Character Analysis
Before we saw these movies, we honestly had no idea that droids could have health problems. But boy oh boy, is General Grievous a wheezing, hacking, sputum-producing barrel of maliciousness.
Originally, General Grievous' asthmatic cough was part of an amusing production idea. George Lucas came in with a cold, so hey, when life gives you a cold, record your pretty voice and turn it into a villain's. It was also intended to spotlight the organic versus synthetic. While Grievous' organs are aging, cyborg technology also has its flaws (perhaps this provides an explanation as to why Darth Vader also has those gasping sound effects). (Source)
Biology of cyborgs aside, Grievous is the secondary antagonist of our film. He is Darth Sidious' mouthpiece, leading the Separatists through vicious threats and misdirection.
Prone to fleeing at the first hint of defeat, he's cowardly but smart. After all, those who run live to fight another day. Although as a character he doesn't really develop much depth (basically, he's an evil droid … there's not much motivation there as opposed to sheer design), he does provide an excuse for some really awesome chase scenes.