title: Examining the latent class structure of CO2 hypersensitivity using time course trajectories of panic response systems.
abstract: OBJECTIVE
  Carbon dioxide (CO2) hypersensitivity is hypothesized to be a robust endophenotypic marker of panic spectrum vulnerability. The goal of the current study was to explore the latent class trajectories of three primary response systems theoretically associated with CO2 hypersensitivity: subjective anxiety, panic symptoms, and respiratory rate (fR).
  
  
  METHODS
  Participants (n = 376; 56% female) underwent a maintained 7.5% CO2 breathing task that included three phases: baseline, CO2 air breathing, and recovery. Growth mixture modeling was used to compare response classes (1…n) to identify the best-fit model for each marker. Panic correlates also were examined to determine class differences in panic vulnerability.
  
  
  RESULTS
  For subjective anxiety ratings, a three-class model was selected, with individuals in one class reporting an acute increase in anxiety during 7.5% CO2 breathing and a return to pre-CO2 levels during recovery. A second, smaller latent class was distinguished by elevated anxiety across all three phases. The third class reported low anxiety reported during room air, a mild increase in anxiety during 7.5% CO2 breathing, and a return to baseline during recovery. Latent class trajectories for fR yielded one class whereas panic symptom response yielded two classes.
  
  
  CONCLUSIONS
  This study examined CO2 hypersensitivity in one of the largest samples to date, but did not ascertain a general population sample thereby limiting generalizability. Moreover, a true resting baseline measure of fR was not measured.
  
  
  CONCLUSIONS
  Two classes potentially representing different risk pathways were observed. Implications of results will be discussed in the context of panic risk research.
authors.affiliation: Virginia Commonwealth University, Department of Psychiatry, Virginia Institute for Psychiatric and Behavioral Genetics, Richmond, VA, USA. Electronic address: rrobersonnay@vcu.edu.
authors.forename: Roxann
authors.initials: R
authors.lastname: Roberson-Nay
authors.affiliation: University of Virginia, Department of Psychology, Charlottesville, VA, USA.
authors.forename: Jessica R
authors.initials: JR
authors.lastname: Beadel
authors.affiliation: University of Virginia, Department of Psychology, Charlottesville, VA, USA.
authors.forename: Eugenia I
authors.initials: EI
authors.lastname: Gorlin
authors.affiliation: Baylor University, Department of Psychology and Neuroscience, Waco, TX, USA.
authors.forename: Shawn J
authors.initials: SJ
authors.lastname: Latendresse
authors.affiliation: University of Virginia, Department of Psychology, Charlottesville, VA, USA.
authors.forename: Bethany A
authors.initials: BA
authors.lastname: Teachman
mesh_terms: D000293:Adolescent; D000328:Adult; D001007:Anxiety / Q000139:chemically induced / Q000175:diagnosis* / Q000523:psychology; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016584:Panic Disorder / Q000139:chemically induced / Q000175:diagnosis* / Q000523:psychology; D011569:Psychiatric Status Rating Scales; D012130:Respiratory Hypersensitivity / Q000139:chemically induced / Q000523:psychology*; D056152:Respiratory Rate / Q000187:drug effects; D012307:Risk Factors; D013997:Time Factors; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide
keywords: Anxiety; Carbon dioxide hypersensitivity; Latent class; Panic; Respiratory; Risk