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

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

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

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

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