Hypercapnia also occurs when the breathing gas is contaminated with carbon dioxide, or respiratory gas exchange cannot keep up with the metabolic production of carbon dioxide, which can occur when gas density limits ventilation at high ambient pressures.In severe hypercapnia (generally 
  
    
      
        
          
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   greater than 10 kPa or 75 mmHg), symptomatology progresses to disorientation, panic, hyperventilation, convulsions, unconsciousness, and eventually death.
"Fountains syndrome: mental retardation, sensorineural deafness, skeletal abnormalities, and coarse face with full lips". J Med Genet. 26 (11): 722–724. doi:10.1136/jmg.26.11.722. PMC 1015742. PMID 2585470. Fryns JP, Dereymaeker A, Hoefnagels M, Van den Berghe H (1987). "Mental retardation, deafness, skeletal abnormalities, and coarse face with full lips: confirmation of the Fountain syndrome". Am J Med Genet. 26 (3): 551–555. doi:10.1002/ajmg.1320260307. PMID 3565469. Dunkle Mary (1996). "Fountain Syndrome". NORD. Retrieved 26 April 2012. "Fountain syndrome". Ailments.com. 2000. Retrieved 29 April 2012. "Childrens Health:Fountain syndrome". WebMD. 2011. Retrieved 30 April 2012. External links

Online Mendelian Inheritance in Man (OMIM): 229120