Bibasilar velcro crackles occur in

Idiopathic pulmonary fibrosis is defined as a progressive fibrosing interstitial pneumonia of unknown etiology,occurring in adults.With the advent of widespread CT scanning,it may present as an incidental finding in an otherwise asymptomatic individual, but more typically presents with progressive breathlessness(which may have been insidious) and a non-productive cough.Constitutional symptoms are unusual.Clinical findings include finger clubbing and the presence of bi-basal fine late inspiratory crackles likened to the unfastening of Velcro. Crackles are more commonly a sign of alveolar disease.Processes that fill the alveoli with fluid may result in crackles. Fine localised crackles are a sign of parenchymal infiltration. Fine end inspiratory crackles over both lung bases may be an early sign of LVF. Coarse crackles are seen in gross pulmonary edema. MECHANISM OF CRACKLES: Bubbling or flow of air through secretions in the bronchial level. sudden opening of successive bronchioles and alveoli with rapid equalisation of pressure causing a sequence of explosive sounds. Crackles without sputum production indicates interstitial lung disease. Crackles with sputum production indicate parenchymal lung disease. Early inspiratory crackles - CHRONIC BRONCHITIS Mid inspiratory crackles - BRONCHIECTASIS Late inspiratory crackles - ASBESTOSIS, PULMONARY FIBROSIS, PNEUMONITIS, INTERSTITIAL LUNG DISEASE, PULMONARY EDEMA Expiratory crackles - CHRONIC BRONCHITIS, PULMONARY EDEMA Reference:Davidson's Medicine-22nd edition,page no:708,ALAGAPPAN 4TH EDITION PAGE 216,217