Overview
This lecture covers the phases and characteristics of normal and abnormal breath sounds, focusing on vesicular and bronchial sounds. It explains their mechanisms of production, typical locations, clinical significance, and proper auscultation techniques.
Phases of Breath Sounds & Respiratory Cycle
- Breath sounds have two phases: inspiration and expiration, which together make up the respiratory cycle.
- These phases are essential for describing lung sounds and their timing.
- Inspiration is an active process, producing louder and higher-pitched sounds due to rapid airflow.
- Expiration is passive, resulting in quieter, lower-pitched, and shorter sounds.
Mechanism of Breath Sound Generation
- Breath sounds are produced by variations in airflow within the airways.
- Turbulent airflow (chaotic in velocity and direction) generates audible vibrations, which can be heard through the chest wall with a stethoscope.
- Laminar airflow (uniform in velocity and direction) is silent and does not produce sound.
- Inspiratory sounds mainly arise from turbulent airflow in the lobar and segmental bronchi.
- Expiratory sounds are produced by turbulent airflow in the larger bronchi and trachea.
- As air moves into the smaller bronchioles and alveoli, the flow becomes laminar and silent.
Vesicular Breath Sounds
- Vesicular breath sounds are the normal sounds heard over most of the lung fields.
- They are soft, low-pitched, and have a gentle, rustling quality, often described as "WOOOOOSH-AHHH."
- There is no pause between inspiration and expiration; the sound is continuous.
- The inspiratory phase is longer, louder, and higher-pitched than the expiratory phase.
- Vesicular sounds are generated by turbulent airflow in the lobar and segmental bronchi during inspiration, while expiration is quieter and shorter.
- Airflow in the alveoli and small bronchioles is laminar and does not produce sound.
- Vesicular breath sounds are best heard during auscultation of the peripheral chest.
Auscultation Technique & Anatomic Considerations
- Auscultation should be performed by placing the stethoscope's diaphragm on standard thoracic areas, covering both anterior and posterior chest surfaces.
- Listen to a complete cycle of inhalation and exhalation at each point, comparing the left and right sides symmetrically as you move downward.
- On the anterior chest, upper and middle lobe sounds predominate; on the posterior chest, lower lobe sounds are more prominent.
- The right lung has three lobes; the left lung has two.
- There are no precise anatomical landmarks for lung auscultation, but commonly accepted locations are used in practice.
- Proper technique involves listening for differences between sides and noting any abnormal sounds.
Bronchial Breath Sounds
- Bronchial breath sounds are loud, hollow, and have a harsh, blowing quality, often compared to the "Darth Vader" breathing sound or the phrase "Koohhhh Purrrrrr."
- There is a distinct pause between inspiration and expiration.
- The expiratory phase is longer and higher-pitched than the inspiratory phase.
- Bronchial sounds are produced by the same mechanism as vesicular sounds: turbulent airflow in the bronchi during inspiration and in the larger airways during expiration.
- Normally, bronchial breath sounds are heard only over the central airways, such as the trachea, sternal edge at the 2nd intercostal space, and posteriorly from vertebral levels C7 to T3.
- Healthy lung tissue and the chest wall filter and dampen these sounds, so they are not heard peripherally under normal conditions.
Clinical Significance of Bronchial Sounds in Periphery
- Hearing bronchial breath sounds in the peripheral lung fields is abnormal and suggests enhanced transmission of airway vibrations through dense tissue or fluid.
- This occurs because solid tissue and fluids transmit vibrations more effectively than air.
- Common causes include:
- Consolidation (e.g., pneumonia), where inflammation increases lung density.
- Dense lung fibrosis
- Lung abscess
- Collapsed lung adjacent to a pleural effusion
- The presence of bronchial breath sounds peripherally indicates underlying pathology and warrants further investigation.
Key Terms & Definitions
- Vesicular breath sounds: Soft, low-pitched, rustling sounds heard over peripheral lung fields, with no pause between inspiration and expiration.
- Bronchial breath sounds: Loud, hollow, blowing sounds with a pause between inspiration and expiration, normally heard over central airways.
- Turbulent airflow: Chaotic air movement that generates audible vibrations.
- Laminar airflow: Smooth, uniform air movement that is silent.
- Consolidation: Lung tissue filled with fluid or cells, increasing the transmission of sound vibrations.
Action Items / Next Steps
- Prepare for the next lecture, which will focus on fine and coarse crackles.
- Review common pathological conditions that affect breath sounds, such as consolidation, fibrosis, abscess, and pleural effusion.
- Practice auscultation techniques, ensuring symmetrical comparison and attention to both normal and abnormal breath sounds.