Scintigraphic appearance of albuterol-induced inhibition of hypoxic pulmonary vasoconstriction.

Alveolar hypoxia is known to result in localized pulmonary arterial vasoconstriction. As a consequence, blood is diverted from poorly ventilated alveoli, maintaining ventilation-perfusion (V/Q) matching and thereby reducing the deleterious effects on gas exchange. An incomplete alveolar hypoxic vasoconstrictive response can be easily demonstrated by radionuclide V/Q lung scanning. A case of albuterol-induced inhibition of hypoxic pulmonary vasoconstriction is described in a patient with steroid-dependent asthma. The utility of V/Q lung scanning as a simple, noninvasive test to detect this phenomenon in patients with primary airway disorders who deteriorate despite appropriate therapy is also briefly discussed.