????????? Blood Gas Analysis and Acid-Base Balance

1
?????????Blood Gas Analysis and Acid-Base
Balance

• ????
• ???

2
?1. ???,?,68?,H 192185 2004-6-30 ?????????
40?,?????,??2-3??, ?????????2???
????,?????,???,?????, ??????,HR
112/?,?????. PH 7.359
Na 134.2 mmol/L PaO2 30.2
mmHg K 3.22 mmol/L PaCO2
110.1 mmHg Cl 76.5
mmol/L SaO2 45
Hb 13.9g/L
BUN 2.1 mmol/L(2.9-8.3) BE 29 mmol/L
CRE 38 ?mol/L(40-100) HCO3
62.6 mmol/L TCO2 66 mmol/L An gap
2.3 mmol/L
3

• ??(Blood Gas) O2, CO2
• ????(Blood-gas Analysis)?????(PH? O2
  ?CO2)???????????????PH?

4
?????????????
? ????????
5
??

• ? ????
• ?????
• ?????
• ?????

? ????????,?????, ????,????,
???? ,???, ???.
6
Table1The Relation Between Altitude(m) and PaO2
(mmHg) Atmospheric Altitude
Pressure PaO2 Sao2
Sea level 760 100
97 3190m 512 67 88 4408m
438 40 75 7600m 282
30 55(Coma)
7
??????

• pH BB
• PaO2 BE
• P(A-a)O2 T-CO2
• SaO2 CO2-CP
• PvO2 AG
• PaCO2
• CaO2
• H2CO3

8

• ? ??????(PaO2)
• (Partial Pressure of Arterial Oxygen)
• ??????????????????
• ???12.6-13.3Kpa(95-100mmHg)
• (100 0.33 ??? ? 5
  )

9
PaO2?? 1.??SaO2, ????? ????
The Oxygen-Hemoglobin Saturation Curve
10
External respiration
2.??O2????, ???????? ??????
Internal respiration
11
3.???? Peripheral chemoreceptors (arotic sinus
or carotid body) (Through cranial nerves 9,10).

12

• PaO2????
• ? ??????
• Hypoventilation

? ?????? Diffusion of O2 low
? V/Q???? V/Q ratio mismatch ? ?-???
Right to left shunting ? ????????? Inhaled PO2
low
13

• ?????(Hypoxemia)
• PaO2?????????
• ?????(Respiratory Failure)
• PaO2lt60mmHg
• ???(Hypoxia)
• ?????PaO2lt40mmHg
• PaO2lt20mmHg,???????

14
? ??-?????(P(A-a)O2) (Alveolar-Arterial
Oxygen Difference) ????????????
Table2 Partial Pressures(mmHg) of O2 and
CO2 Source of Sample PO2
PCO2 Inhaled air
160 0.3
Alveolar air 104
40 Arterial blood
95 40
Venous blood 40
46
15
???? ???????(3-5) ???????
??????(????) ???15-20mmHg,lt 30mmHg?
16

• P(A-a)O2PAO2-PaO2
• PAO2 PiO2 -
• (PB-PH2O) ?FiO2 -
• (760-47)? 20.93 -
• 99(mmHg)

PaCO2
R
PaCO2
R
40
0.8
17
?????????
???? ????
?-?? ???
V/Q?? ??
P(A-a)O2 ?
18

• ?.???????(SaO2)
• (Aterial 0xygen Saturation)
• ???? ? 100
• ???????Hb?????
• ??????????
• ???? 98?0.00310.30(ml) 1.5
• Hb?? 15?1.34?9819.7(ml) 98.5

HBO2
?HB
19
PO2 (mmHg) Saturation of Hb()
10 20 30 40 50 60 70 80 90 100 13.5 35 57 75 83.5 89 92.7 94.5 96.5 97.5
P50??HB?O2????, ???(26.6mmHg,
3.35Kpa)?
The Oxygen-Hemoglobin Saturation Curve
20

• ????
• ? SaO2????????PaO2??
• ? PaO2?SaO2?????,??????
• ? PaO260mmHg ?????
• ?????(???)

