Certified Rehabilitation Registered Nurse (CRRN) Practice Exam

At what level of spinal cord injury does a patient typically become ventilator-dependent?

1. T5

2. C3

3. C2

4. L1

The correct answer is: C2

A patient becomes ventilator-dependent typically with spinal cord injuries at levels C3 and above, as these levels involve the loss of diaphragm function, which is crucial for spontaneous breathing. The cervical spinal cord houses the phrenic nerve, which innervates the diaphragm. Injuries at level C3 indicate that the patient has significant impairment of respiratory function. If the injury is at C3, the nerve supply to the diaphragm is severely compromised, leading to respiratory failure and the need for mechanical ventilation to assist with breathing, as the patient cannot generate adequate tidal volumes or respiratory effort. C2 spinal injuries also lead to ventilator dependence due to the absence of diaphragm control, as the control centers for the diaphragm reside at C3. While spinal injuries at T5 and L1 affect lower trunk and legs but do not impact diaphragm function, they would not lead to the necessity for mechanical ventilation. Therefore, C3 is the critical level at which a patient may require ventilatory support due to compromised ability to breathe independently.