title: Noninvasive assessment of asthma severity using pulse oximeter plethysmograph estimate of pulsus paradoxus physiology.
abstract: BACKGROUND
  Pulsus paradoxus estimated by dynamic change in area under the oximeter plethysmograph waveform (PEP) might provide a measure of acute asthma severity. Our primary objective was to determine how well PEP correlates with forced expiratory volume in 1-second (%FEV1) (criterion validity) and change of %FEV1 (responsiveness) during treatment in pediatric patients with acute asthma exacerbations.
  
  
  METHODS
  We prospectively studied subjects 5 to 17 years of age with asthma exacerbations. PEP, %FEV1, airway resistance and accessory muscle use were recorded at baseline and at 2 and 4 hours after initiation of corticosteroid and bronchodilator treatments. Statistical associations were tested with Pearson or Spearman rank correlations, logistic regression using generalized estimating equations, or Wilcoxon rank sum tests.
  
  
  RESULTS
  We studied 219 subjects (median age 9 years; male 62%; African-American 56%). Correlation of PEP with %FEV1 demonstrated criterion validity (r = - 0.44, 95% confidence interval [CI], - 0.56 to - 0.30) and responsiveness at 2 hours (r = - 0.31, 95% CI, - 0.50 to - 0.09) and 4 hours (r = - 0.38, 95% CI, - 0.62 to - 0.07). PEP also correlated with airway resistance at baseline (r = 0.28 for ages 5 to 10; r = 0.45 for ages 10 to 17), but not with change over time. PEP was associated with accessory muscle use (OR 1.16, 95% CI, 1.11 to 1.21, P < 0.0001).
  
  
  CONCLUSIONS
  PEP demonstrates criterion validity and responsiveness in correlations with %FEV1. PEP correlates with airway resistance at baseline and is associated with accessory muscle use at baseline and at 2 and 4 hours after initiation of treatment. Incorporation of this technology into contemporary pulse oximeters may provide clinicians improved parameters with which to make clinical assessments of asthma severity and response to treatment, particularly in patients who cannot perform spirometry because of young age or severity of illness. It might also allow for earlier recognition and improved management of other disorders leading to elevated pulsus paradoxus.
authors.affiliation: Departments of Pediatrics and Emergency Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA. don.arnold@vanderbilt.edu
authors.forename: Donald H
authors.initials: DH
authors.lastname: Arnold
authors.forename: Cathy A
authors.initials: CA
authors.lastname: Jenkins
authors.forename: Tina V
authors.initials: TV
authors.lastname: Hartert
mesh_terms: D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000403:Airway Resistance / Q000502:physiology; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology*; D001993:Bronchodilator Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D016015:Logistic Models; D008297:Male; D008962:Models, Theoretical; D017063:Outcome Assessment, Health Care; D010092:Oximetry / Q000379:methods*; D010991:Plethysmography / Q000379:methods*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012132:Respiratory Muscles / Q000503:physiopathology; D012720:Severity of Illness Index; D013997:Time Factors
chemical_list: D000305:Adrenal Cortex Hormones; D001993:Bronchodilator Agents