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

Abstract

To determine how anterior advancement of the mandible (ADM) affects spontaneous breathing through the nasal route in healthy human volunteers sedated with intravenous midazolam. In four subjects who exhibited nasal breathing during midazolam sedation (intravenous dose: 0.09+/-0.02 mg x kg(-1), mean +/- SD), we measured respiratory rate (RR), peak nasal inspiratory airflow rate (V(nIpeak)) peak nasal expiratory airflow rate (V(nEpeak), duty ratio (Ti/Ttot) and nasal resistance (Rn) before and after ADM. Nasal resistance was calculated by dividing the difference between nasal mask and oropharyngeal pressure by airflow rate at peak nasal inspiratory airflow. The RR, V(nIpeak), and V(nEpeak) increased following ADM (P<0.001, respectively). On the contrary, Ti/Ttot decreased after ADM (P<0.001). Consequently, ADM decreased Rn from 30.4+/-40.8 to 5.0+/-5.6 (cm H2O x l(-1) x sec(-1)) (mean +/- SD) (P<0.001). In these four subjects, no respiratory airflow was observed through the oral route before and after ADM. Advancement of the mandible decreases nasal resistance, thereby facilitating spontaneous breathing through the nasal route in normal humans sedated with midazolam.