title: Limitations of transcutaneous carbon dioxide measurements for assessing long-term mechanical ventilation.
abstract: OBJECTIVE
  Transcutaneous CO(2) pressure (Ptcco(2)) and transcutaneous O(2) pressure (Ptco(2)) measurements are routinely used in pediatric ICUs in order to avoid serial arterial punctures. The aim of this study was to determine the value of Ptcco(2) assessment during the evaluation of home ventilation in 12 adult patients with COPD or restrictive respiratory failure in the stable state (mean [+/- SD] basal Paco(2), 48.8 +/- 8.3 mm Hg) who were treated by mask or tracheotomy-mediated ventilation.
  
  
  METHODS
  After radial catheter insertion, patients were instructed to breathe spontaneously for 40 min and then to receive ventilation for 40 min according to their individual home ventilation modalities. An in vivo calibration was performed in the initial stage of the study in order to optimize the arterial Pco(2) and Ptcco(2) values. Every 5 min, transcutaneous measurements were performed and simultaneously compared with arterial values.
  
  
  RESULTS
  Ptcco(2) and Ptco(2) were correlated with arterial values (p < 0.0001) except for Paco(2) values of > 56 mm Hg and Pao(2) values of > 115 mm Hg. During ventilation, Paco(2) decreased >or= 4 mm Hg in seven patients. Ptcco(2) variations recorded during consecutive 5-min periods while the patient received mechanical ventilation were well correlated with the arterial variations (p = 0.0033), with a delay of < 5 min.
  
  
  CONCLUSIONS
  Ptcco(2) values and variations accurately reflected Paco(2) values and variations during mechanical ventilation. However, the accuracy of these data seems to be restricted to patients with Paco(2) values of < 56 mm Hg.
authors.affiliation: Service de Pneumologie, Hôpital de Bois-Guillaume, Centre Hospitalier Universitaire de Rouen, 76031 Rouen Cedex, France. antoine.cuvelier@chu-rouen.fr
authors.forename: Antoine
authors.initials: A
authors.lastname: Cuvelier
authors.forename: Bogdan
authors.initials: B
authors.lastname: Grigoriu
authors.forename: Luis Carlos
authors.initials: LC
authors.lastname: Molano
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Muir
mesh_terms: D000368:Aged; D001785:Blood Gas Monitoring, Transcutaneous; D002138:Calibration; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency / Q000097:blood / Q000628:therapy*