ABG TEST MEASURES YJE AMOUNT OF ARTERIAL GASES SUCH AS OXYGEN AND CARBON DIOXIDE

1. ARTERIAL BLOOD GAS ANALYSIS
DR.SHWETA PANCHBUDHE
ASSISTANT PROFESSOR
DATTA MEGHE COLLEGE OF PHYSIOTHERAPY

2. Purpose statement
• At the end of the class the students will be able to,
understand the Defination of ABG, component of
ABG, Disturbance of acid base balance and
compensation

3. LEARNING OBJECTIVES
SR.N
O
LEARNING OBJECTIVES DOMAIN LEVEL CRITERIA
1 Define ABG & Write down
the component of ABG?
cognitive Must know
2 Describe acid base
disturbance
cognitive Must know
3 What is Ph? cognitive Must know
4

4. ARTERIAL BLOOD GAS ANALYSIS
• Defination: It is a diagnostic procedure in which a
blood is obtained from an artery directly by an arterial
puncture

5. INTRODUCTION
• The major function of the pulmonary system (lungs and
pulmonary circulation) is to deliver oxygen to cells and remove
carbon dioxide from the cells.
• If the patient’s history and physical examination reveal evidence
of respiratory dysfunction, diagnostic test will help identify and
evaluate the dysfunction.
• ABG analysis is one of the first tests ordered to assess
respiratory status because it helps evaluate gas exchange in
the lungs.
• An ABG test can measure how well the person's lungs and
kidneys are working and how well the body is using energy.

6. Indication
• To obtain information about patient ventilation (PCO2) ,
oxygenation (PO2) and acid base balance
• Monitor gas exchange and acid base abnormalities for patient
on mechanical ventilator or not
• To evaluate response to clinical intervention and diagnostic
evaluation ( oxygen therapy )
• An ABG test may be most useful when a person's breathing
rate is increased or decreased or when the person has very
high blood sugar levels, a severe infection, or heart failure

7. ABG component
• PH:
measures hydrogen ion concentration in the blood, it
shows blood’ acidity or alkalinity
• PCO2 :
It is the partial pressure of CO2 that is carried by the
blood for excretion by the lungs, known as respiratory
parameter
• PO2:
It is the partial pressure of O2 that is dissolved in the
blood , it reflects the body ability to pick up oxygen from
the lungs
• HCO3 :
known as the metabolic parameter, it reflects the kidney’s
ability to retain and excrete bicarbonate

8. • Arterial blood gas (ABG) refers to the measurement
of PH and the partial pressures of oxygen (O2) and
carbon dioxide (CO2) in arterial blood.
• From these values we can assess the state of acid
base balance in blood and how well lungs are
performing their job of gas exchange.

9. • Our cell use oxygen (o2) to generate energy and
produce carbon dioxide (CO2) as waste.
• Blood supplies cells with the O2 they need and
clears the unwanted co2.
• This process depends on the ability of our lungs to
enrich blood with O2 and rid it of CO2.

10. • Pulmonary gas exchange refers to the transfer of o2
from the atmosphere to the bloodstream
(oxygenation).
• And co2 from the bloodstream to the atmosphere
co2 elimination.

11. • The exchange takes place between tiny air sacs
called alveoli and blood vessels called capillaries.
• Because they each have extremely thin walls and
come into very close contact ( the alveolar –
capillary membrane),co2 and 02 are able to move
between them.

12. • PULMONARY GAS EXCHANGE PARTIAL PRESSURE:
• ABGs help us to assess the effectiveness of gas
exchange by providing measurements of the partial
pressure of o2 and co2 in arterial blood.
• Partial pressure describe the contribution of one
individual gas within a gas mixture such as air to
the total pressure.

13. • When a gas dissolves in liquid ( blood) , the amount
dissolved depends on the partial pressure.
• Po2=partial pressure of o2
• Pao2=partial pressure of o2 in arterial blood.

14. • Gases move from areas of higher partial pressure to
lower partial pressure.
• At the alveolar capillary membrane ,air in the
alveoli has a higher Po2 and lower Pco2 than
capillary blood.
• Thus o2 molecules move from alveoli to blood and
co2 molecules move from blood to alveoli until the
partial pressure are equal.

15. ACID-BASE BALANCE:BASICS
• The term acidity and alkalinity simply refer to the
concentration of free hydrogen ions (H+) in a
solution .
• Concentration can be expressed in nanomoles per
litre (nmol/L)

16. • Solutions with high H+ ( low pH) are acidic and
those with low H+ (high pH) are alkaline.
• The point at which a substance changes from alkali
to acid is the neutral point

17. • An acid is a substance that releases H+ when it is
dissolved in solution.
• Acid increase the H+ concentration of the solution (
lower the pH)
• A base is a substance that accepts H+ when
dissolved in solution.
• Bases lowers the H+ concentration of the solution
(raise the pH.)

18. • A buffer is a substance that can either accept or
release H+ depending on the surrounding H+
concentration
• Human blood has normal pH=7.35-7.45
• H+=35-45nmol/L

19. • If blood pH is below the normal range there is a
acidaemia.
• If it is above the normal range there is alkalaemia
• An acidosis is any process that lowers blood pH
whereas an alkalosis is any process that raises blood
pH

20. What is pH
• It is a negative logarithmic scale ,the negative
means that pH values get lower as the H+
concentration increases
• So a pH of 7.1 is more acidic than 7.2 )
• The logarithmic means that a shift in pH by one
number represents a 10 fold change in H+
concentration
• So 7 is 10 times more acidic than 8

21. DISTURBANCE OF ACID BASE BALANCE
• An acidosis is any process that acts to lower blood
pH.
• If it is due to a rise in Pac02 , it is called a respiratory
acidosis.
• If it is due to any other cause the HCO3 is reduced
and it is called a metabolic acidosis.

