Respiratory Distress syndrome- Case discussion

Case Details

An infant is born prematurely at 28 weeks and has developed increasing difficulty in breathing. His skin starts to turn blue from lack of oxygen(cyanosis).He is diagnosed with Respiratory distress syndrome due to deficiency of lung surfactant . Which of the following is the phospholipid of primary importance in surfactant?

A. Dipalmitoyl phosphatidyl choline

B. Dipalmitoyl phosphatidyl ethanolamine

C. Dipalmitoyl phosphoglyceride

D. Dipalmitoyl phosphatidyl Inositol

E. Dipalmitoyl phosphatidyl serine

 Case discussion

The correct answer is A- Dipalmitoyl phosphatidyl choline.

Respiratory distress syndrome, also known as hyaline membrane disease, occurs almost exclusively in premature infants.

Lung surfactant is a surface-active lipoprotein complex (phospholipoprotein) formed by type II alveolar cells. The proteins and lipids that comprise the surfactant have both a hydrophilic region and a hydrophobic region. By adsorbing to the air-water interface of alveoli with the hydrophilic head groups in the water and the hydrophobic tails facing towards the air, the main lipid component of surfactant, dipalmitoylphosphatidylcholine (DPPC), reduces surface tension.

Lung surfactant is composed of

1) 40% dipalmitoylphosphatidylcholine (DPPC)

2) 40% other phospholipids (PC)

3) 5% surfactant-associated proteins (SP-A, B, C and D)

4) Cholesterol (neutral lipids) and

5) Traces of other substances.

Lung surfactant

Figure- The components are packaged in multilamellar vesicles in the cytoplasm of the type II alveolar cell (figure).

The primary function of lung surfactant is to increase pulmonary compliance and to prevent atelectasis (collapse of the lung) at the end of expiration and to facilitate recruitment of collapsed airways.

In premature infants, respiratory distress syndrome develops because of impaired surfactant synthesis and secretion leading to atelectasis, ventilation-perfusion (V/Q) inequality, and hypoventilation.

Prediction of fetal lung maturity is derived by estimating the lecithin-to-sphingomyelin ratio and/or by testing for the presence of phosphatidylglycerol in the amniotic fluid obtained with amniocentesis.

One course of antenatal corticosteroids reduces the risk of respiratory distress syndrome and neonatal death.

The other phospholipids mentioned in the case are not present in the lung surfactant.

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