Bronchopulmonary Dysplasia

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Definition

Bronchopulmonary Dysplasia on X-ray

Bronchopulmonary dysplasia (BPD) is one of the most common causes of morbidity and mortality in preterm infants. Despite significant advances in preterm infant care over the past few decades, the prevalence of this condition remains high. BPD is a chronic lung condition that is caused by tissue damage to the lungs.

• Usually occurs in immature infants who have had severe lung disease at birth eg neonatal respiratory distress syndrome
• The delicate tissues of the lungs can become injured when the alveoli (air sacs) are hyper inflated (over-stretched) by the ventilation or by high oxygen levels.
• As a result, the lungs become inflamed and additional fluid accumulates within the lungs.
• BPD is marked by inflammation, exudates, scarring, fibrosis, and emphysema, and most commonly presents itself in pre-term infants to 21 days post natal.

Despite significant advances in preterm infant care in the past few decades, including the development of surfactant as well as newer and gentler modes of ventilation, the prevalence of BPD continues to remain high. These new strategies have allowed the survival of very low birth weight infants and resulted in a change in the characteristics of BPD. Jobe coined the term “new BPD” in 1999 to describe the chronic lung disease in preterm infants at that time. This “new BPD” demonstrated much less airway damage and alveolar septal fibrosis when compared to “old BPD” which was characterized by dysmorphic microvasculature and alveolar simplification.

Etiology

Bronchopulmonary dysplasia is a multifactorial pathology that is influenced by a variety of prenatal and postnatal factors affecting the mother and infant. The various prenatal risk factors that influence the development of BPD include:

• Lack of antenatal steroids
• Maternal smoking
• Pregnancy-induced hypertension/preeclampsia
• Hypoxia
• Maternal infection

Similarly, various postnatal factors predispose premature infants to develop BPD including:

• Lung immaturity
• Poor nutrition
• Need for mechanical ventilation
• Oxygen injury
• Infection/sepsis

Pathophysiology

Injury from mechanical ventilation and reactive oxygen species to premature lungs in the presence of antenatal factors predisposing the lungs to BPD form the basis of pathogenesis of BPD in preterm neonates. This myriad of events leads to an exaggerated inflammatory response with an increase in proinflammatory cytokines like interleukin(IL)-6, IL 8, tumor necrosis factor alpha etc along with growth factors (transforming growth factor ) and angiogenic factors (vascular endothelial growth factor, angiopoietin 2) which ultimately results in aberrant tissue repair and arrest in lung development. Dysregulated vascular and arrested alveolar development form the basis of the pathology seen in “new BPD.”

Causes and Risk Factors

BPD occurs in severely ill infants who have received high levels of oxygen for long periods of time or who have been on a ventilator during treatment for respiratory distress syndrome. It is more common in infants born early (premature) whose lungs were not fully developed at birth.

The following risk factors have been identified:

• Premature birth.
• Respiratory Infection.
• Meconium aspiration.
• Congenital heart disease.
• It may also occur as a secondary problem for the neonate attached to a mechanical ventilator.

Signs and Symptoms

The most noted signs in an infant with BPD. The most Common signs of BPD are:

• Shortness of breath
• Cough
• Wheezing

If BPD worsens, the infant will present with:

• Severely difficult breathing with grunting
• The chest and abdomen move in opposite directions with every breath
• Rib retractions: ribs are visible during each breath
• Nasal flaring: nostrils open wide during each breath
• Use of accessory muscles: neck muscles are prominent during each breath
• Rapid breathing rate

Complications of BPD

Pulmonary Edema

BPD is one of the most prevalent morbidities associated with prematurity and carries associations with the following complications:

• Systemic hypertension
• Poor neurodevelopmental outcome
• Pulmonary Hypertension
• Left ventricular hypertrophy and left ventricular dysfunction

Diagnosis

It is difficult to determine whether or not a baby has bronchopulmonary dysplasia (BPD) before he or she is about 14 to 30 days old. By this time the baby should be showing improvement in breathing problems, instead the condition seems to be getting worse and the baby requires more oxygen and assistance from a ventilator.

According to kidshealth.com when making a diagnosis the following factors should be taken into account:

• Prematurity
• Infection
• Mechanical Ventilator dependence for a prolonged period

BPD is confirmed as a diagnosis if the infant requires additional oxygen and continues to shows signs of respiratory distress after 28 days of age. A number of tests are also conducted on newborns with breathing problems to make sure they diagnose their condition correctly.

