title: Objective and subjective measures in recovery from a 35% carbon dioxide challenge.
abstract: OBJECTIVE
  Because hyperventilation, dyspnea, and a feeling of choking are often core features of a panic attack, respiration has been one of the most widely studied physiological parameters in panic disorder (PD) patients. A respiratory subgroup of PD, with distinct etiological pathways, has also been suggested. Investigation of the recovery phase following a respiratory challenge may be a reliable way to establish respiratory impairment in PD patients. The objective of the present study was to investigate the recovery phase from a 35% carbon dioxide challenge in PD patients and in healthy controls, and to test the hypothesis of a different respiratory pattern in patients, compared to control subjects.
  
  
  METHODS
  Eleven nonmedicated PD patients with or without agoraphobia, 11 medicated PD patients, and 11 control subjects took part in a 35% carbon dioxide and 65% oxygen inhalation challenge. Respiratory rate, partial pressure of carbon dioxide, heart rate, and blood pressure were recorded during the baseline phase (10 minutes) and the recovery phase (10 minutes). Visual Analogue Scale of Anxiety and Panic Symptom List scores were collected pre- and post-challenge.
  
  
  RESULTS
  Nonmedicated patients had increased variability in respiratory rate and partial pressure of carbon dioxide during recovery, compared with control subjects and medicated PD patients. Also, PD patients tended to have higher heart rates and to need more time to recover from the challenge than control subjects.
  
  
  CONCLUSIONS
  Results suggest that PD patients have less effective homeostatic control after their physiological equilibrium has been disrupted by a respiratory stressor.
authors.affiliation: Academic Anxiety Center, Mondriaan Zorggroep, School of Mental Health and Neurosciences, Maastricht University, Maastricht, The Netherlands.
authors.forename: Valentina
authors.initials: V
authors.lastname: Niccolai
authors.forename: Marlies A
authors.initials: MA
authors.lastname: van Duinen
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Griez
mesh_terms: D000328:Adult; D000368:Aged; D002245:Carbon Dioxide; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000627:therapeutic use*; D016584:Panic Disorder / Q000175:diagnosis* / Q000523:psychology / Q000628:therapy*; D020127:Recovery of Function
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen