Pneumonia is a lung infection that causes inflammation in the air sacs of one or both lungs. This inflammation fills the air sacs with fluid and pus, making it difficult to breathe. The sounds heard in a patient with pneumonia can provide important clues to the severity, location, and type of pneumonia they have. Listening to lung sounds is an essential part of the physical exam when assessing a patient with suspected pneumonia. In this article, we will review the common adventitious lung sounds associated with pneumonia and what they may indicate about the condition.
Crackles
One of the most common lung sounds heard in pneumonia patients is crackles, which are discontinuous, explosive sounds. Crackles are caused by fluid and pus filling the small airways and alveoli (air sacs) in the lungs. As the patient inhales, these secretions pop open the small airways, creating the crackling sounds.
Crackles can be coarse or fine. Coarse crackles are louder, lower pitched, and more gurgling. They occur in the larger bronchi and indicate fluid or mucus in the larger airways. Fine crackles are soft, high pitched, and more Velcro-like in quality. These occur in the smallest bronchioles and alveoli deep in the lungs.
The location of crackles can provide clues about the areas of lung involved with pneumonia. For example, crackles localized to one lung suggest pneumonia in that lung only. Bilateral crackles indicate both lungs are affected. Crackles at the lung bases indicate involvement of the posterior lung regions, while crackles heard higher up suggest anterior lung involvement.
Causes of Crackles
Crackles are nonspecific and can have several causes besides pneumonia, including:
- Pulmonary edema – Fluid buildup in the lungs
- Interstitial lung disease – Scarring of lung tissue
- Bronchiectasis – Damaged airways
- Lung cancer – Tumor blocking airways
However, in the setting of an acute respiratory infection, new crackles are highly suggestive of pneumonia. Crackles can be a sign that pneumonia is worsening and more of the lungs are becoming inflamed and fluid-filled.
Wheezing
Wheezing is another common lung sound in pneumonia. It is a high-pitched, whistling sound during breathing. Wheezes are caused by narrowed or compressed airways that force air through.
There are two main mechanisms that can cause wheezing in pneumonia patients:
Bronchospasm
The airway inflammation from pneumonia can irritate nerves in the airways, triggering spasms of the bronchial smooth muscle. This narrows the airways and obstructs airflow, leading to wheezing sounds as the patient struggles to breathe.
Mucus obstruction
The increase in mucus production in the airways during pneumonia can also lead to wheezing. As thick mucus accumulates, it can partially clog the airways, forcing air through these narrowed passages.
Wheezing is more common in viral pneumonias, as viruses directly irritate and inflame the airways. Bacterial pneumonia tends to produce crackles more frequently than wheezes.
Stridor
Stridor is an ominous, high-pitched, musical sound on inspiration. It results from upper airway obstruction near the larynx or trachea. Stridor can occur in pneumonia when very swollen lymph nodes compress the upper airway. It is an emergency sign indicating severe respiratory distress.
Pleural Friction Rub
A pleural friction rub is another important lung sound that may be heard in patients with pneumonia. This sound is created when inflamed pleural surfaces rub against each other during breathing.
What is the pleura?
- Two thin membranes lining the outside of the lungs and inside of the chest cavity
- Allow smooth gliding between lung and chest wall
- Produce pleural fluid to lubricate their movement
With pneumonia, the inflamed pleura can become rough and sticky. As the patient inhales and exhales, the two pleural surfaces scrape against each other, creating a rubbing or grating sound called a pleural friction rub.
This coarse, scratchy sound tells you the pleura itself is inflamed, which occurs in pneumonia right below the infected lung tissue. A friction rub is a useful indicator that the inflammatory process has spread outside the lungs.
Decreased Breath Sounds
Although abnormal sounds predominate in pneumonia, sometimes normal lung sounds diminish. This occurs when copious fluid and mucus fill the lung and dampen normal airflow and breathing sounds.
Areas of the lung with very reduced or absent breath sounds likely represent complete consolidation or fluid filling. Dullness to percussion may also be detected over these areas. Decreased breath sounds suggest worsening pneumonia with extensive lung involvement.
Focal Findings
Pneumonia often starts in one area of the lung before spreading more widely. Early on, the lung exam may reveal adventitious sounds and dullness localized to just a single lobe or segment.
For example, crackles at the right lung base indicate right lower lobe pneumonia. As the infection progresses, these abnormal findings become more diffuse. Focal findings provide clues to the pneumonia source before it involves the entire lung.
Putting It All Together
Examples
- An elderly patient with a productive cough, fever, and fine end-inspiratory crackles at the left lung base likely has bacterial pneumonia localized to the left lower lobe.
- A young asthmatic with a viral upper respiratory infection, wheezing throughout all lung fields, may be developing viral pneumonia.
- A patient with diffuse coarse crackles and decreased breath sounds has severe bilateral pneumonia.
Listening carefully to the types and locations of abnormal lung sounds allows providers to assess pneumonia severity, progression, and extent of involvement. This guides treatment decisions and helps monitor response to therapy.
When to Seek Emergency Care
Certain lung sounds and exam findings warrant prompt medical attention to avoid life-threatening respiratory complications:
- Stridor – Indicates critical upper airway narrowing
- Absent breath sounds over large lung areas – Suggests pneumonia is significantly worsening
- Gasping, labored breathing – Signals respiratory muscle exhaustion
- Cyanosis, low oxygen levels – Means patient cannot oxygenate properly
- Altered mental status – Due to oxygen deprivation
Pneumonia can progress rapidly to respiratory failure. The sounds on exam provide vital information about real-time lung status and function. Patients exhibiting signs of impending respiratory arrest require emergency care.
Conclusion
Careful auscultation of the lungs plays a pivotal role in the assessment of community-acquired pneumonia. The presence and nature of adventitious sounds provides key insights into the location, severity and progression of disease. Familiarity with the types of sounds and their implications allows providers to make appropriate triage and treatment decisions. Crackles, wheezes, and pleural rubs reflect the inflammatory burden, while stridor and decreased breath sounds are omens of impending respiratory failure. Recognizing concerning findings on lung exam is crucial for the timely and appropriate care of pneumonia patients.