It has been difficult to show whether implementing a rapid response system (RRS) is effective in reducing important patient outcomes of hospital mortality or cardiopulmonary arrest (CA).1 Part of the problem has been that these are rare events in a children’s hospital, and studies thus far have only involved comparisons with historical controls.2 Bonafide et al3 report an interesting approach to demonstrating RRS effectiveness. Using their newly created critical deterioration event (CDE) metric, they report a statistically significant adjusted reduction in CDE (by 62%) due to both less mechanical ventilation use (by 83%) and less vasopressor use (by 80%) after RRS implementation. Bonafide and colleagues suggest that CDE is a better metric to measure RRS effectiveness than the rare, catastrophic metrics of hospital mortality or CA.