Experimental Pulmonary Arterial Hypertension in the Newborn Calf.

• The study of pulmonary hypertension has been limited by lack of suitable means for producing chronic pulmonary hypertension in animals. Attempts to produce pulmonary hypertension in adult dogs, cats, and sheep by means of pneumoneetomy, hyposia, unilateral pulmonary artery ligation,' and repeated embolization, have resulted in only transient and inconsistent rises in pulmonary arterial pressure. However, Kudolph et al. have shown that moderate pulmonary hypertension can be produced in one-month-old puppies by pneumoneetomy or by ligation of one pulmonary artery. They suggested that the properties of the pulmonary vessels might be different in the immature animal and that this factor might be important in the production of pulmonary hypertension by surgical means.