Arterial Blood Gases

Question 1

what can you get from your ABGs?

Answer 1

• pH
• PaCO2
• PaO2
• HCO3
• base excess

Question 2

normal pH on ABG

Answer 2

7.35-7.45

Question 3

normal PaCO2

Answer 3

35-45mmHg

Question 4

normal PaO2

Answer 4

80-100mmHg

Question 5

normal HCO3-

Answer 5

22-26mEq/L

Question 6

normal base excess

Answer 6

-2 to +2mmol/l

Question 7

what are the rates of oxygen flow in nasal cannulae?

Answer 7

• 1L/min - 24%
• 2L/min - 28%
• 3L/min - 32%
• 4L/min - 36%

Question 8

types of oxygen delivery devices

Answer 8

• nasal cannulae
• venturi masks
• simple oxygen masks
• non-rebreather mask

Question 9

when can you say that a patient is hypoxaemic?

Answer 9

when the patient’s PaO2 is below 10kPa, below 8kPa, they are in respiratory failure

Question 10

features of type 1 respiratory failure

Answer 10

• hypoxaemia

- normocapnia

Question 11

features of type 2 respiratory failure

Answer 11

• hypoxaemia

- hypercapnia

Question 12

why does type 1 respiratory failure occur?

Answer 12

ventilation/perfusion mismatch

Question 13

why does type 2 respiratory failure occur?

Answer 13

alveolar hypoventilation

Question 14

causes of hypoventilation

Answer 14

• increased resistance due to airway obstruction
• reduced compliance of the lung tissue/chest wall
• reduced strength of the respiratory muscles
• drugs acting on the respiratory centre reducing overall ventilation

Question 15

what happens if the pH drops and CO2 levels increase?

Answer 15

respiratory acidosis

Question 16

what condition causes

• a drop in pH
• inc in CO2
• inc in HCO3-

Answer 16

respiratory acidosis with metabolic compensation

Question 17

what condition causes:

• an inc in pH
• a drop in CO2

Answer 17

respiratory alkalosis

Question 18

what condition causes:

• an inc in pH
• a drop in CO2
• a drop in HCO3

Answer 18

respiratory alkalosis with metabolic compensation

Question 19

what is the base excess?

Answer 19

another surrogate marker of metabolic acidosis or alkalosis

Question 20

what does a high base excess entail?

Answer 20

an abnormally high HCO3- in the blood

Question 21

what does a low base excess entail?

Answer 21

a low HCO3- in the blood

Question 22

what types of compensation can happen?

Answer 22

• respiratory

- metabolic

Question 23

how long would respiratory compensation take to kick in and do its work?

Answer 23

immediately by either increasing or decreasing alveolar ventilation to regulate the CO2 levels

Question 24

how long would metabolic compensation take to work?

Answer 24

a few days

Question 25

what would indicate that a person is suffering from a mixed acidosis/alkalosis?

Answer 25

the levels of CO2 and HCO3- would be going to opposite directions (i.e. CO2 increasing, HCO3 decreasing)

Question 26

causes of respiratory acidosis

Answer 26

- respiratory depression - guillain-barre - asthma - COPD - iatrogenic

Question 27

causes of respiratory alkalosis

Answer 27

- anxiety - pain - hypoxia - pulmonary embolism - pneumothorax - iatrogenic

Question 28

causes of metabolic acidosis

Answer 28

- increased acid production/acid ingestion | - decreased acid excretion/rate of GI and renal HCO3 loss

Question 29

lab characteristics of metabolic acidosis

Answer 29

- low pH - low HCO3 - low BE

Question 30

what is the normal anion gap range?

Answer 30

4-12mmol/L

Question 31

what conditions increase the anion gap?

Answer 31

- diabetic ketoacidosis - lactic acidosis - aspirin overdose

Question 32

what decreases the anion gap?

Answer 32

- gastrointestinal loss of HCO3- - renal tubular acidosis - Addison's disease

Question 33

features of metabolic alkalosis on an ABG?

Answer 33

- high pH - high HCO3- - high BE

Question 34

causes of metabolic alkalosis

Answer 34

- gastrointestinal loss of H+ - renal loss of H+ - iatrogenic

Question 35

which conditions cause metabolic alkalosis?

Answer 35

- vomiting - diarrhoea - use of loop/thiazide diuretics - heart failure - nephrotic syndrome - cirrhosis - Conn's syndrome

Question 36

features of a mixed respiratory and metabolic acidosis

Answer 36

- low pH - high CO2 - low HCO3-

Question 37

causes of a mixed metabolic and respiratory acidosis

Answer 37

- cardiac arrest | - multi-organ failure

Question 38

features of mixed respiratory and metabolic alkalosis

Answer 38

- high pH - low CO2 - high HCO3-

Question 39

causes of a mixed respiratory and metabolic alkalosis

Answer 39

- liver cirrhosis in addition to diuretic use - hyperemesis gravidarum - excessive ventilation in COPD