Prehospital Trauma Life Support (PHTLS) Practice Test 2025 – All-in-One Resource to Ensure Exam Success!

In pulmonary contusion, the primary mechanism that interferes with oxygenation is the presence of blood and fluid in the alveoli and interstitial spaces of the lung. This condition leads to a disruption in gas exchange because the accumulation of fluid and blood impairs the ability of oxygen to diffuse from the alveoli into the bloodstream. The presence of these substances creates a barrier between the air in the alveoli and the pulmonary capillaries, which decreases overall oxygen delivery to the body's tissues.

Through pulmonary contusion, the damaged lung tissue can become inflamed and leak, contributing to pulmonary edema. This edema further complicates the situation by increasing the distance that oxygen must travel to reach the blood, thus significantly impairing oxygen saturation levels.

The mechanisms described in the other choices, such as the inability to generate negative intrapleural pressure or changes in vital capacity, could contribute to respiratory compromise, but the most direct and critical issue regarding oxygenation in pulmonary contusion is the impairment caused by the accumulation of blood and fluid in the alveoli and interstitial spaces.