Idiopathic respiratory distress syndrome

  • hyaline membrane disease
  • affects premature infant < 36 weeks
  • deficiency of lipoprotein pulmonary surfactant and structural immaturity of lungs
  • lipoproteins produced by type II pneumocytes
  • concentrated in cell lamellar bodies
  • then transported to cell surface and expressed on alveolar luminal surface
  • lipoproteins combine with surface surfactant proteins A, B, C and D to form tubular myelin
  • tubular myelin lowers alveolar surface tension, prevents acing collapse on expiration
  • if alveoli collapse, poor gas exchange, hypoxia, hypercarbia and acidosis
  • alveolar ducts, terminal bronchioles distended lined by hyaline membranes containing fibrin, cellular debris and fluid. Occurs due to ischemia, barotrauma, increased oxygen concentration in assisted ventilation
clinical features
  • symptomatic within minutes of birth
  • grunting, retractions, cyanosis, tachypnea
  • chest Xray findings may pop up immediately after birth, but usually seen maximum 6-24 hours after birth
Pre therapeutic imaging findings
  • under-aeration of the lungs
  • fine granular opacification, diffuse, symmetrical with air bronchograms (collapsed alveoli with distended bronchioles and alveolar ducts)
  • lesser the dissension of lungs, more the opacification
  • white lungs – atelectasis, edema, hemorrhage and sometimes superimposed infection are the causes
Post treatment imaging findings
  • corticosteroid administration 2 days prior to delivery cause significant reduction in HMD
  • liquid bolus administered via endotracheal tube
  • uneven distribution of steroid leads to areas of atelectasis interspersed with good aeration
  • radiographic findings similar to interstitial emphysema or neonatal pneumonia
  • infants > 27 weeks best respond to steroid
  • infants < 27 weeks, lungs clear up but alveoli poorly developed, hence needs prolonged ventilation, hazy lung and occasionally picture of bronchopulmonary dysplasia
patent ductus arteriosus
  • common in premature infants
  • rigid lungs of HMD, associated hypoxia and hypercarbia causes right to left shunting
  • with surfactant therapy, decrease in pulmonary resistance results in left to right shunting
  • initial treatment with ibuprofen. if ineffective, surgical or endovascular occlusion needed
  • sudden cardiac enlargement, left atrial enlargement, elevation of left main bronchus, varying degrees of pulmonary edema
  • continuous positive airway pressure ventilation used in infants to reduce complications
  • high frequency oscillatory ventilation reduced barotrauma
  • mean airway pressure optimally adjusted if diaphragm at 8th to 10th ribs
  • side effects: pneumothorax, pneumomediastinum, pulmonary interstitial emphysema, pneumopericardium
bronchopulmonary dysplasia or chronic lung disease of prematurity
  • long term complication of IRDS
  • higher incidence in infants with previous Ureaplasma urealyticum pneumonitis
  • diffuse interstitial shadowing, mild to moderate hyperinflation
  • pulmonary vein stenosis is an association, can cause pulmonary hypertension