Study On The Association Between Silent Aspiration And Chronic Obstructive Pulmonary Disease (COPD) Exacerbation

【Background】Chronic Obstructive Pulmonary Disease (COPD) is one of the chronicdiseases with worldwide high incidence and mortality. COPD is characterized bypersistent airflow limitation which is usually progressive and associated with anenhanced chronic inflammatory response in the airway and the lung caused bysmoking or inhaled noxious particles or gas.An exacerbation of COPD is defned as "An event in the natural course ofthe diseases characterized by a change in the patient’s baseline dyspnea, cough,and/or sputum that is beyond normal day-to-day variations,is acute in onset,andmay warrant a change in regular medication in a patient with underlyingCOPD.Exacerbations of COPD are estimated to result in approximately110,000deaths and more than500,000hospitalizations in USA per year, with over$18billion spent in direct costs in USA annually. In addition to the financial burdenrequired to care for these patients, other “costs” such as dismissed fromwork,severe limitations in quality of life (QOL) and lung function decline areimportant features of this condition.Physical status of patients with chronic obstructive pulmonary disease (COPD)could rapidly deteriorate during an acute exacerbation event, from which the recovery time may be several months. Some patients has not been restored to thestate as before when the next exacerbation appear, leading to a progressive declinein the healthy state.In2011GOLD, the frequency of exacerbation events in patientswith COPD within the12months was officially determined as the criterion forevaluation of the disease severity. For the prevention of COPD exacerbations, it isimportant to understand the underlying mechanisms. Previous studies have shownthat approximately50%of exacerbation events are caused by lower respiratorytract infection. However, the pathogenic process of lower respiratory tract infectionis poorly understood. It was also reported that the content of the culture of lowerairway secretions from patients with AECOPD was similar to that from patientswith aspiration pneumonia. Moreover, Cohello observed silent aspiration events inCOPD patients, and Balak Mokhlesn reported a high prevalence of dysphagia inpatients with COPD at the stable stage. These findings suggest that COPDexacerbations may be associated with silent aspiration. To test this hypothesis, weinvestigated the prevalence of silent aspiration and its association with COPDexacerbation in this study.【Objectives】This prospective study was designed to detect the incidence of silent aspiration inacute exacerbation of COPD and COPD-free control patients,and to investigate theimpact of the occurrence of silent aspiration on chronic obstructive pulmonarydisease (COPD) exacerbation.【Methods】In total, we recruited46participants in this study, including31patients withAECOPD and15age-matched COPD-free control patients, who were admitted tothe First Affiliated Hospital of Guangzhou Medical College from December2011to August2012.The participants received a detailed salivary gland scintigraphy anda water drinking test. The patients with COPD were divided into two groups basedon the occurrence of silent aspiration events in the tests. Clinic characteristics andthe frequency of COPD exacerbations of these patients during the past year were compared between the two groups.【Results】1.The frequency of silent aspiration events shown by salivary glandscintigraphy was significantly higher in patients with AECOPD (9/31) than that incontrols (0/15; P=0.021).2.The frequency of COPD exacerbation events was significantly increased inthe patients positive for silent aspiration events compared to the aspiration-freepatients (1.88±0.6and0.91±0.68, respectively, P=0.002).3. The positive rates of silent aspiration events in salivary gland scintigraphyand the water drinking test in patients with AECOPD were9/31and6/31,respectively (P=0.625, Kappa=0.665).【Conclusion】1.Silent aspiration frequently occurs in patients with AECOPD andpredisposes them to COPD exacerbation.2.Water drinking test can be used for initial screening for silent aspiration,whereas salivary gland scintigraphy can serve as a diagnostic tool for theconfirmation of silent aspiration events.