Endotracheal intubation or bag-and-mask ventilation have been the mainstays of airway management for several decades. In 1983, this changed with the invention of the laryngeal mask airway (LMA) which provided ease of placement and hands-free maintenance along with a relatively secure airway. LMA is increasingly being used in all patient population including children and has been found to be very safe and efficacious in various studies.

In the paediatric age group, the outward recoil of the chest wall is low, but the inward lung recoil is similar to that of a young adult. As the Functional Residual Capacity (FRC) is the lung volume at which the outward recoil of the chest wall exactly balances that of the inward recoil of the lungs, this leads to a reduced FRC in children. In awake state, the FRC is maintained by mechanisms such as active diaphragmatic and intercostal expiratory tone, but under general anaesthesia the closing volume tends to increase and the functional residual capacity decreases resulting in atelectasis and subsequent decreased arterial oxygenation. 

The application of adequate tidal volumes and a positive end-expiratory pressure (PEEP) play an important role in counteracting this airway closure and atelectasis in paediatric patients under general anaesthesia. This is usually achieved by using an endotracheal tube. However the ProSeal LMA (PLMA) has been shown to form a more effective seal than the Classic LMA and can be used to deliver PEEP which may improve gas exchange in children.^5.6

There are few studies evaluating the use of PEEP with a supraglottic airway device in the paediatric age group in an attempt to minimise small airway closure. Hence we thought it worthwhile to compare the use of PLMA for pressure controlled ventilation with and without PEEP for improving oxygenation in paediatric patients.