Oxidative stress pathways capable of producing reactive oxidant species. These pathways include nitric oxide synthase pathway, xanthine oxidase pathway, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase pathway, and mitochondrial oxidant-generating pathway. The mitochondrial oxidant-generating pathway is key to oxidative damage of diaphragm muscle inactivity. O2+ superoxide; NO+, nitric oxide. Adapted with permission from .