Use of high humidity does not improve symptoms of croup

For children with moderate to severe croup treated in the emergency department, use of high humidity did not improve symptoms more than low humidity or mist therapy, according to an article in the March 15 issue of JAMA: The Journal of the American Medical Association.

Viral croup is the most common cause of acute upper airway obstruction in children and is diagnosed in up to five percent of children younger than six years old; approximately one percent of these children are hospitalized, according to background information in the article. Symptoms of croup include a "seal-like" barking cough and difficulty breathing. Steam or humidity, thought to soothe the inflamed larynx and decrease the thickness of secretions, has long been used to treat croup. Despite the lack of scientific evidence for its efficacy, blow-by humidity (e.g., humidifiers), croup tents and face masks are still used.

Dennis Scolnik, M.B., Ch.B., and colleagues from the Hospital for Sick Children and University of Toronto, conducted a randomized, single-blind, controlled trial to determine whether humidity improved symptoms of moderate to severe croup in children. One hundred-forty children, aged three months to ten years, who were admitted to the emergency department were randomly treated with either 100 percent humidity (high humidity), 40 percent humidity (low humidity) via a nebulizer or blow-by humidity for 30 minutes.

"Our trial shows that, in children with moderate to severe croup, 100 percent humidity, even when delivered in water-particle size designed to deposit in the larynx, does not result in greater clinical improvement than either controlled delivery of 40 percent humidity (optimally delivered placebo) or humidity delivered using the blow-by method (commonly used placebo)," the researchers write. They also found no significant difference in changes in respiratory rate, heart rate or oxygen saturation at 30 or 60 minutes among the three groups.

"Our results suggest that the use of humidity in children with croup admitted to emergency departments is not warranted," the researchers write. "Humidity may actually have been found useful because of other factors associated with its use such as the comfort of being close to parents or the low temperature used for delivery in certain humidification devices."

http://jama.ama-assn.org/