Review Question - QID 100818

The clinical presentation is consistent for an aspirated object. As a result arterial blood supply for this portion of the lung will decrease due to arterial vasoconstriction.

Hypoxic vasoconstriction is a property unique to pulmonary vasculature. In response to decreased alveolar PO2, blood flow is reduced to poorly ventilated areas to minimize arterial hypoxemia caused by V/Q mismatching. This response is even more potent in the presence of reduced pH and hypercapnia. In other tissues, blood is increased in response to arterial hypoxemia secondary to vasodilation.

Morgan et al. review the diagnosis and treatment of dyspnea. They report the differential diagnosis is composed of four general categories: cardiac, pulmonary, mixed cardiac or pulmonary, and noncardiac or nonpulmonary. They state studies to aid in making the diagnosis include chest radiographs, electrocardiograph and screening spirometry. In selected cases where the test results are inconclusive or require clarification, complete pulmonary function testing, arterial blood gas measurement, echocardiography and standard exercise treadmill testing or complete cardiopulmonary exercise testing may be useful.

Swanson et al. discuss the presentation and management of tracheobronchial foreign bodies. They report findings include fever, stridor, retractions, and decreased breath sounds. Radiographic imaging can be helpful if the object aspirated is radiopaque or if there are signs of hyperexpansion on expiration. They emphasize that negative-imaging studies do not exclude the presence of a foreign body in the airway.

Figure A shows a chest radiograph of a foreign body lodged in the right mainstem bronchus of a child.

Incorrect Answers:
Answer 1: As described above, local alveolar hypoxia causes vasoconstriction, not vasodilation in the lung.
Answer 2: Active hyperemia refers to an increase in blood flow secondary to the accumulation of metabolic byproducts. Active hyperemia is not a response that alters blood flow in the lung.
Answer 3: Unlike the kidney, heart, and brain, autoregulation does not influence the flow of blood in the lung.
Answer 5: Surfactant, synthesized by type II pneumocytes, reduces surface tension in the lung and is not a major factor in blood flow regulation.