Sedative anesthetic procedures outside the operating room may depend on cylinders as
oxygen source. Cylinders have limited storage capacity and a low
oxygen flow rate improves the durability. We conducted the bench study to evaluate the fraction of inspired
oxygen (FiO2) in different
oxygen entrainment devices under low
oxygen flow rate. The purpose of the bench study was to provide information to choose appropriate
oxygen entrainment devices in non-operating room
sedative anesthetic procedures. We utilized a manikin head-test lung-
ventilator model and evaluated eight
oxygen entrainment devices, including four nasal cannulas, two oral
bite blocks, and two masks. Two different minute volumes that defined as the normal ventilation and the
hypoventilation group were evaluated. Three pneuflow resistors were placed in turn in the mouth represented ratio of the nasal/oral breathing. Each condition was sampled 70 times after a 3 min ventilation period. Most devices had few drop in FiO2 according to the increased oral breathing ratio in normal ventilation. Most devices had obvious drop in FiO2 related to the increased oral breathing ratio in
hypoventilation.
Oxygen reservoir units had little effect for accumulating
oxygen in normal ventilation. In the
hypoventilation group,
oxygen reservoir units helped
oxygen retention in local area and maintained a higher
oxygen concentration. There were multiple factors lead to different
oxygen fraction that we measured, such as different devices, respiratory patterns, and
oxygen reservoir units. The result of our bench study provided some information for anesthesiologist to choose appropriate
oxygen entrainment devices in various
sedative anesthetic procedures.