The consensus on the ideal posture for an injured diver has changed over the years and, unfortunately, many training materials for emergency medical technicians do not reflect these trends.
The following observations challenge the advice to place an injured diver in the Trendelenburg position:
- It is often difficult to distinguish Cerebral Arterial Gas Embolism (CAGE) from cerebral Decompression Sickness (DCS);
- Significant Arterial Gas Embolism (AGE) probably occurs in DCS by arterialization of venous bubbles. A head-down position increases venous return;
- In the smaller vessels, bubbles trapped in circulation will travel with blood flow without regard to posture;
- A prolonged head-down position increases cephalic venous volumes and compromises subsequent middle ear equalization, necessary in recompression therapy;
- The Trendelenburg position limits resuscitation;
- Studies show that the recovery of brain function is slower in those positioned head-down than those horizontal (Dutka 1990).
In summary, according to DAN’s Senior Medical Advisor, Dr. Richard Moon, there may be benefit in a transient head-down posture for divers with arterial bubbles, but the balance of opinion and data favors a horizontal position. If the diver is unconscious or vomiting, or if the diver's upper airway is compromised, place them laterally recumbent, either left or right, so that the airway can be effectively managed. Divers who are experiencing neurological symptoms of decompression illness must not be allowed to sit up until inside a recompression chamber.