Work of breathing for cuffed and uncuffed paediatric endotracheal tubes in an in vitro Lung model setting.

Over the last decade, there has been an increasing use of cuffed endotracheal tubes in paediatric anaesthetic practice and in paediatric intensive care. The potential for the smaller internal diameters of the cuffed endotracheal tubes to cause higher airway resistance, requiring higher inspiratory pressures to ventilate, has been debated.

This research report looks at the differences in the work of breathing as well as inspiratory pressures required to achieve good tidal volumes, between the cuffed and uncuffed tubes in in-vitro conditions. 5 neonatal and paediatric lung models, with two different EVITA 4 ventilators were used in the study. Uncuffed Mallinkrodt tubes, sizes 3.5 – 4.5 and Microcuff endotracheal tubes sizes 3 – 4, were used.

This study showed that the cuffed endotracheal tubes with smaller internal diameters (half a size smaller than the equivalent uncuffed tube) resulted in increased work of breathing. This difference was greater in the younger lung models. Use of pressure support reduced the work of breathing by 34% in spontaneous breathing techniques but differences still existed between cuffed and uncuffed tubes. Higher inspiratory pressures were demonstrated in the cuffed tubes in the proximal end, in order to achieve reasonable tidal volumes, however the differences in peak inspiratory pressures at the distal end were not clinically relevant between the two types of tubes.

Limitations of this study are the invitro setting and the fixed nature of the endotracheal tube size for age group which may not reflect clinical variability in the leak around uncuffed tubes in different patients in the same age group .

Take home message:
Cuffed endotracheal tubes result in increased work of breathing when compared to the equivalent sized uncuffed endotracheal tubes. In spontaneously breathing patients, use of pressure support and automated tube compensation, reduces the work of breathing. Higher resistance in smaller cuffed tubes is only at the proximal end and should therefore not impact on their use in small children.

Reviewed by Dr. Priya Sreedharan