21
Bohr????? ??PH??????
The Effects of pH,T, 2-3 DPG on Oxygen
dissociation curve
22

• ? ????????(PvO2)
• ?????????
• (Mixed Venous Partial Pressure of Oxygen )
• ????????????????????
• ???35-45mmHg(4.67-6.0Kpa)
• SvO2 65-75

23

• ????(????????)
• ??????????
• ?????????

24

• ? ??????(CaO2)
• (Arterial Oxygen Content)
• ???????????????
• ???19-21ml(8.55-9.45mmol/L)
• CaO2Hb(g)?1.34?SaO2?PaO2(mmHg)?0.0031
• 15?1.34?98?95?0.003120(ml)

25

• CvO215?1.34?75?40?0.0031
• 15.2(ml)
• CaO2-CvO220-15.25(ml)
• ????,??O2 0.3ml
• ??3????,??O2 6.0ml?

26
???? ? ???????? ? ?? Fick ???????
? ?????? Qs/QT

P(A-a)O2?0.00031
?100
(CaO2- CvO2)P(A-a)O2?0.00031
27

• ?. ?????????(PaCO2)
• (Partial Pressure of Arterial Carbon Dioxide)
  
• ?????????CO2???????
• ???35-45mmHg(4.7-6.0kpa)

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• PaCO2 ????
• ? ????????
• (???????,???CO2 200ml/?)?
• ? ???????????
• ??????(Respiratory acidosis)
• 
  PaCO2gt45mmHg(6.0Kpa)
• ??????(Respiratory alkalosis)
• 
  PaCO2 lt35mmHg(4.67Kpa)
• ? ?????????(????)
• ? ??????????????

29

• ?. ????(Bicarbonate, HCO3)
• ??????????????

Actual bicarbonate(AB) ???????HCO3??,???
22-27mmol/L?
Standard bicarbonate(SB) ???????(T
37º?PaCO2 40mmHg ? SaO2100)
???HCO3??? ?????????,????????????
30
???? 1.????CO2??
CO2 transport in blood
31
???? 2.????
The role of the Carbonic Acid-Bicarbonate
System in the Regulation of Plasma pH.
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• ??? ABSB
• AB???? AB SB
• ?? AB gt SB
• AB???? AB SB
• ?? AB lt SB

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• ? ???(Buffer Bases BB)
• ??????????????????

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??HCO3 ???? Hb HPO42
??? 45-55(50) mmol/L
FigureBuffer System In Body Fluids
35

• ????
• ??????????
• ??????????

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? ???(Bases excess BE )

• ?T 37ºC?PaCO240mmHg?SaO2 100
• ????????PH7.40??????
• ????,????????
• ???03 mmol/L

??????????????????
37

• ? ??CO2??(T- CO2)
• (Total Plasma CO2 Content)
• ?????????CO2???
• ???????HCO3(95)
• ?????CO2
• ??????? (????)

TCO2 HCO3 PaCO2? ?
2440?0.0325.2(mmol/L)
??????HCO3???
38

• ?? .PH?
• ?????????,?????????
• (The negative logarithm of the
  hydrogen ion
• concentration)

Normal
pH Normal
Mixed disorder
39
PH?H ????
40

• ??. CO2???(CO2-CP)
• (Carbon dioxide combining power)

?????,?T37º?PCO240mmHg? PO2
100mmHg?????CO2?????? ???CO2 ?
???50-70ml(21-31 mmol/L)
?????SB?
41

• ?? .?????(Anion Gap AG)
• ???????????????????
• AG(Na K)- (Cl HCO3)
• AG 8-16mmol/L

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Figure Cations and Anions in
Plasma
?? ???????-???? ?? ?????????

