title: Concordance and limits between transcutaneous and arterial carbon dioxide pressure in emergency department patients with acute respiratory failure: a single-center prospective observational study.
abstract: Transcutaneous CO₂ (PtCO₂) is a continuous and non-invasive measure recommended by scientific societies in the management of respiratory distress. The objective of this study is to evaluate the correlation between PtCO₂ and blood pressure of CO₂ (PaCOv) by blood gas analysis in emergency patients with dyspnoea and to determine the factors that interfere in this correlation.
  
  
  
  From January to June 2014, all patients admitted to resuscitation room of the emergency department targeted for arterial blood gases were included prospectively. A sensor measuring the PtCO₂ was attached to the ear lobe of the patient before the gas analysis. Anamnesis, clinical and laboratory parameters were identified.
  
  
  
  90 patients with dyspnoea were included (with 104 pairs of measurements), the median age was 79 years [69-85]. The correlation between PtCO₂ and PaCO₂ was R(2)= 0.83 (p <0.001) but became lower for values of PaCO₂>60 mm Hg. The mean bias (±SD) between the two methods of measurement (Bland-Altman analysis) was -1.4 mm Hg (±7.7) with limits of agreement of -16.4 to 13.7 mm Hg. In univariate analysis, PaO₂ interfered in this correlation. After multivariate analysis, the temperature (OR = 3.01, 95% CI = 1.16-7.09) and the PaO 2 (OR = 1.22, 95% CI = 1.02-1.47) were found to be significant.
  
  
  
  In patients admitted in emergency unit for acute respiratory failure, there is a significant correlation between PaCO₂ and PtCO₂, mainly for values below 60 mm Hg. The two limiting factors of use are hyperthermia and users training.
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. xavier.bobbia@gmail.com.
authors.forename: Xavier
authors.initials: X
authors.lastname: Bobbia
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. pierre.geraud.claret@gmail.com.
authors.forename: Pierre-Géraud
authors.initials: PG
authors.lastname: Claret
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. lpalmier@hotmail.fr.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Palmier
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. robertmichael34000@gmail.com.
authors.forename: Michaël
authors.initials: M
authors.lastname: Robert
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. romainsbs@hotmail.com.
authors.forename: Romain Genre
authors.initials: RG
authors.lastname: Grandpierre
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. clairepenetrat@hotmail.com.
authors.forename: Claire
authors.initials: C
authors.lastname: Roger
authors.affiliation: Emergency Department, Hôpital Tenon, Assistance Publique - Hôpitaux de Paris, 4 Rue de la Chine, Paris, 75020, France. patrick.ray@tnn.aphp.fr.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ray
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. m-sebbane@chu-montpellier.fr.
authors.forename: Mustapha
authors.initials: M
authors.lastname: Sebbane
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. laurent.muller27@orange.fr.
authors.forename: Laurent
authors.initials: L
authors.lastname: Muller
authors.affiliation: Pôle Anesthésie Réanimation Douleur Urgences, Nîmes University Hospital, 4 Rue du Professeur Robert Debré, Nîmes, 30029, France. jean.emmanuel.delacoussaye@chu-nimes.fr.
authors.forename: Jean-Emmanuel de
authors.initials: JE
authors.lastname: La Coussaye
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001784:Blood Gas Analysis / Q000379:methods*; D001795:Blood Pressure Determination; D002245:Carbon Dioxide / Q000097:blood*; D004636:Emergency Service, Hospital; D005260:Female; D005602:France; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000097:blood*
chemical_list: D002245:Carbon Dioxide