Using a circle absorber system, normal breathing of oxygen for 3-5 min achieves optimal oxygenation of the lungs; whereas 4 deep breaths in 30 s does not. However, extending deep breathing to 1.5-2 min and using a high flow of oxygen improves oxygenation of the lungs to the same degree as normal breathing for 3-5 min. This may have important implications for patient safety.

The circle absorber and NasOral systems were equally effective in achieving maximal preoxygenation during tidal volume breathing. Resuscitation bags differed markedly in effectiveness during preoxygenation; those with duck-bill valves without one-way exhalation valves were the least effective. Thus, the use of these bags should be avoided for preoxygenation.

Contrary to previous investigations in healthy patients, the current study demonstrates a high incidence of false-negative results when the SIB is used to confirm tracheal intubation in morbidly obese patients. If the SIB is used, the technique should include compression of the SIB after connection to the tube and should be used in conjunction with other clinical signs and technical aids. The mechanism of false-negative results in these patients seems to be related to reduction of caliber of airways secondary to a marked decrease in functional residual capacity, and collapse of large airways due to invagination of the posterior tracheal wall when sub-atmospheric pressure is generated by the SIB.

No abstract