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By use of a polarographic technic for measuring arterial oxygen tension, venous-arterial shunting in the lungs was investigated in patients with primary and secondary polycythemia before and after treatment and in nonpolycythemic normal and emphysematous subjects.

In the diagnosis of pulmonary embolism by lung scanning, clinical errors of interpretation may arise. Diseases that affect the distribution of pulmonary blood flow, such as pulmonary emphysema and bronchial asthma, may be confused with pulmonary embolism. With the addition of ventilation studies with 133 xenon to the perfusion scans, distinct differences appear between patients with emboli and those with obstructive lung disease. In patients with pulmonary emboli, ventilation is preserved in the areas of decreased perfusion, whereas patients with obstructive lung disease show both decreased ventilation and perfusion in the affected areas.