SummaryThis study assessed the use of the oxygram, specifically thedifferencebetween inspired and end tidal oxygen concentrations, F1‐eto2, to detect hypoventilation in a paediatric population. Ten healthy unpremedicated children, aged 1‐5 years, scheduled for elective minor urologic surgery were studied. A Modulus® II Plus Anesthesia System was used, with Rascal® II Anesthesia Gas Monitor for analysis of anaesthetic and respiratory gases with a Wright spirometer to monitor minute ventilation. Following inhalational induction, intubation, and caudal anaesthetic administration, the children breathed end‐tidal halothane concentrations of 0.5%, 2%, 1.5%, 1.0%, and again 0.5% with measurements of inspired and end‐tidal oxygen and halothane concentrations, end tidal CO2(Petco2), minute ventilation (VE), respiratory rate (f), pulse oximetry saturations (Spo2), heart rate (HR), and mean blood pressure (BP).FI‐ETO2increased proportionately with hypoventilation at 2%, 1.5%, and 1% halothane concentrations compared to the 0.5% halothane group (P<0.0001, 0.0008, and 0.0013 respectively), associated with corresponding increases ofPetco2and decreases of minute ventilation (VE). We conclude the oxygram was effective in monitoring hypoventilation in paediatric patients within the format of the prot