111114 diffusion clinical

Question 1

CO is purely limited by what?

Answer 1

diffusion

Question 2

N2O is limited by

Answer 2

perfusion b/c it doesn’t bind at all to hemoglobin. all of it dissolves in blood

Question 3

if you have anemia, what should you do for DL?

Answer 3

should correct for the anemia. so you know- if then with corrected value, the DL is fine, this means that the anemia is the problem causing the shortness of breath symptoms

Question 4

which is more common: loss of surface area or thickening of alveolar-capillary membrane?

Answer 4

loss of SA

Question 5

emphysematous bullae can cause respiratory insufficiency how?

Answer 5

dead space ventilation

and at borders-compressive atelectasis–a shunt

Question 6

clinically in all cases, what is more significant- diffusion capacity or diffusion capacity corrected for alveolar ventilation?

Answer 6

diffusion capacity

Question 7

diffusion capacity of asthma pt?

Answer 7

normal, or increased

(increased b/c asthma pt may try to suck in a lot of volume to overcome obstruction, and increases thoracic blood volume)

Question 8

smoking makes you suspicious of emphysema or asthma more?

Answer 8

emphysema

Question 9

what conditions can cause increased DL?

Answer 9

anything that causes increased blood flow to lungs

Question 10

what can cause increased distance, leading to lower DL?

Answer 10

silicosis
late stages of CHF (get blood going to interstitium and eventually pulm edema which is blood going into alveoli)

interstitial lung disease/pulmonary fibrosis:
asbestosis
sarcoidosis (granulomas)
collagen vascular dis

Question 11

SLE, RA, scleroderma can cause what types of lung diseases

Answer 11

interstitial lung disease

pulmonary vascular dis (in pulm HTN, reduced amt of capillary bed is perfused due to plexiform lesions and HTN)

Question 12

if you have normal spirometry w reduced DL, what could it be?

Answer 12

pulmonary vascular disease

combined emphysema and interstitial lung diseases (smoking can cause both)

anemia

Question 13

how does smoking affect DL right before the test?

Answer 13

15% of hemoglobin will be saturated with CO, so DL will be low

Question 14

valsalva maneuver

Answer 14

taking deep breath in and increasing intrathoracic pressure so get less venous return and less blood content in lungs

you’d get decreased DL

Question 15

if DL is decreased, what should you look at?

Answer 15

DL/VA

if DL/VA is normal, it’s pure restriction
if DL/VA is low, it’s obstruction or increased dead space

if spirometry is normal–think about pulmonary HTN

if DL is under 50%, consider blood gases, O2 eval w exercise