Advancement of the mandible facilitates nasal breathing in human subjects sedated with midazolam

Purpose: To determine how anterior advancement of the mandible (ADM) affect s spontaneous breathing through the nasal route in healthy human volunteers sedated with intravenous midazolam. Methods: In four subjects who exhibited nasal breathing during midazolam se dation (intravenous dose: 0.09 +/- 0.02 mg.kg(-1), mean +/- SD), we measure d respiratory rate (RR), peak nasal inspiratory airflow rate ((V over dot)( nlpeak)), peak nasal expiratory airflow rate ((V over dot )(nEpeak)), duty ratio(Ti/Ttot) and nasal resistance (Rn) before and after ADM. Nasal resist ance was calculated by dividing the difference between nasal mask and oroph aryngeal pressure by airflow rate at peak nasal inspiratory airflow. Results: The RR, (V over dot)(nlpeak), and (V over dot)(nEpeak) increased f ollowing ADM (P < 0.001 respectively). On the contrary, Ti/Ttot decreased a fter ADM.(P < 0.001). Consequently, ADM decreased Rn from 30.4 +/- 40.8 to 5.0 +/- 5.6 (cmH(2)O . 1(-1).sec(-1)) (mean +/- SD) (P < 0.001). In these f our subjects, no respiratory airflow was observed through the oral route be fore and after ADM. Conclusion: Advancement of the mandible decreases nasal resistance, thereby facilitating spontaneous breathing through the nasal route in normal human s sedated with midazolam.