ROLE OF VENTILATION AND BLOOD FLOW IN PULMONARY CLEARANCE OF INHALATION ANAESTHETICS A Theoretical Study BY

The pulmonary clearance of an anaesthetic agent (£1) represents the amount of pulmonary mixed venous blood cleared of anaesthetic in unit time. Its value depends on alveolar ventilation (VA), pulmonary blood flow (Q) and anaesthetic blood solubility (X) according to the equation: C1=(VA<£)/(VA + X<i). The alveolar ventilation and the blood flow required to clear 1 litre of mixed venous blood of different anaesthetics in unit time have been calculated separately for different values of "VA/Q. For each value of V A / Q it is observed that the higher the blood solubility the higher are both ventilation and blood flow requirements for the pulmonary clearance. For each anaes-thetic agent the higher the V A / Q value the higher the ventilation requirement and the lower the blood flow requirement for pulmonary clearance. The alveolar ventilation efficiency is high at low values of VA/Q, while the blood flow efficiency is high at high VA/Q values. The sum of the alveolar ventilation and blood flow requirement represents the total flow requirement for the pulmonary clearance. The higher the blood solubility the higher is the total flow required for pulmonary clearance. The minimum values of total flow requirement represent the most economical way in the pulmonary clearanc