Acid Base Balance/ABG

Question 1

What is the normal range of pH in the body

Answer 1

7.35-7.45

Question 2

Why is pH balance important

Answer 2

• Vital for bodily functions
• Small changes in pH can cause severe symptoms (Seizures,
arrhythmias)
• Most enzymes function only at ~pH 7.4
• Acid-base balance can affect electrolytes balance in body (Na+, K+, Cl-)
• Can also affect hormone balance
• Arterial Blood Gases (ABG) to monitor acute and chronic conditions
Metabolism produces H+

Question 3

How is H+ produced

Answer 3

Metabolism produces H+ by digestion/oxidation of food

Question 4

How is H+ excreted

Answer 4

In urine, imbalance when kidney problems

Question 5

What produces CO2

Answer 5

Cellular respiration

Question 6

How is CO2 excreted

Answer 6

By lungs, imbalance when respiratory problems

Question 7

What is a buffer

Answer 7

A buffer is a solution of weak acid/base and its
salt
• Able to bind H+ and stabilize pH of solution
• Body contains buffers to mop up excess H+

Question 8

What is the main buffer system in our bodies

Answer 8

The bicarbonate buffer system

The 3 others are
- proteins in calls and plasma
- phosphate as intracellular buffer
- haemoglobin in rbc binds H+

Question 9

How does the body regulate plasma pH

Answer 9

Chemical and physiological buffers

Question 10

How does the bicarbonate buffer system work

Answer 10

CO2 reacts with water to form carbonic acid (H2CO3) which dissociates into bicarbonate (HCO3-) and H+

In basic conditions H2C03 dissociated to H+ and HCO3- which is regulated by kidneys

In acidic conditions H+ is absorbed from extracellular fluid and is converted to H2CO3 which is regulated by the lungs

Question 11

What is the Henderson-hasselbach equation and what is it used for

Answer 11

For calculating blood pH changes with bicarbonate conc and pCO2

Question 12

What is the normal range for
1.pH
2.pCO2
3.HCO3-
4.pO2

Answer 12

1. 7.35-7.45
2. 35-39mmHg or 4.7-6.0kPa
3. 21-29mmol/L
   4.11.3-12.6kPa

Question 13

How is H+ regulated by lungs in
1. Acidosis
2. Alkalosis

Answer 13

1. Increase breathing to expel CO2 (hyperventilation)
2. Decrease in breathing to increase CO2 (hypoventilation)

Question 14

How is H+ regulated by kidneys in
1. Acidosis
2. Alkalosis

Answer 14

1. Kidneys excrete more H+ to increase blood pH, it is released as dihydrogen phosphate (H2PO4-) or ammonium (NH4+)
   Kidneys reabsorb HCO3- back into plasma
2. Kidneys excrete HCO3- and absorb H+ to lower blood pH

It is slower to compensate than lungs - hours/days
Kidney problems lead to metabolic acid-base disorders

Question 15

Symptoms of respiratory acidosis

Answer 15

Question 16

Causes of respiratory acidosis

Answer 16

Choking
Pneumonia
Asthma/COPD

Question 17

What causes respiratory alkalosis

Answer 17

Hyperventilation

Question 18

Symptoms of respiratory alkalosis

Answer 18

Question 19

What causes metabolic acidosis

Answer 19

Increased H+ production or ingestion (drugs/alcohol)

Impaired H+ excretion

Loss of HCO3-

Question 20

What causes metabolic alkalosis

Answer 20

Loss of H+ in vomit

Alkali ingestion

Potassium deficiency

Question 21

Symptoms of metabolic acidosis

Answer 21

Question 22

Symptoms of metabolic alkalosis

Answer 22

Question 23

How is acid-base imbalance compensated in
1. Respiratory disorder
2. Metabolic disorder

Answer 23

1. Renal compensation (occurs slowly)
2. Respiratory compensation (occurs quickly)