SO42- (mEg/L)
Mg2
43
????? 20-30 mmol/L,
??????? gt 30mmol/L,??????
44
????Acid-Base Balance
45
The number of H in the body 2400 nmol
(an adult male, 60Kg) The production of H
Nearly 55,000,000nmol / day
46
Type of Acids in the Body

?A volatile acid (H2CO3)
? Fixed acids (the catabolism of amino acids
and compounds like
phospholipids and
nucleic acids)
Sulfuric acid
Phosphoric acid
? Organic acids Lactic acid (anaerobic
metabolism) Ketone
bodies(starvation or
excessive lipid catabolism)
47
Table3 Range of H in Plasma in Clinical
Conditions Condition H nmol/L pH
Importance Acidemia
gt 100 lt 7.00 Can
be lethal Acidemia 50 - 80
7.10 - 7.30 Clinically
important Normal 40 ? 5
7.40 ? 0.05 Normal Alkalemia
20 36 7.44 7.69
Clinically important Alkalemia lt 20
gt 7.70 Can be
lethal
48
Lines of Defense ? The buffer system ? The
respiratory system ? The renal system
49
? ????

• Table4Whole blood buffers
• Buffer type
  Buffering capacity of
• 
  whole blood()
• Bicarbonate
• plasma
  35
• erythrocyte
  18
• total
  53
• Nonbicarbonate
• Hemoglobin
  35
• Plasma proteins
  7
• Organic phosphate
  3
• Inorganic phosphate
  2
• total
  47

50

• The carbonic acid-bicarbonate buffer system
• is the most importmant(53).

2. HCO3/H2CO3 ratio decides blood pH.
51
Protein buffer systems R-COO- H
RCOOH R-COOH
pH ?
pH ?
NH2
NH2
NH3
Neutral pH
In alkaline medium, amino acid acts an acid and
releases H
In acidic medium, amino acid acts a base and
absorbs H
52
The phosphate buffer system H2PO4-
H HPO42-
53

• ? ???
• Respiratory
• Compensation

??CO2(???) (3-6?????)
54
pH,PaO2 of blood changes
Pco2,pH of CSF changes
Peripheral Chemoreceptors at Carotid and Aortic
bodies
Central chemoreceptors at medulla oblongata
Respiratory control
CSF Cerebrospinal Fluid
55
? ???? Renal Compensation
An Overview of Urine Formation
56
?Secretion of H ? HCO3-/H2CO3 system ? Phosphate
system ? Ammonia ?Reabsorption of bicarbonate
Secretion
Reabsorption
Cotransport
Active transport
Exchange pump
Countertransport
57
Countertransport
Secretion
Active transport
Reabsorption
pH of Urine 6.0(4.5--8)
58

• ? ????????(24-36??)

H
3K
2Na
98 of Potassium of the human body is In the
ICF.
???
59
?????????

• ? ????????????
• ? ??????

60
? ????????????

• ?6???????
• ?? ?? ?? ??
• PaO2mmHg(Kpa) lt60(8.0)
  lt50(6.67) 40(5.33)
• PaCO2 mmHg(Kpa) gt50(6.67)
  gt70(9.33) gt90(12.0)
• SaO2 gt80
  80-40 lt40
• ?? ?
  ??? ??
• ?? ?
  ? ?

61

• ? ??????
• ?????,?????????????
• ???????????
• ????????????
• ????????????, ??????

62

• ?7??????????????
• ?? ?? ?? ??????
  ?? ????
• ?? ?? ??
  ??
• ?? PaCO2 HCO3 ??? HCO3 ? PaCO2
  ?0.07?1.5 ?min 30mmol/L(4.0Kpa)
• ??? HCO3 ? PaCO2 ?0.35?5.58
  3-5? 45mmol/L(6.0Kpa)
• ?? PaCO2 HCO3 ??? HCO3 ? PaCO2
  ?0.2?2.5 ?min 18mmol/L(2.4Kpa)
• ???
  HCO3 ? PaCO2 ?0.5?2.5 3-5?
  12mmol/L(1.6Kpa)
• ?? HCO3 PaCO2 PaCO2 HCO3 ?1.58?2
  12-24h 10mmHg(1.3Kpa)
• ?? HCO3 PaCO2 ?PaCO2 ?HCO3 ?0.9?5
  12-24h 55mmHg(7.3Kpa)

63

• ??????
• ? ???????
• ? ???????
• ? ?????
• ? ?????PH????????
• ? ????????????????????
• ???????????????
• ????????????????

