The relationship between ventilator-associated pneumonia and chronic obstructive pulmonary disease: what is the current evidence?

Chronic obstructive pulmonary disease (COPD) affects approximately 65 million people from which > 25% will require intensive care unit (ICU) admission. Ventilator-associated pneumonia (VAP) is the commonest ICU infection and results in increased morbidity/mortality and costs. The literature on the interaction between COPD and VAP is scarce and controversial. The project aimed to search the literature in order to address the following: (i) Is COPD a risk factor for VAP development? (ii) Does COPD impact the outcome of patients with VAP? (iii) Does VAP development impact the outcome of COPD patients? (iv) Does COPD impact the aetiology of VAP? Current evidence on the topic is controversial. Regarding the impact of VAP on COPD patients, the majority of the existing limited number of studies suggests that VAP development results in higher mortality and longer duration of mechanical ventilation and ICU stay. Also, the majority of the studies exploring the impact of COPD on VAP outcomes suggest that COPD is independently associated with a decrease in survival, although the number of such studies is limited. Regarding the aetiology, Pseudomonas aeruginosa is the most frequent pathogen in VAP patients with COPD. Noteworthy, one study suggests that P. aeruginosa is higher in COPD patients even in the early-onset VAP subgroup. This manuscript provides a comprehensive overview of the available literature on the interaction between COPD and VAP, highlighting the differences and limitations that may have led to controversial results, and it may act as a platform for further research with important clinical implications.