Scuba Geek

Research suggests Maximum Ascent Rate should be 9 m per min July 13, 2006

Posted by Andy Carroll in : Decompression , trackback

Researchers are recommending that the maximum ascent rate be reduced to 9 mtrs per minutes after a study which examined brain lesions in scuba divers. There theory is that ascent rates above that rate are releated to lesions they found in the nervous system.

Of course, we should already be ascending at speeds below 9 mtrs per min, and we should slow this ascent rate the nearer we get to the surface. This post at divester is a reminder why.

Here’s some info from the Abstract;

We studied 30 scuba divers (instructors) without any clinical symptoms. For all of them, we carried out a clinical examination with fatty body mass determination and we questioned them about their diving habits. A brain Magnetic Resonance imaging (MRI), an assessment of maximal oxygen uptake, glycemia, triglyceridemia, and cholesterolemia were systematically carried out. Cerebral spots of high intensity were found at 33 % in the scuba diving group and 30 % in the control group. In the diving group, abnormalities were related to unsafe scuba-diving or metabolic abnormalities. In our study, we did not find a significant relationship between the lesions of the central nervous system, and the age, depth of the dives, number of dives, and ergometric performances (maximal oxygen uptake, V.O (2max), serum level of blood lactate). Nevertheless, we found a significant relationship between the lesions of the central nervous system and ascent rate faster than 10 meters per minute (r = 0.57; p = 0.003) or presence of high level of cholesterolemia (r = 0.6; p = 0.001). We found concordant results using the Cochran’s Test: meaningful link between the number of brain lesions and the speed of decompression (Uexp = 14