Blood gas analysis

Question 1

How do you convert a value into kPa from mmHg?

Answer 1

Divide by 7.5

Question 2

Does the body continually produce acid or bases?

Answer 2

Acid

Question 3

What acts as buffers in the blood?

Answer 3

Proteins
Haemoglobin
Carbonic acid / bicarbonate

Question 4

When can there be an acid-base disturbance?

Answer 4

• Problem with ventilation
• Problm with renal function
• Overwhelming acid or base load the body can’t handle

Question 5

Where are blood samples usually taken from for blood gas analysis?

Answer 5

Radial artery
sometimes femoral when hypotensive
Local anaesthetic used unless in emergency

Question 6

What are the normal values for pH?

Answer 6

7.35 - 7.45

Question 7

What are the normal values for pO2?

Answer 7

12 - 13 kPa

Question 8

What are the normal values for pCO2?

Answer 8

4.5 - 5.6 kPa

Question 9

What are the normal values for Bicarbonate?

Answer 9

22 - 26 mmol/l

Question 10

How is bicarbonate calculated?

Answer 10

calculated from the actual bicarbonate but assuming 37 degrees and a pCO2 of 5.3kPa

Question 11

What is a pulse oximeter?

Answer 11

Continous monitor of oxygenation

Can show hypoxia before patient becomes cyanotic

Question 12

How can oxygen cause blindness in neonates?

Answer 12

Premature babies when nursed in oxygen rich enviroment the vessls can grow and become ruptured bleeding into the eye and causing retonopathy of prematurity

Question 13

What can high oxygen levels cause in patients with COPD?

Answer 13

Hypercapnic respiratory failure

Question 14

What are the adverse effects of high oxygen levels proposed to br due to?

Answer 14

The generation of free radicals

Question 15

What can high oxygen levels cause?

Answer 15

• Collapse of alveoli due to atelectasis
• Irratation to muccous membranes
• Ocular toxicity
• Myocardial damage

Question 16

When is oxygen given?

Answer 16

• Hypoxia but not dyspnoea alone

- In an unstable medical emergancy give high conc. of oxygen then titrate to target once stable

Question 17

In what conditions would a high conc. of inspired oxygen be given?

Answer 17

• Pneumothorax

- Carbon monoxide poisoning

Question 18

In what potentially life-threatening disease would pulse oximetry not identify low oxygen levels?

Answer 18

Carbon monoxide poisoning

Question 19

How much roughly of oxygen is breathed in (kPa)?

Answer 19

20 kPa

Question 20

What is the P/F ratio?

Answer 20

• PaO2 / (what they are breathing) e.g FiO2

-

Question 21

What is the normal alveolar - arterial gradient?

Answer 21

< 3 kPa usually expect the arterial pO2 to be approx 2/3 FiO2

Question 22

What are the normal ranges for the P/F ratio?

Answer 22

>50 = healthy 
<40 = acute lung injury 
<26.7 = ARDS

Question 23

If the pH and pCO2 are changing in the same direction what the primary problem likely to be?

Answer 23

Metabolic, different direction respiratory

Question 24

What is compensation?

Answer 24

Altering of function of the respiratory or renal system in an attempt to correct an acid - base imbalance

Question 25

How do you usually tell if compensation is occuring?

Answer 25

If pCO2 and HCO3- are moving in the same direction

Question 26

What shows that more than one pathology is occuring?

Answer 26

If pCO2 and HCO3- are moving in opposite directions

Question 27

What is type 2 respiratory failure?

Answer 27

The failure of the lungs to eliminate adequate CO2

Question 28

What substance do the kidneys retain in order to compensate for respiratory acidosis?

Answer 28

Bicarbonate

Question 29

What are the causes of hyperventilation?

Answer 29

- Acute severe asthma - Pulmonary embolism - Pulmonary oedema - Anxiety attack

Question 30

How does the kidney compensate for high altitudes?

Answer 30

The kidneys excrete more bicarbonate