**Question:** All of the following are causes of bronchopulmonary dysplasia except –

A. Hypoxia
B. Hyperoxia
C. Infection
D. Prolonged ventilation

**Correct Answer:** **B. Hyperoxia**

**Core Concept:**
Bronchopulmonary dysplasia (BPD) is a chronic lung disease in premature infants, characterized by abnormal lung development and impaired lung function. BPD primarily affects infants born very prematurely and those exposed to high levels of oxygen supplementation. The disease is often seen in infants born at ≤28 weeks of gestation or with birth weights <1000g. **Why the Correct Answer is Right:** Hyperoxia refers to the excessive exposure to oxygen, which may damage lung tissue and increase the risk of BPD. High oxygen levels can lead to alveolar damage, inflammation, and increased production of reactive oxygen species (ROS), causing oxidative stress that contributes to lung injury. **Why Each Wrong Option is Incorrect:** A. Hypoxia (oxygen deficiency) is a significant problem in premature infants, as it can impair lung development and contribute to BPD. Thus, this is not the correct answer. C. Infection (pneumonia) is a common complication in premature infants, but it is not the primary cause of BPD. Infection can exacerbate pre-existing lung injury and contribute to the development of BPD, making it less relevant as an answer compared to hyperoxia. D. Prolonged ventilation refers to the need for mechanical ventilation to support breathing in preterm infants. While prolonged ventilation can contribute to lung injury, the focus here is on the excessive exposure to oxygen, making hyperoxia the more appropriate answer. **Clinical Pearl:** Avoiding or minimizing exposure to high oxygen levels is crucial in preventing bronchopulmonary dysplasia in premature infants. Administering personalized oxygen targets, typically close to room air saturation levels, can help reduce the risk of BPD. This approach is particularly important in infants born very prematurely or with low birth weights, as they are at increased risk for lung injury due to oxidative stress from hyperoxia.