Intraoperative Kinking of Polyvinyl Endotracheal Tubes

Abstract

To the Editor: Kinking of an endotracheal tube (ETT) during anesthesia and surgery is generally uncommon (1), but may occur more commonly if the position of the head and neck overbends the ETT (2,3). If strong bending forces are expected or if the ETT cannot be easily accessed during surgery (e.g., neurosurgery or maxillo-oral surgery), anesthesiologists may choose flexometallic ETTs. We present a small series of intraoperative ETT kinking incidents discovered through our anonymous critical-incident reporting system. Within the last several months, three anonymous critical-incident reports have described intraoperative kinking of polyvinyl ETTs at our institution. All cases involved patients in the supine position undergoing lower limb surgery. Their tracheas were intubated orally with polyvinyl ETTs (Mallinckrodt, Tyco Healthcare Deutschland, NeustadtJDonau, Germany). Approximately one hour after intubation, sudden increases in airway pressures made ventilation impossible. Examination of the circuit revealed kinked ETTs, with the kink hidden in the mouth. Repositioning the ETTs restored luminal patency and adequate ventilation. Polyvinyl ETTs come with preformed bending. Further bending along the concave curve does not compromise the tube’s stability (Fig. 1). Even bending up to reasonable angles into the opposite direction initially does not cause kinking (Fig. 2). However, if the ETT’s temperature is increased to 36°C, the tube softens and kinking occurs at astonishingly low angles (Fig. 3). The kinking typically occurs where the cuff line exits, 18 cm from the tube’s tip, a spot usually hidden in the oral cavity. The outer side of the ETT’s bend, usually marked by the manufacturer, should face nasally. Manufacturers should ideally consider changing the ETT’s design, so that the cuff line exits the tube outside the oral cavity.Figure 1.: Bending of the polyvinyl endotracheal tube along the concave curve does not compromise the tube’s stability.Figure 2.: Bending of the polyvinyl endotracheal tube into the opposite direction at room temperature hardly compromises the tube’s stability.Figure 3.: At body temperature kinking occurs at a low angle if the polyvinyl endotracheal tube is bent in the wrong direction.Matthias Hübler, MD, DEAA Frank Petrasch Department of Anesthesiology and Intensive Care Medicine Carl Gustav Carns University Hospital Technical University Dresden Dresden Germany [email protected]