Acetazolamide increased CTO and Spo2 at 2,590 m by mean values of 2 % ( 95 % CI , 0 % -4 % ) and 2 % ( 95 % CI , 1 % -3 % ) , respectively , and reduced the apnea/hypopnea index by 23.4 / h ( 95 % CI , 14.0-32 .8 / h ) ( P < .05 , all changes ) .