PFTs

Question 1

Obstructive and restrictive PFTs

Answer 1

-See other lectures

Question 2

Extrathoracic airway obstruction 1

Answer 2

• Obstruction in the thorax (COPD) results in an expiratory problem, but obstruction outside the thorax causes an inspiratory problem
• One associated sign: stridor
• The flow volume curve will have a relatively normal expiratory curve (above X axis), but the inspiratory curve will be very blunted (short and square below X axis)
• Common cause: vocal cord dysfunction, which is a variable extra thoracic obstruction since the vocal cords narrow during inspiration, but nor expiration
• The pts tend to be young, smart children/adolescents

Question 3

Extrathoracic airway obstruction 2

Answer 3

• Fixed extrathoracic airway obstruction (stenosis of upper trachea/larynx) has a different flow volume curve than the variable extra thoracic obstruction
• Fixed obstruction has a blunted inspiratory and expiratory curve, so the overall curve is very close to a rectangle

Question 4

Scoliosis

Answer 4

• Scoliosis causes extrinsic compression of the lungs
• One side is compressed (cannot expand on inhalation) and the other side is expanded (cannot compress on exhalation)
• Flow volume curve looks much like restrictive (compressed curve that has a normal shape)
• But the restrictive curve is usually shifted to the right (toward smaller lung values)
• The scoliosis curve is not shifted, just compressed
• Surgery to correct scoliosis usually results in a 60% loss in lung function, and many are placed on ventilators after surgery since their lung function was already compromised even before the surgery