64
(?)?????? (Metabolic acidosis)

• Mechanisms
• ?An increase of acid(not carbonic
  acid)
• ? A decrease of base
• ? Both

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Table8. Common Causes of Metabolic Acidosis
Decrease of Base Diarrhea Gastrointestinal
fistula Intestinal decompression Renal tubular
acidosis
Increase of Acid Ketoacidosis(diabetes
mellitus, starvation, alcoholism) Severe
infection Burns Shock Tissue anoxia Renal
failure Intake of acids or precursors
66
??H ??????(HCO3-/H2CO3?)
???
?PH???
HCO3
?H ???HCO3
????
HCO3
??????
CO2??
20
HCO3

PaCO2
H2CO3
1
67
The signs and symptoms ?Increased rate and
depth of respiration ?Headache ?
Central nervous system depression
Confusion, lethargy, coma. ? Cardiovascular
system dysfunction Ventricular
arrhythmia, Decreased cardiac
contractility. ?Death(brain stem
dysfunction or
cardiovascular dysfunction )
68

• ??????
• pH N or ?? HCO3 ? ?ABSB ?BE??
• PaCO2????
• AG?
• ????
• ?K???,?????

69

• ??,62?,??????
• ????PH 7.17 PaCO2 25mmHg
• K 4.4mmo Na 144mmol/L
• Cl 107mmol/L HCO3 12mmol/L
• ?? PaCO2 HCO3 ? 1.5 8 ? 2
• 12 ? 1.5
  8 26

70
(?)?? Metabolic Alkalosis

• Mechanisms
• ? An increase in base
• ? A decrease of acid
• ? Both

71
Table9. Common Causes of Metabolic Alkalosis
Increase of base Intake of bicarbonate or
bicarbonate precursors Massive transfusion with
citrated blood
Decrease of Acid Emesis Gastric suction
Hyperaldosteronism Hypokalemia
72
??H? ??????(HCO3/ H2CO3?)
???
?PH??
HCO3?
?H ? ???HCO3 ?
????
HCO3 ?
????
CO2???
20
HCO3

PaCO2 ?
H2CO3
1
73
The signs and symptoms ?Shallow breathing
?Postural hypotention(ECF depletion)
? Muscle weakness(hypokalemia) ? Increased
neuromuscular irritability Figuers
and toes tingle, Signs of tetany,
Seizures, Central
nervous system depression,
(Confusion, lethargy, coma) ?Death (brain
stem dysfunction).
74
?????? pH N or ?? HCO3 ? ?ABSB?BE??
PaCO2 ? ???? ?K???
75

• ??,45?,??????????
• ????PH 7.50 PaCO2 53mmHg
• K 2.2mmol/L Na
  140mmol/L
• Cl 86mmol/L
  HCO3 42mmol/L
• ?? ?PaCO2 ?HCO3 ? 0.9?5
• 
  (42-24) ? 0.9 16.2
• PaCO2 40 16.2
  56.2

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(?)??????Respiratory Acidosis

