to the diver or examiner Bladder dysfunction (inability to pass urine) Sphincter (bowel) dysfunction Loss of coordination or control in the limbs Shortness of breath


NOTE: This classification of DCI symptoms and signs is intended to aid selection of subjects for IWR. It is not intended as a guide to selection of divers for referral to definitive care. To be clear, all divers with symptoms in any of the tiers should be discussed with a diving medicine expert as soon as possible.


Appendix II: Airway Protection Protection of the symptomatic diver’s airway is of paramount importance. The workshop consensus recommendation of a maximum oxygen partial pressure of 1.6 ATA minimizes but does NOT REMOVE the risk of seizure. The consequences of aspiration underwater are potentially life threatening. Options to mitigate this risk of aspiration are discussed here-in. All previous IWR protocols


require or strongly advocate the use of a full face mask (FFM), primarily to mitigate the consequences of a hyperoxia-induced seizure underwater. These previous protocols also incorporate breathing near-100% oxygen at


depths in excess of 6m/20 feet, where the inspired oxygen partial pressure is in excess of 1.6 bar/atm. As advantageous as a FFM may be in the event of a seizure underwater (for reducing the probability of drowning), the use of a FFM also imposes some difficulty (and risk) for divers who are not trained in their use; particularly in terms of diver comfort level, proper fit and sealing, and (depending on the specific style of mask) techniques for clearing water from the mask and performing the Valsalva maneuver. In the context of these recommendations, a maximum depth of 6m is advocated for IWR (a depth at which near-100% oxygen is commonly breathed by technical divers for decompression). At 6M, the incidence of hyperoxia- induced seizure is extremely low and the potential net benefits of using a FFM depend on the degree of training and familiarity the afflicted diver already has with this equipment prior to attempting IWR. Therefore, a “gag strap” is recommended in cases where the symptomatic diver is not already trained in the proper use of a FFM, or when a FFM is not available. The purpose of the gag strap is


the same as the full face mask; to prevent loss of the mouthpiece / gas supply and to provide a degree of airway protection in the event of loss of consciousness. Although more controversial than a full face mask for this purpose, the gag strap is arguably supported by data. Gemp et al1[1] reported 54 underwater loss of consciousness


Advantages include: 1 The airway is maximally protected (not perfectly) from ambient water in the event of a seizure.


2 Should a seizure occur, the tender has more options for a controlled ascent.


3 Allows for communication with the symptomatic diver if appropriately wired.


4 Adds additional thermal protection. 5 Lessens jaw fatigue by not requiring a mouthpiece.


Disadvantages include: 1 Minimum cost of approximately 500-750 USD. 2 It may not be an adequate fit to the symptomatic diver’s face.


3 Optimal safe use requires training, including techniques on clearing, purging, and adjusting the usual five point strap system.


4 Vomitus may be difficult to clear, creating a second risk of aspiration.


5 The FFM may not be suitable for use with a rebreather.


events in military divers leading to only 3 fatal drownings. In this series there were 26 cases of CNS oxygen toxicity with seizures, with an 11.5% major complication rate: two deaths (caught under a barge) and one non- fatal moderate water aspiration. The use of the Drager-style gag strap with strap and lip sealing flange was used in all cases. Although this is an uncontrolled series, and notwithstanding the potential for other factors to influence outcome in the military setting, the unexpectedly high survival following these events suggests that gag straps are effective in most cases. Improvisation of gag straps by divers is not encouraged. However, a recent informal survey


of a few manufacturers by a former US Navy diver revealed a lack of familiarity with a regulator retention strap save for the ones that are available for specific rebreathers. It therefore does not appear that a purpose-built, commercially manufactured regulator retention strap would be readily available to divers, possibly encouraging improvisation, with mixed results. It has also been suggested that involuntary contraction of the masseter muscles during a grand mal seizure could result in damage to the mouthpiece, possibly leaving fragments in the mouth or causing a leak. It must be noted, however, that this study involved the use of the Drager gag strap which has several important design features that probably enhance efficacy. Similar straps can be purchased and are recommended.


FULL FACE MASK: THIS IS THE TRADITIONAL “BEST PRACTICE”


Judgment should be used when making the decision to use a Full Face Mask.


Regulator Retention Strap (“Gag Strap”) This consists of a strap around the head/neck attached to the second stage regulator and a rubberized flexible flange around the mouth, preventing loss of regulator and a barrier to water in the event of seizure.


Advantages include: 1 Less costs than a FFM estimate less than 100 USD. 2 Requires minimal training. 3 Quick to set up and implement. 4 Reduce jaw fatigue during long dives. 5 Acceptable effectiveness. (A published report (Gemp) demonstrated 3 deaths from 54 seizures).


Disadvantage include: 1 Not as protective of the airway as a FFM. 2 Properly designed devices are not widely available.


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