Final answer:
Residents with head or spinal cord injuries should be re-positioned every two hours to prevent complications and ensure their well-being.
Step-by-step explanation:
A resident with a head or spinal cord injury should be re-positioned at least every two hours to prevent pressure ulcers and to promote circulation and comfort. More frequent repositioning may be needed depending on the individual's condition and the recommendations of healthcare professionals. It is crucial to follow a care plan that is tailored to the specific needs of the individual with a head or spinal cord injury.