Cardiopulmonary effects of partial pulmonary arterial obstruction in dogs.

Major obstruction to pulmonary artery blood flow such as occurs in massive pulmonary embolism is usually accompanied by a sharp decline in arterial blood oxygen tension. This phenomenon has long been recognized, and over 25 years ago Mendlowitz suggested that it was due to a decrease in the permeability of the alveolar-capillary membrane to oxygen transfer." Later Turino and his associates stated that the actual diffusing capacity was not affected appreciably unless the blood flow declined by over 50 per cent.2 Searching for factors other than diffusing capacity, we chose to study the hypoxemia subsequent to diminished pulmonary blood flow by experimentally reducing the flow to a moderate degree, sufficient to produce hypoxemia but not sufficient to produce shock.