M103 T4 L4

Question 1

How does pulse oximetry work?

Answer 1

put the finger probe on
light emitting diode and a receiver on the other side
the light goes through the finger and essentially detects the light with the receiver

Question 2

What is PaO2 measured by?

Answer 2

an abg analyser

Question 3

What might affect / nullify the results of pulse oximetry?

Answer 3

highly pigmented skin - lower reading than expected

nail varnish - completely nullifies the result

Question 4

What is Type 1 respiratory failure usually caused by?

Answer 4

some kind of intrinsic lung disease affecting the airways or the vasculature

Question 5

What is Type 2 respiratory failure usually caused by?

Answer 5

(brain) a reduction in ventilatory drive - this could be caused by an overdose of a sedative medication
(muscle) reduced neuromuscular power - some kind of myopathy
(receptors) resetting of chemoreceptors that drive ventilation

Question 6

How is the base excess affected in metabolic alkalosis & acidosis?

Answer 6

increases in metabolic alkalosis

decreases in metabolic acidosis

Question 7

What are the physiological causes of hypoxaemia?

Answer 7

V/Q mismatch
Right-to-left shunt
Diffusion impairment
Hypoventilation
Low inspired pO2

Question 8

equation for a-a gradient

Answer 8

PAO2 = PIO2 – (PaCO2/0.8)

Question 9

What is the function of the a-a gradient?

Answer 9

indicates the integrity of the alveolocapillary membrane and the effectiveness of gas exchange
disease / pathology of the alveolocapillary unit widens the gradient

Question 10

What is hypoxaemia where the a-a gradient widens caused by?

Answer 10

V/Q mismatch, diffusion limitation and shunt

Question 11

What is the most common cause of hypoxaemia?

Answer 11

V/Q mismatch

Question 12

How does V/Q change in different parts of the lungs?

Answer 12

V/Q ratio is higher at apex and low at the base

Question 13

What is the name of the mechanism by which V/Q mismatches are compensated for? (HypPulVas)

Answer 13

hypoxic pulmonary vasoconstriction

Question 14

What are symptoms of a high V/Q ratio?

Answer 14

when ventilation is in excess of perfusion

Question 15

What compensation can occur for hypoxaemia?

Answer 15

a compensatory rise in total ventilation

Question 16

How is hypoxaemia due to V/Q mismatch corrected?

Answer 16

supplemental oxygen

Question 17

What are the common causative conditions of Hypoxaemia?

Answer 17

(ABCC.PH-ILD)

asthma
COPD
bronchiectasis
cystic fibrosis
ILD 
pulmonary hyptertension

Question 18

What happens in a pulmonary shunt?

Answer 18

blood from the right side of the heart enters the left side of the heart without taking part in gas exchange
so it misses the pulmonary circulation
has a poor reaction to oxygen therapy

Question 19

What are the signs of a pulmonary shunt?

Answer 19

A-a gradient is elevated
pCO2 is normal
Poor response to oxygen therapy

Question 20

What are the common causes of a pulmonary shunt?

Answer 20

pneumonia
pulmonary oedema
acute respiratory distress syndrome
pulmonary arteriovenous malformations

Question 21

What are the causes of diffusion limitation?

Answer 21

pulmonary fibrosis

hypoxaemia

Question 22

Why is hypercapnea not usually associated with diffusion limitation?

Answer 22

CO2 is 20x more soluble than O2 and is less likely to be affected by diffusion limitation

Question 23

What are the signs of diffusion limitation?

Answer 23

shows a good response to oxygen therapy
A-a gradient is elevated
PaCO2 is normal

Question 24

What does the A-a gradient look like in hypoventilation?

Answer 24

Normal A-a gradient (low PAO2 then subsequent low PaO2)

Question 25

How does hypoventilation react to oxygen therapy?

Answer 25

If hypoxaemia is present it is easily corrected by oxygen therapy but hypoventilation and hypercapnoea can persist

Question 26

What are the causes of hypoventilation?

Answer 26

Impaired central respiratory drive (brain) a disease of the spinal cord, NMJ or nerve (neural) a myopathy in respiratory muscles (muscular)

Question 27

What are the signs of hypoventilation?

Answer 27

shows good response to oxygen therapy A-a gradient is normal PaCO2 is high

Question 28

What does the Beer-Lambert-Bougeur law state?

