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Updated: Aug 14, 2026

Expired CO2 Measurement in Intubated or Spontaneously Breathing Patients from the Emergency Department
Published on: January 29, 2011
[Severe head injuries: effects of pre-hospital mechanical ventilation on capnia]
J S David1, M P Cresta, A Souab
1Département d'anesthésie-réanimation VII, Hôpital Edouard-Herriot, Lyon, France.
Objective:
To assess the effect on PaCO2 of mechanical ventilation during prehospital management of severely head-injured patients.
Study Design:
Retrospective observational study.
Patients:
Severely head-injured patients with Glasgow coma score < or = 8. All patients were sedated, with the trachea intubated and the lungs mechanically ventilated.
Methods:
According to the capnia measured at the admission in the neurosurgical intensive therapy unit they were allocated into one of the following three groups: hypocapnia group (PaCO2 < 30 mmHg), recommended capnia group (PaCO2 = 30-38 mmHg) and hypercapnia group (PaCO2 > 38 mmHg).
Results:
Out of the 42 patients with similarly severe head injuries, 19% were included in the recommended capnia group (PaCO2: 34 +/- 2 mmHg), 38% in the hypocapnia group (PaCO2: 23 +/- 3 mmHg) and 43% in the hypercapnia group (PaCO2: 47 +/- 7 mmHg). In all except three, PaO2 was above 95 mmHg. The settings of ventilatory parameters on the ventilators were similar.
Conclusion:
In 81% of patients, mechanical ventilation was inadequate as far as PaCO2 levels are concerned. Major hypocapnia and hypercapnia carry a potential risk for cerebral ischaemic. Therefore it is recommended to monitor PETCO2 during prehospital transport in medical ambulances and to determine arterial blood gases at arrival of severely head-injured patients in the admission unit for emergencies.
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