TNF and chronic obstructive pulmonary disease: Direct measurement of markers of systemic inflammation including CRP or IL‐6, as well as blood leukocyte numbers would also be beneficial in the understanding of the pathology observed within the vasculature as a study by Zeng et al. has shown that serum levels of IL‐6 are significantly enhanced in patients with COPD, when compared to control subjects, although levels of CRP and TNFα remained unchanged (Zeng et al., 2019).