Interpreting ABG 1

Question 1

What is T1RF

Answer 1

Hypoxia without hypercapnia due to high A-a gradient

Question 2

What is T2RF

Answer 2

Hypoxia without hypercapnia - involves hyperventilation

Question 3

Hypoxia

Answer 3

Insufficient oxygen in tissues

Question 4

Hypoxaemia

Answer 4

Low PaO2

Question 5

Will you be hypoxic if you are hypoxaemic

Answer 5

Yes

Question 6

VBG not ABG

Answer 6

• FiO2 = 21%
• pO2 = 8%
• SO2 = 98%
• Hb = 150

Question 7

Stroke

Answer 7

• FiO2 = 21%
• pO2 = 11
• SO2 = 98%
• Hb = 130

Question 8

COPD

Answer 8

• FiO2 = 21%
• pO2 = 9.6
• SO2 = 88%
• Hb = 155

Question 9

Anaemia

Answer 9

• FiO2 = 21%
• pO2 = 11
• SO2 = 98%
• Hb = 58

Question 10

What is FiO2

Answer 10

Fraction of inspired oxygen - normally 21%

Question 11

What is Pi

Answer 11

Pressure of inspired air

Question 12

What is PAO2

Answer 12

How well Hb attaches to RBCs

Question 13

What is PAO2

Answer 13

PP of oxygen in alveoli

Question 14

What is PaO2

Answer 14

PP of oxygen in arteries

Question 15

Alveolar-arterial gradient

Answer 15

PAO2 - PaO2

Question 16

What is SO2

Answer 16

Oxygen bound to Hb

Question 17

Does CO2 or O2 diffuse more easily

Answer 17

CO2

Question 18

Are PACO2 and PaCO2 equal?

Answer 18

Assumed to be

Question 19

Function of chemoreceptors

Answer 19

detect increase in PaCO2 and correct any rise by increasing ventilation but PaO2 is not so quickly corrected

Question 20

What is PaCO2 proportional to

Answer 20

(VCO2 x k) / VA

Question 21

PAO2

Answer 21

(FiO2(Pi-PH2O)) - (PaCO2/RER)

Question 22

PaO2

Answer 22

(FiO2(Pi-PH2O)) - (PaCO2/RER) - (A-a gradient)

Question 23

How does poor diffusion from lung to blood occur?

Answer 23

Thick membrane, small SA and increased circulation time

Question 24

Examples of poor diffusion from lung to blood

Answer 24

Pulmonary fibrosis

Exercise

Question 25

How does V/Q mismatch occur?

Answer 25

Blood not getting to lung or/and air not getting to alveoli

Question 26

Examples of V/Q mismatch

Answer 26

PE Atelectasis Pulmonary oedema

Question 27

How does shunt occur?

Answer 27

Blood bypassing lungs

Question 28

Examples of V/Q mismatch

Answer 28

Ventricular septal defect

Question 29

How is oxygen saturation increased

Answer 29

Increase in FiO2

Question 30

Where is ventilation regulated

Answer 30

Respiratory centre in brainstem

Question 31

SO2

Answer 31

Oxygen saturation in blood

Question 32

SaO2

Answer 32

Saturation in arterial blood

Question 33

How is PaO2 dictated

Answer 33

Alveolar ventilation, matching ventilation with perfusion and concentration of o2 in air

Question 34

V/Q mismatch

Answer 34

Not all blood in lungs meets well-ventilated alveoli and not all alveoli are perfused with blood

Question 35

Why is hyperventilating good?

Answer 35

Shifting more air in and out of alveoli to blow off CO More blood passing through can offload more CO Lowers CO Non-shunted blood compensates for high CO

Question 36

Nasal prongs

Answer 36

Fi o 2 < 40%. Comfortable and convenient. Fi o 2 non-specific: depends on flow rate (1–6 L/min) and ventilation.

Question 37

Standard face mask

Answer 37

Fi o 2 30–50% at flow rates 6–10 L/min but imprecise. May cause CO  2 retention at flows less than 5 L/min (rebreathing) and, therefore, not useful for providing lower  Fi o 2 .

Question 38

high-flow face mask

Answer 38

Fi o 2 24–60%. Delivers fixed, predictable  Fi o 2 . Ideal for providing controlled, accurate O  2 therapy at low concentrations.

Question 39

Face mask with reservoir

Answer 39

Fi o 2 60–80%. Can achieve even higher  Fi o 2 with a tight-fitting mask. Useful for short-term use in respiratory emergencies.

Question 40

Endotracheal intubation

Answer 40

Fi o 2 21–100%. Used in severely unwell patients with very high O  2 requirements, especially in patients with ventilatory failure. The patient is sedated and mechanically ventilated.

Question 41

Metabolic acidosis

Answer 41

any process other than rise in PaCO2 that lowers blood pH - caused by too much metabolic acid or too much base excretion - hyperventilation big symptom

Question 42

Raised anion gap

Answer 42

lactic acidosis, ketoacidosis, renal failure, poisoning, rhabdomyolysis

Question 43

Normal anion gap

Answer 43

renal rube acidosis, diarrhoea, adrenal insufficiency, ammonium chloride ingestion, urinary diversion, drugs - normally caused by loss of HCO3-

Question 44

What do kidneys do with reduced HCO3-

Answer 44

Retain Cl-

Question 45

DKA triad

Answer 45

High anion gap metabolic acidosis Elevated plasma glucose Ketone presence

Question 46

Metabolic alkalosis causes

Answer 46

gastric secretions, potassium depletion, Cushing syndrome, Conn syndrome, diarrhoea