[Incidence, pathogenesis and importance of nocturnal hypoxaemia in patients with chronic obstructive pulmonary disease].

Noctural hypoxaemia (NH) in patients with chronic obstructive pulmonary disease (COPD) was first described over 40 years ago, however, its importance is not fully established. NH is defined most frequently as a drop in oxygen saturation below 90% and it occurs in almost all COPD patients PaO2 < 55 mmHg and in 30-40% of those with PaO2 < 60 mmHg. The main reason for NH is alveolar hypoventilation which is most pronounced during ohase REM. It is known that even short term episodes of NH increase pulmonary artery pressure, yet, the impact of chronic, isolated NH on pulmonary hypertension development was not found. Also, the relationship of induced by NH cardiac arrythmias with sudden death in COPD was not documented and association of NH with prognosis in COPD was not proved. Actually, there is no need to perform NH examination routinely. According to the ATS/ERS latest standards, the determination of NH can be helpful to qualify COPD patients with PaO2 55-65 mmHg to longterm oxygen therapy.