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Auscultation is the term for listening to the internal sounds of the body, usually using a stethoscope. Auscultation is performed for the purposes of examining the circulatory system and respiratory system (heart sounds and breath sounds), as well as the gastrointestinal system (bowel sounds). It is an integral part of physical examination of a patient and is routinely used to provide strong evidence in including or excluding different pathological conditions that are manifested clinically in the patient.
The stethoscope comprises a bell and a diaphragm. The bell is most effective at transmitting lower frequency sounds, while the diaphragm is most effective at transmitting higher frequency sounds. In other words, the bell is designed to hear low pitched sounds and the diaphragm is designed to hear high pitched sounds. They are connected via rubber tubing to the ear pieces. These should be worn facing forward as the ear canals run anteriorly.
Respiratory Examination:
Ask the patient to disrobe, as this will allow the stethoscope to be placed directly on the chest.
Make sure the patient is sitting upright in a relaxed position, where this is possible.
You should then instruct the patient to breathe a little deeper than normal through the mouth.
The bell/diaphragm of the stethoscope is then placed against the chest wall.
Auscultation of the lungs should be systematic, including all lobes of the anterior, lateral and posterior chest.
Usually the APEX of the lungs bilaterally (2cm superior to medial 1/3 of clavicle)
Superior Lobes anterior (2nd intercostal space mid clavicular line) and posterior (Between C7 & T3)
Inferior Lobes bilaterally anterior (6th intercostal space, mid-axillary line) and posteriorly (between T3 & T10)
Middle lobe right anterior only (4th intercostal space mid-clavicular line)
The examiner should begin at the top, compare side with side and work towards the lung bases.
The examiner should listen to at least one ventilatory cycle at each position of the chest wall.
The examiner should identify four characteristics of breath sounds: pitch, amplitude, distinctive characteristics and duration of the inspiratory sound compared with the expiratory sound.
Normal Lung Sounds
Vesicular
Are usually quiet, mostly inspiratory, with a distinctive pause before a quieter expiratory phase. They are soft and low pitched with a rustling quality during inspiration and are even softer during expiration. These are the most commonly auscultated breath sounds, normally heard over the most of the lung surface. They have an inspiration/expiratory ratio of 3 to 1 or I:E of 3:1.
Bronchovesicular
These are heard over the 1st and 2nd intercostal spaces and the interscapular area. The inspiratory and expiratory phases are roughly equal in length. They reflect a mixture of the pitch of the bronchial breath sounds heard near the trachea and the alveoli with the vesicular sound.
Listen to bronchovesicular sounds
Bronchial
These are normally heard over the manubrium. Expiratory phase is greater than inspiratory. The expiratory pitch is high and intensity is loud. Hollow, tubular sounds that are lower pitched.
Tracheal
These sound are heard directly over the trachea. Inspiratory phase equals the expiratory phase. The sound is very loud and the pitch very high.
Abnormal Lung Sounds
Crackles
Crackles (rales) are caused by excessive fluid (secretions) in the airways. It is caused by either an exudate or a transudate. Exudate is due to lung infection e.g pneumonia while transudate such as congestive heart failure. A crackle occurs when a small airways pop’s open during inspiration after collapsing due to loose secretions or lack of aeration during expiration (atelectasis). Crackles are much more common in inspiratory than in expiratory.
Crackles are high-pitched and discontinuous. They sound like hair being rubbed together. There are three different types; fine, medium and coarse.
Fine are typically late inspiratory and coarse are usually early inspiratory. Fine crackles could suggest an interstitial process; e.g pulmonary fibrosis, congestive heart failure.
Medium crackles are high pitched, very brief and soft. It sounds like rolling a strand of hair between two fingers.
Coarse crackles are louder, more low pitched and longer lasting. They indicate excessive fluid on the lungs which could be caused by aspiration, pulmonary oedema from chronic heart disease, chronic bronchitis, pneumonia.
Wheezes
Wheezes are an expiratory sound caused by forced airflow through collapsed airways. Due to the collapsed or abnormally narrow airway, the velocity of air in the lungs is elevated. Wheezes are continuous high pitched hissing sounds. They are heard more frequently on expiration than on inspiration. If they are monophonic it us due to an obstruction in one airway only but if they are polyphonic than the cause is a more general obstruction of airways. Where the wheeze occurs in the respiratory cycle depends on the obstructions location[, if wheezing occurs in the expiratory phase of respiration it is usually connected to broncholiar disease. If the wheezing is in the inspiratory phase, it is an indicator of stiff stenosis whose causes range from tumours to scarring. One of the main causes of wheezing is asthma other causes could be pulmonary edema, interstitial lung disease and chronic bronchitis.
Rhonchi
Rhonchi are caused by obstruction or secretions in the bronchial airways. They are coarse, continuous low pitched rattlings sounds that are heard on inspiration and expiration that sound very much like snoring. They can be heard in patients with pneumonia, bronchiectasis, chronic obstructive pulmonary disease (COPD), chronic bronchitis or cystic fibrosis.
Pleural Rub
Pleural Rub produces a creaking or brushing sound. These occur when the pleural surfaces are inflamed and as a result rub against one another. They are heard during both inspiratory and expiratory phases of the lung cycle and can be both continuous and discontinuous. Pleural rub can suggest pleurisy, pneumothorax or pleural effusion.
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