The baseline PaCO2 value of patients receiving an airway was not different from that of patients without an airway ( median [ 10th-90th quantile ] = 56.0 mm Hg [ 46.0-68 .4 ] vs 54.1 mm Hg [ 45.6-65 .6 ] , respectively ; P = 0.33 ; 95 % CI for location shift = -2.30 to 7.20 ) .