title: Resting end-tidal CO2 and negative affectivity.
abstract: OBJECTIVE
  Dhokalia, Parsons, and Anderson (Psychosom Med 1998;60:33-37) found a positive correlation between a trait measure of negative affectivity (NA; neuroticism) and resting end-tidal fractional concentration of CO2 (FetCO2) (fractional-concentration of end-tidal carbon dioxide) in a nonclinical sample. This contrasts sharply with studies reporting a negative association of FetCO2 with state measures of NA and with studies reporting no or a negative relationship between FetCO2 and trait NA. In two studies we aimed to clarify this paradox.
  
  
  METHODS
  In the first study, 110 participants (83 women) completed the PANAS and a Checklist for Psychosomatic Symptoms in daily life. FetCO2 was measured noninvasively during 5 minutes via a nose cannula connected to a capnograph. In the second study, FetCO2 of high (N= 20, 10 men) and low (N= 20, 10 men) NA participants was sampled once with a nasal cannula and once while breathing through a mouthpiece for 6 minutes each during rest, completion of the NEO-PI-R questionnaire, and completion of a verbal knowledge test.
  
  
  RESULTS
  The first study found no association between trait NA and resting FetCO2 after partialling out the effects of gender, menstrual phase, and use of oral contraceptives. The second study showed that FetCO2 increased significantly in the high NA group only when the particpants filled out the questionnaires, regardless of its type.
  
  
  CONCLUSIONS
  Overall, no association between dispositional NA and cross-situational FetCO2 was observed. Apparently inconsistent findings may be caused by lack of control for hormonal status and mental load during testing.
authors.affiliation: Department of Psychology, University of Leuven, Belgium. Ilse.Vandiest@psy.kuleuven.ac.be
authors.forename: Ilse
authors.initials: I
authors.lastname: Van Diest
authors.forename: Sofie
authors.initials: S
authors.lastname: Vuerstaek
authors.forename: Inge
authors.initials: I
authors.lastname: Corne
authors.forename: Steven
authors.initials: S
authors.lastname: De Peuter
authors.forename: Stephan
authors.initials: S
authors.lastname: Devriese
authors.forename: Karel P
authors.initials: KP
authors.lastname: Van de Woestijne
authors.forename: Omer
authors.initials: O
authors.lastname: Van den Bergh
mesh_terms: D000293:Adolescent; D000328:Adult; D001007:Anxiety / Q000503:physiopathology*; D001944:Breath Tests / Q000295:instrumentation; D002245:Carbon Dioxide / Q000097:blood*; D003276:Contraceptives, Oral; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000209:etiology* / Q000523:psychology; D008297:Male; D008597:Menstrual Cycle; D011581:Psychological Tests; D011602:Psychophysiologic Disorders / Q000209:etiology / Q000503:physiopathology / Q000523:psychology; D013315:Stress, Psychological / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D013732:Test Anxiety Scale
chemical_list: D003276:Contraceptives, Oral; D002245:Carbon Dioxide