Sublingual capnometry: a new noninvasive measurement for diagnosis and quantitation of severity of circulatory shock

Abstract

Objective: To investigate the feasibility and predictive value of sublingual Pco2 (P(SL)CO2) measurements as a noninvasive and early indicator of systemic perfusion failure.

Design: A prospective, criterion study.

Setting: Emergency department and medical and surgical intensive care units of an urban community medical center.

Participants and patients: Five normal human volunteers and 46 patients with acutely life-threatening illness or injuries.

Interventions: Intra-arterial or automated cuff blood pressure and arterial blood lactate (LAC) were measured concurrently with P(SL)CO2.

Results: P(SL)CO2 in five healthy volunteers was 45.2 +/- 0.7 mm Hg (mean +/- sD). Twenty-six patients with physical signs of circulatory shock and LAC >2.5 mmol/L had a P(SL)CO2 of 81 +/- 24 mm Hg. This contrasted with patients admitted without clinical signs of shock and LAC of <2.5 mmol/L who had a P(SL)CO2 of 53 +/- 8 mm Hg (p < .001). The initial P(SL)CO2 of 12 patients who died before recovery from shock was 93 +/- 27 mm Hg, and this contrasted with 58 +/- 11 mm Hg (p < .001) in hospital survivors. Increases in P(SL)CO2 were correlated with increases in LAC (r2 = .84; p < .001). When P(SL)CO2 exceeded a threshold of 70 mm Hg, its positive predictive value for the presence of physical signs of circulatory shock was 1.00. When it was <70 mm Hg, it predicted survival with a predictive value of 0.93.

Conclusion: P(SL)CO2 may serve as a technically simple and noninvasive clinical measurement for the diagnosis and estimation of the severity of circulatory shock states.