TNF and chronic obstructive pulmonary disease: In 2013, Nural et al. evaluated serum CRP, TNFα, and asymmetric dimethylarginine (ADMA) levels among three groups of patients with OSAS alone, COPD, and OVS in the pre- and post-CPAP (continuous positive airway pressure) periods; and identified lower levels of pre-CPAP ADMA in the OSAS alone group than in the COPD group (24).