🫀🫁Cardio & Resp🫀🫁 - Arterial Blood Gases & Acid-Base Regulation

Question 1

Why is pH used as a measurement for [H+]?

Answer 1

Tiny numbers for [H+] are inconvenient

Question 2

How is pH calculated?

Answer 2

-log10[H+]

Question 3

How is [H+] calculated from pH?

Answer 3

10^(-pH)

Question 4

What is an acid?

Answer 4

An acid is any molecule that has a loosely bound H+ ion that it can donate
H+ ions are also called protons

Question 5

What is the pH paradox?

Answer 5

A greater concentration of H+ ions refers to a lower pH

Question 6

What is a base?

Answer 6

A base is an anionic (negatively charged ion) molecule capable of reversibly binding protons (to reduce the amount that are ‘free’)

Question 7

What is the bodies main source of acids?

Answer 7

Question 8

What can changes in ventilation do?

Answer 8

Change the amount of CO2 in the blood - the pCO2

Question 9

What is the result of hyperventilation?

Answer 9

Gets rid of CO2 from the blood
Shifts equilibrium towards a (respiratory) alkalosis
Results in respiratory alkalosis, if not compensated

Question 10

What is the result of hypoventilation?

Answer 10

Lower amount of CO2 removed from blood
Respiratory acidosis

Question 11

In what situations could there be respiratory alkalosis, AND hypoxaemia?

Answer 11

Classic scenarios:
High altitude
Pulmonary disease
Mechanical ventilation (if a patient has ARDS)
If the cause of hyperventilation is low oxygen, they can co-exist

Question 12

In what situation can there be respiratory acidosis?

Answer 12

Hypoventilation - COPD etc…

Question 13

What is the body’s rapid compensatory response to pH changes

Answer 13

Changes in ventilation

Question 14

What is the body’s slow compensatory response to pH changes?

Answer 14

Changes in HCO3 and H+ retention/secretion in the kidneys

Question 15

What is the ideal pH for blood?

Answer 15

7.35-7.45

Question 16

What are the potential pH states for blood?

Answer 16

Acidosis(/acidaemia)
Alkalosis
Normal

Question 17

What are the aetiologies of pH imbalances?

Answer 17

Respiratory (acidosis or alkalosis)
Metabolic (acidosis or alkalosis)
Mixed (respiratory and metabolic)
Normal

Question 18

What are the options for compensatory status of the body?

Answer 18

Uncompensated
Partially compensated
Fully compensated

Question 19

What are the potential oxygenation states for the body?

Answer 19

Hypoxaemia
Normoxaemia
Hyperoxaemia

Question 20

What is BE?

Answer 20

Base excess
Shows shift of levels of base in the blood from normal levels
Values of -2 - 2 are seen as normal
<-2 suggests compensation to make the blood more acidic
>2 suggests compensation to make the blood more alkaline

Question 21

What ABG is shown here?

Answer 21

Uncompensated respiratory alkalosis with moderate hypoxaemia

Question 22

Give the ABG readings for these patients

Answer 22

A - Normal with mild hypoxaemia
B - Uncompensated respiratory acidosis with very mild hypoxaemia
C - Uncompensated respiratory alkalosis with severe hypoxaemia