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. Author manuscript; available in PMC: 2018 Sep 1.
Published in final edited form as: Anesthesiology. 2017 Sep;127(3):502–514. doi: 10.1097/ALN.0000000000001719

Figure 6.

Figure 6

Hypothetical model of inputs determining (A) inspiratory and (B) expiratory phase duration. Intrinsic activity (Iintrinsic) is modified by opioid-sensitive inputs from the preBötzinger Complex (FpreBötC), the tachypneic area of the parabrachial nucleus (FtPBN) and additional brainstem sites (Fadditional). Systemic opioids reduce these inputs by the factor “r”. FpreBötC increases (+) inspiratory duration (TI) while FtPBN and Fadditional decrease (−) TI. Systemic opioids reduce these inputs resulting in a net increase in TI. All opioid-sensitive inputs decrease TE. Systemic opioids reduce these inputs resulting in a large increase in TE.