title: Patterns of hypocapnia on tilt in patients with fibromyalgia, chronic fatigue syndrome, nonspecific dizziness, and neurally mediated syncope.
abstract: OBJECTIVE
  To assess whether head-up tilt-induced hyperventilation is seen more often in patients with chronic fatigue syndrome (CFS), fibromyalgia, dizziness, or neurally mediated syncope (NMS) as compared to healthy subjects or those with familial Mediterranean fever (FMF).
  
  
  METHODS
  A total of 585 patients were assessed with a 10-minute supine, 30-minute head-up tilt test combined with capnography. Experimental groups included CFS (n = 90), non-CFS fatigue (n = 50), fibromyalgia (n = 70), nonspecific dizziness (n = 75), and NMS (n =160); control groups were FMF (n = 90) and healthy (n = 50). Hypocapnia, the objective measure of hyperventilation, was diagnosed when end-tidal pressure of CO2 (PETCO2) less than 30 mm Hg was recorded consecutively for 10 minutes or longer. When tilting was discontinued because of syncope, one PETCO2 measurement of 25 or less was accepted as hyperventilation.
  
  
  RESULTS
  Hypocapnia was diagnosed on tilt test in 9% to 27% of patients with fibromyalgia, CFS, dizziness, and NMS versus 0% to 2% of control subjects. Three patterns of hypocapnia were recognized: supine hypocapnia (n = 14), sustained hypocapnia on tilt (n = 76), and mixed hypotensive-hypocapnic events (n = 80). Hypocapnia associated with postural tachycardia syndrome (POTS) occurred in 8 of 41 patients.
  
  
  CONCLUSIONS
  Hyperventilation appears to be the major abnormal response to postural challenge in sustained hypocapnia but possibly merely an epiphenomenon in hypotensive-hypocapnic events. Our study does not support an essential role for hypocapnia in NMS or in postural symptoms associated with POTS. Because unrecognized hypocapnia is common in CFS, fibromyalgia, and nonspecific dizziness, capnography should be a part of the evaluation of patients with such conditions.
authors.affiliation: Department of Internal Medicine A, the Bnai-Zion Medical Center and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel. Naschitz@tx.technion.ac.il
authors.forename: Jochanan E
authors.initials: JE
authors.lastname: Naschitz
authors.forename: Renata
authors.initials: R
authors.lastname: Mussafia-Priselac
authors.forename: Yulia
authors.initials: Y
authors.lastname: Kovalev
authors.forename: Natalia
authors.initials: N
authors.lastname: Zaigraykin
authors.forename: Gleb
authors.initials: G
authors.lastname: Slobodin
authors.forename: Nizar
authors.initials: N
authors.lastname: Elias
authors.forename: Itzhak
authors.initials: I
authors.lastname: Rosner
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D004244:Dizziness / Q000097:blood / Q000503:physiopathology*; D010505:Familial Mediterranean Fever / Q000503:physiopathology; D005221:Fatigue / Q000503:physiopathology; D015673:Fatigue Syndrome, Chronic / Q000097:blood / Q000503:physiopathology*; D005260:Female; D005356:Fibromyalgia / Q000097:blood / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D006985:Hyperventilation / Q000097:blood / Q000150:complications / Q000503:physiopathology*; D016857:Hypocapnia / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011187:Posture; D012189:Retrospective Studies; D019462:Syncope, Vasovagal / Q000097:blood / Q000503:physiopathology*; D013610:Tachycardia / Q000209:etiology / Q000503:physiopathology; D018667:Tilt-Table Test