Administering a high concentration of oxygen to a weakly breathing, injured diver is the best treatment to increase the likelihood of a successful outcome.
This section explains how rescuers would normally give oxygen to divers in a scuba emergency situation - and how DAN® oxygen-delivery systems work.
Breathing pure oxygen increases the oxygenation of any hypoxic body tissues.
It also helps to flush out any dissolved nitrogen, or nitrogen present as a bubble formation.
But, to achieve maximum benefit, the concentration of inspired oxygen should be as near to 100% as possible.
The reason is that 'one hundred percent' oxygen does not contain inert gases - especially nitrogen.
As a result, all dive operations should carry suitable emergency oxygen equipment, and having an appropriately trained and qualified PADI Emergency Oxygen Provider at the dive site is highly recommended.
In an ideal world, all divers should have access to oxygen if it's needed after a dive. For maximum benefit, oxygen breathing should begin as soon as possible for scuba diving injuries, especially lung overexpansion and DCS.
What if only a limited supply of oxygen is available? In this case, it should be given in high concentrations from the time that the injury is recognised and it should continue until the supply of oxygen is exhausted.
Sufficient supply should be available for the anticipated transport time that it takes to evacuate the victim from the dive site to an appropriate medical facility, such as the nearest hospital.
It's also important not to stop giving oxygen too soon. Even if the initial symptoms start to disappear after starting oxygen first aid, they can reappear later and they are likely to worsen. You can contact the DAN hotline for advice about providing oxygen to an injured diver.
Most modern systems are designed for conscious and unconscious victims. But, portable oxygen units specifically manufactured for the treatment of diving injuries are limited.
To help maximise the benefits in diving injuries and more easily achieve 100% oxygen, a demand delivery system should be used - whenever possible.
A demand valve system with a tight-sealing oronasal mask can deliver near 100% oxygen extremely efficiently to a conscious and unconscious diver if they are breathing slowly and strongly enough to trigger the demand valve effectively.
What about a breathing, injured diver who cannot use a demand valve? In this case, they can breathe high oxygen concentrations via a non rebreather mask. It would have a flow rate around fifteen (15) litres per minute - as long as the reservoir bag doesn't run empty.
Plus, a non-breathing diver can be ventilated with relative ease and safety using a resuscitation mask attached to an oxygen outlet with a flow rate of ten (10) to fifteen (15) litres per minute (lpm).
Pro Tip: The Divers Alert Network (DAN) has been instrumental in the development of oxygen delivery units that offer a simple, safe, and efficient means of providing oxygen to injured divers.
Continue giving oxygen until the supply is depleted. Interrupt temporarily if the diver vomits, regurgitates, has a seizure, or has difficulty breathing from the equipment.
But, resume oxygen provision as soon as possible - and never leave an injured diver or oxygen equipment unattended.
Using a Resuscitation Mask with a Non-breathing Diver
When managing a diving incident, it is important to know how different oxygen-delivery systems function and which mask to use.
Thus, there are three ways scuba divers can deliver oxygen to an injured diver. So, for a weakly breathing diver, you would normally provide oxygen using a nonrebreather mask.
In general, rescuers use the oronasal mask because it is versatile and effective. For example, a breathing, injured diver would usually receive a high fraction of oxygen.
Plus, you can use them with default oxygen regulators (e.g. demand valve oxygen units) or with manually triggered ventilators (MTVs).
Here's the thing:
The air-cushioning at the edge of oronasal masks adapt to different face shapes. Plus, you can tighten the elastic straps to help you get a good seal. The oxygen inlet allows for the administration of a supplemental oxygen supply (e.g. when ventilating a non breathing diver).
You can reuse an oronasal mask. But, you should replace the one-way valve and keep it clean.
The unit can deliver up to twenty (20) minutes of oxygen at a flow rate of twelve (12) litres per minute (lpm).
Pro Tip: Always use proper hand positioning at the perimeter (e.g. two hands to create an effective seal). A breathing, responsive, diver may feel more comfortable holding the mask in place by themselves.
Some distressed injured divers will find it difficult to activate a demand valve. In this case, a nonrebreather mask may be the best available option for providing oxygen first aid.
But, non rebreather masks are single-use only. The attached reservoir bag captures the oxygen flow into the mask and delivers a "continuous" supply. Nonetheless, a non rebreather mask:
It's important to adjust the nosepiece and to secure the elastic strap. But, because a nonrebreather mask will use a continuous flow of oxygen, it is going to exhaust the supply faster than other oxygen delivery systems.
The use of a bag valve mask (BVM) is only for a diver who is unable to breathe by themselves. Thus, they are single-use devices and need disposing after using them to provide ventilations.
Rescuers tend to find it less tiring than delivering rescue breaths through a pocket mask. Plus, most BVMs have a flexible tube that you can connect to the continuous-flow outlet of an oxygen delivery unit. Having the reservoir bag means they can deliver high concentrations of oxygen.
This part is important:
It usually needs two rescuers to operate a bag valve mask. One to maintain a good mask seal and maintain an open airway. The other needs to squeeze the bulb and deliver the ventilations.
Even so, the technique used by each rescuer will affect the concentration of oxygen delivered. You need to avoid gas leaks by maintaining the seal. In most cases, an injured diver will not be able to secure the bag mask to their own face.
The DAN® 'Emergency Oxygen for Scuba Diving Injuries course' provides divers with knowledge and skills to safely administer oxygen to injured divers.
Pro Tip: The short tutorial video [1:05 seconds] presented by DAN Southern Africa explains how to set up a basic oxygen first aid kit with a demand valve assembly.