Elevated blood glucose is a well recognised and common pathophysiological response to acute illness. The underlying mechanisms include acute increases in hepatic glucose production and peripheral insulin resistance, driven by increases in glucocorticoids, catecholamines and proinflammatory cytokines.1 Acute hyperglycaemia can occur in any acutely unwell patient, irrespective of baseline glucose tolerance, if the illness is sufficiently severe. Acute hyperglycaemia is associated with poor outcomes from a wide range of acute illnesses including myocardial infarction,2 stroke,3 trauma4 and pneumonia.5

The data in relation to hyperglycaemia and acute exacerbations of chronic obstructive pulmonary disease (COPD) are now beginning to emerge. In a previous study, more than 50% patients with acute exacerbations of COPD had random blood glucose ⩾7 mM during their hospital stay.6 This retrospective study could not fully elucidate the relative contributions of acute illness, steroid therapy and underlying diabetes to development of hyperglycaemia. Nevertheless blood glucose ⩾7 mM was significantly associated with increased risk of death or prolonged hospital stay, and the absolute risk of this composite adverse outcome increased by 15% for each 1 mM increase in blood glucose.

It is also known that acute hypercapnic respiratory failure is an independent predictor of poor outcome for patients with COPD exacerbations. Non-invasive ventilation (NIV) reduces the likelihood of endotracheal intubation, treatment failure and mortality.7 Moretti and colleagues found that “metabolic complications” of COPD exacerbations, including hyperglycaemia defined as blood glucose >11 mM, were independently associated with “late failure” (>48 h) of NIV after initial success.8 In this study only ∼7% patients had blood glucose >11 mM and the relationship between more moderate hyperglycaemia (>6–11 mM) and outcomes was not determined. Interestingly all of the patients with late NIV failure who had admission blood glucose >11 mM subsequently developed pulmonary infection, which may …