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

Yasuko Kawauchi, MD^*, Tsutomu Oshima, MD PhD, Satomi Suzuki, MD^*, Yuhji Saitoh, MD PhD^* and Hidenori Toyooka, MD PhD

^* From the Departments of Anesthesiology, School of Medicine, Tokyo Medical and Dental University, Tokyo,
Gifu University School of Medicine, Gifu and the
Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.

Address correspondence to: Tsutomu Oshima MD, Department of Anesthesiology and Critical Care Medicine, Gifu University School of Medicine, 40 Tsukasamachi, Gifu-City, Gifu 500-8705, Japan. Phone: 81-58-267-2295; Fax: 81-58-267-2961; E-mail: oshimat{at}cc.gifu-u.ac.jp

Purpose: To determine how anterior advancement of the mandible (ADM) affects spontaneous breathing through the nasal route in healthy human volunteers sedated with intravenous midazolam.

Methods: In four subjects who exhibited nasal breathing during midazolam sedation (intravenous dose: 0.09 ± 0.02 mg•kg^{- 1}, mean ± SD), we measured respiratory rate (RR), peak nasal inspiratory airflow rate ( _nIpeak), peak nasal expiratory airflow rate ( _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.

Results: The RR, _nIpeak, and _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 (cmH₂O•l^–1•sec^{- 1}) (mean ± SD) (P < 0.001). In these four subjects, no respiratory airflow was observed through the oral route before and after ADM.

Conclusion: Advancement of the mandible decreases nasal resistance, thereby facilitating spontaneous breathing through the nasal route in normal humans sedated with midazolam.

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				Y Kawauchi, T Oshima, Y Saitoh, and H Toyooka Flumazenil abolishes midazolam-induced increase in the work of nasal breathing Can J Anesth, December 1, 2000; 47(12): 1216 - 1219. [Abstract]