title: Evaluation of a transcutaneous carbon dioxide monitor ("TOSCA") in adult patients in routine respiratory practice.
abstract: BACKGROUND
  Non-invasive measurement of oxygenation is routine in adult clinical practice but transcutaneous monitoring of PCO(2) (PtcCO(2)) is used much less due to technical difficulties with earlier transcutaneous electrodes.
  
  
  OBJECTIVE
  Our aim was to determine the reliability of estimating arterial PCO(2) (PaCO(2)) using a recently introduced combined SaO(2)/PtcCO(2) monitor ("TOSCA", Linde Medical Systems) in adult patients in routine clinical respiratory practice.
  
  
  METHODS
  PtcCO(2) was measured in patients requiring arterial blood gases for clinical reasons. Ten minutes after the probe had been attached to an earlobe PtcCO(2) was recorded, immediately before arterial blood sampling. The PCO(2) values obtained were compared by Bland-Altman analysis.
  
  
  RESULTS
  Samples were taken from 48 unselected patients with varied pathology. There were no technical problems. Median age was 56 years (range 20-86 years). The mean difference between PaCO(2) and PtcCO(2) was -0.04kPa, sd of the difference 0.67kPa. Bland-Altman analysis showed generally good agreement between the two measurements across the range of PaCO(2) values (4-10.9kPa). Four of 48 measurements showed a PCO(2) difference >1kPa with no technical or clinical explanations apparent.
  
  
  CONCLUSIONS
  The accuracy of estimation of PaCO(2) by the TOSCA transcutaneous electrode was generally good and the device appears promising for use in routine clinical respiratory practice.
authors.affiliation: Department of Respiratory Medicine, Freeman Hospital, Newcastle upon Tyne, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Parker
authors.forename: G J
authors.initials: GJ
authors.lastname: Gibson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000502:physiology*; D004566:Electrodes; D006801:Humans; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods; D011446:Prospective Studies; D015203:Reproducibility of Results; D012140:Respiratory Tract Diseases / Q000503:physiopathology
chemical_list: D002245:Carbon Dioxide