20. CHANGES IN PLASMA MATRIX METALLOPROTEINASE-9 CONCENTRATIONS IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE IN AND OUT OF EXACERBATION AT MILITARY HOSPITAL 103 IN 2023. Vietnam Journal of Community Medicine, v. 65, n. CĐ 3 - Bệnh viện Phổi Trung ương, 15 May2024.