Neonatal lung injury
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The document discusses strategies to prevent lung injury in preterm infants requiring mechanical ventilation. It notes that preterm infants have structurally immature lungs that are often surfactant deficient, fluid filled, and not supported by a stiff chest wall, making them highly susceptible to lung injury from ventilation. It emphasizes establishing and maintaining an optimal functional residual capacity to prevent atelectrauma through techniques like nasal CPAP, early surfactant administration, and lung recruitment maneuvers while aiming to use the lowest possible oxygen levels and pressures to avoid volutrauma and oxygen toxicity. The goal is to open and stabilize recruited areas of the lung to allow for a more homogeneous distribution of tidal volumes without overinflation.
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Neonatal lung injury
- 1. Neonatal lung injury Antonio Souto acasouto@bol.com.br Médico coordenador Unidade de Medicina Intensiva Pediátrica Unidade de Medicina Intensiva Neonatal Hospital Padre Albino Professor de Pediatria nível II Faculdades Integradas Padre Albino Catanduva / SP
- 2. UTI Pediátrica & Neonatal Hospital Padre Albino •30 breaths/min •Distend the lungs more than 40,000 times per day It is surprising that mechanical ventilation is not more harmful Dr. Antonio Souto acasouto@terra.com.br 2013
- 3. UTI Pediátrica & Neonatal Hospital Padre Albino The lungs of the very preterm infant •Structurally immature and are often surfactantdeficient, fluid-filled, and not supported by a stiff chest wall •Antenatal exposure to inflammatory mediators, surfactant dysfunction, high chest wall compliance, antioxidant deficiency, infection, and malnutrition •Increase the susceptibility to lung injury •Limit the ability to repair the damage Dr. Antonio Souto acasouto@terra.com.br 2013
- 4. UTI Pediátrica & Neonatal Hospital Padre Albino •The process of supporting gas exchange in the very low birth weight infant may have lifelong consequences •In the delivery room where we must support a safe transition from fetal to neonatal life •Support gas exchange and normalize lung inflation from the first breath is important Dr. Antonio Souto acasouto@terra.com.br 2013
- 5. UTI Pediátrica & Neonatal Hospital Padre Albino •Specific decisions about respiratory care practice during the first day of life influence the outcome of a very low birth weight infant •Failure to decrease ventilatory support may increase the risk of developing chronic lung disease, intraventricular hemorrhage, and retinopathy of prematurity Several studies show that optimizing lung recruitment reduces lung inflammation, improves surfactant function, and decreases lung injury. Dr. Antonio Souto acasouto@terra.com.br 2013
- 6. UTI Pediátrica & Neonatal Hospital Padre Albino Ventilator pattern influenced the efficacy of exogenously delivered surfactant •Loss of FRC (lung de-recruitment) •increased lung injury •decreased the efficacy of the surfactant therapy •IMV + inadequate PEEP will increase lung injury Dr. Antonio Souto acasouto@terra.com.br 2013
- 7. UTI Pediátrica & Neonatal Hospital Padre Albino •High tidal volume and zero EEP Severe lung injury Marked increases in circulating tumor necrosis factor and macrophage inflammatory protein •Large tidal volumes and low end expiratory lung volumes Synergistic increase in lung and serum cytokine concentrations •The use of a lung recruitment strategy is protective. Both end-expiratory and end-inspiratory lung volumes are important. Dr. Antonio Souto acasouto@terra.com.br 2013
- 8. UTI Pediátrica & Neonatal Dr. Antonio Souto Hospital Padre Albino acasouto@terra.com.br 2013
- 9. UTI Pediátrica & Neonatal Dr. Antonio Souto Hospital Padre Albino acasouto@terra.com.br 2013
- 10. UTI Pediátrica & Neonatal Hospital Padre Albino Lung Injury Inadequate alveolar stability and atelectasis Atelectrauma •Loss of alveolar recruitment is both a consequence and a cause of lung injury •Alveolar units are prone to collapse (ARDS/RDS) •Recruitment and subsequent “de-recruitment” cause lung injury Recruitment of lung volumes protects against ventilator-induced lung injury and also reduces the need for high levels of inspired oxygen Dr. Antonio Souto acasouto@terra.com.br 2013
- 11. UTI Pediátrica & Neonatal Hospital Padre Albino Lung Injury Volutrauma An important cause of ventilator-induced lung injury is regional overdistension of alveoli and airways. Large tidal volume breaths Damage •pulmonary capillary endothelium •alveolar and airway epithelium •basement membranes Dr. Antonio Souto acasouto@terra.com.br 2013
