Use of Direct Laryngoscope Improves a Hypopharyngeal Position of Laryngeal Mask Airway / 대한마취과학회지

BACKGROUND: Laryngeal mask airway (LMA) partly can be replaced for a role of endotracheal tube intraoperatively. Even with selecting one from various insertion techniques of LMA, one cannot achieve its perfect hypopharyngeal position. Furthermore, which is chosen by most anesthesiologists in this country, use of muscle relaxant for LMA insertion appears to have a harmful effect on its position. We tried to confirm whether we can improve the hypopharyngeal position of LMA with additional elevation of epiglottis using direct laryngoscope during LMA insertion. METHODS: Forty healthy patients scheduled for surgical procedure under general anesthesia were randomly divided to two groups; Laryngoscope group (n=20) and Jaw thrust group (n=20). No premedicant was administered. Anesthesia was induced with thiopental, vecuronium plus 2~3 vol% enflurane in oxygen. Full muscular relaxation was judged by no adductor response of thumb to train-of-four stimuation. In Jaw thrust group, using Brain's standard technique with additional jaw thrust, LMA was inserted, while in Laryngoscope group, LMA was introduced into oral cavity and advanced farther with additional elevation of epiglottis with direct laryngoscope. Bronchoscopic grading of hypopharyngeal position of LMA was performed. Blood pressure and heart rate were recorded at arrival (control), preintubation and until postintubation 5 minutes at 1 minute interval. Each measured values were compared between groups. RESULTS: Bronchoscopic grade of Laryngoscope group was significantly better than that of Jaw thrust group (p<0.001). Mean arterial pressure and heart rate changes were not different between groups. Conclusion: In the case of LMA insertion using muscle relaxant, we can markedly improve the hypopharyngeal placement of LMA with help of direct laryngoscope.

The Ventilatory Effect of Intratracheal Pulmonary Ventilation in Rabbits with Acute Respiratory Failure / 대한마취과학회지

BACKGROUND: New methods of ventilation are devised to minimize airway pressure increase because high pressure ventilation might result in barotrauma and hemodynamic compromise. Intratracheal pulmonary ventilation(ITPV) was developed to allow a decrease in physiological dead space during mechanical ventilation. ITPV can be applied broadly when it combined with pressure controlled ventilation(PCV) to make a hybrid ventilation(HV). We intended to compare the respiratory effect of HV with volume controlled ventilation(VCV) and PCV. METHODS: Oleic acid of 0.06 ml/kg was injected to induce acute respiratory failure in rabbits. To reduce anatomic dead space, a reverse thrust catheter(RTC) was introduced into an endotracheal tube(ETT) through an adapter and positioned just above the carina inside the ETT. VCV and PCV were compared with HV by measuring peak inspiratory pressure(PIP) and dead space(VD) at various respiratory rates(RR) from 20 breaths/min to 120 breaths/min. Gas flowed through the RTC at the flow rate of 1 liter/min during HV. RESULTS: The values of VD of VCV were 37+/-10 ml, 29+/-11 ml, 23+/-5 ml, and 18+/-3 ml at respiratory rate of 20 breaths/min, 40 breaths/min, 80 breaths/min and 120 breaths/min, respectively. The values of VD of PCV were 33+/-6 ml, 28+/-7 ml, 23+/-5 ml, and 18+/-3 ml, respectively. The values of VD of HV were 25+/-13 ml, 15+/-8 ml, 9+/-5 ml, and 8+/-4 ml, respectively. The VD of HV were significantly lower than those of VCV and PCV at the same RR. The PIP was lower in HV than in VCV and PCV at the same RR. CONCLUSION: It can be concluded that HV, as a modification of ITPV, can be applied to acute respiratory failure in rabbits to minimize airway pressures and dead space of mechanical ventilation.