The effects of hypercapnia

Thank you for the illuminating article by Johnny E. Brian MD about CARBON DIOXIDE, NARCOSIS AND DIVING ,sorry for my delayed response due to 7 hour time difference AND work obligation,however i will appriciate if you can help me inturpute AND understand better the paragraphs from this article, mainly the statement about " depressed respiratory response to elevation of CO2" did the study looks at it as a medical condition AND therefore in need of medical care OR is it a diving phisyologigcal condition beacuse of the conditions of these studies, they are less helpful in ...determining allowable exercise levels in technical AND cave diving, where exertion is less but over a longer period of time ... The depressed respiratory response to elevation of CO2 appears to vary greatly between individuals, with some divers being normal AND other having a very depressed CO2 response The primary cause for CO2 elevation during diving, then, is exertion coupled with increased gas density. Stress increases the metabolic rate AND can contribute to increased CO2 production. Rebreathing expired gas containing CO2 will also elevate PCO2. However, significant rebreathing seems unlikely with standard demand-valve scuba regulators, as they have minimal dead space