Nocturnal hypoxaemia and cor pulmonale in severe chronic lung disease

The relation between daytime and nocturnal hypoxaemia on one hand and right ventricular failure (RVF) and hypertrophy (RVH) on the other was studied in 21 patients with severely reduced ventilatory capacity. RVH was assessed by myocardial scintigraphy, vector cardiography and echocardiography. Seven patients had suffered from acute RVF at least once. They had lower vital capacity and PaO2 and higher PaCO2 than patients without a history of RVF. They also had a more severe nocturnal hypoxaemia. They did not, however, have more severe RVH than patients without a history of RVF. Blood gases during daytime were not related to RVH. Oxygen saturation during sleep had a weak inverse relationship to RVH determined with scintigraphy, but not with the other methods. Nocturnal hypoxaemia was closely related to hypoxaemia and hypercapnia during daytime. A difference between daytime PaO2 and PaCO2 less than 2 kPa could with reasonable accuracy identify patients with nocturnal hypoxaemia.