For decades, parents and pediatricians have relied on humid air to relieve the barking cough and noisy breathing of croup, a common childhood condition that sometimes sends worried families to the emergency room. Now a new review of evidence suggests that the long relied-on remedy has little medical benefit.
"Typically you get people to run a hot bath or shower in the bathroom. Or you get them to boil a kettle in the room, or have hot water in the corner of the room," said lead reviewer Michael Moore, a family doctor at Three Swans Surgery in Salisbury, England. "That's the kind of first-aid advice that is often given at the point of first contact with a health care professional."
Moore's team searched the medical literature looking for evidence that that well-worn suggestion actually works. None of the trials evaluated humid air treatments given at home. But the review brings together data from three studies on 135 children with croup who were treated in the emergency room.
"We haven't shown any benefit from using the moisturized air in the emergency department, and there's no particular reason to think that it would work better at home," Moore said. But he added that it's possible that some benefit exists that the measures do not pick up, so the researchers recommend more research in community settings.
The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.
Croup is a set of symptoms that causes swelling in the upper part of the airway and affects the voice box. The condition usually is caused by a viral infection. Young children are especially susceptible to croup because the infants and toddlers have narrower airways than older children and adults.
Physicians rate the severity of croup by noting signs of labored breathing and poor oxygen intake. The croup score and health outcomes for the children treated with moist air were not significantly different than the scores for the patients who received no treatment, the review found.
"I think that probably the successes that were attributed to humidity in the past were due to the calming effect of the parent believing that they were doing something, the child taking deeper breaths, the child getting over the spasmodic element of the croup, and then just getting better," said Dennis Scolnik, an emergency room pediatrician at The Hospital for Sick Children/Toronto in Ontario, Canada.
"I think humidity probably wouldn't harm. But I think it's a false sense of security," Scolnik said.
The finding that moist air does not help croup should be no surprise to physicians who've been trained or kept up-to-date in the last five to eight years, Scolnik said. But he added that popular beliefs are hard to root out of medical practice and common use.
"It's probably going to take as much as a generation of doctors — and through that parents — 10, 15, 25 years to work its way out of the system. Most of our parents are going to come in and say 'Oh, you're not giving humidity, why not?'" Scolnik said.
Scolnik says he now suggests calming techniques that can be tried at home for mild croup. And he educates parents about the signs of severe illness that require a trip to the hospital.
"Bad is: they are a little bit drowsy, lethargic, pale, sucking in very hard with each breath, or the oxygen level is not good, or the sound is very marked. So for those kids we do have much more effective, known proven effective treatments."
For moderately severe croup, physicians use nebulized (given by mist) adrenaline — sometimes call epinephrine — to quickly to relieve symptoms. Steroids are often then prescribed to reduce inflammation of the vocal chords over several hours.
"I think what we are saying is that there's no real place for moist air in the emergency room as a treatment for croup. If you've got a child that's unwell enough for treatment you might as well go ahead with the definitive treatment," Moore said.