Comparison of age-based and height-based formula for tracheal tube size in cardiac children

Area of Science:

• Pediatric Anesthesiology
• Cardiothoracic Surgery
• Medical Device Sizing

Background:

• Accurate endotracheal tube (ETT) sizing is critical for pediatric cardiac surgery.
• Existing formulas for ETT size prediction include age-based formula (ABF) and height-based formula (HBF).
• The effectiveness of these formulas in children with failure to thrive (FTT) requires further evaluation.

Purpose of the Study:

• To compare the predictive accuracy of ABF and HBF for uncuffed ETT size in pediatric cardiac patients.
• To assess formula performance in children with and without FTT.
• To determine the optimal ETT selection strategy based on formula predictions.

Main Methods:

• Retrospective study of 260 pediatric cardiac patients aged 2-7 years.
• Comparison of actual uncuffed ETT size with sizes predicted by ABF [ID (mm) = age (years)/4 + 4] and HBF [ID (mm) = height (cm)/30 + 2].
• Analysis of prediction accuracy and the coverage provided by a range of ETT sizes.

Main Results:

• ABF and HBF demonstrated similar prediction accuracy: 50.8% and 50.4% respectively (p=1.0).
• A range of three ETT sizes (predicted, one above, one below) covered 95.8% (ABF) and 93.5% (HBF) of patients (p=0.24).
• In patients with FTT, both formulas correctly predicted ETT size in 56.6% of cases.

Conclusions:

• Age-based and height-based formulas are equivalent for predicting ETT size in pediatric cardio-surgical patients, irrespective of physical development.
• The simpler age-based formula can be recommended for clinical use.
• Ensuring availability of three ETT sizes (predicted, +/- one size) is crucial for optimal patient management.