Vocal Fremitus - Physiology and Clinical Applications

Introduction

As a medical professional, understanding the basics of respiratory system assessment is paramount. Vocal fremitus refers to the vibrations transmitted through the chest wall during vocalization. This article aims to provide a comprehensive overview of vocal fremitus, including the underlying physiology, technique of assessment, and clinical significance.

What Is Vocal Fremitus?

Vocal fremitus, or tactile vocal fremitus, is the vibration or tremors felt over the chest wall during vocalization. The word "fremitus" is derived from the Latin word "fremere," which means "to murmur." It occurs due to the transmission of sound waves generated by vocal cords during speech, which causes a vibration of the air column in the tracheobronchial tree. These vibrations are transmitted to the chest wall and can be palpated by the examiner using the hands.

What Are the Principles of Sound Transmission Involved in the Physiology of Vocal Fremitus?

To understand the physiology of vocal fremitus, it is essential to understand the principles of sound transmission. Sound waves are generated when air is moved through the vocal cords, causing them to vibrate. These sound waves are transmitted through the tracheobronchial tree to the lung tissue, causing it to vibrate. The vibration of the lung tissue is then transferred to the chest wall, which can be felt as vocal fremitus. The intensity of the pulses depends on the frequency and amplitude of the sound waves, the thickness of the chest wall, and the amount of air in the lungs.

What Is the Proper Technique for Assessing Vocal Fremitus?

• Assessment of Vocal Fremitus: Assessment of vocal fremitus requires proper positioning of the patient, correct technique, and a thorough understanding of the underlying physiology. The patient should be seated upright with their arms crossed over their chest while the examiner places the palms of their hands firmly against the patient's chest. The patient is then instructed to say "ninety-nine" or "blue moon" repeatedly while the examiner assesses the intensity of the vibrations over different chest areas.

• Technique of Assessment: To assess vocal fremitus, the examiner places the palm or the ulnar edge of the hand firmly on the patient's chest while the patient speaks. The patient is instructed to repeat a word or phrase with a high-pitched vowel sound, such as "ee" or "oo." The examiner then compares the intensity of the vibrations felt over various chest areas. This assessment is usually done bilaterally at the exact anatomical location to check for any asymmetry.

What Factors Can Affect the Vocal Fremitus?

Several factors can affect the transmission of sound waves through the lung tissue to the chest wall, resulting in variations in vocal fremitus. These factors include the thickness of the chest wall, the amount of air in the lungs, the frequency and amplitude of the sound waves, and the patient's position.

1. The thickness of the chest wall can affect the intensity of vocal fremitus, with thinner chest walls resulting in greater power. This is because thinner chest walls allow for more excellent transmission of sound waves from the lung tissue to the chest wall. In contrast, thicker chest walls can dampen the transmission of sound waves, resulting in a lower intensity of vocal fremitus.

2. The amount of air in the lungs can also affect the intensity of vocal fremitus, with greater air volume resulting in decreased power. This is because increased air volume leads to a more excellent dissipation of sound waves through the lung tissue, resulting in a lower intensity of vibration transmitted to the chest wall.

3. The frequency and amplitude of the sound waves can also affect the intensity of vocal fremitus. Higher frequency and amplitude sound waves tend to transmit more effectively through lung tissue, resulting in greater power of vibration transmitted to the chest wall.

4. Finally, the patient's position can also affect the intensity of vocal fremitus. A patient lying down or in a supine position may have different patterns of lung expansion and sound transmission, leading to variations in vocal fremitus.

What Is the Clinical Significance of Vocal Fremitus in Diagnosing Respiratory Disorders?

Vocal fremitus is an essential physical examination finding that can aid in diagnosing various respiratory disorders. Increased vocal fremitus is typically observed in conditions such as pneumonia, lung abscess, and pulmonary edema, where the lung tissue is consolidated. Decreased vocal fremitus is generally observed in states such as pneumothorax, pleural effusion, and emphysema, where the lung tissue is hyperinflated, or fluid accumulates in the pleural cavity. In some cases, asymmetric vocal fremitus can signify a mass lesion or a pleural effusion.

What Are the Limitations of Vocal Fremitus?

Despite its clinical utility, vocal fremitus has several limitations. It is subjective and can vary depending on the examiner's experience, the patient's voice quality, and the pressure applied during palpation. Moreover, it may not be reliable in patients with obesity or thick chest walls, as the vibrations may not be palpable.

What Are the Potential Causes of Abnormal Vocal Fremitus?

1. Abnormal vocal fremitus can be a sign of underlying respiratory conditions. Increased vocal fremitus is typically observed in states such as pneumonia, lung abscess, and pulmonary edema, where the lung tissue is consolidated. Consolidation occurs when air spaces in the lung become filled with fluid, pus, or other materials, reducing the amount of air in the lung tissue. This increases the transmission of sound waves through the lung tissue to the chest wall, resulting in increased vocal fremitus.

2. Decreased vocal fremitus is typically observed in conditions such as pneumothorax, pleural effusion, and emphysema, where the lung tissue is hyperinflated or fluid accumulates in the pleural cavity. Hyperinflation occurs when the air sacs in the lungs become overinflated, reducing the amount of lung tissue in contact with the chest wall. This results in decreased transmission of sound waves through the lung tissue to the chest wall, resulting in decreased vocal fremitus.

3. Asymmetric vocal fremitus can signify a mass lesion or a pleural effusion. A mass lesion refers to an abnormal growth of tissue in the lung or chest wall, which can obstruct airflow and decrease vocal fremitus. A pleural effusion refers to an abnormal accumulation of fluid in the pleural cavity, which can cause a shift in the position of the lungs and lead to an asymmetric distribution of vocal fremitus.

Conclusion

Vocal fremitus is a proper physical examination technique that can provide valuable information about the underlying respiratory condition. It is a simple, non-invasive, and cost-effective technique that can aid in diagnosing various respiratory diseases. However, it is essential to remember that vocal fremitus is subjective and may not always be reliable. Hence, it should be used with other clinical and diagnostic tools to arrive at an accurate diagnosis.