Reliable procedure to switch from volume controlled to pressure controlled ventilation assuring tidal volume during anesthesia

A procedure to assist the switching from volume controlled to pressure controlled ventilation assuring tidal volume is proposed. The method, based on a linear model of the dynamical behavior of the ventilatory system, identifies the main mechanical parameters of the system and is able to evaluate the pressure support value to set in pressure controlled ventilation in order to guarantee the necessary tidal volume to the patient. Extensive in vitro tests showed that the method reliably calculate the appropriate pressure support value leading to percent difference on tidal volume delivered equal to (1.3 /spl plusmn/ 0.6)%, i.e. less than 7 ml on a tidal volume of 500 ml. A low sensitivity to respiratory rate value was also observed. In consideration of the low error values obtained, it is possible to consider the proposed method as a valuable support to the physician during anesthesia delivery.