National Physical Therapy Examination (NPTE) Practice Exam

In a patient with a pulmonary embolism, what factor most likely contributes to hypoxemia?

1. Poor ventilation in the lungs

2. An ineffective cough

3. Poor perfusion in the lungs

4. Retained secretions in the lungs

The correct answer is: Poor perfusion in the lungs

In a patient with a pulmonary embolism, hypoxemia is primarily due to poor perfusion in the lungs. A pulmonary embolism is characterized by a blockage in one or more pulmonary arteries, typically caused by blood clots that travel to the lungs from the deep veins in the legs or other parts of the body. This blockage leads to a significant reduction in blood flow to the affected areas of the lung, impairing gas exchange. When the perfusion is compromised, even if the ventilation remains normal, the mismatch between ventilation and perfusion results in inadequate oxygenation of the blood. This is referred to as a V/Q (ventilation/perfusion) mismatch, where areas of the lung may be appropriately ventilated but not perfused, leading to a decrease in the amount of oxygen entering the bloodstream. Consequently, this lack of adequate blood flow results in hypoxemia, as oxygen cannot be effectively transported to the systemic circulation. Other factors, such as poor ventilation or retained secretions, can contribute to respiratory issues but are not as directly related to the hypoxemia seen in pulmonary embolism as poor perfusion is. An ineffective cough can result in retained secretions, which might lead to secondary infections or atelectasis, but the primary cause