Figure 1.

A: normal breathing requires the integration of rhythmogenic, modulatory, and sensory feedback mechanisms. Opioid overdose can suppress all of these important mechanisms of respiratory control, leading to OIRD. B: human brainstem schematic illustrating key sites in the pons and medulla that mediate OIRD. Ventral view is shown on the left, and transverse sections are shown on the right. Colors in B correspond to mechanisms depicted in A. NTS, nucleus tractus solitarius; OIRD, opioid-induced respiratory depression; preBOTc, preBӧtzinger complex.