Figure 1.

Markov model state transition diagram.

Note: The arrows reflect the fact that a patient can remain in the same state for several cycles.

Abbreviations: GOLD, Global Initiative for Chronic Obstructive Lung Disease; GOLD II, GOLD classification indicating moderate COPD; COPD, chronic obstructive pulmonary disease; GOLD III, GOLD classification indicating severe COPD; GOLD IV, GOLD classification indicating very severe COPD; No Ex, no exacerbation; Ex, exacerbation; SevEx, severe exacerbation.