Am. J. Respir. Crit. Care Med.,
Volume 159, Number 3, March 1999, 728-732
Aspiration of Airway Dead Space
A New Method to Enhance CO2 Elimination
EDOARDO
DE ROBERTIS,
SIGURDUR E.
SIGURDSSON,
BJÖRN
DREFELDT,
and
BJÖRN
JONSON
Departments of Clinical Physiology and Anaesthesia and Intensive Care, University Hospital of Lund, Lund, Sweden; and
Department of Anaesthesia and Intensive Care, University "Federico II", Naples, Italy
Alveolar ventilation and CO2 elimination during mechanical ventilation can be enhanced by reducing
dead-space ventilation. Aspiration of gas from the dead space (ASPIDS) is a new principle, according
to which gas rich in CO2 during late expiration is aspirated through a channel ending at the distal
end of the tracheal tube. Simultaneously, fresh gas injected into the inspiratory line fills the airway
down to the same site. We hypothesized that ASPIDS would allow a reduction of tidal volume (VT)
and airway pressure (Paw). To test our hypothesis we studied six anaesthetized and mechanically
ventilated pigs (24 ± 4 kg). The intention was to decrease VT while keeping PaCO2 constant by using
ASPIDS. VT was reduced by decreasing the minute ventilation (
E) in two steps, of 1.8 L/min ( E 
1.8) and 2.2 L/min ( E 2.2), respectively, and by increasing respiratory rate (RR) from 20 to 46 breaths/min. At ASPIDS, peak Paw was reduced by 35% at E 1.8 and at E 2.2 (p < 0.001), and
by 20% at an RR of 46 (p < 0.01). PaCO2 was maintained or reduced at ASPIDS. No intrinsic positive
end-expiratory pressure developed. Arterial blood pressure and heart rate were unaffected. The results show that ASPIDS allows a reduction in VT and Paw while PaCO2 is kept constant. ASPIDS does
not lead to problems associated with jet streams of gas or with gas humidification, and can be developed as a safe technique.
