Week4 - ABG/Spirometry Masterclass

Question 1

Why do physios measure O2 and CO2 in patients’ blood (4)?

Answer 1

To evaluate respiratory status, diagnose impairments, guide treatment decisions and monitor treatment response.

Question 2

What are the two main ways oxygen is carried in the blood?

Answer 2

Dissolved in plasma (PaO2) or Bound to Hb (SaO2).

Question 3

What does saturation mean with regard to O2 in blood?

Answer 3

Describes the % of O2 bound to Hb among RBCs.

Question 4

What is the difference between SaO2 and SpO2?

Answer 4

SaO2 = Arterial blood sample; SpO2 = Non-invasive Pulse oximetry.

Question 5

How is PaO2 measured?

Answer 5

Arterial Blood Gas sample.

Question 6

Define hypoxemia.

Answer 6

Low blood oxygen - PaO2 <80mmHg.

Question 7

Define hypoxia.

Answer 7

Insufficient oxygen delivered to the tissues.

Question 8

True or False - Pulse oximetry can detect rising PaCO2.

Answer 8

False - It only measures oxygenation, not ventilation (important in COPD).

Question 9

Normal arterial PaO2?

Answer 9

80 to 100mmHg.

Question 10

If PaO2 is <60mmHg, what symptoms may occur?

Answer 10

Stimulation of ventilation and tachycardia.

Question 11

If PaO2 is <55mmHg, what symptoms may occur?

Answer 11

Short-term memory changes and confusion.

Question 12

What are two chronic adaptations to hypoxemia?

Answer 12

Polycythemia and Pulmonary Hypertension.

Question 13

When recording PaO2 and SpO2, what must you record?

Answer 13

Level of O2 and the Type of O2 therapy.

Question 14

What is FiO2?

Answer 14

Fraction of Inspired Oxygen - 0.21/21%.

Question 15

What is the ‘sea level’ normal ratio of PaO2 (80-100) to FiO2?

Answer 15

400 to 500mmHg.

Question 16

What important component must be considered when interpreting PaO2?

Answer 16

The ratio will change depending on any supplementary O2 the patient might be on - FiO2.

Question 17

How do we classify respiratory reserve based on PaO2:FiO2 ratio?

Answer 17

> 300 = sufficient reserve; 200-300 = marginal; <200 = little/no reserve.

Question 18

What condition is associated with a PaO2:FiO2 <200 with non-cardiac pulmonary oedema?

Answer 18

Acute Respiratory Distress Syndrome (ARDS).

Question 19

Difference between acidosis vs acidemia?

Answer 19

Acidosis is the process; Acidemia is the low value of pH in the blood - same for Alkalinity as well.

Question 20

Normal pH? What is the maximum compatible with life?

Answer 20

7.35 to 7.45; Life range = 6.8 to 7.8.

Question 21

What is considered acidosis and alkalosis?

Answer 21

<7.35 is acidosis and >7.45 is alkalosis.

Question 22

Normal PaCO2?

Answer 22

35 to 45mmHg.

Question 23

If the value of PaCO2 is greater than 45, what does this indicated?

Answer 23

Respiratory Acidosis.

Question 24

If the value of PaCO2 is less than 35, what does this indicate?

Answer 24

Respiratory Alkalosis.

Question 25

Normal bicarbonate (HCO3)?

Answer 25

22 to 26 mEq/L.

Question 26

A HCO3 value greater than 26 indicates?

Answer 26

Metabolic Alkalosis.

Question 27

A HCO3 value less than 22 indicates?

Answer 27

Metabolic Acidosis.

Question 28

Normal Base Excess (BE)?

Answer 28

-2 to +2 mEq.

Question 29

Effect of hypoventilation vs hyperventilation on PaCO2 and pH?

Answer 29

Hypo. = increase CO2 = acidosis; Hyper = decrease CO2 = alkalosis.

Question 30

Define full vs partial compensation.

Answer 30

Full = pH returns to normal range; Partial = pH is still outside range despite compensation.

Question 31

What is the three-step systemic approach to interpreting ABGs?

Answer 31

Look at pH --> Look at PaCO2 --> Look at HCO3.

Question 32

Why are respiratory acid-base disorders especially important to physios?

Answer 32

Because physios can directly intervene to change ventilation.

Question 33

List causes of respiratory acidosis vs alkalosis.

Answer 33

Acidosis = hypoventilation, i.e., T2RF/NM disorders/trauma; Alkalosis = hyperventilation, i.e., anxiety/pain/altitude/sepsis/ventilator settings.

Question 34

What is the normal FEV1/FVC ratio?

Answer 34

>70%.

Question 34

True or False - A spirometry value can be determined off of one trial?

Answer 34

False - There needs to be repeated trials.

Question 35

What does a reduced FEV1 ratio indicate?

Answer 35

Obstructive disease.

Question 36

When determining the severity of the obstruction, how is it graded (%)?

Answer 36

>80 = mild; 50-75% = moderate; 30-49% = severe; <30% = very severe.

Question 37

What does a reduced FVC % predicted (<80%) indicate?

Answer 37

Restrictive disease.

Question 38

A patients spirometry shows FEV1/FVC 65% and FVC 60% predicted - what is the interpretation?

Answer 38

Mixed obstructive and restrictive pattern.

Question 39

How is Type 1 Respiratory Failure characterised?

Answer 39

Hypoxemic respiratory failure; Low PaO2 <60 with normal or low CO2.

Question 40

How is Type 2 Respiratory Failure characterised?

Answer 40

Hypercapnic respiratory failure; Low PaO2 <60 AND high CO2 >45mmHg.