Medical progressReducing Lung Injury during Neonatal Resuscitation of Preterm Infants
Section snippets
Volutrauma
High VT that causes overdistention of the lung plays a key role in VILI. Animal studies have demonstrated that lung injury can occur during resuscitation with just a few large manual inflations.7, 8 In their classic experiments with mature animals, Dreyfuss et al9 and Hernandez et al10 showed that lung injury was caused mainly by high VT ventilation, not by high pressure. Many lesions occurred within 2 minutes of starting ventilation; however, when the VT was controlled so as to avoid lung
Atelectrauma
Atelectrauma involves alveolar damage as a result of transient and repeated collapse and reopening of alveoli and respiratory bronchioles during the respiratory cycle. Lung injury occurs when the lung is repeatedly reinflated from atelectasis, subjecting the alveoli to high shear forces.2 Cytokines are released,11 and leukocytes accumulate and are activated in the lungs,2 causing damage characterized by epithelial disruption, hyaline membrane formation, airway cell loss, increased alveolar
High Inspired Oxygen Injures the Lungs
Randomized controlled trials have shown that resuscitating asphyxiated newborn infants with air reduces mortality compared with resuscitation with 100% oxygen.21 A high fraction of inspired oxygen (FiO2) is toxic to lung tissue in animal and human experimental models; both term and preterm subjects may develop lung injury when treated with a high FiO2 for prolonged periods.3 Very preterm infants are particularly susceptible to free-radical damage, because antioxidant mechanisms are not fully
Prophylactic Versus Rescue Surfactant Strategy
Systematic reviews of randomized control trials have demonstrated that prophylactic surfactant therapy reduces mortality, air leaks, and initial inspired oxygen requirements26, 27, 28, 29, 30 for infants < 30 weeks' gestation or with birth weight < 1250 g.31 But these trials were conducted in an era when most very preterm infants were electively intubated and antenatal steroid treatment or early CPAP was rare, and thus it is possible that these data do not apply to the present era. Ammari et al
Respiratory Support at Birth: Implementing Available Knowledge
In a preterm infant, knowledge about the causes and prevention of lung injury must be applied from birth, instead of waiting until the infant is in the NICU.
Measuring and Targeting VT
A lung-protective strategy should be implemented immediately after birth. The volume difference between FRC and TLC is small in very preterm infants;2, 12 therefore, relying on a fixed inflation pressure and subjective assessment of chest rise4 may result in harm due to either underventilation or overventilation. PPV during neonatal resuscitation is conventionally pressure-limited; however, the purpose of the pressure is to deliver an appropriate VT. Lung compliance, and thus the peak
Face Mask Leaks
Ventilation with a face mask is the primary technique used to support infants who are breathing inadequately immediately after birth. The often large and variable gas leak between the mask and face is a major problem with this technique, however.35, 36, 40 Face mask leaks are frequent even for experienced operators and can significantly affect the delivered VT.40 The VT changes as the leak changes, even when the same inflating pressure is used. In practice, this means that for the same
Peep and CPAP
PEEP is used in the NICU during mechanical ventilation to help maintain end-expiratory lung volume, and CPAP is used to support lung volume and improve gas exchange in nonintubated neonates with respiratory failure. Neither of these treatments is mandated in neonatal resuscitation guidelines, however. The very preterm infant has difficulty maintaining FRC and upper airway patency for many reasons.42 CPAP or PEEP can reduce the risk of atelectrauma and improve respiratory function in various
The Best Device for Respiratory Support During Resuscitation
Currently, there is little evidence to guide clinicians' choice of ventilation device; however, any device chosen must provide PEEP or CPAP to facilitate the development of FRC immediately after birth, improve oxygenation, and reduce atelectrauma. T-piece devices allow operators to adjust both PEEP and CPAP.56, 57, 58 A flow-inflating resuscitation bag can provide PEEP, but the pressure delivered is highly variable and operator-dependent,59 making it very difficult to provide a consistent
Pulse Oximetry
Because observations of newborn infants' color are inaccurate and imprecise,62 using color to determine the appropriate FiO2 during resuscitation seems illogical. Oximetry readings of heart rate and oxygen saturation can be obtained from the newborn's right hand or wrist within 90 seconds of birth.63 After birth, an increasing heart rate is the key sign of the infant's successful transition to the extrauterine environment. Pulse oximetry can display the heart rate continuously during
Discussion
The information presented herein is from applicable animal studies and extrapolations from clinical studies in neonatal intensive care. Unfortunately, human data are scanty, and clinical trials are needed. Undertaking a good, detailed randomized study involving the emergency situation of neonatal resuscitation is very difficult, however. Waiting for clinical studies to evaluate the techniques described herein will delay improvement in the care of high-risk infants immediately after birth.
When
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2024, Resuscitation PlusExogenous surfactant therapy
2022, Goldsmith's Assisted Ventilation of the Neonate: An Evidence-Based Approach to Newborn Respiratory Care, Seventh EditionPhysiologic Changes during Neonatal Transition and the Influence of Respiratory Support
2021, Clinics in PerinatologyLung Protection During Mechanical Ventilation in the Premature Infant
2021, Clinics in Perinatology
Dr Schmölzer is supported in part by a Royal Women's Hospital Postgraduate Research Degree Scholarship. Dr Davis is supported in part by an Australian National Health and Medical Research Council (NHMRC) Practitioner Fellowship. This research is supported by NHMRC program grant 384100. The authors declare no conflicts of interest, real or perceived.