title: Sublingual capnography: a clinical validation study.
abstract: OBJECTIVE
  To compare sublingual PCO(2) (PslCO(2)) measurements with gastric intramucosal PCO(2) (PimCO(2)) as well as with the traditional indexes of tissue oxygenation in hemodynamically unstable ICU patients.
  
  
  METHODS
  A prospective, validation study.
  
  
  METHODS
  The medical and coronary ICUs of a community teaching hospital.
  
  
  METHODS
  Consecutive patients with severe sepsis, septic shock, or cardiogenic shock requiring pulmonary artery catheterization for hemodynamic management.
  
  
  METHODS
  During the first 24 h of ICU admission, the PslCO(2), PimCO(2), and blood lactate concentrations as well conventional hemodynamic and oxygenation parameters were recorded every 4 to 6 h. The PslCO(2)-PaCO(2) and PimCO(2)-PaCO(2) differences were used as indexes of tissue dysoxia. These variables were correlated with each other as well as with the traditional markers of tissue oxygenation.
  
  
  RESULTS
  Seventy-six data sets were obtained on 22 patients. Fifteen patients had severe sepsis/septic shock, and 7 patients did not have sepsis. A patient with ischemic bowel who had a large PimCO(2)-PslCO(2) difference (60.2 mm Hg) was excluded. The initial PslCO(2) and PimCO(2) measurements were 43.5 +/- 10.4 mm Hg and 42.8 +/- 10.9 mm Hg, respectively (correlation coefficient [r] of 0.86; p < 0.001). The mean PslCO(2) and PimCO(2) for the entire data set were 48.0 +/- 13.4 mm Hg and 46.1 +/- 12.3 mm Hg, respectively (r = 0.78; p < 0.001). Ten patients died. The initial PslCO(2)-PaCO(2) difference was 9.2 +/- 5.0 mm Hg in the survivors and 17.8 +/- 11.5 mm Hg in the nonsurvivors (p = 0.04). The initial PimCO(2)-PaCO(2) difference was 8.4 +/- 4.8 mm Hg in the survivors and 16.1 +/- 13.7 mm Hg in the nonsurvivors (p = 0.08, not significant). The initial PslCO(2)-PaCO(2) difference correlated with the initial mixed venous-arterial CO(2) gradient (r = 0.66; p = 0.001), but correlated poorly with the initial blood lactate concentration (r = 0.38), mixed venous PO(2) (r = 0.05), and systemic oxygen delivery (r = - 0.39).
  
  
  CONCLUSIONS
  In this study, sublingual capnometry yielded measurements that correlated well with those of gastric tonometry. PslCO(2) may serve as a technically simple and noninvasive clinical measurement of tissue dysoxia in critically ill and injured patients.
authors.affiliation: Critical Care Medicine, The Mercy Hospital of Pittsburgh, Pittsburgh, PA 15219-5166, USA. pmarik@zbzoom.net
authors.forename: P E
authors.initials: PE
authors.lastname: Marik
mesh_terms: D000138:Acidosis / Q000175:diagnosis*; D000368:Aged; D019296:Capnography; D016638:Critical Illness; D005260:Female; D005745:Gastric Acidity Determination; D006439:Hemodynamics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D011446:Prospective Studies; D018805:Sepsis / Q000503:physiopathology*; D012770:Shock, Cardiogenic / Q000503:physiopathology*; D012772:Shock, Septic / Q000503:physiopathology*