Pulmonary mechanics during respiratory distress syndrome in the prediction of outcome and differentiation of mild and severe bronchopulmonary dysplasia

Abstract

Pulmonary mechanics was prospectively and longitudinally studied in a cohort of 58 infants who suffered from respiratory distress syndrome. The aim was to determine if early compliance and resistance measurements had additional value to simple clinical variables in predicting poor outcome ie nonsurvival or severe bronchopulmonary dysplasia (BPD) at 28 days. Second, we wanted to determine whether and when the recently described type 1 (mild) BPD and type 2 (severe) BPD could be differentiated by means of lung function tests. In a logistic model, neither lung compliance nor pulmonary resistance at days 1 and 4 of life were selected as predictive variables. On the other hand, gestational age and the ventilatory index no. 1 (ventilator frequency x maximal inspiratory pressure) on day 3 were the best early predictors of poor outcome. Type 2 BPD was characterized by a lower lung compliance and a higher pulmonary resistance than type 1 BPD, although the differences were only significant at 28 days. In conclusion, pulmonary function tests were not helpful in the early prediction of poor outcome at 28 days. They might, however, be of value in the follow-up of BPD patients after 28 days.

Respiratory mechanics in ventilated preterm infants: early determinants and outcome

“…210,256,270 In contrast to these findings, acute lung inflammation is often less severe in extremely immature infants. One might think that in these infants long-term respiratory morbidity would be less severe as well.…”

“…19,46,70,89,137,160,256 Increased respiratory system resistance may both contribute to development of lung damage and be a manifestation of CLD itself. Airway damage secondary to endotracheal intubation, positive pressure, and/or high oxygen concentrations may cause increased respiratory system resistance, as may increased pulmonary blood flow or left heart failure secondary to a patent ductus arteriosus (PDA) causing peribronchial oedema.…”

“…Therefore, the number of a priori selected predictors was limited, increasing the risk of missing valuable predictors, for example, ventilator conditions, which have been studied as potential predictors of respiratory course before. 91,137,214,256,270 Since in small data sets regression coefficients tend to overestimate, we used the heuristic shrinkage method to correct for this effect. However, external prospective validation in a comparable group of infants is still recommended before widespread use of the prediction models can be encouraged.…”

“…In addition, endotoxin-stimulated secretion of several proinflammatory cytokines, like tumour necrosis factor, IL-1 and IL-6 by alveolar macrophages, may be decreased after administration of surfactant. 256 Hence, surfactant treatment may decrease the granulocyte accumulation and oedema that is partly caused by mechanical ventilation. 129 Furthermore, surfactant also inhibits neutrophil superoxide production 5 and has been shown to reduce bacterial growth in experimentally induced group-B streptococcal infection in immature rabbits.…”

“…Results relating these parameters to respiratory outcome are conflicting, particularly with regard to the development of CLD. 19,70,89,91,137,160,219,256 Moreover, most of these studies were performed before the use of prenatal corticosteroids and the introduction of exogenous surfactant therapy. As a consequence of these recent developments in perinatal care, the survival of more immature infants has increased.…”