Persisting hypoxaemia is an insufficient measure of adverse lung function in very immature infants

Abstract

Background Bronchopulmonary dysplasia (BPD), defined as protracted neonatal hypoxaemia, is considered a risk factor for respiratory disease in adulthood. The relationship between this diagnosis and the actual lung injury appearing in very immature infants is, however, unknown. Objectives To compare lung function at term in very immature infants and full-term infants, and to determine how degree and duration of neonatal hypoxaemia are related to other aspects of lung function. Design and methods All surviving, consecutive infants with gestational age below 28 weeks from a geographically defined area were eligible. The alveolararterial oxygen pressure difference was assessed as a measure of oxygenation failure. At term, functional residual capacity and gas-mixing efficiency were measured by multiple-breath nitrogen washout, and compliance and conductance of the respiratory system by the occlusion method. The results were compared to those in 50 full-term controls. Main results Thirty-seven of 46 eligible infants were included. The preterm infants differed markedly from the full-term infants in all lung functions tested. Infants diagnosed as having BPD had more compromised lung function than those without, but the latter group differed markedly from the full-term group in functional residual capacity, compliance and gas-mixing efficiency. Only the mechanical variables were correlated to hypoxaemia at 36 weeks postmenstrual age

Is persistent need for supplemental oxygen a good indicator of adverse pulmonary outcome in very immature infants?

“…The findings reported by Hjalmarson et al 2 are in agreement with previous publications that have shown that extreme preterm infants frequently have abnormal lung function later in life, independent of their initial respiratory course compared with infants born at term 3 4. These abnormalities are characterised by lower specific lung compliance and lung volume, combined with airway obstruction that can lead to impaired gas distribution in the distal lung.…”

Lung function at term in extremely preterm-born infants: a regional prospective cohort study

“…Increased Vt is also consistent with results from studies using the multiple-breath washout method. 10 25 However, it contrasts the findings of studies where tidal breathing parameters were assessed with mask-based methods, such as the studies by Schmalisch et al 26 and Hjalmarson and Sandberg. 27 They found that preterm-born infants with chronic lung disease had lower Vt compared with term-born controls, and that a higher V’E was instead related to a substantially higher RR.…”

Respiratory consequences of prematurity: evolution of a diagnosis and development of a comprehensive approach

“…To date, the accuracy at predicting respiratory outcomes based on oxygen requirement at 36 weeks is similar to that at 37 weeks, and not substantially improved at 40 weeks 54 supporting the possible dissociation between surrogate measure and clinical disease. Further, it was recently confirmed that lung disease in very preterm infants represents a pathophysiological continuum that may have lasting effects independent of the current 36-week, oxygen-based definitions 55 . This continuum needs to be evaluated in its entirety to provide more precise clinical surrogates of disease severity and to monitor the effect of interventions in improving outcomes.…”