RESUMO
Conventional endotracheal tubes have high intrinsic resistive properties due to their high outer-to-inner diameter ratio. This has significant disadvantages in the treatment of the small neonatal or pediatric patient as work of breathing increases with decreasing internal radius. Diagnostic and therapeutic procedures, including suctioning, may be very difficult in patients with small endotracheal tubes. We therefore measured airway resistance and pressure differential during simulated mechanical ventilation using proximal and distal endotracheal tube flow transducers. Conventional and new, ultrathin-walled endotracheal tubes reinforced with flat stainless steel or a novel, crush-proof nickel-titanium alloy were compared using fixed ventilator settings. Ventilation through the ultrathin-walled tubes resulted in a significantly reduced airway resistance (p < or = 0.01). These new ultrathin-walled endotracheal tubes showed flow characteristics typical of much larger conventional endotracheal tubes: the 3.2-mm internal diameter had an airway resistance (Raw) of 36, while a standard 2.5-mm internal diameter endotracheal tube had a Raw of 146. Both endotracheal tubes have identical external diameters of 3.6 mm. We conclude that ultrathin-walled endotracheal tubes could have a significant role in the treatment of the ventilated child by facilitating interactive ventilation and maintenance of airway patency and may make procedures such as fiberoptic endoscopy and intrapulmonary ventilation using reverse-thrust catheters possible in the small child.