Introduction to Bronchopulmonary Dysplasia (BPD)

Watching your baby in the Neonatal Intensive Care Unit (NICU) is one of the most difficult experiences a parent can face. When doctors begin talking about Bronchopulmonary Dysplasia (BPD), it can feel like one more overwhelming hurdle. BPD is a chronic lung disease of prematurity that occurs when a baby’s lungs do not develop as expected after an early birth ^[1][2].

Because your baby was born early, their lungs were forced to take over the job of breathing before they were fully formed. While the medical team works to support your baby, the very treatments that save their life—like supplemental oxygen and mechanical ventilators—can sometimes cause irritation to these fragile tissues ^[3][4].

Understanding “New” vs. “Old” BPD

In the past, BPD was often defined by heavy scarring and damage (fibrosis) caused by older, high-pressure ventilators ^[1]. Today, thanks to gentler equipment and better treatments like surfactant (a liquid that helps the lungs stay open), the condition has changed.

Doctors now refer to this as “New BPD.” Rather than thick scars, the primary issue is arrested alveolar simplification ^[1][5]. Alveoli are the tiny air sacs in the lungs where oxygen enters the blood. In New BPD, these sacs stop dividing and growing. Instead of millions of small, efficient air sacs, the lungs develop fewer, larger, and less efficient sacs ^[5].

Why Does This Happen?

BPD is rarely caused by a single event. Instead, it is the result of several factors working together:

• Prematurity: The more premature a baby is, the higher the risk, because their lungs are at a very early stage of development ^[6].
• Oxidative Stress: While oxygen is vital, high concentrations can lead to a “redox imbalance,” which causes oxidative stress—a type of chemical stress that damages developing lung cells ^[4][7].
• Inflammation: Infections like sepsis (blood infection) or chorioamnionitis (infection of the fetal membranes) trigger inflammation that can disrupt lung growth ^[8][9].
• Mechanical Injury: Even with modern equipment, the pressure and volume of air from a ventilator can cause volutrauma (over-stretching) or barotrauma (pressure damage), leading to ventilator-induced lung injury (VILI) ^[3][10].

How Common is BPD?

Because medical care has improved, more extremely premature and extremely low birth weight (ELBW) infants are surviving. This means BPD has actually become more common in NICUs ^[11][12]. Depending on how it is defined, incidence rates can range from 6% to 57% among very premature babies ^[6][11].

When is a Diagnosis Made?

A formal diagnosis of BPD is typically not made the moment a baby starts having trouble. Instead, doctors wait until a baby reaches 36 weeks postmenstrual age (the age they would be if they were still in the womb) ^[13][6].

At this 36-week milestone, doctors assess the baby’s need for respiratory support. Many NICUs use a “physiological definition,” which may include a room air challenge ^[13]. In this test, the medical team carefully lowers the baby’s supplemental oxygen to see if they can maintain healthy oxygen levels (usually $\ge$ 90%) while breathing normal room air ^[13][14]. If a baby still needs extra oxygen or pressure support at this stage, they are diagnosed with BPD, which helps the team plan for their long-term care ^[13][14].

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