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Trauma. 2009 Jan;66(1):26-31.

The utility of early end-tidal capnography in monitoring ventilation status

after severe injury.

Warner KJ, Cuschieri J, Garland B, Carlbom D, Baker D, Copass MK, Jurkovich

GJ, Bulger EM.

Department of Trauma Surgery, Harborview Medical Center, Seattle, Washington

98104, USA. keirw@...

BACKGROUND: An arterial CO2 (PaCO2) of 30 mm Hg to 39 mm Hg has been shown

to be the ideal target range for early ventilation in trauma patients;

however, this requires serial arterial blood gases. The use of end-tidal

capnography (EtCO2) has been recommended as a surrogate measure of

ventilation in the prehospital arena. This is based on the observation of

close EtCO2 Pa(CO2) correlation in healthy patients, yet trauma patients

frequently suffer from impaired pulmonary ventilation/perfusion. Thus, we

hypothesize that EtCO2 will demonstrate a poor reflection of actual

ventilation status after severe injury.

METHODS: Prospective observational study on consecutive intubated trauma

patients treated in our emergency department (ED) during 9 months. Arterial

blood gas values and concomitant EtCO2 levels were recorded. Regression was

used to determine the strength of correlation among all trauma patients and

subgroups based on injury severity (Abbreviated Injury Score and Injury

Severity Score) and physiologic markers of perfusion status (lactate, shock

index, and arterial base deficit).

RESULTS: During 9 months, 180 patients were evaluated. The EtCO2 Paco2

correlation was poor at R2 = 0.277. Patients ventilated in the recommended

EtCO2 (range, 35 to 40) were likely to be under ventilated (Pa(CO2) > 40 mm

Hg) 80% of the time, and severely under ventilated (Pa(CO2) > 50 mm Hg) 30%

of the time. Correlation was best for patients with isolated traumatic brain

injury and worst for those with evidence of poor tissue perfusion.

CONCLUSION: EtCO2 has low correlation with Pa(CO2), and therefore should not

be used to guide ventilation in intubated trauma patients in the ED. Better

strategies for guiding prehospital and ED ventilation are needed.