Answer 28

that the attenuation of light depends on the properties of the materials through which the light is travelling

Question 29

What causes the VQ mismatch in Type 1 respiratory failure?

Answer 29

the reduction in PaO2 but the lack of change in PaCO2 | ventillation issue

Question 30

What causes underventilation in Type 1 respiratory failure?

Answer 30

the ics in PaCO2 and dcs in PaO2

Question 31

What physiological states are associated with Type 1 & 2 respiratory failure?

Answer 31

1 - hypoxia | 2 - hypoxia with hypercapnia

Question 32

What group of patients usually experience hypercapnia?

Answer 32

people with COPD | makes it harder for them to breathe

Question 33

What is the normal pH of a litre of blood in terms of PaCO2?

Answer 33

PaCO2 of 40 mmHg

Question 34

What is the most common type of sleep apnoea?

Answer 34

obstructive sleep apnoea

Question 35

What is above normal for obstructive sleep apnoea?

Answer 35

5 or more obstructive apnoeas per hour

Question 36

What are statistical criteria features of hypopnea?

Answer 36

50% reduction in airflow 4% oxygen desaturation and/or arousal from sleep

Question 37

What gases are delivered by a Venturi mask?

Answer 37

specific concentrations of oxygen by mixing oxygen with inhaled air

Question 38

What apparatus makes up a Venturi mask?

Answer 38

a face mask and reservoir bag device

Question 39

What mask delivers oxygen?

Answer 39

Hudson mask | uncontrolled and controlled mask

Question 40

What are the causes of a V/Q mismatch?

Answer 40

reduced ventillation | reduced perfusion

Question 41

What causes reduced ventilation (VQ mismatch)?

Answer 41

hypoventilation, low FiO2

Question 42

What causes reduced perfusion (VQ mismatch)?

Answer 42

diffusion impairment or pulmonary shunt (low perfusion)

Question 43

What does pulse oximetry measure?

Answer 43

oxygen saturation of Hb in the capillary beds

Question 44

What is SaO2 measured by?

Answer 44

abg analyser and a pulse oximeter

Question 45

What is the normal blood pH range?

Answer 45

7.35-7.45

Question 46

What three organs are involved in acid-base homeostasis?

Answer 46

lungs, kidneys and brain

Question 47

What structures are involved in acid-base homeostasis?

Answer 47

chemical buffers in blood blood cells (erythrocytes) the lungs, kidneys and brain

Question 48

Why isn't the base excess widely used in metabolic acidosis and alkalosis?

Answer 48

its utility in interpreting blood gas results is controversial

Question 49

What could cause an impaired central drive, resulting in hypoventilation?

Answer 49

drug overdose, brainstem infarction, primary alveolar hypoventilation

Question 50

What could cause an impaired central respiratory drive, resulting in hypoventilation?

Answer 50

diseases of the spinal cord, NMJs or nerves

Question 51

What causes Myasthenia gravis?

Answer 51

antibodies destroying the communication between nerves and muscle

Question 52

How is the body affected in Myasthenia gravis?

Answer 52

weakness of the skeletal muscles

Question 53

How is Guillain-Barré syndrome pronounced?

Answer 53

geeyan baray

Question 54

What is an example of a spinal cord disease that could cause hypoventilation?

Answer 54

ALS

Question 55

What is an example of a nerve disease that could cause hypoventilation?

Answer 55

Guillian-Barre syndrome

Question 56

What is an example of an NMJ disease that could cause hypoventilation?

Answer 56

myasthenia gravis

Question 57

What are the first symptoms of Guillian-Barre syndrome?

Answer 57

weakness and tingling in extremities

Question 58

How does Guillian-Barre syndrome progress?

Answer 58

weakness and tingling in extremities quickly spread, eventually paralyzing the whole body

Question 59

What is the cause of Guillian-Barre syndrome?

Answer 59

unknown, but 2/3 of patients report symptoms of an infection in the six weeks before (respiratory, GI infections or zika virus)

Question 60

What is the effect of hypoventilation in healthy and unhealthy lungs?

Answer 60

healthy lungs - will not cause sufficient hypoxia | lung disease - will cause sufficient hypoxia

Question 61

What is hypoxaemia where the a-a gradient is normal caused by?

Answer 61

hypoxia and hypoventilation