Physiological dead space & arterial to end-tidal CO2 difference under controlled normocapnic ventilation in young...

Physiological dead space and its components were determined in 27 young, otherwise healthy anaesthetised individuals before start of surgery. A squarewave inspiratory flow pattern and an end inspiratory pause (25 and 10% of cycle time respectively) were used at a respiratory rate of around 16 bpm with minute ventilation adjusted to maintain normocapnia. The physiological dead space was found to be 2.23 ml/kg with anatomical dead space forming 110.66 +/- 27.55 ml out of 125.55 +/- 27.06 ml. While VD alv was positively correlated to pause pressure, VD ant was correlated to age, weight, and body surface area. Mean arterial end tidal carbon dioxide difference was quite low (0.24 +/- 0.44 kPa).