(Extra) Auscultation (Jennifer A. Pryor)

 

Auscultation

Auscultation involves listening to and interpreting sounds produced within the thorax. It's facilitated by a stethoscope, comprising a diaphragm and bell connected to earpieces via tubing.

Stethoscope Components:

• Diaphragm: Used for listening to breath sounds.
• Bell: Ideal for very low frequencies, especially heart sounds like the third and fourth heart sounds.
• Both the diaphragm and bell must be intact for proper sound transmission.
• Tubing should be relatively short to minimize sound absorption.
• Earpieces, typically made of plastic or rubber, should fit snugly within the ears, pointing slightly forward to maximize sound transmission into the auditory canal.
• A teaching stethoscope (refer to Fig. 1.6) allows both experienced and inexperienced physiotherapists to hear the same sounds simultaneously (Ellis, 1985).

Procedure:

• Chest auscultation should ideally be performed in a quiet room with the chest exposed.
• Patients are instructed to take deep breaths through an open mouth to minimize interference from nasal turbulence.

Breath Sounds:

• Normal breath sounds result from turbulent airflow in the trachea and large airways.
• These sounds, comprising high, medium, and low frequencies, can be heard directly over the trachea.
• Higher frequencies are attenuated by normal lung tissue, resulting in softer and lower-pitched breath sounds over the periphery.
• Previously, it was thought that higher-pitched sounds were generated by the bronchi (bronchial breath sounds) and lower-pitched ones by airflow into the alveoli (vesicular breath sounds).
• It's now known that normal breath sounds represent the filtering of 'bronchial' breath sounds generated in large airways.
• Though technically incorrect, normal breath sounds are still sometimes referred to as 'vesicular' or 'bronchovesicular'.
• Normal breath sounds are heard all over the chest wall throughout inspiration and briefly during expiration.

Bronchial Breath Sounds

Bronchial breath sounds are the normal sounds of the trachea and large airways, transmitted through lung tissue that lacks air and therefore does not attenuate higher frequencies. As a result, the sounds heard over consolidated lung areas resemble those heard over the trachea.

• Characteristics:
  • Loudness and Pitch: Bronchial breath sounds are loud, high-pitched, and have a harsh quality.
  • Timing: They are heard equally throughout inspiration and expiration, with a short pause between the two. This differs from normal breath sounds, which are fainter, lower pitched, and absent during the latter half of expiration.
• Obstruction and Absence:
  • If the bronchus supplying an area of consolidated lung is obstructed (e.g., by carcinoma or a large sputum plug), bronchial breath sounds may not be heard as the obstruction blocks sound transmission.

Diminished Breath Sounds

Diminished breath sounds occur due to a reduction in the initial generation of sound or an increase in sound attenuation.

• Causes:
  • Reduced flow, caused by factors such as pain or muscle weakness, leads to globally diminished breath sounds as patients cannot breathe deeply.
  • In emphysema patients, parenchymal destruction and hyperinflation cause greater attenuation of normal breath sounds.
• Localized Diminished Sounds:
  • Obstruction of a bronchus by a tumor or large sputum plugs can cause locally diminished breath sounds.
  • Localized accumulation of air or fluid in the pleural space can also block sound transmission, resulting in absent breath sounds.

Added Sounds

Wheezes (Previously Called 'Rhonchi')

Wheezes are musical tones produced by airflow vibrating a narrowed or compressed airway.

• Types:
  • Fixed Monophonic Wheeze: Caused by a single obstructed airway.
  • Polyphonic Wheezes: Due to widespread disease.
• Causes:
  • Narrowing of the airway due to bronchospasm, mucosal edema, sputum, or foreign bodies.
• Timing:
  • Wheezes are first heard during expiration when airways are normally compressed.
  • With severe narrowing, wheezes may also occur during inspiration.
• Pitch:
  • High-pitched wheezes indicate near-total obstruction.
  • The volume of wheeze may not always correlate with the severity of obstruction. For example, moderate asthmatics may have loud wheezes, while very severe asthmatics may exhibit a 'quiet chest' due to insufficient airflow to cause wheezes.
• Low-Pitched Wheezes:
  • Caused by sputum retention and may change or clear after coughing.

