After IRB approval, imaging of children with neuroblastoma from the ages of 1 month to 10 years old was analyzed. Prior to the protocol change, we used an intravenous propofol infusion (150–250 mcg/kg/min) with nasal cannula. Following the protocol change, children’s airway was supported with a laryngeal mask airway (LMA) or an anesthesia mask with a strap connected to a Jackson-Rees circuit (Fig. 1). Air blender (FiO2 < 30%) was used to prevent absorption atelectasis . Higher propofol infusion rate (250–300 mcg/kg/min) was used to allow children to tolerate in situ airway. Air flow and AP valve in the circuit were adjusted to maintain CPAP (5 to 10 cmH2O) . We titrated infusion rate according to respiratory parameter (SpO2 > 95%) and hemodynamical parameter (mean arterial pressure above 40 mmHg).
A single, blinded pediatric radiologist graded the severity of atelectasis according to previously described scale  and determined whether there was significant atelectasis to confound image quality or not.
Statistics were calculated using Mcnemar’s test due to paired observations from children receiving imaging both pre- and post-protocol implementation.