Elimination of apparatus dead space--a simple method for improving CO2 removal without increasing airway pressure.

During mechanical ventilation the apparatus dead space can be eliminated by insufflating through one lumen of a tracheal double-lumen tube and allowing expiration through the other. In six intravenously anesthetized pigs, this technique resulted in an 18% (1 kPa) decrease in PaCO2 compared with insufflating through both lumens (32 ml rebreathing volume). Oxygenation, airway pressures, and tidal volumes were unchanged. Flushing the trachea with fresh gas during the expiratory phase did not improve the efficiency of ventilation. It is concluded that elimination of apparatus dead space improves CO2 removal without increasing airway pressures and tidal volumes, and it is suggested that minimization of apparatus dead space should be tried before more advanced ventilatory modes are considered.