Effects of expiratory tracheal gas insufflation in patients with severe head trauma and acute lung injury.

OBJECTIVE: This study analyzed the effect of phasic tracheal gas insufflation at mid- to end-expiration in patients with severe head trauma and acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). DESIGN AND
SETTING: A prospective interventional study in a 16-bed intensive care unit. PATIENTS: Seven patients with severe head trauma (Glasgow Coma Scale <9) and ALI/ARDS.
INTERVENTIONS: Patients were ventilated in assist/control mode with a ventilatory strategy providing adequate oxygenation (PaO(2) >70 mmHg) and normocapnia (PaCO(2) between 35-40 mmHg). Mid to end expiratory tracheal gas insufflation at 8 l/min flow rate was delivered for 90 min while normocapnia was maintained by simultaneous reductions in tidal volume. We measured (hemodynamics, oxygenation, lung mechanics, and cerebral parameters) in basal situation and during and after tracheal insufflation. MEASUREMENTS AND
RESULTS: Tracheal gas insufflation allowed a significant decrease in tidal volume from 9.1 to 7.2 ml/kg, with associated reduction in driving pressure (plateau pressure minus positive end-expiratory pressure, PEEP) from 18.1 to 13.2 cm H(2)O. Total PEEP increased from 9.3 to 12.7 cm H(2)O due to the generation of lung hyperinflation. Oxygenation improved slightly during tracheal gas insufflation, and this improvement remained after stopping tracheal insufflation. No changes in hemodynamic or cerebral parameters were observed during the study.
CONCLUSIONS: In patients with severe head trauma and ALI receiving mechanical ventilation, expiratory tracheal gas insufflation allowed the targeted arterial PCO(2) level to be maintained together with a substantial reduction in tidal volume.