Stridor

 

Stridor may be heard better without a stethoscope by putting your ear close to the patient's mouth and asking the patient to breathe in and out. As indicated earlier, it is a sign atlarge airway narrowing either in the larynx, trachea or main bronchi.

 

Crackles

 

In a sense the term crackles is self-explanatory. Problems arise because of various descriptions that are often added such as coarse, medium, fine, wet or dry. These add little to our understanding; nonetheless, it is possible to distinguish two main types. The first occurs when there is fluid in the larger bronchi and a coarse bubbling sound can be heard that clean or alters as secretions causing the sound are shifted on coughing or deep breathing. The sound of other 'fine' crackles can be imitated by roiling the hairs of your temple together between your fingers. They occur in inspiration and are high-pitched, explosive sounds. The mechanism of their production is thought to be as follows. Many conditions lead to premature closure of the small airways at the end of expiration. During the succeeding inspiration, these units can only be reopened by overcoming the surface tension that keeps them closed. When they eventually 'pop open" crackles are produced. During inspiration, larger bronchi will open before smaller ones so crackles from chronic bronchitis and bronchiectasis tend to occur early. Conditions that largely involve the alveoli, such as left ventricular failure, fibrosis and pneumonia tend to produce crackles later on inspiration. This distinction is of clinical value. Note whether the crackles are localised. This would be expected in pneumonia and mild cases of bronchiectasis. Pulmonary Oedema and fibrosing alveolitis typically affect both lung bases equally. Normal people, especially smokers, may have a few basal

crackles; these often clear with a few deep breaths.

 

Pleural rub

 

This is caused by the inflamed surfaces of the pleura rubbing together. The sound has been likened to new leather when it is bent or more vividly to the creaking noises made in a sailing ship heeling to the wind which you may have experienced from films if not in reality. Some idea of the quality of the sound can be obtained by placing one hand over the ear and rubbing the back of that hand with the fingers of the other. Pleural rubs are usually heard on both inspiration and expiration.

 

At first you may think that you are moving the stethoscope on the chest. Sometimes coarse crackles can sound like rubs; a cough will shift the former. If there is any pain, ask the patient to point to the site of the pain, this often localises the rib too. Rubs are heard in all varieties of pleural inflammation such as in pneumonia and pulmonary embolism. Any effusion will separate the pleura and the rub may well go but sometimes remain above the effusion.

 

Absent or diminished breath sounds are always an abnormal finding warranting investigation. Fluid, air, or solid masses in the pleural space all interfere with the conduction of breath sounds (pneumonia, pneumo-, hydro-, haemothorax, tumor of lung or mediastinal, emphysema of lungs, atelectasis, airways obstruction, a foreign body in the bronchus). Diminished breath sounds in certain segments of the lung can alert the doctor to pulmonary areas that may benefit from postural drainage and percussion. Increased breath sounds following pulmonary therapy indicate improved passage of air through the respiratory tract.

Voice sounds are also part of auscultation of the lungs. Normally voice sounds or vocal resonance is heard, but the syllables are indistinct. They are elicited in the same manner as vocal fremitus, except that the doctor listens with the stethoscope. Consolidation of the lung tissue produces three types of abnormal voice sounds.

1. Whispered pectoriloquy, in which the child whispers words and the nurse, hears the syllables.

2.  Bronchophony, in which the child speaks words that are not distinguishable but the vocal resonance is increased in intensity and clarity.

3.  Egophony, in which the child says "ee," which is heard as the nasal sound "ay" through the stethoscope.

Decreased or absent vocal resonance is caused by the same conditions that affect vocal fremitus.

Various pulmonary abnormalities produce adventitious sounds that are not normally heard over the chest. They are not alterations of normal breath sounds but rather sounds that occur in addition to normal or abnormal breath sounds. They are often referred to as the three "R’s": rales (from the French word meaning "rattle"), rhonchi, and rubs. Considerable practice with an experienced tutor is necessary to differentiate the various types of adventitious sounds. Often it is best to describe the type of sound heard in the lungs rather than to try and label it correctly.

Rales result from the passage of air through fluid or moisture. They are more pronounced when the child takes a deep breath. Even though the sound may seem continuous, it is actually composed of several discrete sounds, each originating from the rupture of a small bubble. The type of rales is determined by the size of the passageway and the type of exudate the air passes through. They are roughly divided into three categories: fine, medium, and coarse.

Fine rales (sometimes called crepitant rales) can be simulated by rubbing a few strands of hair between the thumb and index finger close to the ear or by slowly separating the thumb and index finger after they have been moistened with saliva. The result is a series of fine crackling sounds. Fine rales are most prominent at the end of inspiration and are not cleared by coughing. They occur in the smallest passageways, the alveoli and bronchioles.

Medium rales are not as delicate as fine rales and can be simulated by listening to the "fizz" from recently opened carbonated drinks or by rolling a dry cigar between the fingers. They are prominent earlier during inspiration and occur in the larger passages of the bronchioles and small bronchi.

Coarse rales are relatively loud, coarse, bubbling, gurgling sounds that occur in the large airways of the trachea, bronchi, and smaller bronchi. Often they clear partially during coughing. They are frequently heard in dying patients because the cough reflex is depressed, allowing thick secretions to accumulate in the trachea and major bronchi. Because they are so common when death is imminent, coarse rales are often called "the death rattle."

