Correspondence  |   November 2017
In Reply
Author Notes
  • Graduate School of Medicine, Chiba University, Chiba, Japan (S.I.).
  • (Accepted for publication July 5, 2017.)
    (Accepted for publication July 5, 2017.)×
Article Information
Correspondence   |   November 2017
In Reply
Anesthesiology 11 2017, Vol.127, 897-898. doi:10.1097/ALN.0000000000001829
Anesthesiology 11 2017, Vol.127, 897-898. doi:10.1097/ALN.0000000000001829
We thank Drs. Zhou and Wang for their thoughtful comments on our study.1  Certainly, many factors may influence the tidal volume during anesthesia induction. We previously reported that progressive muscle paralysis induced by rocuronium injection did not change the tidal volume during facemask ventilation without airway maneuvers in adult subjects with normal upper airway anatomy.2  In contrast to Ikeda et al.’s study,2  the tidal volume progressively improved in both non–sleep disordered breathing and sleep disordered breathing groups in Sato et al.’s study.1  We believe there are three major differences between Ikeda et al.’s and Sato et al.’s study designs: anesthesia depth, initial airway patency, and airway maneuvers by the anesthetists. It is our opinion that anesthesia depth contributes little to time dependence of the tidal volume, given that pharyngeal collapsibility increases only slightly by increasing anesthesia depth with propofol, however, the pharyngeal collapsibility profoundly increases immediately after loss of consciousness.3  The pharyngeal airway was initially open in Ikeda et al.’s study but was not controlled in Sato et al.’s study. We suspect that the pharyngeal airway initially closed, particularly in Sato et al.’s patients with sleep disordered breathing; subsequently, surface adhesive forces of the pharyngeal airway mucosa may have played a role in making reopening of the airway difficult.4  We believe that minor adjustments made for each individual patient throughout the airway maneuver process by the anesthetists, as well as the gradual progression of muscle paralysis and anesthesia depth, will lead to achievement of a more successful and constant airway maneuver. Regrettably, we did not measure the change in rigidity of the neck and mandible, nor the process of proper head extension and mandible advancement during mask ventilation.
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