Child's hypoxemia after inhaling peanut

[Oak]

A 3 yr old child is brought to the emergency room after inhaling a peanut. The peanut has lodged in the right mainstem bronchus, largely occluding it. The child is cyanotic, and non-invasive transcutaneous monitoring reveals a PO2 of 60 mm Hg. Which of the following mechanisms best accounts for the child's hypoxemia?

A. Decreased capacity of pulmonary diffusion
B. Decreased PO2 in inspired air
C. Hypoventilation of central origin
D. Hypoventilation of peripheral origin
E. Inequalities of ventilation and perfusion

[Hero]

Bronchial obstruction by peanut-->decreased ventilation but nothing wrong to perfusion. That's why answer (E)--Inequalities of V and Q

[bishnurath]

................e..............

[JNUS]

Answer :

E. Inequalities of ventilation and perfusion

[Oak]

Thats right folks the correct answer is E. Inequalities of ventilation and perfusion contribute to hypoxia in many settings. In this case, blood goes to both lungs (perfusion), but air is prevented from entering one of the lungs (ventilation). Because the right lung is being perfused, but not ventilated, hypoxemia ensues when the deoxygenated blood from the right lung mixes with oxygenated blood from the left lung. If the inadequate ventilation of the lung persists long enough, the lung tissue itself can be damaged, causing a secondary local dilation of arterioles, making the problem even worse. Peanuts are notorious for producing this type of problem in young children because of their size and shape, which allows them to lodge in the trachea or main bronchus after aspiration.

Decreased diffusion capacity (choice A) can occur when the blood-gas barrier is thickened (e.g., diffuse interstitial fibrosis, sarcoidosis, asbestosis, respiratory distress syndrome), when the surface area of the blood-gas barrier is reduced (e.g., pneumonectomy, emphysema), or when less hemoglobin is available to carry oxygen (e.g., anemia, pulmonary embolism).

Decreased PO2 in inspired air (choice B) is seen at high altitudes and when the settings are wrong during artificial ventilation.

Hypoventilation of central origin (choice C) is seen in morphine and barbiturate overdose.

Hypoventilation of peripheral origin (choice D) is seen in poliomyelitis and chest trauma.