6. Auscultation of the respiratory system, origin of the respiratory sounds

Question 1

Define sound:

Answer 1

combination of vibrations with different frequencies

Question 2

Define noise:

Answer 2

no special underlying relation among frequencies, no periodic character

Question 3

General rules av auscultation:

Answer 3

– the animal should stand still
– a certain examination order should be followed (from the front to the back from up to down in each third of the thorax)
– silent circumstances

Question 4

Physical basis of the origin of the respiratory sounds:

Answer 4

1. Air flows from the higher to the lower pressure place

2. Narrowing in the way of air

Question 5

What does turbulence depend on?

Answer 5

Turbulence depends on the diameter of the airways and the speed of the airstream

Question 6

Describe a normal respiratory sound:

Answer 6

Blow-like sound, developed in the upper airways

Stronger during inspiration and slighter during expiration

Question 7

What does the normal respiratory sound contain?

Answer 7

1. Weak stenotic noise originated from the nose and pharynx conducted through the bronchus, lung, chest wall
2. Weak blow noise turbulence before tracheal bifurcation,
   after bifurcation laminar spread

Question 8

How can the respiratory sound reach our ears?

Answer 8

Resonance

sound -> lung -> chest wall -> diminish -> some of it reflected from bordering places depending on acoustic impedance

Question 9

Give the formula of acoustic impedance:

Answer 9

(Z = d x s)

Z=density of the material kg/m3 x speed of the sound m/s

Question 10

How does the tissue influence the transmitted sound?

Answer 10

1. if the impedance of the tissues are quite similar (as when an
   infiltrated lung lies against the thoracic wall) large part of the sound
   is transmitted
2. if different, the intensity of the sound is diminished/reduced
   (healthy lung, chest wall)

Question 11

Examination order:

Answer 11

I. Directly audible sounds (ear)

II. Indirect auscultation (stethoscope)

Question 12

I. Directly audible sounds (ear):

Answer 12

–Nose (discharge, tumour, polyp, nasopharyngeal stenosis)
– Larynx (paralysis, collapse, oedema, laryngitis, tumour)
– Trachea (collapse, hypoplasia, trauma, tumour)

Question 13

II. Indirect auscultation (stethoscope):

Answer 13

– Larynx
– Trachea
– Thorax