Rhonchi (rales) are sounds produced as air passes through narrowed passageways, regardless of the cause, such as exudate, inflammation, spasm, or tumor. Rhonchi are continuous, since sound is produced as long as air is being forced past an obstruction. Although they are often more prominent during expiration, they are usually present during both phases of respiration. Rhonchi are classified according to pitch as sibilant or sonorous.

Sibilant rhonchi are high pitched, musical, wheezing, or squeaking in character. The wheezing quality is often more pronounced on forced expiration. Sibilant rhonchi are produced in the smaller bronchi and bronchioles.

Sonorous rhonchi are low pitched and often snoring or moaning in character. They are produced in the large passages of the trachea and bronchi. Like coarse rales, they can be partly cleared by coughing. Some clinicians classify sonorous rhonchi as coarse rales, or vice versa.

The other adventitious sound of importance is the pleural friction rub. Its sound can be simulated by cupping one hand to the ear and rubbing a finger of the other hand across the cupped hand. The most common site for a friction rub to be heard is the lower antero-lateral chest wall (between the midaxillary and midclavicular lines), the area of greatest thoracic mobility.

 

Classifacation and mechanism of  origin of dry rales

Dry rales, or rhonchi, may be due to various causes. The main one is constriction of the lumen in the bronchi. Constriction may be total (in bronchial asthma), non-uniform (in bronchitis), or focal (in tuberculosis or tumour of the bronchus). Dry rales can be due to (1) spasms of smooth muscles of the bronchi during fits of bronchial asthma; (2) swelling of the bronchial mucosa during its inflammation; (3) accumulation of viscous sputum in the bronchi which adheres to the wall of the bronchus and narrows its lumen; (4) formation of fibrous tissue in the walls of separate bronchi and in the pulmonary tissue with subsequent alteration of their ar­chitectonics (bronchiectasis, pneumosclerosis); (5) vibration of viscous sputum in the lumen of large and medium size bronchi during inspiration and expiration: being viscous, the sputum can be drawn (by the air stream) into threads which adhere to the opposite walls of the bronchi and vibrate like strings.

According to the quality and pitch of the sounds produced, dry rales are divided into sibilant (high-pitched and whistling sounds) and sonorous rales (low-pitched and sonoringsounds). High-pitched rales are produced when the lumen of the small bronchi is narrowed, while low-pitched sonorous rales are generated in stenosis of medium calibre and largecalibre bronchi or when viscous sputum is ac­cumulated in their lumen.

Propagation and loudness of dry rales depend on the size of the affected area in the bronchial tree, on the depth of location of the affected bronchi, and the force of the respiratory movements. When the walls of a medium size and large bronchi are affected to a limited extent, rhonchi are insignificant and soft. Diffuse inflammation of the bronchi or bronchospasm arising during attacks of bronchial asthma is attended by both high-pitched sibilant and low-pitched sonorous rales which vary in tone and loudness. These rhonchi can be heard at a distance during expiration.

 

Classifacation and mechanism of  origin of moist rales

Moist rales are generated because of accumulation of liquid secretion (sputum, oedematous fluid, blood) in the bronchi through which air passes. Air bubbles pass through the liquid secretion of the bronchial lumen and collapse to produce the specific cracking sound. This sound can be simulated by bubbling air through water using a fine tube. Moistrales are heard during both the inspiration and expiration, but since the air velocity is higher during inspiration, moist rales will be better heard at this respiratory phase.

Depending on the calibre of bronchi where rales are generated, they are classified as fine, medium and coarse bubbling rales. Fine bubbling rales are generated in fine bronchi and are percepted by the ear as short multiple sounds. Rales originating in the finest bronchi and bronchioles are similar to crepitation from which they should be differentiated. Medium bubbling rales are produced in bronchi of a medium size and coarse bubbling rales in large calibre bronchi, in large bronchiectases, and in pulmonary cavities (abscess, cavern) containing liquid secretions and communicating with the large bronchus. Large bubbling rales are characterized by a lower and louder sound.

Moist rales originating in superficially located large cavities (5-6 cm and over in diameter) may acquire a metallic character. If segmentary bronchiectases or cavities are formed in the lung, rales can usually be heard over a limited area of the chest. Chronic bronchitis or marked congestion in the lungs associated with failure of the left chambers of the heart is as a rule attended by bilateral moist rales of various calibre, which occur at the symmetrical points of the lungs.

Depending on the character of the pathology in the lungs, moist rales are subdivided into consonating or crackling, and non-consonating or bubbling rales. Consonating moistrales are heard in the presence of liquid secretions in the bronchi surrounded by airless (consolidated) pulmonary tissue or in lung cavities with smooth walls surrounded by consolidated pulmonary tissue. The cavity itself acts as a resonator to intensify moist rales. Moist consonating rales are heard as if just outside the ear. Consonating rales in the lower portions of the lungs suggest inflammation of :he pulmonary tissue surrounding the bronchi. Consonating rales heard in the subclavicular or subscapular regions indicatetuberculous infiltration or cavern in the lung.

Non-consonating rales are heard in inflammation of bronchial mucosa (bronchitis) or acute oedema of the lung due to the failure of the left chambers of the heart. The sounds produced by collapsing air bubbles in he bronchi are dampened by the "air cushion" of the lungs as they are conducted to the chest surface.