THE PHYSIOLOGICAL CONSEQUENCES OF LUNG DISEASE

Question 1

what is ventilation?

Answer 1

the exchange of air between lungs and atmosphere

Question 2

what is minute ventilation?

Answer 2

tidal volume x respiratory rate

Question 3

what is alveolar ventilation?

Answer 3

(tidal volume - dead space) x respiratory rate

Question 4

what is Fick’s law of diffusion?

Answer 4

the rate of transfer of a gas through a sheet of tissue is proportional to the tissue area and the difference in gas partial pressure between the 2 sides, and inversely proportional to the tissue thickness

Question 5

how does the rate of diffusion differ between oxygen and carbon dioxide?

Answer 5

carbon dioxide diffuses across membranes 20x faster than oxugen

Question 6

outline hypoxic pulmonary vasoconstriction?

Answer 6

this is a haemostatic mechanism where intrapulmonary arteries constrict in response to alveolar hypoxia, diverting blood to better oxygenated lung segments and thereby optimising ventilation/perfusion matching and systemic oxygen delivery

Question 7

what happens If we get a ventilation and perfusion mismatch?

Answer 7

gas exchange within the affected alveoli will be impaired

Question 8

what is poiseuilles law?

Answer 8

an equation but the most important bit to remember is that resustnce is inversly proportional to the radius to the power of 4

Question 9

what is a flow volume loop?

Answer 9

a plot of inspiratory and expiratory flow (on the Y-axis) against volume (on the X-axis) during the performance of maximally forced inspiratory and expiratory maneuvers.

Question 10

what would the flow volume loop look like in restrictive lung diseases?

Answer 10

a smaller loop seen on both inspiration and expiration

Question 11

what would a flow volume loop look like in obstructive lung disease?

Answer 11

only the inspiratory loop is affected, expiratory loop is normal size

Question 12

what shifts the oxygen dissociation curve to the right?

Answer 12

increase in PaCO2
decrease in pH
increase in temp

Question 13

what shifts the oxygen dissociation curve to the left?

Answer 13

increased oxygen affinity
increase in pH
decrease CO2
decrease in temp

Question 14

what are some signs of hypercapnia?

Answer 14

fatigue
drowsiness
mild headache
feeling disorientated/dizzy
SOB
aterixis
flushed skin

Question 15

At what pH is acidaemia?

Answer 15

<7.35

Question 16

at what pH is alkalaemia?

Answer 16

> 7.45

Question 17

what is type 1 respiratory failure?

Answer 17

low oxygen

normal/low CO2

Question 18

what is type 2 respiratory failure?

Answer 18

low oxygen

high CO2

Question 19

whats the pathology behind type 1 respiratory failure?

Answer 19

damage to lung tissue which prevents adequate oxygenation of the blood. However, the remaining normal lung is still sufficient to excrete carbon dioxide.
e.g. pulmonary oedema, pneumonia, COPD, asthma, PE, pulmonary hypertension

Question 20

whats the pathology behind type 2 respiratory failure?

Answer 20

alveolar ventilation is insufficient to excrete the carbon dioxide being produced. Inadequate ventilation is due to reduced ventilatory effort or inability to overcome increased resistance to ventilation. It affects the lung as a whole, and therefore carbon dioxide accumulates
e.g. COPD, drug overdose, myasthenia gravis, head ansd neck injuries etc

Question 21

what does a FEV1:FVC ratio look like in obstructive lung diseases?

Answer 21

<70% due to reduced FEV1 but normal FVC

Question 22

what does a FEV1:FVC ratio look like in restrictive lung diseases?

Answer 22

> 70%

as FEV1 and FVC are both decreased

Question 23

what are examples of obstructive lung diseases?

Answer 23

asthma
COPD
bronchiectasis

Question 24

what are examples of restrictive lung diseases?

Answer 24

pulmonary fibrosis
obesity
chest wall deformities
neuromuscular disorders

Question 25

whats the difference between obstructive and restrictive lung diseases?

Answer 25

restrictive lung diseases mean theres difficulty fully filling the lungs with air
obstructive lung diseases are where its hard to exhale all the air