title: Assessment of acute asthma severity in the ED: are heart and respiratory rates relevant?
abstract: BACKGROUND
  Assessment of acute asthma severity in the emergency department (ED) determines the appropriate initial therapy. The aim of this study was to evaluate the usefulness of heart and respiratory rates as determinants of severity of asthma exacerbations.
  
  
  METHODS
  It was a pooled analysis of individual patient data from different controlled clinical trials performed over a 9-year period. The sample was characterized by patients with a diagnosis of asthma, age 18 to 50 years, and a forced expiratory volume in the first second (FEV1) or a peak expiratory flow less than or equal to 50% of predicted at ED presentation.
  
  
  RESULTS
  One thousand one hundred ninety-two severe acute asthmatics (age 33.9 ± 10.3 years and FEV1 = 27.4% ± 9.7%) were enrolled. Two-thirds of patients were categorized as having severe acute asthma (FEV1, 31%-50% of predicted) and the remaining third as life-threatening asthma (FEV1, ≤30% of predicted). There were no relationships between the intensity of airway obstruction as measured by the FEV1 and the degree of tachycardia (r = 0.05, P > .1) or tachypnea (r = 0.06, P > .1). Only 22% and 19% of the patients, respectively, met the heart rate and respiratory rate requirements for acute severe asthma (≥120/min and ≥25/min, respectively). In contrast to FEV1 and arterial oxygen saturation, baseline heart and respiratory rates did not predict admissions of patients at the end of treatment.
  
  
  CONCLUSIONS
  This pooled analysis suggests a poor performance of heart and respiratory rates as determinants of acute asthma severity in the ED.
authors.affiliation: Departamento de Emergencia, Hospital Central de las Fuerzas Armadas, Av 8 de Octubre 3020, Montevideo 11300, Uruguay. Electronic address: gustavo.javier.rodrigo@gmail.com.
authors.forename: Gustavo J
authors.initials: GJ
authors.lastname: Rodrigo
authors.affiliation: Unidad de Medicina Respiratoria, Hospital de Niños "O Allassia", Santa Fe, Argentina. Electronic address: hugoneffen@arnet.com.ar.
authors.forename: Hugo
authors.initials: H
authors.lastname: Neffen
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000175:diagnosis*; D004636:Emergency Service, Hospital; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D056152:Respiratory Rate; D012189:Retrospective Studies; D012720:Severity of Illness Index; D055815:Young Adult