Lack of Benefit from Mist Therapy in Children with Croup

Abstract

Source: Neto GM, Kentab O, Klassen TP, et al. A randomized controlled trial of mist in the acute treatment of moderate croup. Acad Emerg Med. 2002;9:873–879.Humidified air is commonly recommended for home therapy of croup and is still used in many emergency departments. However, there is little proof that it works. These Canadian authors randomized children presenting with croup to the emergency department of the Children’s Hospital of Eastern Ontario into 2 groups. One group received humidified oxygen via a nebulizer and the other group received no mist. Children were enrolled if they had a syndrome consistent with croup (hoarseness, stridor, and barking cough) and had a croup score of 2 or more. The croup clinical scoring system was described in 1978 and has been shown to be valid and reliable and to accurately reflect a changing clinical exam.1 The score evaluates 5 clinical findings and has a range from zero (normal exam) to 14 (severe symptoms). Children were excluded if they had epiglottitis, chronic respiratory disease, tuberculosis, varicella or recent varicella exposure, oxygen saturation less than 92%, or asthma with wheezing at the time of the croup episode. All children received an oral dose of dexamethasone (6 mg/kg) at entry to the study. Inhaled epinephrine or budesonide were given by the treating physician as needed. During the 3- year study period, 71 children age 3 months to 6 years were enrolled with 35 (median age 18 months) assigned to the mist group and 36 (median age 22.5 months) to the no-mist group. Patient characteristics were similar at baseline including age, duration of symptoms, percent with asthma, and percent that used mist at home prior to the ED visit. Both groups had a median croup score of 4 at the beginning of the study. Measurements were taken every 30 minutes for a total of 2 hours, or until the croup score became less than 2. Both groups improved over time, with an average change from baseline in the croup score of −2.9 for the mist group compared to −2.6 for the no-mist group (P=.58). There was no difference between the 2 groups in the change from baseline in oxygen saturation, heart rate, or respiratory rate. In addition, at each 30-minute interval, physicians, research assistants and the parents rated the change in the patient’s condition and comfort level since arrival using a 15-point Likert scale. There were no differences in any of the observers’ global assessment of change scores between the 2 treatment groups.Mist therapy for children with croup has been a part of our armamentarium since the 19th century. Mist has been generated from croup kettles, croup tents, mist sticks, and face tents. Two prior studies have tried to assess the benefit of mist therapy.2,3 Both had small numbers of patients and one did not use a control group. Neither showed clinical benefits of nebulized water or humidified air. The current investigators conclude that mist therapy provides no significant benefit in children with moderate croup who present to the emergency department. Although some children were treated with epinephrine and budesonide delivered through a nebulizer in a mist-like condition, excluding these patients from the analysis did not change the results. It is unclear why the authors chose humidified oxygen to generate mist instead of humidified air. However, if oxygen made a difference, the advantage would have been to the mist group with either improvement in the clinical croup score or in oxygen saturation. Neither was found. It is unclear if mist therapy is helpful in patients with croup who are treated at home. Most home humidifiers produce droplets too large to reach the lower respiratory tract.4 Since 25 children in the study had already tried humidity at home, it is possible that these mist treatment failures diluted the groups so that no difference would be found even if one did exist. Since mist therapy did not cause any apparent harm, it will not be surprising to find this treatment still recommended to anxious parents as home therapy.We think it would be a mistake if mist therapy was completely dismissed on the basis of the scant evidence available. Croup is a syndrome, not a single disease. The most common forms are acute laryngotracheitis (ALT) and spasmodic croup (SC). ALT is associated with multiple viruses, and is usually a febrile illness associated with coughing throughout the day. SC is an afebrile illness characterized by nighttime cough over successive nights usually remitting during the day, and may reflect hypersensitivity or partial immunity caused by prior infection resulting in local airway edema.5 Before discarding cold mist we should assess its utility in groups of patients with well-defined croup syndromes and, if possible, etiologies. The common wisdom of centuries may not be…all wet!