You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Managing comorbidity in COPD: a difficult task. Chronic obstructive pulmonary disease is a public health problem that results in high morbidity, disability and mortality. Comorbidities are highly prevalent in COPD patients because of aging, common risk factors and pathways, rising mortality, and disability. In this review article we present the most prevalent co-morbidities in COPD patients, we face the issue of multimorbidity and discuss the practical management approach relevant to chest physicians and general practitioners. Issues on comorbidities management according to general guidelines as well as their implications for COPD are raised. The aim is to give clinicians an easy update with specific recommendations for each comorbidity. The implications of several medications used for comorbidities in COPD in terms of benefits, concerns, medication preference, medication avoidance and contraindications are also discussed.
{"Chemical": []}