11. Acid-Based Regulation

Question 1

What is the partial pressure of oxygen on the arterial side of circulation?

Answer 1

> 10kPa

Question 2

What is the partial pressure of oxygen on the venous side of circulation?

Answer 2

5.3kPa

Question 3

What is the saturation of O2 on the arterial side of circulation?

Answer 3

> 95%

Question 4

What is the saturation of O2 on the venous side of circulation?

Answer 4

~75%

Question 5

What is the partial pressure of CO2 on the arterial side of circulation?

Answer 5

4.7-6.4kPa

Question 6

What is the partial pressure of CO2 on the venous side of circulation?

Answer 6

6.1kPa

Question 7

Define Alkalaemia

Answer 7

Refers to higher than normal pH of blood

Question 8

Define Acideaemia

Answer 8

Refers to lower than normal pH of blood

Question 9

Define Alkalosis

Answer 9

Describes circumstances that will decrease [H+] and increase pH

Question 10

Define Acidosis

Answer 10

Describes circumstances that will increase [H+] and decrease pH

Question 11

What did the Pitts and Swan experiment show?

Answer 11

The blood has enormous buffering capacity that can react almost immediately to imbalances in the pH

Question 12

How do you calculate pH?

Answer 12

-log10[H+]

Question 13

What is the unit for H+

Answer 13

Eq/L –> equivalence per litre

Equivalence system basically counts the charges. H+ = 1 eq. There is barely any [H+] in the blood

Question 14

Where are the two categories of acids?

Answer 14

Respiratory acid (CO2 = carbonic acid)
Metabolic acid (Pyruvic acid, lactic acid)

Question 15

Which category of acid is greater?

Answer 15

Respiratory acids are greater - most of the acid produced is from CO2

Question 16

What Henderson-Hasselbalch equation

Answer 16

pH = pK + log10 ([HCO3-]/[CO2])

Question 17

What is arterial and venous pH?

Answer 17

Arterial pH = 7.4

Venous pH = 7.36

Question 18

What are the basic guidelines of PaO2?

Answer 18

>10kPa = normal
8-10kPa = mild hypoxaemia
6-8kPa = moderate hypoxaemia
<6kPa = severe hypoxaemia

Question 19

What are the compensatory mechanisms to changes in pH?

Answer 19

RAPID compensatory response to change CO2 elimination and therefore alter pH - Changes in ventilation
SLOW compensatory response response to increase/decrease pH - Changes in HCO3- and H+ retention/secretion in the kidenys

Question 20

An acidaemia will need…

Answer 20

an alkalosis to correct

Question 21

An alkalaemia will need…

Answer 21

an acidosis to correct

Question 22

What is the physiological optimum pH?

Answer 22

7.4

Question 23

What is standard tidal volume?

Answer 23

500ml

Question 24

What is standard breathing rate?

Answer 24

12 breaths per minute

Question 25

What does hypoventilation cause?

Answer 25

A lower than normal pH
Higher than normal PaCO2
Normal base excess - Bicarbonate concentration is correct for the PaCO2

Uncompensated Respiratory Acidosis

Question 26

What does the body do in response to uncompensated respiratory acidosis?

Answer 26

There will be a need to reduce H+

1) The body will produce more HCO3- from erythrocytes
2) The kidneys will absorb more HCO3-

Question 27

What does hyperventilation cause?

Answer 27

Higher than normal pH
Lower than normal PaCO2
Normal base excess

Uncompensated Respiratory Alkalosis

Question 28

What does diarrhoea cause?

Answer 28

Lower than normal pH
Normal levels of PaCO2
Lower than normal base excess - Loss of HCO3- in diarrhoea

Uncompensated Metabolic Acidosis

Question 29

What does vomiting cause?

Answer 29

Higher than normal pH - loss of H+ in vomit
Normal levels of PaCO2
Higher than normal base excess - HCO3 is high compared to H+

Uncompensated Metabolic Alkalosis