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. Author manuscript; available in PMC: 2017 Jun 8.
Published in final edited form as: Anesthesiology. 2014 Dec;121(6):1175–1183. doi: 10.1097/ALN.0000000000000462

Figure 1.

Figure 1

Protocol design. Baseline measurements were recorded during wakefulness and at three different levels of carbon dioxide (0, +4 and +8mmHg elevations above baseline). Subjects were then randomized for order to receive either propofol or sevoflurane first, starting at the same dose (estimated ED50) for each volunteer. To establish similar levels of shallow and deep anesthesia for each volunteer, a pain stimulus was applied to assess the depth of anesthesia. Depending on the response, the dosage was increased or decreased by 50% to arrive at a new dose of the drug. The same three levels of carbon dioxide (CO2, 0, +4, and +8mmHg) were applied during anesthesia. Spontaneous swallows were recorded during all conditions.