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Acad Emerg Med. 2003 Apr;10(4):303-8.

The self-inflating bulb as an airway adjunct: is it reliable in children weighing less than 20 kilograms?

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Department of Emergency Medicine, Children's Hospital and Health Center, San Diego, CA, USA.



To confirm the ability of the self-inflating bulb to indicate endotracheal tube (ETT) position in children weighing less than 20 kilograms, and to determine whether the presence of air in the stomach affects the bulb's accuracy.


This single-blind, prospective, single-cohort, repeated-measures, equivalence study was conducted in the operating room of a children's hospital. Seventy patients weighing less than 20 kilograms were enrolled. All patients had an uncuffed ETT placed in both the trachea and the esophagus. Measurements were initially obtained on both tubes without the presence of air in the stomach using the on-deflate method (the bulb is compressed after attachment to the ETT). Five mL/kg of air was then insufflated into the stomach and two additional measurements were obtained on each patient. The order in which the bulb was checked was determined by a computer-generated permuted block randomization scheme. The blinded assessor told the anesthesiologist when to start and stop the clock after each intervention. Five seconds was used as the cutoff time for which the clock was stopped. If the bulb re-expanded within 5 seconds, then the tube was considered to be in the trachea; if it did not re-expand, then this was considered to be an esophageal intubation.


Median patient age was 2 years. The on-deflate method without air in the stomach had a sensitivity of 100% and a specificity of 94% for detecting tracheal intubations. With air in the stomach, the bulb had a sensitivity of 97% and a specificity of 96% (95% confidence interval [95% CI] for the difference between methods: sensitivity -3 to 10; specificity -10 to 7). The inaccuracy rate for the on-deflate method without air in the stomach was 3%, whereas the inaccuracy rate with air in the stomach was 4% (Delta -1, 95% CI = -5 to 4). There were no false positives or false negatives in the 24 patients weighing between 5 and 10 kilograms.


The self-inflating bulb is a reliable method of detecting endotracheal tube position in children weighing less than 20 kg, even with the use of uncuffed endotracheal tubes. Furthermore, the presence of air in the stomach, simulating field conditions, does not affect bulb effectiveness in detecting endotracheal tube position.

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