Increased Reid&;s index is increased in which of the following

The Reid Index is a mathematical relationship that exists in a human bronchus section observed under the microscope. It is defined as ratio between the thickness of the submucosal mucus secreting glands and the thickness between the epithelium and cailage that covers the bronchi A normal Reid Index should be smaller than 0.4, the thickness of the wall is always more than double the thickness of the glands it contains.Chronic smoking causes submucosal gland hyperophy and hyperplasia, leading to a Reid Index of >0.5 indicating chronic bronchitis