Blood Gas Analysis

Question 1

1kPa is how many mmHg

Answer 1

7.5mmHg

Question 2

How do you convert H+ ion concentration to pH

Answer 2

80 - (H+) = The two decimal places after 7

Question 3

What are the buffers for physiology?

Answer 3

Proteins, haemoglobin and carbonic acid/bicarbonate

Question 4

What do acid-base disturbances result from?

Answer 4

• Issues with ventilation,
• Issues with renal function,
• Overwhelming acid or base load

Question 5

What are the normal physiological values

Answer 5

pH - 7.35-7.45
pO2 - 12-13 kPa
pCO2 - 4.5-5.6 kPa
Bicarbonate - 22-26mmol/l.

Question 6

How to calculate Standard bicarbonate and what is it?

Answer 6

It is calculated from the actual bicarbonate but assuming 37 degrees and a PCO2 is 5.3kPa. It reflects the metabolic component of acid base balance

Question 7

What other clues are there when doing an ABG?

Answer 7

History, Examination, what are they breathing, urea and electrolytes, haemoglobin, glucose, arterial blood gases and a CXR

Question 8

How to assess an arterial blood gas?

Answer 8

1) Look at the pO2 and oxygenation,
2) Assess the pH,
3) Determine the primary problem.

Question 9

What are the adverse side effects of high oxygen levels

Answer 9

• Increases risk hypercapnic respiratory failure in acute exacerbations of COPD.
• Increases mortality survivors of cardiac arrest, mortality intensive care patients and in acute severe asthma.
• Generates free radicals
• Lung toxicity (collapse of alveoli due to atelectasis and irritating to mucous membranes.

Question 10

What are the theraputic uses of high inspired concentration of oxygen

Answer 10

Pneumothorax and carbon monoxide poisoning.

Question 11

How can you calculate the partial pressure of oxygen in the alveolar?

Answer 11

2/3 x the FiO2

Question 12

What is P/F ratio?

Answer 12

It is the PO2/FiO2. If it is above 50 then the person is healthy. If it is under 40 then acute lung injury and if it is under 26.7 then it is ARDS

Question 13

What are the two options if the pH is between 7.35 and 7.45?

Answer 13

Normal or a mixed acid base abnormality.

Question 14

If the pH and pCO2 are changing in the opposite directions then what does this suggest?

Answer 14

• Respiratory problem.

Question 15

If pCO2 and pH are changing in the same direction?

Answer 15

• The the primary problem is probably metabolic.

Question 16

What is the pH proportional too?

Answer 16

HCO3/PCO2

Question 17

What is compensation?

Answer 17

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

Question 18

What is the difference between acute and respiratory acidosis?

Answer 18

Acute - Much lower pH because compensatory mechanisms haven’t set in yet. Whereas in chronic the pH is not as low as compensatory mechanism have started working

Question 19

What are the causes of hyperventilation?

Answer 19

• Acute severe asthma,
• Pulmonary embolism,
• Pulmonary oedema,
• Anxiety attack (must rule out other options first)

Question 20

What occurs at high altitude?

Answer 20

Hypoxaemia is induced by hyperventilation is prominent and compensation occurs by renal excretion of bicarbonate.