ABSTRACT
Selection of an appropriately sized endotracheal tube (ETT) is essential (19). Resistance to breathing is markedly increased as the diameter of the ETT decreases. If the diameter of the tube is halved, resistance increases 16-fold. To minimize resistance to breathing, the largest diameter tube that can be easily and safely passed should be used. If the ETT is too long, resistance to expiration will also increase (doubling the length will double the resistance to flow) and the risk of excessive
equipment dead space or inadvertent endobronchial intubation increases (20).
