Elsevier

Seminars in Neonatology

Volume 8, Issue 1, February 2003, Pages 63-71
Seminars in Neonatology

Bronchopulmonary dysplasia: changes in pathogenesis, epidemiology and definition

https://doi.org/10.1016/S1084-2756(02)00192-6Get rights and content

Abstract

Bronchopulmonary dysplasia (BPD) continues to be one of the most common long-term complications associated with preterm birth. Its incidence is increasing as the survival of extreme premature infants improves, but its clinical presentation is milder than the original description of Northway and collaborators. In contrast to the classic BPD that was strongly related to mechanical injury and oxygen toxicity, current forms of the condition are more related to immaturity, perinatal infection and inflammation, persistent ductus arteriosus and disrupted alveolar and capillary development. Many different definitions of BPD have been proposed, most of which are based on the duration of supplemental oxygen requirement. The different definitions can produce strikingly different incidence figures, which may account for the wide variations in the condition reported in the literature. Some of the limitations of the criteria most commonly used to diagnose BPD are discussed in this article.

Introduction

The introduction of antenatal steroids, postnatal surfactant therapy and modern respiratory care has made the severe classic presentation of Bronchopulmonary dysplasia (BPD) originally described by Northway et al.1 much less common. It has instead been replaced by a milder clinical form, often found in small premature infants who survive after prolonged mechanical ventilation. Many of these infants present initially with no, or mild, respiratory distress syndrome (RDS) that responds rapidly to surfactant therapy and instead require prolonged mechanical ventilation because of apnea and poor respiratory effort.2 These infants have thus not been exposed to high airway pressures or high inspired oxygen concentrations, the two main factors invoked in the pathogenesis of the original form of BPD. It is this milder form of illness that had been referred to as chronic lung disease or ‘new BPD’ and is now again being called simply BPD.

Section snippets

Clinical presentation of the new BPD

With rare exceptions, BPD is preceded by the use of mechanical ventilation early in life. The initial indications for mechanical ventilation may include respiratory failure from RDS or pneumonia, or poor respiratory effort. An increasing number of small infants have mild respiratory disease and initially receive ventilation with a low pressure and oxygen concentration. This is often followed by a few days with minimal or no need for supplemental oxygen (a ‘honeymoon’ period). After a few days

Risk factors for BPD

Many factors, alone or in combination, have been implicated in the pathogenesis of BPD. Because BPD occurs almost exclusively in premature infants who have received mechanical ventilation and oxygen therapy, prematurity, mechanical trauma and oxygen toxicity have been implicated as crucial factors in the pathogenesis of BPD.4, 5, 6 Other factors that appear to play an important role in pathogenesis include inflammation (alone or associated with infection),7, 8, 9, 10, 11, 12, 13, 14, 15, 16

Incidence of BPD

The incidence of BPD reported in the literature varies widely, this wide variation in incidence being related to several factors. The first factor involves differences in patient susceptibility and management in different populations and institutions. A more important factor, however, relates to inconsistencies in the definition of BPD (discussed in greater detail subsequently). The incidence of BPD, defined as oxygen dependency at 36 weeks postmenstrual age (PMA), in infants with a birthweight

Definition of BPD

As previously mentioned, the lack of uniformity in the diagnostic criteria of BPD is prevalent throughout the literature and is responsible for much of the variation in incidence of BPD between reports (Table 1). The different diagnostic criteria for BPD have largely been based on a single clinical criterion, the need for prolonged oxygen therapy, which serves as a marker for chronic respiratory failure.

In the 1970s, we proposed criteria to define BPD as oxygen dependency during the first month

Summary

In summary, BPD continues to be a major health problem for the increasing number of surviving extremely premature infants. Its clinical presentation and pathogenesis have changed so preventive strategies must be responsive to these changes. Although definitions and diagnostic criteria for BPD have been numerous, as well as having their limitations, it becomes critical to arrive at standard criteria for the diagnosis of BPD when this is used as a major end point in clinical research or when

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