- 12. UTI Pediátrica & Neonatal Hospital Padre Albino Lung Injury Volutrauma Fluid, protein, and blood to leak into the airways, alveoli, and the lung interstitium •Interfering with lung mechanics •Inhibiting surfactant function •Promoting lung inflammation Dr. Antonio Souto acasouto@terra.com.br 2013
- 13. UTI Pediátrica & Neonatal Hospital Padre Albino Preterm infant • Lung immaturity, alveolar atelectasis, and edema decrease the gas volume • Only a small portion of the lung may be recruited and available for ventilation TV of 10 mL/kg delivered may be equivalent to mL/kg mL/kg 20 to 30 mL/kg and will result in volutrauma Dr. Antonio Souto acasouto@terra.com.br 2013
- 14. UTI Pediátrica & Neonatal Hospital Padre Albino Lung Injury Oxygen toxicity Oxygen-induced lung injury •Overproduction of superoxide, hydrogen peroxide, and perhydroxyl radicals •The premature is particularly vulnerable •Antioxidant systems develop during the last trimester Dr. Antonio Souto acasouto@terra.com.br 2013
- 15. UTI Pediátrica & Neonatal Hospital Padre Albino Lung Injury Oxygen toxicity Reactive oxygen metabolites •Overwhelm the antioxidant system •Oxidize enzymes •Inhibit protein and DNA synthesis •Decrease surfactant synthesis •Cause lipid peroxidation. Dr. Antonio Souto acasouto@terra.com.br 2013
- 16. UTI Pediátrica & Neonatal Hospital Padre Albino Lung Injury Oxygen toxicity Prolonged hyperoxia initiates a lung injury sequence that can lead to inflammation, diffuse alveolar damage, progressive pulmonary dysfunction, and death. Dr. Antonio Souto acasouto@terra.com.br 2013
- 17. UTI Pediátrica & Neonatal Hospital Padre Albino Cytokines and biotrauma in ventilator-induced lung injury Pulmonary and systemic inflammatory responses to acute lung injury Significant potential exists for the lungs to interact with, and contribute to, the circulating pool of inflammatory cells. Dr. Antonio Souto acasouto@terra.com.br 2013
- 18. UTI Pediátrica & Neonatal Dr. Antonio Souto Hospital Padre Albino acasouto@terra.com.br 2013
- 19. UTI Pediátrica & Neonatal Dr. Antonio Souto Hospital Padre Albino acasouto@terra.com.br 2013
- 20. UTI Pediátrica & Neonatal Hospital Padre Albino Mechanical ventilation affects the numbers of inflammatory cells and the expression of soluble mediators within the lungs •Increased lung neutrophil accumulation •Increased inflammatory mediators bronchoalveolar lavage •Increased expression of tumor necrosis factor– [alpha] by alveolar macrophages Manifestations of lung injury were almost completely abrogated in granulocyte-depleted rabbits granulocyteDr. Antonio Souto acasouto@terra.com.br 2013
- 21. UTI Pediátrica & Neonatal Hospital Padre Albino alveolarInjure the alveolar-capillary barrier •Efflux of inflammatory mediators into the general circulation. •A systemic inflammatory response can also be promoted by translocation of bacteria and endotoxin from the air spaces into the circulation. •Findings in recent human studies in adults show that ventilatory strategy has an impact on pulmonary and systemic cytokines and that these changes are associated with multisystem organ failure. Dr. Antonio Souto acasouto@terra.com.br 2013
- 22. UTI Pediátrica & Neonatal Hospital Padre Albino Cytokines are likely to play a role in the various interrelated processes that lead to VILI and other MV-related complications, such as MODS and possibly ventilator associated pneumonia. Dr. Antonio Souto acasouto@terra.com.br 2013
- 23. UTI Pediátrica & Neonatal Hospital Padre Albino Strategies to Prevent Lung Injuries What is the definition of optimal lung volume? •Lung disease or lung injury •FRC is decreased •Generally the dependent areas, is collapsed •Inhomogeneous pattern of inflation A goal of respiratory support is to open these areas and to normalize FRC Dr. Antonio Souto acasouto@terra.com.br 2013
- 24. UTI Pediátrica & Neonatal Hospital Padre Albino Optimal lung inflation Lung volume at which the recruitable lung is open but not overinflated •intrapulmonary shunt is decreased •lung volume effects on cardiac output are minimized •oxygen delivery is optimized Dr. Antonio Souto acasouto@terra.com.br 2013
- 25. UTI Pediátrica & Neonatal Hospital Padre Albino Lung is recruited •Surfactant and alveolar interdependence keep it inflated •The pressure to open the lung is higher than the pressure needed to keep it open •MAP or EEP can be decreased not below the closing pressure of the majority of the alveoli Dr. Antonio Souto acasouto@terra.com.br 2013
- 26. UTI Pediátrica & Neonatal Hospital Padre Albino Changes in lung volume are dependent on regional lung compliance Optimal is the tidal volume that creates a homogeneous delivery of each breath to the open lung units without creating volutrauma •The most important volume to optimize is FRC •An open lung allows more uniform distribution of each tidal volume breath and reduces the potential for volutrauma Dr. Antonio Souto acasouto@terra.com.br 2013
- 27. UTI Pediátrica & Neonatal Dr. Antonio Souto Hospital Padre Albino acasouto@terra.com.br 2013
- 28. UTI Pediátrica & Neonatal Hospital Padre Albino How might we measure optimal lung volume? •Thoracic expansibility •X ray •PaCO2/Minute volume (RR/TV) •PaO2/FiO2/PEEP •Heart frequency Dr. Antonio Souto acasouto@terra.com.br 2013
- 29. UTI Pediátrica & Neonatal Hospital Padre Albino •Low lung volume •Chest radiograph showing atelectasis along with a PaO2/PAO2 ratio demonstrating poor oxygenation •Lung volume is too high. •Chest radiograph shows lung hyperinflation and there are clinical signs of decreased cardiac output Optimal is somewhere between the two Dr. Antonio Souto acasouto@terra.com.br 2013
- 30. UTI Pediátrica & Neonatal Hospital Padre Albino How do we safely establish and normalize FRC in neonates with immature and atelectatic prone lungs? Dr. Antonio Souto acasouto@terra.com.br 2013
- 31. UTI Pediátrica & Neonatal Hospital Padre Albino atelectrauma? What can we do clinically to prevent atelectrauma? •Three techniques: •Nasal SIMV/Continuous positive airway pressure (CPAP) •Exogenous surfactant therapy •Lung recruitment strategy Strategies to improve lung recruitment include prone positioning and sustained lung-inflation maneuvers. Dr. Antonio Souto acasouto@terra.com.br 2013
- 32. UTI Pediátrica & Neonatal Hospital Padre Albino CPAP 2000;105:1194Pediatrics 2000;105:1194-201 •Comparing nurseries that more commonly use assisted ventilation with nurseries that use CPAP in the initial treatment of very low birth weight infants •most of the increased risk of chronic lung disease most was explained “simply by the initiation of ventilation.” mechanical ventilation.” •Practice differences influence outcome Dr. Antonio Souto acasouto@terra.com.br 2013
- 33. UTI Pediátrica & Neonatal Hospital Padre Albino When to provide mechanical ventilation? A problem is the potential risks of waiting to intervene •delaying the “appropriate” use of surfactant Well-designed trials in which CPAP is compared with early intubation are needed Dr. Antonio Souto acasouto@terra.com.br 2013
- 34. UTI Pediátrica & Neonatal Hospital Padre Albino Surfactant •When used early, decreases lung injury •Within minutes oxygenation improves in most infants •Increase in FRC •Improved ventilation-perfusion matching •Decrease in intrapulmonary shunt •Stabilize recruited lung volume and prevents atelectasis Dr. Antonio Souto acasouto@terra.com.br 2013
- 35. UTI Pediátrica & Neonatal Hospital Padre Albino What is the correct target PaCO2? •Moderate hypercarbia protects the brain from hypoxicischemic injury •Hypocarbia increases the injury •Hypercapnic acidosis can protect the lung from acute injury However •Hypercarbia increases cerebral blood flow •Decreases systemic pH •In animals, increase in retinopathy Dr. Antonio Souto acasouto@terra.com.br 2013
- 36. UTI Pediátrica & Neonatal Hospital Padre Albino Thus, a “normal” PaCO2 value should normal” remain the target until more data from human studies are available Dr. Antonio Souto acasouto@terra.com.br 2013
- 37. UTI Pediátrica & Neonatal Hospital Padre Albino oxygenPreventing oxygen-induced lung injury STOP-ROP Study Group. Supplemental Therapeutic Oxygen for STOPPrethreshold Retinopathy Of Prematurity (STOP-ROP), a (STOPrandomized, controlled trial. I: primary outcomes. Pediatrics 2000;105:2952000;105:295-310 •Neonates •conventional oxygen pulse oximetry at 89% to 94% •supplemental pulse oximetry at 96% to 99% •Pneumonia, exacerbations of chronic lung disease, or both •8.5% conventional vs 13.2% supplemental 8.5% Dr. Antonio Souto acasouto@terra.com.br 2013
- 38. UTI Pediátrica & Neonatal Hospital Padre Albino oxygenPreventing oxygen-induced lung injury oximetry, Tin W, Milligan DW, Pennefather P, Hey E. Pulse oximetry, severe weeks retinopathy, and outcome at one year in babies of less than 28 weeks 84:F106gestation. Arch Dis Child Fetal Neonatal Ed 2001; 84:F106-F110 •Oxygen for 8 weeks •saturation of 88% to 98% X saturation of 70% to 90% •saturation of 88% to 98% saturation •severe retinopathy 5 times more often •more often developed chronic lung disease Dr. Antonio Souto acasouto@terra.com.br 2013
- 39. UTI Pediátrica & Neonatal Hospital Padre Albino Keep in your mind Dr. Antonio Souto If these strategic principles are followed, we can reduce the pulmonary and systemic inflammatory changes ventilatorassociated with ventilatorinduced lung injury and hopefully promote better longlong-term health. acasouto@terra.com.br 2013
- 40. UTI Pediátrica & Neonatal Dr. Antonio Souto Hospital Padre Albino acasouto@terra.com.br 2013