Pulmonary disease may set in motion a chain of events that ultimately leads to hypertrophy--or even failure--of the heart's right ventricle. The most common cause is chronic obstructive disease, which deprives the lungs of oxygen and produces pulmonary hypertension. But other disorders that raise pulmonary artery pressure also may be responsible. The thin right ventricle, which must work harder to overcome this increased resistance, ends up resembling the thick left ventricle. Comprehensive treatment of the primary lung condition at home usually enables the patient with chronic cor pulmonale to be more active and prevents frequent hospitalizations. Controlled-dose supplemental oxygen therapy is particularly effective, according to recent studies. Bronchospasm or bronchial infection super-imposed on the chronic lung condition may prove too much for the already strained right ventricle. Right ventricular failure calls for hospitalization and vigorous treatment, which may include mechanical ventilation, phlebotomy, antibiotics, steroids, digitalis, diuretics, and correction of electrolyte disturbances.