title: End-tidal pCO2 in blood phobics during viewing of emotion- and disease-related films.
abstract: OBJECTIVE
  Many patients with blood, injection, and injury (BII) phobia respond to specific stimuli with vasovagal dysregulation and fainting. However, little is known about the role of hyperventilation in the distress of these patients. Hyperventilation, defined by subnormal arterial pCO2 levels, induces anxiety and may promote the development of fainting. We studied end-tidal pCO2 in 12 patients with BII phobia and 14 nonanxious controls during presentation of emotional films.
  
  
  METHODS
  Ten film clips were shown, two in each of 5 categories: pleasant, unpleasant, neutral, BII-related (surgery), and asthma-related (portraying labored breathing). For each subject, two subsets were created, each containing one clip from each category. For one subset, the instruction was simply to view the film, and for the other subset, to view the film while tensing the leg muscles. PCO2, heart rate, blood pressure, and leg electromyogram were recorded continuously during viewing, and self-report of symptoms and emotion was collected after each film.
  
  
  RESULTS
  Patients reported the greatest anxiety and disgust during surgery films. PCO2 was relatively stable throughout all categories except surgery films, during which minima were below 30 mm Hg, indicating significant hypocapnia. Cardiovascular variables suggested biphasic patterns in two patients with BII phobia. These patients, together with one additional patient and one control who were close to fainting after or during one surgery film, also showed a marked fall in pCO2) Leg muscle tension raised heart rate and systolic blood pressure for all films, but was not related to near-fainting or endurance in surgery film viewing.
  
  
  CONCLUSIONS
  Hyperventilation is part of the fear response of patients with BII phobia, but was transitory in experimental fear induction using surgery films. Its role in real-life exposure and fainting deserves further study.
authors.affiliation: Psychological Institute III, University of Hamburg, Hamburg, Germany. thomas.ritz@uni-hamburg.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Ritz
authors.forename: Frank H
authors.initials: FH
authors.lastname: Wilhelm
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Gerlach
authors.forename: Antje
authors.initials: A
authors.lastname: Kullowatz
authors.forename: Walton T
authors.initials: WT
authors.lastname: Roth
mesh_terms: D000328:Adult; D001249:Asthma / Q000523:psychology; D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis; D005239:Fear / Q000502:physiology* / Q000523:psychology; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009040:Motion Pictures; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D010698:Phobic Disorders / Q000150:complications / Q000503:physiopathology*; D012129:Respiratory Function Tests; D013514:Surgical Procedures, Operative / Q000523:psychology*
chemical_list: D002245:Carbon Dioxide