Final answer:
The muscle that helps assess diaphragm function to assess for deep NMB is the dorsal respiratory group (DRG) in the region of the medulla oblongata.
Step-by-step explanation:
The muscle that helps assess diaphragm function to assess for deep neuromuscular blockade (NMB) is the dorsal respiratory group (DRG) in the region of the medulla oblongata. The DRG stimulates the contraction of the diaphragm and intercostal muscles to induce inspiration. By assessing the function of this muscle, the degree of NMB can be determined.