Chest
Volume 113, Issue 1, January 1998, Pages 65-70
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Clinical Investigations
Effects of Long-term Oxygen Therapy on Pulmonary Hemodynamics in COPD Patients: A 6-Year Prospective Study

https://doi.org/10.1378/chest.113.1.65Get rights and content

Objective

To investigate effects of 6 years of domiciliary oxygen therapy on pulmonary hemodynamics in a large group of COPD patients.

Design

Prospective longitudinal study with serial measurements.

Setting

Research institute of pulmonary diseases.

Patients

Ninety-five patients (72 men, 23 women), mean age 58±9 years, had COPD but were free of any other serious disease. Functional characteristics at entry, mean±SD, were as follows: FVC=2.24±0.51 L; FEV1=0.84±0.31 L; PaO2=55±6 mm Hg; PaCO2=48±9 mm Hg; mean pulmonary arterial pressure (PAP)=28±11 mm Hg; and pulmonary vascular resistance (PVR)=353±172 dynescm-5.

Methods

Pulmonary hemodynamics were investigated using Swan-Ganz thermodilution catheters. After initial assessment, all patients were started on a regimen of long-term oxygen therapy (LTOT). Follow-up consisted of medical examination, spirometry, and arterial blood gas analysis every 3 months. Pulmonary artery catheterization was repeated every 2 years.

Results

Seventy-three subjects survived 2 years of LTOT. In 39 subjects catheterized after 2 years, PAP fell from 25±8 to 23±6 mm Hg (not significant [NS]). From 31 patients who completed 4 years of LTOT, hemodynamic data were obtained in 20. In these 20 patients, PAP averaged 24±7 mm Hg at entry, and 23±5 and 26±6 mm Hg after 2 and 4 years, respectively (NS). In 12 patients who completed 6 years of LTOT, PAP was 25±7 at entry, and 21±4, 26±7, and 26±6 mm Hg at 2, 4, and 6 years, respectively (p<0.01 for 2 vs 6 years). PVR was 313±159 dynes.cm-5 at entry, and 268±110, 344±82, and 332±205 dyneS'cm-5 at 2, 4, and 6 years, respectively (NS). During 6 years of follow-up, PaO2 decreased from 61±3 to 46±9 mm Hg (p<0.001) and PaCO2 increased from 44±13 to 49±9 mm Hg (p<0.01).

Conclusion

LTOT for 14 to 15 h/d resulted in a small reduction in pulmonary hypertension after the first 2 years followed by a return to initial values and subsequent stabilization of PAP over 6 years. The long-term stabilization of pulmonary hypertension occurred despite progression of the airflow limitation and of hypoxemia.

Section snippets

Materials and Methods

Ninety-five consecutive COPD patients, 72 male and 23 female, who were qualified for LTOT between 1986 and 1991, participated in the study. The diagnosis of COPD was based on generally accepted criteria.15 Qualification criteria for LTOT were described elsewhere.16 Briefly, to qualify, patients had to present with stable hypoxemia (PaO2<55 mm Hg) assessed in the steady-state period of the disease. Also patients with moderate hypoxemia (PaO2=56 to 65 mm Hg) were accepted for LTOT if signs of

Results

From 95 enrolled patients, 73 survived 2 years. Thirty-nine subjects agreed to be catheterized again. On average, they had been using oxygen for 14.7 h/d. Results of the initial and the second catheterization are shown in Table 3. There were no significant changes in the studied variables.

Thirty-one patients completed 4 years of LTOT. Twenty-one agreed to have the third pulmonary catheterization. The average oxygen use in that group was 13.5 h/d. The results of all three catheterizations

Discussion

To our knowledge, this is the longest prospective study describing effects of breathing supplemental oxygen on pulmonary hemodynamics in patients with severe COPD, complicated by hypoxic PH. The results of our investigation are strengthened by intermediate data taken at regular intervals. The study has clearly shown that LTOT administered for approximately 14 h/d induced a small reduction of PH during the first 2 years of LTOT. Thereafter, PH returned to the initial level and showed

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