A pulmonary physiologist notes that the lung characteristics of individuals who

Question

A pulmonary physiologist notes that the lung characteristics of individuals who lack surfactant and those with pulmonary fibrosis are similar. Which of the following occurs in patients who lack surfactant but not in patients with pulmonary fibrosis?

a. Collapse of small alveoli and expansion of large alveoli

b. Decreased lung compliance

c. Decreased total lung capacity

d. Increased work of breathing

e. Intrapleural pressures more subatmospheric than normal

Defend your answer by describing why each of the other answers are not correct

Explanation / Answer

a.Collapse of small alveoli and expansion of large alveoli:This happens to some extent in people due to lack of surfactant. In small alveoli, surface tension is kept in check by surfactant in normal people to minimize the effect.In infants with respiratory distress syndrome, this condition worsens.

b.Decreased lung compliance: Decreased lung compliance is observed in patients with pulmonary fibrosis. The lungs become stiffer,fibrotic in nature and lose their distensibility.

c.Decreased total lung capacity: This is seen in patients who lack surfactant and are suffering from pulmonary fibrosis. Lack of pulmonary surfactant coupled with the scarring decrease the lung capacity.

d.Increased work of breathing: In patients diagnosed with pulmonary fibrosis the lung tissue becomes thickened, scarred and stiff. The lungs tend to work more to supply oxygen to the bloodstream.The tension on the lung surface increases due to lack of surfactant and increased effort is needed to initiate an act of breathing.

e.Intrapleural pressures more subatmospheric than normal: In a normal individual,the pressure within the pleural cavity is less than the atmospheric pressure. But when the pleral cavity is damaged due to infection with subsequent lack of surfactant, the Intrapleural pressures become more subatmospheric than normal.

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