As crackles are not specific for IPF, they must prompt a thorough diagnostic process. Causes
The cause of IPF is unknown but certain environmental factors and exposures have been shown to increase the risk of getting IPF. Cigarette smoking is the best recognized and most accepted risk factor for IPF, and increases the risk of IPF by about twofold. Other environmental and occupation exposures such as exposure to metal dust, wood dust, coal dust, silica, stone dust, biologic dusts coming from hay dust or mold spores or other agricultural products, and occupations related to farming/livestock have also been shown to increase the risk for IPF. There is some evidence that viral infections may be associated with idiopathic pulmonary fibrosis and other fibrotic lung diseases. Pathogenesis
Despite extensive investigation, the cause of IPF remains unknown. The fibrosis in IPF has been linked to cigarette smoking, environmental factors (e.g. occupational exposure to gases, smoke, chemicals or dusts), other medical conditions including gastroesophageal reflux disease (GERD), or to genetic predisposition (familial IPF). However, none of these is present in all people with IPF and therefore do not provide a completely satisfactory explanation for the disease.IPF is believed to be the result of an aberrant wound healing process including/involving abnormal and excessive deposition of collagen (fibrosis) in the pulmonary interstitium with minimal associated inflammation.
Updated international guidelines were published in 2022, which some simplification in diagnosis and the removal of antacids as a possible adjunct therapy. Signs and symptoms
In many people, symptoms are present for a considerable time before diagnosis. The most common clinical features of IPF include the following:
Age over 50 years
Dry, non-productive cough on exertion
Progressive exertional dyspnea (shortness of breath with exercise)
Dry, inspiratory bibasilar "velcro-like" crackles on auscultation (a crackling sound in the lungs during inhalation similar to Velcro being torn apart slowly, heard with a stethoscope). Clubbing of the digits, a disfigurement of the finger tips or toes (see image)
Abnormal pulmonary function test results, with evidence of restriction and impaired gas exchange.Some of these features are due to chronic hypoxemia (oxygen deficiency in the blood), are not specific for IPF, and can occur in other pulmonary disorders. IPF should be considered in all patients with unexplained chronic exertional dyspnea who present with cough, inspiratory bibasilar crackles, or finger clubbing.Assessment of "velcro" crackles on lung auscultation is a practical way to improve the earlier diagnosis of IPF. Fine crackles are easily recognized by clinicians and are characteristic of IPF.If bilateral fine crackles are present throughout the inspiratory time and are persisting after several deep breaths, and if remaining present on several occasions several weeks apart in a subject aged ≥60 years, this should raise the suspicion of IPF and lead to consideration of an HRCT scan of the chest which is more sensitive than a chest X-ray.