Mechanisms of Hypoxemia and Hypocapnia in Pulmonary Embolrsm

Mechanisms of hypoxemia and hypocapnia in pulmonary embolism (PE) are incompletely understood. We studied 10 patients at diagnosis (D) and five of these again after 10 to 14 d of heparin treatment (T). Patients had right heart catheterization, assessment of ventilation-perfusion ratio (VA/OJ distribution by inert gas, radioisotopic perfusion and ventilation scans, and angiography. At 0, two-thirds of the pulmonary circulation was obstructed, patients were hypoxemic (Pa02 =63.0 ± 11.7 mm Hg) and hypocapnic (Pac02 =30.0 ± 4.1 mm Hg), mixed venous oxygen pressure (PVo2) was reduced (30.9 ± 3.9 mm Hg), minute ventilation (VE) markedly increased (14.1 ± 5.1 l/min), and cardiac output measured by applying the Fick principle to arteriovenous oxygen content difference (