From the Guidelines
Bronchial breath sounds are caused by conditions that increase sound transmission through consolidated or fluid-filled lung tissue, such as pneumonia, pulmonary edema, atelectasis, pulmonary fibrosis, and pleural effusion. These conditions create a more solid medium that enhances sound transmission from the larger airways to the chest wall, allowing bronchial sounds to be heard in peripheral lung regions where vesicular sounds should dominate 1. The most common causes of bronchial breath sounds can be remembered by the following key points:
- Pneumonia, where infection leads to alveolar filling with inflammatory exudate
- Pulmonary edema, where fluid accumulates in lung tissue due to heart failure or other causes
- Atelectasis, where lung tissue collapses and becomes airless
- Pulmonary fibrosis, where lung tissue becomes scarred and dense
- Pleural effusion above the fluid level These conditions are associated with increased morbidity and mortality, and their diagnosis and management are crucial to improve quality of life 1.
The pathogenesis of chronic bronchitis, a condition that can lead to bronchial breath sounds, involves airway inflammation and excessive bronchial secretions, which can activate the afferent limb of the cough reflex 1. The cause of cough in patients with chronic bronchitis is multifactorial, and airway inflammation and excessive bronchial secretions are likely to play a key role.
In terms of etiology, cigarette smoking is responsible for 85 to 90% of cases of chronic bronchitis and COPD, and other risk factors include increasing age, male gender, childhood respiratory infections, frequent lower respiratory tract infections, occupational exposures, and asthma 1. The identification of chronic cough and sputum production due to occupational exposures is not commonly made by clinicians, yet it has been estimated that in as many as 15% of patients with chronic bronchitis and COPD, occupational exposure is the cause.
Overall, the diagnosis and management of conditions that lead to bronchial breath sounds are crucial to improve quality of life and reduce morbidity and mortality. A thorough clinical evaluation, including a detailed medical history and physical examination, is essential to identify the underlying cause of bronchial breath sounds and develop an effective treatment plan.
From the Research
Causes of Bronchial Breath Sounds
The causes of bronchial breath sounds can be attributed to various lung conditions. Some of the key causes include:
- Pneumonia: A study published in 2007 2 found that computerized dynamic imaging of breath sounds can distinguish pneumonia from normal lungs.
- Pleural effusion: The same study 2 also found that this technique can differentiate between pleural effusion and healthy controls.
- Tracheal obstruction: A case study published in 2002 3 reported a patient with a spherical tumor arising from the main carina, causing variable tracheal obstruction and resulting in unusual breath sounds.
- Bronchial and bronchiolar diseases: A review published in 1994 4 discussed various bronchial and bronchiolar abnormalities, including bronchiectasis, asthma, and bronchiolitis, which can cause changes in breath sounds.
- Bronchial breathing caused by pneumonia: A study published in 2002 5 developed a computer-based method to detect bronchial breathing caused by pneumonia, which can be useful for quantitative monitoring of patients at risk of developing pneumonia.
Underlying Conditions
Some underlying conditions that can lead to bronchial breath sounds include:
- Cystic fibrosis: Characterized by bronchial wall thickening, bronchiectasis, and mucus plugs in the bronchi 4.
- Allergic bronchopulmonary aspergillosis: Characterized by central, varicose or cystic bronchiectasis, predominantly in the upper lobes, with mucoid impaction in the bronchi 4.
- Asthma: Characterized by bronchial wall thickening due to inflammation, bronchial dilatation, and air trapping 4.
- Bronchiolitis obliterans: Manifested by direct and indirect signs on CT scans, including centrilobular branching structures and nodules, and bronchiectasis and bronchiolectasis 4.