Study objective: It is suggested that oxygen flow be increased by 1 L/min during sleep in COPD patients undergoing long-term oxygen therapy (LTOT) in order to avoid nocturnal desaturations. The purpose of this study was to investigate the occurrence of nocturnal desaturations while breathing oxygen in COPD patients receiving LTOT.
Setting: Inpatient/university hospital.
Patients: We studied 82 consecutive COPD patients. Their functional characteristics were as follows (mean +/- SD): FVC, 2.15 +/- 0.69 L; FEV(1), 0.87 +/- 0.33 L; PaO(2), 51.6 +/- 5 mm Hg; and PaCO(2), 47 +/- 8 mm Hg.
Measurements: Overnight pulse oximetry (PO) was performed twice: (1) while breathing air and (2) while breathing supplemental oxygen assuring satisfactory diurnal resting oxygenation (mean PaO(2) during oxygen breathing, 67 +/- 6 mm Hg; mean arterial oxygen saturation [SaO(2)] during oxygen breathing, 93%).
Results: PO performed while patients were breathing air showed a mean overnight SaO(2) of 82.7 +/- 6.7%. Patients spent 90% of the recording time with an SaO(2) of < 90%. While breathing oxygen, 43 patients (52.4%) remained well oxygenated. Their mean overnight SaO(2) while breathing oxygen was 94.4 +/- 2.1%, and time spent with saturation < 90% was 6.9 +/- 8.6%. Thirty-nine patients (47.6%) spent > 30% of the night with an SaO(2) of < 90% while breathing supplemental oxygen. Their mean overnight SaO(2) while breathing oxygen was 87.1 +/- 4.5%, and time spent with an SaO(2) of < 90% was 66.1 +/- 24.7% of the recording time. Comparison of ventilatory variables and daytime blood gases between both groups revealed statistically significantly higher PaCO(2) on air (p < 0.001) and on oxygen (p < 0. 05), and lower PaO(2) on oxygen (p < 0.05) in the group of patients demonstrating significant nocturnal desaturation.
Conclusions: We conclude that about half of COPD patients undergoing LTOT need increased oxygen flow during sleep. Patients with both hypercapnia (PaCO(2) > or = 45 mm Hg) and PaO(2) < 65 mm Hg while breathing oxygen are most likely to desaturate during sleep.