title: The panic disorder respiratory ratio: a dimensional approach to the respiratory subtype.
abstract: OBJECTIVE
  The respiratory ratio is a dimensional construct of the respiratory subtype of panic disorder (PD). The respiratory subtype has been correlated with an increased sensitivity to CO₂ inhalation, positive family history of PD and low comorbidity with depression. The objective of our study was to determine whether the respiratory ratio is correlated with CO₂-induced panic attacks and other clinical and demographic features.
  
  
  METHODS
  We examined 91 patients with PD and submitted them to a double-breath 35% CO₂ challenge test. The respiratory ratio was calculated based on the Diagnostic Symptom Questionnaire (DSQ) scores recorded in a diary in the days preceding the CO₂ challenge. The scores of the respiratory symptoms were summed and divided by the total DSQ score.
  
  
  RESULTS
  The respiratory ratio was correlated with CO₂ sensitivity, and there was a non-statistically significant trend towards a correlation with a family history of PD.
  
  
  CONCLUSIONS
  The positive correlation between the respiratory ratio and the anxiety elicited by the CO₂ inhalation indicates that the intensity of respiratory symptoms may be proportional to the sensitivity to carbon dioxide.
authors.affiliation: Laboratory of Panic and Respiration, Universidade Federal do Rio de Janeiro, Brazil . rafaelcrfreire@gmail.com
authors.forename: Rafael Christophe
authors.initials: RC
authors.lastname: Freire
authors.forename: Isabella
authors.initials: I
authors.lastname: Nascimento
authors.forename: Alexandre Martins
authors.initials: AM
authors.lastname: Valença
authors.forename: Fabiana Leão
authors.initials: FL
authors.lastname: Lopes
authors.forename: Marco André
authors.initials: MA
authors.lastname: Mezzasalma
authors.forename: Valfrido Leão de
authors.initials: VL
authors.lastname: Melo Neto
authors.forename: Walter Araujo
authors.initials: WA
authors.lastname: Zin
authors.forename: Antonio Egidio
authors.initials: AE
authors.lastname: Nardi
mesh_terms: D000293:Adolescent; D000328:Adult; D001008:Anxiety Disorders / Q000503:physiopathology; D002245:Carbon Dioxide / Q000502:physiology; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D016584:Panic Disorder / Q000503:physiopathology*; D011237:Predictive Value of Tests; D056152:Respiratory Rate / Q000502:physiology*; D017678:Sex Distribution; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide