1、Neonatal Respiratory Distress Syndrome (NRDS),Tongji Hospital,Neonatal Respiratory Distress Syndrome (NRDS) or: Hyaline Membrane Disease (HMD),Most common cause of respiratory failure in the first days Occurring in 12% of newborn infants (GA 2628w, 50%, 3031w, less than 2025%) Mortality 50% at 20 yr
2、s ago, Survive 8090% now High risk: IDM, GA37w, multi preg., C-section, asphyxia, cold stress, history of prior affected, male or white infants Low risk: chronic or pregnancy-associated hypertension, maternal opiate addiction, PROM, antenatal corticosteroid,Lung Development,Embryonic Lung Developmen
3、tFetal Lung Development(Pseudoglandular, Canalicular, Terminal Saccular) Postnatal Lung Development,Embryonic Lung Development,primitive lung main bronchi,lobar bronchi,segmental bronchi,Fetal Lung Development,Pseudoglandular Stage 7th 16th week,Primitive bronchial tree Terminal bronchioles,Fetal Lu
4、ng Development,Canalicular Stage 16th 24th weekTerminal Saccular Stage 24th 36th week,Respiratory bronchioles,Transitory saccules and ducts,Postnatal Lung Development,Postnatal Development birth 8 year,Alveolar period,Secondary alveolar septa,Alveolar ducts and alveoli,Surfactant,start synthesis in
5、2024w increase in 2832w meet demands after 35w double in alveolar within 24h adult level after 37d half-life 1224h renew in 2448,90% reuse,Surfactant Composition,Phospholipid 90% (neutral 5%)saturated 50 unsaturated 35 Protein 10 (albumin 5%)SP-A, 3035kDa, 18 ologomer, hydrophilicD, 43kDa, 12 oligom
6、erSP-B, 8kDa, dimer, hydrophobicC, 4kDa, dimer,Function of Pulmonary Surfactant,Decrease alveolar surface tension, reduce respiratory work Maintain alveoli inflation and functional residual capacity Accelerate lung fluid absorption, reduce alveolar effusion Pathogen Opsonization, alveolar macrophage
7、 activation Effects: improve oxygenation, ameliorate ventilation/perfusionanti-inflammationFluid surface tensionPressure (P) =,2xsurface tension(),radius (r),Etiology and Pathophysilogy,Surfactant lowers the surface tension of alveolar membranePulmonary immaturity results in surfactant deficiencyAlv
8、eoli collapse at the end of expiration leads to respiratory failureSurfactant deficiency can arise after asphyxia/shock and acidosis,Pathology,atelectasis, pulmonary edema, vascular congestion, hemorrhage, generalized capillary leak and mucosal necrosis leads to the small air filled terminal airways
9、, the respiratory bronchioles and alveolar ducts, being surrounded by collapsed alveoli filled with debris in a near uniform distribution (hyaline membranes),Pathophysiology,Lack of alveolar surfactant in the lungs of infants Avery and Mead, Am J Dis Child 1959 progressive atelectasis loss of functi
10、onal residual capacity (FRC) alteration of ventilation-perfusion ratioWeak respiratory muscles and compliant chest wall impair alveolar ventilationDiminished oxygenation, cyanosis and acidosis increased pulmonary vascular resistance (PVR) right-to-left shunting through ductus arteriousus intrapulman
11、ary ventilation-perfusion mismatch,Clinical Presentation,Present at birth or within several hours after birth: tachypnea grunting retractions cyanosis with increasing oxygen requirementsPhysical findings: rales poor air exchange use of accessory muscles of breathing nasal flaring abnormal patterns o
12、f respiration with apnea,Radiographic Changes of RDS,a bell shaped thorax with diffuse and symmetrical “ground glass” infiltrates, air bronchograms and decreased lung volume or severe bilateral opacity characterized by the term of “white out”,Laboratory Findings,Respiratory and metabolic acidosisPho
13、spholipid (PL)/ Sphingomyelin (S) 2:1; or Phosphatidyl glycerol (PG) negative Shaking Test Add 1 mL of 95% alcohol to 1 mL of gastric fluid, shake for 15 seconds, watch for foam formation,Diagnosis and Differential Diagnosis,“Wet lung” or transient respiratory distressAmniotic fluid or meconium aspi
14、ration syndromeGroup B hemolytic Streptococcus pneumoniaDiaphragmatic hernia,Treatment,Careful assessment and resuscitation Adequate ventilation, oxygenation, circulation and temperature must be assured Surfactant replacement therapy (natural/synthetic) Ventilatory management (CPAP, IPPV, PEEP) Acid
15、-base and electrolyte homeostasis Closure of patent ductus arteriousus (PDA) Supportive treatment Antibiotic,Respiratory Management,Continuous Positive Airway Pressure (CPAP)Indication: when FiO20.6, PaO270mmHg; or frequent apnea Complication: PAL (pulmonary air leak) BPD (bronchopulmonary dysplasia
16、; or CLD)RLF (retrolental fibroplasia)VAP (ventilator-associated pneumonia),Application of Pulmonary Surfactant,Intratracheal instillation: 50200mg/kg, 612h interval Neonatal Respiratory Distress Syndrome (NRDS) meconium aspiration syndrome (MAS) Pneumonic Respiratory failure Acute lung injury, ARDS
17、 Respiratory failure after open-chest surgery or lung transplantation,Prevention,Careful maternal care and fetal monitoring Avoidance of asphyxia and infection at birth Maternal glucocorticoids (betamethasone, 12mgX2, im, 24h apart, dexamethasone, 6mgX4, im, 6h apart) Preventive use of surfactant,The most effective way to prevent RDS is to prevent preterm delivery. If preterm delivery is inevitable, attempts to “mature the fetus” are reasonable.,
