Lung Sounds Quiz

1.

In a normal subject, breathing quietly at rest, which phase of breathing has a longer duration?

A.

Inspiration
B.

Expiration

Correct Answer
B. Expiration

Explanation
During expiration while at rest airflow is passive, driven by elastic recoil. During inspiration active muscle effort produces a greater flow. In addition, during expiration the airways narrow with a corresponding increase in resistance to flow compared with the resistance to flow during inspiration. By extending the duration of expiration these effects are diminished so that the same volume of air that entered the lung can exit.

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2.

When listening to the chest of a normal subject which phase of the respiratory cycle is louder?

A.

Inspiration
B.

Expiration

Correct Answer
A. Inspiration

Explanation
Airflow and associated turbulence within the airways is the major source of breath sounds. The branching network of the lung is such that inspiratory in-flow creates more turbulence and sound delivery to the lung because of flow separation at branch points whereas during expiration out-flow is converging. If inspiration has a shorter duration than expiration then inspiratory airflow must be somewhat greater than expiratory airflow. Higher flow when breathing in will create a louder signal than the lower flow when breathing out.

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3.

Fine, high pitch inspiratory crackle sounds usually originate from:

A.

Air passing through fluid in small (less than 2mm in diameter) airways
B.

Collapsed small airways that snap open
C.

Small pleural effusions
D.

Asthma

Correct Answer
B. Collapsed small airways that snap open

Explanation
Crackles, also called rales, are brief, snapping-like sounds that can be heard in inflammatory or fibrotic pulmonary disease and in pulmonary congestion secondary to cardiac, kidney and other diseases. The sound of each crackle is generated by the sudden inspiratory re-opening of an airway that collapsed during the preceding exhalation. The sound is caused by the rupture of the fluid film that adheres to airway walls as they open. Experimental studies are consistent with the opening of previously collapsed small airways as the source of these sounds. Course, low pitch crackles may be created by the bubbling of air moving through fluid in large airways. If so, they are generally inspiratory and expiratory, and diminish or disappear with cough. Small pleural effusions do not compress lung parenchyma sufficiently to create crackles, but pleural friction rubs may resemble crackles.

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4.

Lung sounds can be classified as either continuous or discontinuous.Crackles and pleural friction rubs are?

A.

Continuous
B.

Discontinuous

Correct Answer
B. Discontinuous

Explanation
It is the brief, intermittent, randomly repetitive character of these sounds that makes them discontinuous, contrary to sounds that persist (e.g. asthmatic wheeze), and therefore they are considered discontinuous.

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5.

A complete breath cycle in a healthy person has how many distinct acoustic intervals that should be identified by the examiner?

A.

Six
B.

Two
C.

Four

Correct Answer
C. Four

Explanation
As noted on the CD there are four separate “chunks” of acoustic information with each respiratory cycle — two silent intervals and two brief intervals of airflow.

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6.

In which of these diseases are high pitch, fine, inspiratory crackles likely to be heard??

A.

Interstitial disease with fibrosis
B.

Pulmonary edema secondary to heart failure
C.

Bacterial Pneumonia
D.

Small pleural effusions

Correct Answer(s)
A. Interstitial disease with fibrosis
B. Pulmonary edema secondary to heart failure
C. Bacterial Pneumonia

Explanation
See question 3 for an explanation of fine crackles. Small airway collapse and reopening occurs in both stiff, fibrotic lungs and in lungs that are congested and edematous from pneumonia or heart failure. In patients with pulmonary fibrosis or pneumonia the crackles are unchanged when the patient position is changed. On the other hand in patients with heart failure the distribution of crackles is often gravity dependent and changes according to the patient’s posture (sitting – reclining etc).

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7.

What is more important in making a quick assessment of the severity of an asthma attack?

A.

The breathing pattern (respiratory rate, inspiratory/expiratory duration ratio, use of accessory respiratory muscles).
B.

The intensity of the wheezing sounds

Correct Answer
A. The breathing pattern (respiratory rate, inspiratory/expiratory duration ratio, use of accessory respiratory muscles).

Explanation
During a severe asthma attack when the patient is in extreme respiratory distress there may be little or no audible wheezing (the so-called silent lung). Following bronchodilator administration wheeze may appear indicating resumption of airflow.

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