Abstract: Objective To compare the effects of transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) and mask ventilation on oxygenation and duration of safe apnea after induction of general anesthesia in the elderly patients with tooth less. Methods Fifty elderly patients with tooth less(missing more than 10 teeth) were divided into facemask group (group M) and THRIVE group (group T). In the preoxygenation stage before induction of anesthesia, facemask was used in group M, while THRIVE was used in group T. After the induction of general anesthesia, group M underwent pressure-controlled ventilation, and group T adjusted the flow to 70 L/min. After the muscle relaxant was injected for 4 min, group M stopped the mask ventilation, while group T continued ventilation. When the duration of safe apnea reached 8 min or the level of pulse oxygen saturation (SpO₂) dropped to 95%, the experiment was terminated, and the endotracheal intubation was performed immediately with a visual laryngoscope. The cases with duration of safe apnea reaching 8 min, reoxygenation time, and the levels of arterial partial pressure of oxygen(PaO₂), arterial partial pressure of carbon dioxide(PaCO₂), heart rate(HR), mean arterial pressure(MAP) in different time points were recorded. The ventilation and endotracheal intubation-related complications were recorded and compared between the two groups. Results All the patients in group T had a duration of safe apnea of 8 min, while only 6 patients (24%) in group M had a duration of safe apnea of 8 min (P<0.05). Compared with group M, the reoxygenation time in group T was significantly shorter (P<0.05). The level of PaO₂ in the two groups increased after preoxygenation. During simulating apneic tracheal intubation period, the level of PaO₂ decreased significantly in group M, while decreased slightly in group T(P<0.05). Compared with the basic level, the level of PaCO₂ during apneic period increased signifcantly in both groups, especially in group T (P<0.05). There were no significant differences in the hemodynamic indicators and the incidence rate of the complications related to endotracheal intubation and ventilation between the two groups (P>0.05). Conclusions Compared with facemask, THRIVE can significantly prolong the duration of safe apnea after induction of general anesthesia in the elderly patients with tooth less and reduce the reoxygenation time.

Key words: transnasal humidified rapid-insufflation ventilatory exchange, aged, tooth less, apenic oxygenation, duration of safe apnea