A 20-year-old female patient has called 911 for chest pain. On scene, you find that she has shallow breathing with an SpO2 reading of 91% on room air. She states she was in a car crash yesterday and diagnosed in the hospital with broken ribs. Her pain is right where the ribs are broken, and she rates the pain as a 10/10. Breath sounds are present bilaterally. In this situation, the EMT should attribute the hypoxia to which cause?

A) The fractured ribs have pierced the lung, causing it to collapse
B) Swelling from the rib fractures has compressed the lung
C) The patient is bleeding into the lungs, compressing the alveoli
D) Pain from rib injury prevents full expansion of the chest cage

D) Pain from rib injury prevents full expansion of the chest cage