Hypoxemia in patients with COPD: cause, effects, and disease progression

Abstract

Chronic obstructive pulmonary disease (COPD) is a leading cause of death and disability internationally. Alveolar hypoxia and consequent hypoxemia increase in prevalence as disease severity increases. Ventilation/perfusion mismatch resulting from progressive airflow limitation and emphysema is the key driver of this hypoxia, which may be exacerbated by sleep and exercise. Uncorrected chronic hypoxemia is associated with the development of adverse sequelae of COPD, including pulmonary hypertension, secondary polycythemia, systemic inflammation, and skeletal muscle dysfunction. A combination of these factors leads to diminished quality of life, reduced exercise tolerance, increased risk of cardiovascular morbidity, and greater risk of death. Concomitant sleep-disordered breathing may place a small but significant subset of COPD patients at increased risk of these complications. Long-term oxygen therapy has been shown to improve pulmonary hemodynamics, reduce erythrocytosis, and improve survival in selected patients with severe hypoxemic respiratory failure. However, the optimal treatment for patients with exertional oxyhemoglobin desaturation, isolated nocturnal hypoxemia, or mild-to-moderate resting daytime hypoxemia remains uncertain.

Association between hemoglobin and prognosis in patients admitted to hospital for COPD

“…Both low and high values are encountered in COPD, though the distribution varies highly with the population studied. Historically, especially before the introduction of domiciliary oxygen, secondary polycythemia was a striking feature in COPD, but today the prevalence seems to be low 11. Instead, anemia might be more common, with a reported prevalence of 6.2%–46.3% 12,13…”

Portable Automated Oxygen Administration System for hypoxaemic patients

“…Over 80 % of the patients with advanced disease enrolled in the National Emphysema Treatment Trial were using some form of oxygen therapy (Kent et al. 2011). 90 % of COPD deaths were estimated to occur in low and middle income countries due to lack of proper long term oxygen treatment (European COPD Coalition 2015).…”

DNA damage and repair capacity in lymphocyte of chronic obstructive pulmonary diseases patients during physical exercise with oxygen supplementation

“…However, in more severe disease, V/Q mismatching and peripheral oxygen extraction are increased [6], and dynamic hyperinflation contributes to alveolar hypoventilation, with resultant exertional hypoxemia [7]. Studies have shown an increased systemic oxidative stress response after strenuous exercise in patients with COPD [8, 9].…”

“…This effect appears particularly marked in chronically hypoxemic subjects, in whom markers of oxidative stress are significantly increased in peripheral muscle specimens at rest and following exercise. However, supplemental oxygen can reduce pulmonary hypertension and frequency of exacerbations, increasing exercise tolerance [6], thereby releasing more energy for locomotor muscles [12]. …”

“…However, the role of the supplemental oxygen in this scenario is little known. While often considered as an attractive therapeutic option, the use of supplemental oxygen is not free of risk or adverse consequences (DNA damage, for example) [6]. It was shown that supplemental oxygen provides short-term symptom relief and improves exercise performance, but longer-term data are lacking [14].…”