The reliability of endtidal CO₂ in spontaneously breathing children during anaesthesia with Laryngeal Mask Airway^TM, low flow, sevoflurane and caudal epidural

Background: Noninvasive devices for monitoring endtidal CO₂ (PECO₂) are in common use in paediatric anaesthesia. Questions have been raised concerning the reliability of these devices in spontaneous breathing children during surgery. Our anaesthetic technique for elective infraumbilical surgery consists of spontaneous breathing through a Laryngeal Mask Airway (LMA^TM), low fresh gas flow, sevoflurane and a caudal epidural. We wanted to compare PECO₂ and arterial CO₂ (PaCO₂) during surgery.

Methods: Twenty children, aged 1–6 years, scheduled for infraumbilical surgery, were studied and one arterial sample was taken 45 min after induction of anaesthesia. PECO₂, inspiratory PCO₂, oxygen saturation, heart rate, respiratory rate, mean arterial blood pressure and expiratory sevoflurane concentration were measured every 5 min. The respiratory and circulatory parameters were stable during surgery.

Results: The mean PaCO₂ – PECO₂ difference was 0.15 (0.16) kPa [1.1 (1.2 mmHg)].

Conclusions: PECO₂ is a good indicator of PaCO₂ in our anaesthetic setting.