Crackles (Previously Called 'Crepitations' or 'Rales')

Crackles are clicking sounds heard during inspiration, caused by the opening of previously closed alveoli and small airways.

• Types:
  • Early vs. Late: Early crackles occur when bronchioles open, often heard in bronchiectasis and bronchitis. Late crackles occur when alveoli and respiratory bronchioles open, often heard in pulmonary edema and pulmonary fibrosis.
  • Fine vs. Coarse: Fine crackles are characteristic of late inspiratory crackles in conditions like pulmonary edema and pulmonary fibrosis, while coarse crackles are associated with bronchioles opening, as seen in bronchiectasis and bronchitis.
  • Localized vs. Widespread: Crackles can be localized or widespread depending on the underlying condition.

Severe crackles in conditions like pulmonary edema and pulmonary fibrosis may become coarser and start earlier in inspiration.

Auscultation Findings

Localized Crackles

Localized crackles may occur in dependent alveoli gradually closed by compression from the lung above.

• Resolution:
  • This early feature of subsegmental lung collapse resolves with deep breathing or coughing.
• Features of Pulmonary Edema:
  • Crackles of pulmonary edema are more marked basally but only transiently clear after coughing.
• Differentiation Challenges:
  • Differentiating between subsegmental lung collapse and pulmonary edema can be difficult.
  • Auscultation may not always clarify the situation.
• Clinical Indicators:
  • Elevation of jugular venous pressure and peripheral edema suggest pulmonary edema.
  • Ineffective cough, recent anesthesia, and pyrexia suggest sputum retention leading to subsegmental lung collapse.

Pleural Rub

Pleural rub is a creaking or rubbing sound occurring with each breath when pleural surfaces are roughened by inflammation, infection, or neoplasm.

• Variability:
  • Pleural rubs range from localized and soft to loud and generalized, sometimes palpable.
• Differentiation:
  • Sometimes difficult to differentiate from crackles.
  • Heard equally during inspiration and expiration, often recurring in reverse order during expiration.

Vocal Resonance

Vocal resonance is the transmission of voice through airways and lung tissue to the chest wall, heard through a stethoscope.

• Testing Method:

  • Usually tested by instructing the patient to repeat '99' (similar to vocal fremitus felt with hands).

• Effect of Lung Condition:

  • Normal lung attenuates higher frequencies, making speech a low-pitched mumble.
  • Consolidated lung transmits all sounds better, especially high frequencies, resulting in louder, higher-pitched transmitted sounds.

• Whispering Pectoriloquy:

  • Over areas of consolidation, whispered speech becomes clear and intelligible, known as 'whispering pectoriloquy'.

  
  

  
  
  
  
  

Sputum Assessment

• At the end of the respiratory examination, it is often beneficial to instruct the patient to perform huffing maneuvers to a low lung volume to assess the presence of retained secretions.
• Any sputum produced should be examined for color, consistency, and quantity.

Sputum Analysis	Description	Causes
Saliva	Clear watery fluid
Mucoid	Opalescent or white	Chronic bronchitis without infection, asthma
Mucopurulent	Slightly discolored, but not frank pus	Bronchiectasis, cystic fibrosis, pneumonia
Purulent	Thick, viscous: Yellow Dark green/ Brown Rusty Red currant jelly	Haemophilus, Pseudomonas, Pneumococcus, mycoplasma, Klebsiella
Frothy	Pink or white	Pulmonary edema
Haemoptysis	Ranging from wood specks to frank blood and old blood (dark brown)	Infection (tuberculosis, bronchiectasis), infarction, carcinoma, vasculitis, trauma, also coagulation disorders, cardiac disease
Black	Black specks in mucoid secretions	Smoke inhalation (fires, tobacco, heroin), coal dust