Q. A neonate born 4 hours ago is having difficulty breathing. The baby was born at 28 weeks’ gestation. He is tachypneic and is fl aring and grunting. The baby’s heart rate is 120/min, blood pressure is 100/60 mm Hg, and respiratory rate is 55/min. What is this baby’s lung lacking?
(A) Angiotensin-converting enzyme
(B) Collagen
(C) Dipalmitoyl phosphatidylcholine
(D) Elastase
(E) Functional cilia
Ans: C.
This baby was born prematurely, and therefore his lungs have not fully developed. Type II pneumocytes in the lungs are responsible for secreting surfactant (dipalmitoyl phosphatidylcholine). Additionally, a lecithin:sphingomyelin ratio <2.0 is associated with a greater risk of neonatal respiratory distress syndrome. This baby is showing signs of neonatal respiratory distress syndrome due to the lack of surfactant.
Answer A is incorrect. Angiotensin-converting enzyme (ACE) is found primarily in the lungs but is also present throughout the body. ACE is a key enzyme involved in the renin-angiotensin system and converts angiotensin I to angiotensin
II, a potent vasoconstrictor. However, it is not associated with neonatal distress syndrome.
Answer B is incorrect. Collagen is an important part of the connective tissues in lungs. However, it is not associated with neonatal respiratory
Answer D is incorrect. Elastase is an endogenous proteolytic enzyme in the lung that is normally broken down by α1-antitrypsin. In patients with α1-antitrypsin deficiency, however, there is an increased level of elastase, which leads to
lung tissue destruction and emphysema.
Answer E is incorrect. Cilia dysfunction may result in decreased mucus clearance from lungs and predispose patients to recurrent respiratory infections that can cause increased respiratory distress
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Source: Ganong Physio
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