22. • An alkalosis is any process that acts to increase
blood pH.
• If it is due to a fall in Paco2, it is called respiratory
alkalosis
• If it is due to any other cause the HCO3 is raised and
it is called metabolic alkalosis.

23. • Paco2=Respiratory acidosis
• Paco2=Respiratory alkalosis
• HCO3=Metabolic alkalosis
• HCO3= Metabolic acidosis
• Formula: HENDERSON HASSELBALCH FORMULA
• pH=p Ka+ log[HCO3] /[CO2]
• pH=[HCO3]/[CO2]
• Acidity= bicarbonate /carbon dioxide
• A=B/CD

24. ARTERIAL BLOOD ANALYSIS REFERENCE RANGE IN ADULTS
pH 7.35-7.45
Pao2 10.7-13.3KPa( 80-100mmHg)
PaCO2 4.7-6.0KPa (35-45mmHg)
HCO3 22-26mmol/L
Base excess
-2 To +2

25. • Compensation :
• Change in Pco2 are controlled by lungs & changes in
bicarbonate are controlled by kidney
• The respiratory and metabolic system works together to keep
the body’s acid-base balance within normal limits.
• The respiratory system responds to metabolic based PH
imbalances in the following manner:
* metabolic acidosis: ↑ respiratory rate and depth (↓PaCO2)
* metabolic alkalosis: ↓ respiratory rate and depth (↑PaCO2)
• The metabolic system responds to respiratory based PH
imbalances in the following manner:
*respiratory acidosis: ↑ HCO3 reabsorption
*respiratory alkalosis: ↓HCO3 reabsorption

26. • Respiratory acidosis:
• Because there is no response from the kidneys yet
to acidosis the HCO3 will remain normal
Phase PH PaCO2 HCO3
UNCOMPENSATED ↓ ↑ ------
Phase PH PaCO2 HCO3
PARTIAL
COMPENSATED
↓ ↑ ↑

27. • The kidneys start to respond to the acidosis by increasing
the amount of circulating HCO3
• PH return to normal PaCO2 & HCO3 levels are still
high to correct acidosis
PHASE pH Paco2 HCO3
FULL
COMPENSATED
N ↑ ↑

28. • Respiratory alkalosis
• Because there is no response from the kidneys yet
to acidosis the HCO3 will remain normal
• The kidneys start to respond to the alkalosis by
decreasing the amount of circulating HCO3
PHASE pH Paco2 HCO3
UNCOMPENSATED ↑ ↓ _____
PHASE pH Paco2 HCO3
PARTIAL
COMPENSATED
↑ ↓ ↓

29. • PH return to normal PaCO2 & HCO3 levels
are still low to correct alkalosis
PHASE pH Paco2 HCO3
FULL
COMPENSATED
N ↓ ↓

30. • Metabolic acidosis
• Because there is no response from the lungs yet to
acidosis the PaCO2 will remain normal
• The lungs start to respond to the acidosis by decreasing
the amount of circulating PaCO2
PHASE pH Paco2 HCO3
UNCOMPENSATED ↓ ______ ↓
PHASE pH Paco2 HCO3
PARTIAL
COMPENSATED
↓ ↓ ↓

31. • PH return to normal PaCO2 & HCO3 levels are still low to
correct acidosis
PHASE pH Paco2 HCO3
FULL
COMPENSATED
N ↓ ↓

32. • Metabolic alkalosis
• Because there is no response from the lungs yet
to alkalosis the PaCO2 will remain normal
• The lungs start to respond to the alkalosis by
increasing the amount of circulating PaCO2
PHASE pH Paco2 HCO3
UNCOMPENSATED ↑ -------- ↑
PHASE pH Paco2 HCO3
PARTIAL
COMPENSATED
↑ ↑ ↑

33. PH return to normal PaCO2 & HCO3 levels
are still high to correct alkalosis
Phase PH PaCO2 HCO3
FULL
COMPENSATED
N ↑ ↑

34. • Example 1
• Jenny is a 45-year-old female admitted to the nursing unit
with a severe asthma attack. She has been experiencing
increasing shortness of breath since admission three hours
ago.
Her arterial blood gas result is as follows
Clinical Laboratory:
pH 7.22
PaCO2 55
HCO3 25

35. Follow the steps:
• 1. Assess the pH. It is low therefore,
we have acidosis.
• 2. Assess the PaCO2. It is high and in the
opposite direction of the pH.
• 3. Assess the HCO3. It has remained
within the normal range (22-26).

36. • Acidosis is present (decreased pH) with the
PaCO2being increased, reflecting a primary
respiratory problem.
• For this patient, we need to improve the
ventilation status by providing oxygen
therapy, mechanical ventilation or by
administering bronchodilators.

37. • Example 2
John is a 55-year-old male admitted with a recurring
bowel obstruction. He has been experiencing
intractable vomiting for the last several hours,
Here is his arterial blood gas result
Clinical Laboratory:
pH 7.50
PaCO2 42
HCO3 33

38. Follow the steps again:
• 1. Assess the pH. It is high (normal 7.35-
7.45), therefore, indicating alkalosis.
2. Assess the PaCO2. It is within the normal
range (normal 35-45).
3. Assess the HCO3. It is high (normal 22-26)
and moving in the same direction as the pH.

39. Alkalosis is present (increased pH) with the HCO3
increased, reflecting
a primary metabolic problem. Treatment of this
patient might include administration of I.V. fluids
and measures to reduce the excess base.

40. QUESTIONS?
• Define ABG?
• Write down the components of ABG?
• Describe acid base imbalance with an suitable
examples?
• Define compensation? Give any one example

41. REFERENCE
• CASH