Regardless of the apparatus used and the magnitude of the dead space, the leak induced when a poorly fitting facemask was used dramatically reduced the dead space of the breathing system - to near optimal conditions - by moving the alveolar gas elimination point to within the facemask itself. There was minimal relationship between size of the facemask and functional dead space however, the provision of 22-mm female inlets to facemasks achieved proportionately less functional dead space than with 15-mm male inlets.

We found that functional dead space was too large to allow for spontaneous ventilation of the lungs when a breathing filter was fitted. Abstract: Dead space is the portion of each tidal volume that does not take part in gas exchange and represents a good global index of the efficiency of the. Total functional dead space was measured in various combinations of this equipment applied to a spontaneous ventilation lung model with parameter settings appropriate for infants of 7-8 kg.

Untested assumptions have been made with regard to functional dead space in facemasks, filters and breathing systems used in children for the administration of inhalation anaesthesia.

Functional dead space lungs