Which statement about ventilation and perfusion is correct?
a. When a lung region becomes hypoxic, small arteries constrict in response.
b. When a lung region becomes hypoxic, small arteries dilate in response.
c. A high ventilation/perfusion (V/Q) ratio occurs when pulmonary gas exchange is impaired.
d. A low V/Q ratio occurs when a well-ventilated lung area is poorly perfused.

Answer to Quiz Time: a. When a lung region becomes hypoxic, small arteries feeding that region sense hypoxia in alveolar gas and constrict in response. Constriction redirects blood away from the hypoxic region to better-oxygenated lung areas.

Learn more by reading the continuing nursing education article “Caring for patients in respiratory failure.”