• Mechanism
• Hypoventilation

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Table10. Common Causes of Respiratory Acidosis
Impaired Gaseous Exchange Chronic obstructive
pulmonary disease Pneumonia Severe asthma
Pulmonary edema ARDS Obstructive sleep apnea
Impaired neuromuscular function Guillain-Barre
syndrome Chest injury or surgery Hypokalemia Respi
ratory muscle fatigue Respiratory
depressant drugs(barbiturates,
narcotics) Central sleep apnea
78
The signs and symptoms ?Headache(cerebral
vasodilation ) ?Cardiovascular dysfunction
Tachycardia,cardiac arrythmias,
hypotention. ? Neurologic
abnormalities Blurred vision,
tremors, vertigo, disorientation,
lethargy, coma.
79
?????? pH N or ?? HCO3 ?
(acute lt 32mmol / L,
chronic lt 45mmol / L) PaCO2 ?
?????
80
??,75?,??COPD? ????PH 7.350 PaCO2 60
mmHg K 3.6mmol/L
Na 140mmol/L Cl
90mmol/L HCO3 32mmol/L ?? ? HCO3 ?
PaCO2 ? 0.35?5.58 (60-40)?
0.35 7 HCO3 24 7 31
81
(?)?????? Respiratory Alkalosis

• Mechanisms
• Hyperventilation
  

82
Table11. Common Causes of Respiratory Alkalosis
Hyperventilation Anxiety, pschological
distress Prolonged sobbing Hypoxemia Stimulation
of the brain stem(salicylate overdose,
meningitis, head injury )
83
The signs and symptoms ? Diaphoresis
? Neuromuscular irritability
Paresthesias, numbness and
tingling in fingers or
around the mouth,
84
?????? pH ?? HCO3 ? PaCO2 ?
???? ?K???
85
??,40?,??????? ????PH 7.350
PaCO2 20 mmHg K
3.6mmol/L Na 140mmol/L
Cl99mmol/L HCO3 14mmol/L
?? ? HCO3 ? PaCO2 ? 0.5?2.5
(40 - 20) ? 0.5
10 HCO3 24
10 14
86
(?) ????????? Mixed Acid-Base
Imbalances
87
1.?? ??
?? ???????,????? ?????
??????
88

• ????
• ?PaCO2?
• ??? HCO3 ? gt 24? PaCO2
  ?0.35?5.58
• ? HCO3 gt 45mmol/L(??)
• ? ? K ? Cl ?

89

• 2. ????
• ?????????,???????

???? ? PaCO2? ?
??HCO3 ? lt 24? PaCO2 ? 0.35?5.58
? AG? ? ?K ?
Cl?
90

• 3. ????
• ?????,??????????

???? PH ? PaCO2?
HCO3 ?????, ??? ?
K ? Cl
91
4. ???? ??????,??,???,??, ????

• ????
• PaCO2?
• HCO3 ? lt 24-? PaCO2
  ?0.5?2.5
• AG?
• PH

92
5. ?????? (Triple-acid-base disorders
TABD ) ????????????,????45?

• ???????????,?????
• ??????,??,
• ?????,????
• ???????(??)??????,
• ????????

93

• ??????
• ?AG???, ?AG ?HCO3
• ?AG
  ??AG ? 12
• ??HCO3 ??HCO3 ?AG
• ??HCO3 ???HCO3 ????

94

• ????
• PaCO2?
• HCO3 ? ???
• ??HCO3 gt 24? PaCO2 ?0.35?5.58
• AG ?

95

• ?????
• PH 7.35 PaO2 40mmHg PaCO2
  90 mmHg
• K 3.6mmol/L Na 142mmol/L
• Cl 70mmol/L HCO3 37mmol/L
• AG 142 ?37 ? 70 35
• ?AG 35 ? 12 23
  
• ??HCO3 37 23 60
• ??HCO3 24 ? PaCO2 ?
  0.35?5.58
• 
  24 (90-40)? 0.35 41.5

96
?1. ???,?,68?,H 192185 2004-6-30 PH
7.359 Na
134.2 mmol/L PaO2 30.2 mmHg
K 3.22 mmol/L PaCO2 110.1 mmHg
Cl 76.5 mmol/L SaO2 45
Hb 13.9g/L
BUN 2.1 mmol/L(2.9-8.3) BE
29 mmol/L CRE 38
?mol/L(40-100) HCO3 62.6 mmol/L(gt45)
97
??

• ?????????
• ????????????????????

98
Thanks