Effect of 3 week oxygen therapy on functional and haemodynamic parameters in chronic obstructive pulmonary disease

Sixteen patients with advanced chronic obstructive pulmonary disease (COPD) and stable chronic respiratory failure (pO2 less than 60 mm Hg, pCO2 greater than 45 mm Hg) were given 2-3 L/min oxygen 18 hours/day for 3 weeks. These were serially assessed for changes in pO2, pCO2, ECG, chest radiographs and haemodynamics. Initially all patients were in grade IV heart failure. There was no change in lung function after oxygen treatment but right descending pulmonary artery diameter and cardiothoracic ratio decreased significantly (P less than 0.01), as also the height of the P wave in ECG (P less than 0.05). There were significant changes in mean pO2 (51.8 to 61.9 mmHg; P less than 0.01), pCO2 (55.3 to 47.6 mmHg; P less than 0.001), mean pulmonary artery pressure (41.8 to 34.5 mmHg; P less than 0.01) and pulmonary vascular resistance (PVR) (346.4 to 163.3 dynes; P less than 0.05). The initial (P less than 0.05) and 3 week (P less than 0.01) pO2 levels correlated with the right descending pulmonary artery diameter. The height of the P wave also correlated with pO2 (P less than 0.01). The changes in pO2 levels correlated with those of the PVR and pulmonary blood flow (P less than 0.05). Three week oxygen therapy resulted in objective improvement in advanced COPD cases.