It would depend on the mechanism of damage. Sometimes the phrenic nerve can be injured via mechanical damage. If this is the case, there is a second phrenic nerve which innervates the other side of the diaphragm. With a single diaphragm patients can survive, but will often have some level of respiratory insufficiency. Bilateral Phrenic nerve paralysis is sometimes seen with neuropathic disorders and can lead to severe respiratory insufficiency. Overall, it would depend on how much of the diaphragm is injured or denervated and what underlying conditions are present when the damage occurs.
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