From the Research
Crackles in a patient with pulmonary embolism (PE) occur due to atelectasis and inflammatory changes, as the affected lung tissue becomes poorly ventilated, leading to collapse of alveoli and release of inflammatory mediators, causing fluid accumulation and sudden reopening of airways during inspiration. This is supported by a study published in 2021 1, which highlights the pathophysiology of pulmonary infarction in acute PE, including the recruitment of bronchial arteries as a primary source of perfusion, leading to alveolar hemorrhage and tissue necrosis.
More generally, crackles (also called rales) are discontinuous, brief popping sounds produced when previously collapsed or fluid-filled alveoli suddenly reopen during inspiration. They can be classified as:
- Fine crackles (high-pitched, short sounds heard late in inspiration, often in interstitial lung diseases)
- Coarse crackles (lower-pitched, longer sounds heard throughout inspiration, common in conditions with airway secretions) Various conditions cause crackles through different mechanisms, including:
- Pulmonary edema (fluid in alveoli)
- Pneumonia (inflammatory exudate)
- Bronchiectasis (excessive secretions)
- Fibrotic lung diseases (stiff alveoli that collapse during expiration) The timing, location, and quality of crackles provide valuable diagnostic information about the underlying pathology affecting the lungs, as noted in a study published in 2023 2, which discusses the association between chronic obstructive pulmonary disease (COPD) and PE, and the importance of considering PE in the differential diagnosis of COPD exacerbations.
In the context of PE, the presence of crackles can indicate a more severe disease course, with a higher risk of complications such as pulmonary infarction and post-PE syndrome, as discussed in a study published in 2018 3. Therefore, early recognition and management of PE are crucial to prevent long-term sequelae and improve patient outcomes.