Examination of the respiratory system II.:
Auscultation
Lajos Gergely, MD, PhD
3rd Dept. of Internal Medicine, Inst. of Internal Medicine
Medical and Health Science Center, University of Debrecen
History
René-Théophile-Hyacinthe Laennec (February 17, 1781- August 13,
1826), French physician; inventor of the stethoscope. Dr. Laennec was born in
Quimper, Brittany and studied medicine at the Hôpital de la Charité, Paris
qualifying in 1804. He invented the stethoscope in 1816, while working at the
Hôpital Necker.
In his 1819 work, "De l'Auscultation Mediate," Rene Laennec
described the normal and abnormal chest sounds he heard with his newly
invented medical instrument, the stethoscope, and attached clinical
significance to these sounds by comparing them with pathologic autopsy
findings. Although the shape of Laennec's original wooden-tube stethoscope
has changed radically, the general principles and clinical correlations of
chest auscultation are the same now as they were in the early 19th century.
Lung auscultation points (normal situation !)
POSTERIOR
ANTERIOR
Factors affecting breath sounds
Airflow velocity
Distance from point of origin
Airway patency
Condition of the pleura and chest wall
Factors affecting breath sounds (detailed)
Airflow velocity. Forceful exhalation and inhalation increase airflow velocity and cause greater air
turbulence, greater amplitude of vibration in the bronchial wall, and a louder breath sound. Conversely, if
the patient's rate or volume of respiration is so low that the air moves very slowly, less turbulence and,
therefore, much less amplitude of normal breath sounds is produced. This is true for tracheal and
bronchial breath sounds but may be less of a factor with vesicular breath sounds.
Distance from point of origin. Lung sounds are progressively filtered and attenuated as they travel
toward the periphery through the chest wall. Filtering means that breath sounds generated at various
frequencies are transmitted differently; this contributes to differences in acoustic quality of sounds heard
at the mouth, upper chest, and lung base, as described below.
Sounds heard at the trachea and mouth, with a frequency between 200 and 2,000 Hz, are relatively
unfiltered. At the level of the main-stem bronchi, the frequency is 200 to 1,000 Hz; at the lung base, it is
200 to 400 Hz.
Airway patency. Patency, of course, is necessary for transmission of breath sounds. Occlusion of a
segmental or lobar bronchus by tumor or extrinsic compression creates a barrier to sound transmission.
This obliterates or decreases the intensity of breath sounds that are perceived at the periphery.
Condition of pleurae and chest wall. Processes that separate the visceral and parietal pleurae,
such as pleural effusion, pleural thickening, pleural tumor, and pneumothorax, decrease the loudness of
lung sounds by interposing a sound barrier between the source of breath sound generation and the chest
wall. Increased density of the chest wall caused by obesity, pleural tumor, or inflammation likewise can
dampen normal breath sounds.
Normal breath sounds consist of those heard over the
entire lung field and consist of an inspiratory and expiratory phase.
Tracheal: These breath sounds are high-pitched and loud, with a harsh and hollow (or
"tubular) quality. The inspiratory and expiratory phases are of equal duration, and there is
a definite pause between phases. Tracheal breath sounds usually have very little clinical
usefulness.
Bronchial: Normally heard over the upper manubrium, these breath sounds directly
reflect turbulent airflow in the main-stem bronchi. They are loud and high-pitched but not
quite as harsh and hollow as tracheal breath sounds, the expiratory phase is generally
longer than the inspiratory phase, and there is usually a pause between the phases.
Bronchovesicular: These breath sounds are normally heard in the anterior first and
second intercostal spaces and posteriorly between the scapulas, where the main-stem
bronchi lie. The inspiratory and expiratory phases are about equal in duration, with no
pause between phases. Bronchovesicular sounds are soft and less harsh than bronchial
breath sounds and have a higher pitch than vesicular sounds.
Vesicular: Audible over peripheral lung fields, these breath sounds are soft and lowpitched, without the harsh, tubular quality of bronchial and tracheal breath sounds. The
inspiratory phase is about three times longer than the expiratory, with no pause between
phases (7).
Abnormal lung sounds (basics)
Unusual location. Bronchial breathing heard at any location other
than the upper manubrium indicates the presence of pulmonary
consolidation or atelectasis in that area. Such breathing may also be
heard in areas of pulmonary fibrosis. It is believed that the consolidated,
atelectatic, denser lung transmits sound generated the larger airways
without significant loss of higher frequencies. Thus, the quality of the
sound is much the same as if it were heard over the upper airway.
Qualitative differences. In contrast to the above situation, breath
sounds are greatly reduced in intensity when there is hyperinflation
(as occurs in severe emphysema) or when there is significant air trapping
(as occurs in severe asthma). Theoretically, a hyperaerated, less dense
lung transmits breath sounds poorly.
Different normal and abnormal lung sounds
Normal
Abnormal
Adventitious
tracheal
absent/decreased
crackles (rales)
vesicular
bronchial
wheeze
bronchial
rhonchi
bronchovesicular
stridor
pleural rub
mediastinal crunch
(Hamman's sign)
Continuous lung sounds:
1. Wheezes (represent airway obstruction)
•
•
High pitched
Low pitched
Discontinuous adventitious sounds are classified as either:
1. Crackles sound like brief bursts of popping bubbles. They are
most commonly associated with the sudden opening of closed
airways.
