Chest
Volume 117, Issue 3, March 2000, Pages 679-683
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Clinical Investigations
COPD
Incidence of Nocturnal Desaturation While Breathing Oxygen in COPD Patients Undergoing Long-term Oxygen Therapy

https://doi.org/10.1378/chest.117.3.679Get rights and content

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; 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 nocturnal desaturation.

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.

Section snippets

Materials and Methods

We studied 82 consecutive COPD patients (54 men and 28 women; mean age, 60.2 ± 8.2 years) who were eligible for LTOT. Diagnosis of COPD was established based on commonly accepted criteria.3, 4 Indications for LTOT were stable hypoxemia, defined as (1) Pao2 < 55 mm Hg, or (2) Pao2 between 55 and 59 mm Hg if hypoxemia coexisted with one of the following signs: signs of pulmonary hypertension on chest radiograph (15 patients), signs of right ventricle hypertrophy on ECG (16 patients), or elevated

Results

As expected, all patients desaturated during the night while breathing air, and the T90 was 90% (Table 2 ). While breathing oxygen, the mean overnight Sao2 in the group as a whole was satisfactory (90.9 ± 5.0%). However, we found that many patients spent an important part of the night in desaturation (Sao2 < 90%). Using a cutoff point of a T90 of > 30%,7 we divided the study group into “nondesaturators” (43 subjects, 52.4%) and“ desaturators” (39 subjects, 47.6%). Functional characteristics and

Discussion

We found that almost half of COPD patients eligible for LTOT desaturated during sleep despite breathing oxygen at an airflow ensuring good oxygenation at rest and while awake. To our best knowledge, our study is the first to assess the incidence of nocturnal desaturation in such a large nonselected group of COPD patients. Previous observations were based on much smaller groups.

As early as 1977, Flick and Block11 first reported nocturnal desaturations in COPD patients receiving oxygen. Of 10

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