The Scuba Dive Ascent
Reduce the Risk of an Air Embolism or the Bends While Ascending
Care needs to be taken when ascending to the surface, as this is the most dangerous time during a scuba dive. How to manage both an emergency and normal ascent.
The ascent is the most important part of any scuba dive. Statistics, safety reports and general diving practices show that the ascent is the time when most diving accidents occur.
The Bends
Two of the major hazards in diving are the Bends and an air embolism, both directly associated with breathing compressed air at depth and the ascent. The Bends occurs when nitrogen absorbed into the tissues during a dive is released too quickly into the blood stream when the body is de-pressurised.
The casual diver usually says “I don't have to worry. The Bends only occurs on deep dives”. Ascending too fast can cause a minor case of the Bends. Simply running out of air and not relying on a buddy’s air can lead to a mad dash for the surface which can mean the nitrogen doesn’t have enough time to absorb back into the bloodstream.
Air Embolism
The other major hazard of the ascent is an air embolism, which occurs when air expanding in the lungs during the ascent bursts the lungs. This is a direct result of holding the breath on ascent. It can be from panic or again when a diver runs out of air and attempts a free ascent.
A Safe Ascent
So how to make the ascent safer? First off, never get in the situation where a free ascent is needed. Simply, never run out of air. Sounds simple but all divers at some time are guilty of this problem. Reducing this risk should be part of the dive plan.
Divers should keep close together and be aware of the location of the buddy's alternate air supply. Divers should be prepared to buddy-breathe at any time. Divers who go through air quickly should inform the divemaster and buddy before the dive. These are all things to be aware of that will reduce the need to make that free ascent, or uncontrolled panic rush, to the surface.
With a secure air supply, and even on a shallow dive, take the ascent slowly. Stop around the ten to twenty foot mark for a minute or three. On a boat dive, wait ten feet below the surface while the previous divers exit the water. This can be easier than fighting the swells on the surface, but don't wait directly below the diver as they could fall back in or drop something.
An emergency ascent should be slow and careful. Air in the lungs expands on the ascent and should be enough to get a diver to the surface.
Enjoyable Ascent
Some great times can be had hovering just below the boat at the end of a dive surveying the scene below. On a reef with good visibility it can be spectacular. Fish come back to explore the area divers have passed. Or there might be a couple of divers still far below, their lazy bubbles slowly meandering to the surface.
On a shore dive during the ascent, poke around the ten or twenty foot mark before exiting. There is usually something to find! Sinkers for making into weights, dive knives that other divers have lost. Or even an oyster bed ripe for the picking.
All these activities slow the ascent that small fraction. And that small fraction is so important. If there is one more law, rule or maxim for scuba diving it should read “beware the ascent.”