2. Pleural Rubs are an indication of pleural inflammation and
sounds like two pieces of sandpaper rubbing together throughout
each inspiration and expiration.
Crackles
Crackles are discontinuous, nonmusical, brief sounds heard more commonly
on inspiration. They can be classified as fine (high pitched, soft, very brief) or
coarse (low pitched, louder, less brief). When listening to crackles, pay special
attention to their loudness, pitch, duration, number, timing in the respiratory cycle,
location, pattern from breath to breath, change after a cough or shift in position.
Crackles may sometimes be normally heard at the anterior lung bases after a
maximal expiration or after prolonged recumbency.
The mechanical basis of crackles: Small airways open during inspiration and collapse
during expiration causing the crackling sounds. Another explanation for crackles is
that air bubbles through secreations or incompletely closed airways during expiration.
Conditions:
ARDS
asthma
bronchiectasis
chronic bronchitis
consolidation
early CHF
interstitial lung disease
pulmonary edema
Wheeze
Wheezes are continuous, high pitched, hissing sounds heard
normally on expiration but also sometimes on inspiration. They are
produced when air flows through airways narrowed by secretions, foreign
bodies, or obstructive lesions.
Note when the wheezes occur and if there is a change after a deep breath
or cough. Also note if the wheezes are monophonic (suggesting
obstruction of one airway) or polyphonic (suggesting generalized
obstruction of airways).
Conditions:
asthma
CHF
chronic bronchitis
COPD
pulmonary edema
Other sounds
Rhonchi
Rhonchi are low pitched, continous, musical sounds that are similar to wheezes. They usually imply
obstruction of a larger airway by secretions.
Stridor
Stridor is an inspiratory musical wheeze heard loudest over the trachea during inspiration. Stridor
suggests an obstructed trachea or larynx and therefore constitutes a medical emergency that requires
immediate attention.
Pleural Rub
Pleural rubs are creaking or brushing sounds produced when the pleural surfaces are inflammed or
roughened and rub against each other. They may be discontinuous or continuous sounds. They can
usually be localized a particular place on the chest wall and are heard during both the inspiratory and
expiratory phases.
Conditions:
pleural effusion
pneumothorax
Mediastinal Crunch (Hamman’s sign)
Mediastinal crunches are crackles that are synchronized with the heart beat and not respiration. They are
heard best with the patient in the left lateral decubitus postion. As with stridor, mediastinal crunches
should be treated as medical emergencies.
Conditions:
pneumomediastinum
Kwamura T. et al. , Radiation Medicine. 2003, 21(6): 258-266
Purpose: The purpose of our study was to clarify the correlation between
respiratory sounds and the high-resolution CT (HRCT) findings of lung diseases.
Materials and Methods: Respiratory sounds were recorded using a stethoscope in 41
patients with crackles. All had undergone inspiratory and expiratory CT. Subjects
included 18 patients with interstitial pneumonia and 23 without interstitial pneumonia.
Two parameters, two-cycle duration (2CD) and initial deflection width (IDW) of the
"crackle," were induced by time-expanded waveform analysis. Two radiologists
independently assessed 11 HRCT findings. An evaluation was carried out to determine
whether there was a significant difference in the two parameters between the presence
and absence of each HRCT finding.
Results: The two parameters of crackles were significantly shorter in the interstitial
pneumonia group than the non-interstitial pneumonia group. Ground-glass opacity,
honeycombing, lung volume reduction, traction bronchiectasis, centrilobular nodules,
emphysematous change, and attenuation and volume change between inspiratory and
expiratory CT were correlated with one or two parameters in all patients, whereas the
other three findings were not. Among the interstitial pneumonia group, traction
bronchiectasis, emphysematous change, and attenuation and volume change between
inspiratory and expiratory CT were significantly correlated with one or two parameters.
Conclusion: Abnormal respiratory sounds were correlated with some
HRCT findings.
Pneumonia
Typical crackles + dull percussion
Other symptoms:
Fatigue
Fever
Shortness of breath
Early stage (little infiltration) may not have
radiological signs.
Advanced pneumonia (X-Ray +) may not have
crackles
Bronchitis
Characteristic auscultation (may be the
only positivity establishing the diagnosis !!)
Acute – chronic very different history,
present complaints
Pleuritis (sicca) /Pleuritis humida !/
Characteristic pain provoked by breathing
Typical auscultation: pleural rub
Reduced chest (diaphragm) movement
Humida: DIFFERENT
Much less pain
No rub
Reduced normal lung sounds
Reduced diaphragm movement, elevated
diaphragm
Pneumonothorax (PTX)
No normal breathing sounds
Hyperresonant percussion sound
Usually some pain
Patient may have shortness of breath
Life threatening situation !!!
IMMEDIATE ACTION NEEDED.
Airway obstruction
EMERGENCY SITUATION in some cases
Auscultation: wheezing sound
Cause: mucus, foreign bodies, external
compression, allergic hyperreactivity oedema
Usually some action is needed:
Suction of the airways
Bronchoscopy
Tracheostomy/conicotomy if upper airway
obstruction suspected
Left sided heart failure
Pulmonary congestion
Vesicular sounds with some bronchial
obstruction due to oedema
Fine crackles pulmonary oedema (initial)
Coarse crackles + polyphonic wheezes severe pulmonary oedema (ICU !)