Alveolar dead space was higher in infants with BPD compared to infants with RDS ( p = 0.03). In the controls, the alveolar dead space was 0.49 (0.30–1.16) ml/kg which was lower than in infants with BPD, but similar to infants with RDS. There were also no significant differences in the physiological dead space between infants with mild, moderate or severe BPD ( p = 0.187). Within the BPD group, there was no significant difference in the physiological dead space in those who survived to discharge versus those who died before discharge ( p = 0.915). There was no significant difference ( p = 0.37) in the physiological dead space between infants with RDS or BPD. The physiological dead space was higher in infants with RDS or in those with evolving/established BPD than in term controls (<0.001). Term infants had similar PaCO 2 levels to infants with RDS, but infants with BPD had higher PaCO 2 levels. Respiratory rate was 35 (31–39) bpm in the term infants and was higher in preterm infants with RDS or BPD. The control infants had expired tidal volumes of 6.4 (5.4–7.6) ml/kg which were lower than the expired tidal volumes of infants with RDS or BPD ( p = 0.009). Positive end expiratory pressure (cmH 2O)ĭata presented as median with interquartile range (IQR) in brackets. Partial arterial pressure of carbon dioxide (mmHg) Term born infants with no underlying respiratory disease who required invasive mechanical ventilatory support for poor perinatal adaptation (term controls), preterm infants with acute RDS, and preterm infants supported by invasive ventilation for longer than 1 week who were classified as having evolving 9 or established BPD were recruited. 12 All preterm infants who required intubation and ventilation received surfactant. Infants were intubated, as per unit policy, with shouldered Cole’s endotracheal tubes (ETT). Infants were supported by volume-targeted or pressure-controlled time-cycled ventilation using the SLE6000 neonatal ventilator (SLE, Croydon UK). Term and preterm infants were eligible for recruitment into the study if they were receiving invasive mechanical ventilation, but did not have major congenital or chromosomal abnormalities. Approval was given by the London Camden and King’s Cross Research Ethics Committee (REC reference: 18/LO/1602). Infants were recruited from 1 January 2019–1 September 2020 after written informed parental consent was obtained. We further aimed to determine whether the size of the dead space influenced the alveolar ventilation in mechanically ventilated infants.Ī prospective study of ventilated infants at King’s College Hospital NHS Foundation Trust neonatal intensive care unit was undertaken. The aim of this study was to determine if the physiological dead space in prematurely born infants with RDS or evolving/established bronchopulmonary dysplasia (BPD) was greater than in term controls with no respiratory disease. 10 A previous study has shown that a reduction in alveolar ventilation resulted in hypercapnia in ventilated infants with respiratory distress syndrome (RDS). In contrast, knowledge of the alveolar ventilation (the volume of air that reaches the alveoli per minute) provides information on the volume of gas taking part in gas exchange at the alveolar–capillary interface. Minute ventilation fails to adequately describe ventilation efficiency as it does not differentiate between alveolar (effective) and dead space ventilation. 6 In pulmonary diseases in infants, there are a variety of pathologies and hence the dead space is not predictable and has rarely been reported. Alveolar dead space comprises alveoli which are ventilated, but not supplied by the pulmonary arterial circulation, or alveoli which are atelectatic. The anatomical dead space is the total volume of the conducting airways from the nose or mouth to the terminal bronchioles, and in ventilated infants includes the apparatus dead space (endotracheal tube and flow sensor). The physiological dead space is the anatomical dead space plus alveolar dead space. 4, 5Īn important influence on the appropriate size of the delivered volume during mechanical ventilation is the size of the dead space, the volume of inhaled gas that does not take part in gas exchange. ![]() 3 Inappropriately small tidal volumes can be associated with a prolonged duration of mechanical ventilation, a pro-inflammatory state and an increased work of breathing. 2 Delivery of inappropriately large tidal volumes can lead to alveolar over-distension and development of chronic respiratory morbidity. 1 Use of volume-targeted ventilation is a lung protective strategy as it potentially avoids too high or too low delivered volumes. Newborn infants often require respiratory support with invasive mechanical ventilation, unfortunately such infants can develop chronic respiratory morbidity.
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