title: Hypocapnia in patients with chronic neck pain: association with pain, muscle function, and psychologic states.
abstract: OBJECTIVE
  The aim of this study was to investigate whether patients with chronic neck pain have changes in their transcutaneous partial pressure of arterial carbon dioxide (PtcCO2) and whether other physical and psychologic parameters are associated.
  
  
  METHODS
  In this cross-sectional study, 45 patients with chronic idiopathic neck pain and 45 healthy sex-, age-, height-, and weight-matched controls were voluntarily recruited. The participants' neck muscle strength, endurance of the deep neck flexors, neck range of movement, forward head posture, psychologic states (anxiety, depression, kinesiophobia, and catastrophizing), disability, and pain were assessed. PtcCO2 was assessed using transcutaneous blood gas monitoring.
  
  
  RESULTS
  The patients with chronic neck pain presented significantly reduced PtcCO2 (P < 0.01). In the patients, PtcCO2 was significantly correlated with strength of the neck muscles, endurance of the deep neck flexors, kinesiophobia, catastrophizing, and pain intensity (P < 0.05). Pain intensity, endurance of the deep neck flexors, and kinesiophobia remained as significant predictors into the regression model of PtcCO2.
  
  
  CONCLUSIONS
  Patients with chronic neck pain present with reduced PtcCO2, which can reach the limits of hypocapnia. This disturbance seems to be associated with physical and psychologic manifestations of neck pain. These findings can have a great impact on various clinical aspects, notably, patient assessment, rehabilitation, and drug prescription.
authors: Department of Physiotherapy, Technological Educational Institute of Lamia, Greece.
authors: Zacharias
authors: Z
authors: Dimitriadis
authors: Eleni
authors: E
authors: Kapreli
authors: Nikolaos
authors: N
authors: Strimpakos
authors: Jacqueline
authors: J
authors: Oldham
mesh_terms: D000223:Adaptation, Psychological; D000328:Adult; D017677:Age Distribution; D001784:Blood Gas Analysis; D016022:Case-Control Studies; D059350:Chronic Pain; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016857:Hypocapnia / Q000175:diagnosis / Q000453:epidemiology*; D015994:Incidence; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000503:physiopathology*; D009334:Neck Muscles / Q000503:physiopathology; D019547:Neck Pain / Q000175:diagnosis / Q000453:epidemiology*; D010147:Pain Measurement; D011594:Psychometrics; D012016:Reference Values; D012132:Respiratory Muscles / Q000503:physiopathology*; D012720:Severity of Illness Index; D017678:Sex Distribution; D055815:Young Adult