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
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; FEV1, 0.87 ± 0.33 L;
Pao2, 51.6 ± 5 mm Hg; and
Paco2, 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
Pao2 during oxygen breathing, 67 ± 6 mm Hg;
mean arterial oxygen saturation [Sao2] during
oxygen breathing, 93%).
Results: PO performed while
patients were breathing air showed a mean overnight
Sao2 of 82.7 ± 6.7%. Patients spent 90% of
the recording time with an Sao2 of < 90%.
While breathing oxygen, 43 patients (52.4%) remained well oxygenated.
Their mean overnight Sao2 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 Sao2 of < 90% while breathing
supplemental oxygen. Their mean overnight Sao2
while breathing oxygen was 87.1 ± 4.5%, and time spent with an
Sao2 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
Paco2 on air (p < 0.001) and on oxygen
(p < 0.05), and lower Pao2 on oxygen
(p < 0.05) in the group of patients demonstrating significant
Conclusions: We conclude that
about half of COPD patients undergoing LTOT need increased oxygen flow
during sleep. Patients with both hypercapnia
(Paco2 ≥ 45 mm Hg) and
Pao2 < 65 mm Hg while breathing oxygen are
most likely to desaturate during sleep.