HEMODYNAMIC-EFFECTS OF OXYGEN-THERAPY IN PATIENTS WITH ACUTE EXACERBATIONS OF CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

The effects of oxygen therapy in patients with stable COPD have been p reviously reported; however, the hemodynamic changes induced by oxygen therapy in patients during acute exacerbations of COPD are less well known. To investigate the hemodynamic effects of controlled oxygen the rapy in patients with acute exacerbations of COPD shortly after arrivi ng at the hospital, we studied 15 consecutive patients who came to the emergency room with acutely decompensated COPD that did not require m echanical ventilation. Patients were monitored with a pulmonary artery catheter and a radial artery catheter. Oxygen uptake was calculated h y the modified Fick equation. Arterial and venous blood gas levels and hemodynamic parameters were measured while breathing room air (baseli ne) and after 30 min on oxygen therapy via face mask. Measurements wer e repeated after 24 and 48 h. The fractional concentration of oxygen i n the inspired gas (FIo2) administered was adjusted to keep the PaO2 a bove 55 mm Hg. All patients had a PaO2 below 45 mm Hg at the beginning of the study. After 30 min of oxygen therapy, there was a significant (p<0.05) increase in arterial oxygen saturation (from 62 +/- 16 to 87 +/- 9 percent), mixed-venous oxygen pressure (from 25 +/- 5 to 43 +/- 11 mm Hg), and oxygen delivery (from 11.1 +/- 3.7 to 19.3 +/- 8.9 ml/ kg.min). Oxygen uptake did not change significantly (from 4.1 +/- 1.2 to 4.3 +/- 1.6 ml/kg.min). The oxygen extraction ratio decreased from 37.5 +/- 10.1 to 25.3 +/- 9.6 percent. These changes were maintained d uring the following 48 h. There were no significant changes in cardiac output and systemic vascular resistance. A trend toward lower values of pulmonary vascular resistance did not reach statistical significanc e. We conclude that oxygen therapy in patients with acute exacerbation s of COPD that do not require mechanical ventilation increases oxygen delivery without changes in cardiac output or oxygen uptake.