Table 2. Consequences of nocturnal hypoxaemia and hypercapnia in chronic obstructive pulmonary disease (COPD)

Parameter/outcome	Acute consequences	Chronic consequences
Sleep structure	Altered in severe COPD, but inconsistent improvement of sleep with oxygen administration	Worse sleep among pink puffers (mild desaturators) than blue bloaters (severe desaturators)
Arrhythmias	Observed during severe sleep desaturations; prevented by oxygen administration	Risk not directly documented
Pulmonary artery pressure	Increased	Inconsistent finding with regard to differences between desaturators and nondesaturators
Diurnal blood gases		Similar wake blood gas evolution among desaturators and nondesaturators; possible worsening of blood gases in severe COPD suggested by beneficial effects of ventilatory treatment
Mortality	Some suggestion that death may preferentially occur at night among patients with exacerbations (not systematically evaluated)	Prognosis independent of nocturnal hypoxaemia measured in stable conditions
Cardiovascular and cerebrovascular risk	Increased ventricular ectopic events during periods of hypoxaemia	Increased, possibly as a result of increased sympathetic activity and altered peripheral vascular tone due to recurrent nocturnal hypoxia
Inflammatory mechanisms	Pronounced activation among desaturators