Physostigmine did not significantly ( P > 0.46 ) reduce the total number of ventilatory arrhythmias on either room air or O2 ( 13.4 18.8 events/h [ mean SEM ] , 95 % confidence interval [ CI ] = -9.9 to 62.7 ; and 6.2 8.0 , 95 % CI = -3.1 to 28.7 , respectively ) .