MEDizzy - A 53-year-old man while in the hospital because of a serious

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Respiratory System

A 53-year-old man while in the hospital because of a serious motor vehicle accident develops signs of respiratory failure. A chest x-ray reveals a complete “white-out” of both lungs, while a chest CT scan reveals extensive bilateral ground-glass opacifications of the lung parenchyma consistent with diffuse alveolar damage. Laboratory evaluation finds severe hypoxemia that does not improve with 100% oxygen. Which of the following histologic abnormalities is most likely to be seen in a biopsy specimen taken from his lungs?

ExplanationDiffuse damage to the alveolar wall is the initial and basic lesion in acute respiratory distress syndrome (ARDS). Protein-rich edema fluid then leaks into the alveolar spaces and combines with fibrin and dead cells to produce hyaline membranes that line the alveoli. These hyaline membranes are the characteristic histologic feature of ARDS. Other names for ARDS include adult respiratory failure, shock lung, traumatic wet lung, pump lung, and diffuse alveolar damage (DAD). These many names reflect the fact that there are many different causes of adult respiratory distress syndrome including sepsis, pneumonia, infections (viral), aspiration, trauma, fat emboli, smoke inhalation, drug reaction or overdose, shock, and burns. This syndrome is characterized clinically by the rapid onset of severe, life-threatening respiratory insufficiency. In the acute edematous stage, the lungs are congested (pulmonary congestion) and show pulmonary edema with interstitial inflammation. Collapsed, airless pulmonary parenchyma is called atelectasis and can also be seen in ARDS