History and Objectives: Nocturnal hypoxemia in patients with chronic obstructive pulmonary disease (COPD) is a frequent side effect. Because there is frequent occurrence pulmonary hypertension and cardiac arrhythmia in these patients, it is important to diagnose and treat nocturnal hypoxemia. In this research we investigated the changes of hypertension and hypoxemia during day and night in patients with COPD who were referred to the internal medicine ward of Shaheed Beheshti hospital in 1999.

Materials and Methods: A descriptive study was conducted on 68 patients with COPD. Arterial blood gas measurement was performed from radial artery in supine position in duplicates in the day and at night. Mean PaO2 and PaCO2 during day and night and changes of mean PaO2 in different levels of hypercapnia were determined.

Results: Night time decrease in PaO2 and SaO2 and increase in PaCO2 was significant compare to the day time values (Day: PaO2=62.2±13.9 mmHg, night: 57.6±12.2, P<0.001, day: SaO2=88±7.5%, night: SaO2=66±9%, P<0.001, day: PaCO2=46±7.5 mmHg, night: PaCO2=47.6±8 mmHg, P<0.001). The decrease in PaO2 during night in patients with PaO2<60 mmHg was more than in patients with PaO2>60 mmHg (7.4±12.7 mmHg, 1.4±7.6 mmHg, respectively, P=0.019). In patients with PaCO2<45 mmHg and PaCO2>45 mmHg, PaO2 in the day and night were 66.8±12.7 mmHg, 62.1±10.4 mmHg, 57.7±13.8 mmHg, 53.1±12.4 mmHg respectively. The amount of changes in both groups was 6.97% and 7.85% respectively.

Conclusion: Hypoxemic and hypercapnia are increased during night in patients with COPD. The amount decrease in nocturnal hypoxemia depends on its amount in the day. The amount of decrease in hypoxemia depends on the degree of hypercapnia. In patients with COPD, who has hypercapnia and hypoxemia, O2 delivery in the night and the improvement of hypoxemia is very important.