Short answer: Yes. In an urgent situation you can file an expedited appeal and request an external review at the same time, without waiting to finish the internal process. An urgent internal appeal must be decided within about 4 business days, and an expedited external review within 72 hours.
Normally you complete the internal appeal before an external review, but urgent care is an exception. If waiting for the standard process would seriously jeopardize your life or your ability to regain maximum function, you can file an expedited (faster) appeal and ask for an external review at the same time.
For an expedited internal appeal, a final decision must come as quickly as your condition requires, and at least within 4 business days after your request is received (it can be delivered verbally, then confirmed in writing within 48 hours). Expedited external reviews are decided as soon as possible, no later than 72 hours after the request.