RESULTS	Clinical signs of respiratory depression included an increase in supplemental oxygen use in 25 of the 74 propofol patients and 31 of the 71 propofol/alfentanil patients ( effect size 9.9 % , 95 % CI = -5.9 % to 25.7 % ) , the use of bag-valve mask apparatus in seven patients in the propofol group and 12 in the propofol/alfentanil group ( effect size = 5.6 % , 95 % CI = -3.5 % to 18.4 % ) , airway repositioning in 13 propofol patients and 20 propofol/alfentanil patients ( effect size = 10.6 % , 95 % CI = -3.0 % to 24.2 % ) , and stimulation to induce breathing in 11 propofol patients and 20 propofol/alfentanil patients ( effect size = 13.3 % , 95 % CI = 0.1 % to 26.5 % ) .\