Lectures on respiratory Lectures on respiratory physiology physiology Acid-Base Balance Acid-Base Balance
Acid-Base Balance
Feb 07, 2016
Acid-Base Balance. Lectures on respiratory physiology. Some definitions. An acid is a molecule that releases hydrogen ions in solution A base is a molecule that can accept a hydrogen ion A buffer is a substance that can reversibly bind hydrogen ions. - PowerPoint PPT Presentation
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Lectures on respiratory physiologyLectures on respiratory physiology
Acid-Base BalanceAcid-Base Balance
Some definitions
• An acid is a molecule that releases hydrogen ions in solution
• A base is a molecule that can accept a hydrogen ion
• A buffer is a substance that can reversibly bind hydrogen ions
Titration curve for the bicarbonate buffer system
CO2 + H2O H+ + HCO3-
[H2CO3][H+] x [HCO3
-]
AT EQUILIBRIUM,
K =
[H+] x [HCO3-]
SOLUBILITY x PCO2 =
H2CO3CA
Law of Mass Action
0.03 x PCO2
[H+] x [HCO3-]K =
WHICH, AFTER TAKING LOGS, BECOMES:
pH = pK + Log( ) [HCO3-]
0.03 x PCO2
- THE HENDERSON - HASSELBALCH EQUATION
Derivation of normal pH
Davenport Diagram
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
pH = 6.1 + Log( ) [HCO3-]1.2
PCO2 = 40
7.40
24NORMAL
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
PCO2:40
3020
10
6080100
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50
PLA
SMA
[H
CO
3- ], m
eq/l
pH
pH = pK + Log( ) [HCO3-]0.03 x PCO2
4080
20BUFFERLINE
N
ACID - BASE DISTURBANCES:
* RESPIRATORY ALKALOSIS
* RESPIRATORY ACIDOSIS
* METABOLIC ACIDOSIS
* METABOLIC ALKALOSIS
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
RESPIRATORY ACIDOSIS:
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
N
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
RESPIRATORY ACIDOSIS:
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
N
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
RESPIRATORY ACIDOSIS:
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
N
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
RESPIRATORY ALKALOSIS:
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
N
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
RESPIRATORY ALKALOSIS:
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
N
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
METABOLIC ACIDOSIS:
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
N
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
METABOLIC ACIDOSIS:
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
N
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
METABOLIC ALKALOSIS
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
METABOLIC ALKALOSIS
4080
20BUFFERLINE
H+ + HCO3- CO2 + H2O
6.8 7.0 7.2 7.4 7.6 7.8 8.00
10
20
30
40
50PL
ASM
A [
HC
O3- ],
meq
/l
pH
COMPENSATED RESPIRATORY ACIDOSIS
4080
20BUFFERLINE
COMPENSATED METABOLIC ALKALOSIS
Oxygen Delivery to Tissues
CAPILLARIES
CAPILLARIES
DIFFUSION
HEART ANDCIRCULATION
TISSUE
VENTILATION
THE OXYGEN TRANSPORT SYSTEM
LUNGS
PERFUSION
DIFFUSION
Fick equation for diffusion through a tissue sheet
Distribution of PO2 between capillaries
Critical PO2 for mitochondrial respiration
Classification of tissue hypoxia:
* Anemic hypoxia* Hypoxic hypoxia
* Circulatory hypoxia* Histotoxic hypoxia
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