To the Editor An 11-year-old boy was admitted to the emergency room after falling 15 m. His trachea was intubated in the field with a 5.5-mm inner diameter (ID) cuffed Rusch® endotracheal tube (ETT, Teleflex Medical, Research Triangle Park, NC), pulse oximeter saturation was 100%, and the ETT position was confirmed by capnography and chest radiograph. Ventilation became increasingly difficult (peak airway pressures of 30–35 cm H2O), breath sounds were barely audible, chest movements were minimal, and the end-tidal carbon dioxide was in the high 40s. The patient was urgently transported to the computed tomography (CT) suite, where after the initial scan sequences, ventilation became more difficult and the patient's trachea was reintubated with a styletted 5.5-mm ID cuffed ETT with immediate improvement of all respiratory variables. Examination of the initial CT images revealed a grossly overinflated ETT cuff causing collapse of the ETT lumen with almost complete airway obstruction (Fig. 1).Figure 1: Computed tomography of the head and anterior neck (sagittal image) showing the large, overinflated cuff and the collapsed endotracheal tube.Despite the suggestive CT imaging, we remained uncertain about the mechanism of the ETT collapse and decided to try to reproduce it in vitro. We placed the cuff of five 5.5-mm ID ETTs (Hi-Lo®; Mallinckrodt Co., Juárez, Mexico, the type of ETT we use in our institution) within the barrel of a 20-mL syringe and inflated the tube's cuff. We were unable to produce an ETT collapse in any of the ETTs studied even after cuff inflation with 20 mL of air, which developed a cuff pressure well above the maximal pressure (120 cm H2O) measurable with a cuff manometer (Cufflator #8199; Posey Co., Arcadia, CA). We repeated the in vitro test with three 6.0 Rusch ETTs (the type used for the prehospital intubation in our patient) and the lumens of the ETTs collapsed at lower volumes (12.5, 14.3, and 15 mL, respectively) and pressure >120 cm H2O (Fig. 2).Figure 2: Cuffed Rusch® endotracheal tube, 6.0-mm inner diameter, filled with contrast fluid, showing the collapsed tube after inflation of the cuff with 15 mL of air.When ETT cuff pressures are not monitored, cuff pressures greater than the recommended 20 to 30 cm H2O may develop. In one study, ETT cuff pressures were within the recommended ranges in only 27% of the patients.1 In the prehospital setting, most cuff pressures exceeded 40 cm H2O and required correction.2 In our in vitro trial, only the Rusch but not the Mallinckrodt ETT collapsed upon extreme overinflation of the cuff. The difference may stem from the quality of the polyvinyl chloride tube and hence from different compliances of the ETT wall. Although the findings in our in vitro model might resemble those of the in vivo situation, there are some differences. First, the human trachea has a greater compliance than that of a syringe barrel. Second, we did not warm the ETT and the syringe to body temperature but we theorize that warming would have made the ETT even softer (less rigid), thus requiring even less volume for cuff inflation to collapse the ETT. The patient's clinical timeline suggests that the obstruction worsened over time, possibly because of the temperature effect on the ETT tube, resulting in almost complete obstruction. Practitioners should be aware of the differences among different ETTs and the possibility that certain tubes may have the propensity to collapse after cuff overinflation. Dan Davis, MD Joseph Murphy, MDRadu B. Pop, MS Department of Anesthesiology and Pain Management University of Texas Southwestern Medical School and Children's Medical Center at Dallas Dallas, Texas Peter Szmuk, MD Department of Anesthesiology and Pain Management University of Texas Southwestern Medical School and Children's Medical Center at Dallas Dallas, Texas Outcomes Research Consortium The Cleveland Clinic Cleveland, Ohio [email protected] or [email protected]
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Jun 28, 2013
H E Kobbernagel + 2
Open Access