According to the National heart, lung and blood institute these tests include:

• Blood tests. Blood samples are checked to see whether the baby has enough oxygen in his or her blood.
• Chest x-rays. It shows larger areas of air and changes from inflammation or infection. It also shows areas of the lung that have collapsed and may help confirm that the lungs aren't developing normally. On a chest x – ray, the lung tissue appears spongy.
• Echocardiogram. The use of sound waves to create a moving picture of the heart. Echocardiogram is used to rule out congenital heart defects or pulmonary arterial hypertension as the cause of the breathing problems.

Doctors grade BPD as mild, moderate, or severe, depending on how much supplemental oxygen the baby needs and how long he or she needs it.

Prevention

There are a number of things a mother can do to prevent her baby from being born before their lungs have fully developed:

• During pregnancy, regular check ups with the doctor should be done.
• Dietary supplements are essential, along with good, healthy eating habits.
• Avoid smoking, consuming alcohol and taking illegal drugs.
• It is vital that the mother-to-be is controlling any chronic diseases (e.g. Diabetes, Hypertension etc.) with proper medication.
• Mothers-to-be must make sure that they attend to all cuts and bruises as soon as possible to prevent infections and other easily attainable communicable diseases.

Medical Management

The global aim in the management of infants with BPD is to support them while lung growth occurs, limit further injury to the lungs, optimize lung function and detect complications associated with BPD. According to the National Heart, Lung and Blood Institute, medical management of a child with RDS and possibly BPD includes:

Breathing Support

The baby is usually put on a mechanical ventilator. The ventilator, which is connected to a breathing tube that runs through the baby's mouth or nose into the windpipe, can be set to help a baby breathe or to completely control a baby's breathing. It also is set to give the amount of oxygen the baby requires. With help breathing, the baby's lungs have a chance to develop.

Surfactant Replacement Therapy

The baby is given surfactant to open his or her lungs until the lungs have developed enough to start making their own surfactant. Surfactant is given through a tube that is attached to the ventilator, which pushes the surfactant directly into the baby's lungs.

Medication

Medication is usually prescribed to reduce swelling in the airways and improve the flow of air in and out of the lungs. These medications include:

• Bronchodilators – Bronchoconstriction and airway hyper reactivity.
• Diuretics - Pulmonary edema, and removal of extra fluid in the lungs.
• Steroids - To decrease airway inflammation.
• Vasodilators - Cor pulmonale.
• Antibiotics - Control infections
  

Supportive Therapy

Treatment in the NICU is designed to limit stress on the baby and meet his or her basic needs of warmth, nutrition, and protection. According to the National Heart, Lung and Blood Institute, such treatment usually includes:

• Using a radiant warmer or incubator to keep your baby warm and reduce the chances of infection.
• Ongoing monitoring of blood pressure, heart rate, breathing, temperature and the amount of oxygen in the baby's blood.
• Monitoring fluid intake to make sure that fluid doesn't build up in the baby's lungs.
  

Physiotherapy Management

It must be noted that infants with Bronchopulmonary Dysplasia are cared for in the Neonatal Intensive Care Unit.

The mainstay of physiotherapy treatment is to clear the chest of secretions. This can be done by:

• Vibrations and light percussions.
• Changing positions helps to mobilise secretions out of the small airways.
• Suctioning and mucolytics may be an option for tenacious sputum and when the child has difficulty coughing.
  

Evidence

There is limited evidence for the role of physiotherapy in the treatment of BPD. A study carried out by Gomez-Comesa et al, reported that physiotherapy treatment in the NICU was effective in improving BPD in prematurely born children with respiratory distress syndrome. Physiotherapy assisted in reducing the number of days that ventilation and hospitalization were required and favoured the prevention of future disabilities.

Prognosis

BPD is a chronic illness that persists beyond discharge from the hospital and into adulthood. Infants with BPD have a 50% chance of readmission to the hospital during their first year of life. They have an increased risk of developing reactive airway disease, asthma, emphysema, and RSV bronchiolitis. BPD also affects their growth and neurodevelopmental outcome. VLBW infants with BPD are more likely to have delays in fine and gross motor skills, and language.

Infants with BPD are at high risk for cardiopulmonary sequelae like pulmonary hypertension (PH), cor pulmonale, and systemic hypertension.