Vital capacity and patient controlled sevoflurane inhalation result in similar induction characteristics

To compare patient controlled inhalational induction (PCI) with the most commonly used sevoflurane induction technique, vital capacity inhalational induction (VCI).

Following approval of the Research Ethics Board, 124 outpatients undergoing knee arthroscopy were randomly assigned to receive either PCI or VCI sevoflurane followed by laryngeal mask airway (LMA) insertion and sevoflurane maintenance. In the PCI group, the circle circuit was not primed. The patients were asked to hold the facemask themselves and breathe normally with sevoflurane 8% in oxygen at a flow rate of 4 L x min(-1). In the VCI group, the circle circuit was primed and patients were asked to take vital capacity breaths with sevoflurane 8% at an oxygen flow rate of 8 L x min(-1). The LMA was inserted as soon as the patient's jaw was relaxed. Time from induction to LMA insertion was recorded and insertion conditions rated. The amount of sevoflurane used for LMA insertion was calculated. Vital signs were monitored at one-minute intervals until ten minutes after LMA insertion.

Demographic data were comparable. There were no differences with respect to LMA insertion time (PCI - 3.4 min vs VCI - 3.3 min), laryngospasm (PCI - 7% vs VCI - 5%), mean arterial pressure, heart rate, SaO(2) as well as patient's overall satisfaction.

PCI was comparable to VCI in sevoflurane induction with respect to the speed of induction, side effects during induction and patient satisfaction. However, PCI requires no special training and is widely applicable to all patient populations.