Key Points
- To measure anatomical, physiological, and alveolar dead space along with the arterial to end-tidal carbon dioxide tension difference during spontaneous and artificial ventilation under anesthesia.
- Conducted physiological measurements on 12 fit patients anesthetized for routine surgical procedures.
- Assessed respiratory parameters during both spontaneous and artificial respiration across tidal volumes ranging from 163 to 652 ml (BTPS).
- Physiological dead space below the carina approximated 0.3 times the tidal volume and consistently exceeded anatomical dead space, with alveolar dead space ranging from 15 to 231 ml in proportion to tidal volume.
- Anatomical dead space matched predicted normal values above a tidal volume of 350 ml (BTPS) but decreased proportionally below 350 ml.
- Mean arterial to end-tidal CO2 tension difference was 4.6 ± 2.5 mm Hg and remained independent of tidal volume, arterial CO2 tension, and whether ventilation was spontaneous or artificial.
Structured PICO
PPopulation12 fit patients anesthetized for routine surgical procedures
IInterventionObservation during spontaneous and artificial respiration
OOutcomeAnatomical dead space, physiological dead space, and arterial to end-tidal CO2 tension differencesurrogate
In anesthetized patients, physiological dead space exceeds anatomical dead space and is proportional to tidal volume, while the arterial to end-tidal CO2 difference remains constant regardless of respiration type.