Reduced pain scores in a pilot clinical trial of inhaled nitric oxide (NO). Visual analog pain scores are shown over the first 6 hours of emergency department treatment of vaso-occlusive pain crisis in 10 children with sickle cell disease treated with inhaled NO 80 ppm for the first 4 hours, compared to 10 treated with placebo gas. The reduction in pain score in the treatment group is significant by repeated measures analysis of variance (P = .02).¹⁷