Lung Volume, Breathing Pattern and Ventilation Inhomogeneity in Preterm and Term Infants

Abstract

BackgroundMorphological changes in preterm infants with bronchopulmonary dysplasia (BPD) have functional consequences on lung volume, ventilation inhomogeneity and respiratory mechanics. Although some studies have shown lower lung volumes and increased ventilation inhomogeneity in BPD infants, conflicting results exist possibly due to differences in sedation and measurement techniques.Methodology/Principal FindingsWe studied 127 infants with BPD, 58 preterm infants without BPD and 239 healthy term-born infants, at a matched post-conceptional age of 44 weeks during quiet natural sleep according to ATS/ERS standards. Lung function parameters measured were functional residual capacity (FRC) and ventilation inhomogeneity by multiple breath washout as well as tidal breathing parameters. Preterm infants with BPD had only marginally lower FRC (21.4 mL/kg) than preterm infants without BPD (23.4 mL/kg) and term-born infants (22.6 mL/kg), though there was no trend with disease severity. They also showed higher respiratory rates and lower ratios of time to peak expiratory flow and expiratory time (t PTEF/t E) than healthy preterm and term controls. These changes were related to disease severity. No differences were found for ventilation inhomogeneity.ConclusionsOur results suggest that preterm infants with BPD have a high capacity to maintain functional lung volume during natural sleep. The alterations in breathing pattern with disease severity may reflect presence of adaptive mechanisms to cope with the disease process.

Functional evidence for continued alveolarisation in former preterms at school age?

“…Thus, the pathophysiology of the premature lung is complex, with many factors contributing and interacting. Whether the association of minute ventilation with Scond indicates an adaptive mechanism upon increased Scond, or a primary regulatory response cannot be answered by our data [15]. The mechanism for this pattern of ventilation inhomogeneity could be explained by the fact that these children were born during the late canalicular-early saccular period of lung development, when the peripheral conducting airways are already developed and thus vulnerable, while the alveolar regions develop later and continue to grow after birth [35].…”

“…However, few studies have specifically examined ventilation inhomogeneity as a biomarker of peripheral lung function, and with inconclusive results. Two studies in preterm infants showed contradictory results, one with elevated ventilation inhomogeneity [14] and the other with no sign for ventilation inhomogeneity [15]. At school-age only one study examined ventilation inhomogeneity in former preterm children, showing mildly elevated ventilation inhomogeneity in 58% of them [10].…”

Evidence of unexpected oxidative stress in airways of adolescents born very pre-term

“…Lung function abnormalities are detectable early in life after premature birth [4,29], and carry a substantial risk of long-term respiratory disease [30] because a poor lung function in the first months of life is known to track over time with a greater risk of airway obstruction in childhood [31] and young adulthood [32].…”

Effect of time and body position on ventilation in premature infants

“…EEL in spontaneously breathing preterm infants is maintained above passive resting volume through a combination of mechanisms which include braking of the expiratory flow to prolong the time constant of the respiratory system, decreasing the expiratory time by increasing respiratory rate, and using respiratory muscle activity to dynamically elevate EEL (30,31). In the infants on CPAP there was an increased EEL at 2 h which corresponded with improved homogeneity and increased regional ventilation of the posterior lung.…”