Lung Sounds | Respiratory Auscultation Sounds

Lung sounds are a critical diagnostic tool in prehospital care, offering valuable insights into a patient’s respiratory status. Understanding and recognising abnormal lung sounds can aid in early diagnosis and timely intervention, often before other clinical signs become apparent. This article explores the common lung sounds and their significance.

Lung Lobe Locations

The lungs are divided into lobes, which are anatomically positioned in both the right and left lungs, though their distribution differs between the two sides:

The right lung is composed of three lobes:

Superior Lobe:

Located at the top of the right lung. It extends from just above the clavicle down to the fourth rib at the front.

Middle Lobe:

Situated below the upper lobe. It occupies the area between the fourth and sixth ribs on the anterior chest but is smaller and primarily heard from the front.

Inferior Lobe:

The largest lobe, positioned at the base of the right lung. Extends from approximately the sixth rib downwards, occupying the majority of the posterior chest region.

The left lung has only two lobes due to the space taken by the heart:

Superior Lobe:

Positioned at the top of the left lung. Extends from above the clavicle to about the sixth rib anteriorly.

Inferior Lobe:

Located beneath the upper lobe. Occupies much of the posterior chest, extending from about the sixth rib downwards, similar to the right lower lobe.

Chest Auscultation  

Lung sounds, or breath sounds, are the noises created by air passing through the respiratory system. These are most effectively heard using a stethoscope during chest auscultation. Auscultation involves listening to the sounds produced by airflow during breathing, while also paying attention to any additional (adventitious) sounds that may occur throughout the respiratory cycle.

In prehospital care, auscultation of lung sounds can be challenging due to noise from the environment. However, it remains a vital assessment tool in the prehospital environment. To optimise auscultation:

Choose a quiet environment: Turn off any unnecessary noise sources if possible.

Use a quality stethoscope: Ensure it is functioning properly and that the earpieces are correctly inserted.

Follow a systematic approach: Start from the upper lung fields, moving downwards and comparing left to right to identify asymmetry.

Chest Auscultation Locations

When auscultating the chest, it’s essential to follow a systematic approach that ensures you compare corresponding areas on both the left and right sides as you progress.

Place the diaphragm of the stethoscope on each of the designated areas of the chest wall to ensure that all regions of the lungs are assessed. Listen carefully to breath sounds during both inspiration and expiration, paying attention to the quality and volume of the sounds, and note any adventitious or abnormal sounds.

Auscultating both sides of the chest at each location allows for direct comparison and enhances the ability to detect localized abnormalities. Be sure to include auscultation of the back and sides of the chest as well, as this can provide additional important clinical information.

Breath Sounds

Breath sounds are differentiated by their location, intensity, pitch and duration of their inspiratory and expiratory phases. There are four types of breath sounds: tracheal, bronchial, vesicular, and bronchovesicular.

Location Heard: Over the trachea

Intensity: Very Loud

Pitch: High Pitch

Inspiratory & Expiratory Ratio: Equal

Location Heard: Over the manubrium (just above clavicles)

Intensity: Loud

Pitch: High Pitch

Inspiratory & Expiratory Ratio: Inspiratory Shorter Than Expiratory

Location Heard: Most of the lung field

Intensity: Quiet/Soft

Pitch: Low Pitch

Inspiratory & Expiratory Ratio: Inspiratory Longer Than Expiratory

Location Heard: 1st and 2nd Intercostal Spaces next to sternum

Intensity: Medium

Pitch: Intermediate Pitch

Inspiratory & Expiratory Ratio: Equal

Adventitious (Abnormal) Sounds

Adventitious Sounds are abnormal breath sounds heard during auscultation and can provide important clues about underlying respiratory conditions

Wheezes are high-pitched, musical sounds that occur when air passes through narrowed airways. They are most commonly heard during exhalation but can also occur during inhalation in severe cases.

Wheezes are typically associated with bronchoconstriction, inflammation, or obstruction in the airways. Conditions like asthma, chronic obstructive pulmonary disease (COPD), and bronchitis are common causes. Wheezing can also occur in allergic reactions or anaphylaxis, where swelling narrows the airways.

Coarse crackles are loud, low-pitched, bubbling or gurgling sounds heard primarily during inhalation. These crackles are often described as similar to the sound of pouring water out of a bottle or a bubbling noise. They are usually longer in duration and more pronounced compared to fine crackles.

Coarse crackles typically indicate fluid or mucus in the larger airways. Conditions that commonly produce coarse crackles include pulmonary oedema (often due to heart failure), bronchiectasis, pneumonia, and chronic bronchitis. In these conditions, excess secretions or fluid fill the larger airways, creating the distinct sound.

Fine crackles are soft, high-pitched, and short-duration sounds, typically heard at the end of inspiration. They are often described as similar to the sound of rubbing hair between your fingers close to your ear or the sound of Velcro being pulled apart. Fine crackles are shorter and more subtle compared to coarse crackles.

Fine crackles are associated with conditions that affect the smaller airways and alveoli. Common causes include pulmonary fibrosis, early pulmonary oedema, and interstitial lung diseases. Fine crackles can also be heard in the later stages of pneumonia or in cases of atelectasis (collapse of alveoli).

Stridor is a harsh, high-pitched sound most commonly heard during inspiration. It results from partial obstruction of the upper airway, and the sound is often loud enough to be heard without a stethoscope. Stridor typically suggests a narrowing of the trachea or larynx.

Stridor is a hallmark of upper airway obstruction, often due to conditions such as epiglottitis, anaphylaxis, croup, or foreign body aspiration. It can also be seen in traumatic injuries to the neck or airway, tumours in the airway, or laryngeal oedema following intubation.

Rhonchi are low-pitched, continuous sounds that are often described as having a rattling or snoring quality. They are heard primarily during exhalation and may clear or change after coughing, as they result from secretions or mucus in the larger airways.

Rhonchi are typically associated with conditions that produce excessive mucus or secretions in the airways, such as bronchitis, pneumonia, or chronic bronchitis seen in COPD. They may also be present in cystic fibrosis or patients with lung infections where mucus production is excessive.

Pleural rub is a grating or creaking sound that occurs when the inflamed pleural surfaces (lining of the lungs and chest wall) rub against each other. It is heard during both inhalation and exhalation and can be localised to specific areas of the chest.

Pleural rub is associated with pleuritis (inflammation of the pleura), which can occur due to pleural effusion, pneumonia, pulmonary embolism, or lung cancer. It can also be caused by autoimmune disorders such as lupus or rheumatoid arthritis, which may inflame the pleura.

Key Points

Bibliography

Proctor, J. and Rickards, E. (2020). How to Perform Chest Auscultation and Interpret the Findings. Nursing Times. https://www.nursingtimes.net/clinical-archive/assessment-skills/how-to-perform-chest-auscultation-and-interpret-the-findings-06-01-2020

Zimmerman, B. and Williams, D. (2022). Lung sounds. https://www.ncbi.nlm.nih.gov/books/NBK537253