The purpose of this study is to compare changes in breathing patterns elicited by hypoxic stress and/or anesthetic stress in mice. Spontaneously breathing anesthetized mice whose tracheae were intubated with a tracheal cannula were challenged with hypoxic stress and/or sevoflurane-induced anesthetic stress while ventilation was measured with a pneumotachograph. When anesthesia was maintained at a light level with inhalation of 2.3 % sevoflurane (0.7 MAC), exposure to severe hypoxic gas (5% O2 in N2) triggered a breathing pattern characterized by gasping respiration. Inhalation of a high concentration of sevoflurane (6.5 %: 2.0 MAC) under hyperoxia elicited the same gasping. Also, the combination of mild hypoxia (inhalation of 10 % O2 in N2) and moderate sevoflurane anesthesia (3.25 %: 1.0 MAC) consistently elicited the same gasping, while mild hypoxic and moderate anesthetic stress alone did not elicit any gasping. These findings suggest that both hypoxia-induced gasping and sevoflurane-induced gasping could be generated by the same intrinsic mechanism within the brainstem.
Keywords: Breathing patterns; Gasping; Hypoxia; Sevoflurane anesthesia.
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