Cold air keeps croup at bay, and now a study proves it

Cold winter air really does improve croup symptoms, at least temporarily. Inspired by anecdotal reports, researchers in Sweden investigated the effects of breathing in cold air in pediatric patients who presented with croup. The study, published in Pediatrics, investigated whether a 30-minute exposure to outdoor cold air (temperatures of -10°C or colder) might improve mild to moderate croup symptoms before the onset of action of steroids. “Exposure to cold air is often reported beneficial in daily practice by parents, but documented evidence to support this measure lacks,” the researchers wrote. The study was conducted in young patients with croup presenting to a pediatric emergency department (ED) during cold days and nights when outdoor air temperatures were -10°C or colder. Those cold days also correlated with when parainfluenza viruses and other viruses associated with causing croup were prevalent. The study was conducted from Nov. 1, 2016, to May 31, 2021. All children aged three months to 10 years presenting to a tertiary pediatric ED in Geneva, Switzerland were eligible to participate if the outdoor air was cold enough, and they were diagnosed with croup using the Westley Croup Score (WCS). Scores needed to be two or higher and patients needed standard treatment with a single-dose of oral dexamethasone. A total of 118 children met the criteria, and were randomized into one of two groups: one with a cold-air intervention, or to a control group who stayed in the ED with normal indoor air temperatures. There were 59 children in each group. They had a mean age of 32 months, and 36 (31%) participants were female. Once the children were triaged and diagnosed, they were given treatment with dexamethasone then randomly assigned to either wait outside for 30 minutes in sight of the triage desk, or stay indoors. Blankets were made available to the outdoor groups. At the half hour mark, patients in the intervention group were brought back indoors and assessed immediately. The primary outcome was clinical improvement with a decrease in WCS score of two points or more. “The number of patients showing a reduction of at least two points in WCS at 30 minutes after triage was significantly higher in patients allocated to the outdoor cold air exposure group compared with patients who remained at indoor room temperature,” the study said. Patients who had initially presented with moderate croup got the most benefit from breathing in the cold air. However, the benefit was short-lived. An hour after coming back indoors, the effect of the intervention no longer differed between the warm and cold air groups. Follow-up visits a week after the ED visit found that the number of children who no longer had symptoms was slightly higher in the intervention group, but this finding was not statistically significant. Cold air can affect different parts of the respiratory system differently, the authors said. “Exposure to cold air has been shown to cause inflammation of the lower respiratory tract and to trigger bronchial hyperresponsiveness, bronchoconstriction, and asthma, (but) the effects of cold air at the laryngeal level are more uncertain,” the study said. The authors stated that “More studies are needed to assess the efficacy of cold air exposure.” But are Canadian doctors familiar with the beneficial effects of cold air on croup patients? “Yes, of course,” said Dr. David Wyatt Johnson, a pediatrician and professor of medicine at the University of Calgary. “All clinicians who routinely care for children with croup are aware that exposure to cold air seems to substantially decrease children's respiratory distress.” He was not part of the study but stated that it “provides the first rigorously controlled experimental evidence in humans proving that cold air decreases respiratory distress.” Previous evidence was in animal studies. While it is difficult to prove exactly why many specific treatments work, “in the case of croup and cold air, we're pretty certain,” he told the Medical Post. “We know that croup is caused by swelling of viral-infected tissue that makes up the upper airway. Breathing in cold air causes the small blood vessels in this upper airway tissue to constrict resulting in decreased upper airway swelling. This, in turn, allows the child to breath more easily.” As such, doctors, as well as parents, can take advantage of cold air. And while it may be temporary, short-term relief can help. “Although this is not really new, it’s important advice to provide to parents. Existing parent education pamphlets advise parents, at discharge from hospital or the emergency department, if their child has a re-occurence of difficulties breathing at home, to bundle them up warmly and take them out into the cold air. Breathing problems typically improve within minutes of being outside.”

Cold air keeps croup at bay, and now a study proves it

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