This power point will help the physiotherapists for arterial blood gas analysis. This will inform about the acid-base balance in body. It will also tells about the indications and sites of taking ABG. it will gives the knowledge on components and compensation of ABG. it will hive detail information about respiratory acidosis and alkolosis & metabolic acidosis and alkalosis with its reasoning and clinical signs.

1. ATERIAL BLOOD GAS
ANALYSIS
DR. ANERI PATWARI

2. INTRODUCTION
 Blood gas analysis is crucial
to the assessment of
problems related to
1. acid–base balance
2. Ventilation
3. and oxygenation.
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3. A LOOK AT ACIDS AND BASES
The body constantly works to maintain a balance (homeostasis) between acids
and bases. Without that balance, cells can’t function properly. As cells use
nutrient to produce the energy, two by-products are formed H+ & CO2.
Acid-base balance depends on the regulation of the free hydrogen ions
Even slight imbalance can affect metabolism and essential body functions.
Several conditions as infection or trauma and medications can affect acid-base
balance
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5. WHY ABG
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.
An ABG test can measure how well the person's lungs and kidneys are
working.
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7. 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 )
are frequently
used to monitor
the condition of
patients in the
critical care
setting and to
help modify
respiratory
interventions
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8. SITES FOR OBTAINING ABG
 Radial artery ( most common )
 Brachial artery
 Femoral artery
Radial is the most preferable site used because:
 It is easy to access
 It is not a deep artery which facilitate palpation, stabilization and
puncturing
 The artery has a collateral blood circulation
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9. COMPONENETS
• Measures hydrogen ion concentration in the blood, it
shows blood’ acidity or alkalinity
Ph
• It is the partial pressure of CO2 that is carried by the
blood for excretion by the lungs, known as respiratory
parameter
Pco2
• It is the partial pressure of O2 that is dissolved in the
blood , it reflects the body’s ability to pick up oxygen
from the lungs
Po2
• Known as the metabolic parameter, it reflects the
kidney’s ability to retain and excrete bicarbonate
Hco3
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10. NORMATIVE DATA
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12. HENDERSON-HASSELBALCH EQUATION
(H-H eq)
 The H-H eq is specific for calculation of pH of bicarbonate buffer system of the blood.
 pH=6.1 + log {[HCO3-]/PaCO2*0.03}
 Can be conceptually written as
pH ≈ Kidney control of [HCO3-]
Lung control of PCO2
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13. ACID-BASE DISORDERS
ACID-BASE PH PCO2 HC03
RESPIRATORY
ACIDOSIS
N
RESPIRATORY
ALKALOSIS
N
METABOLIC
ACIDOSIS
N
METABOLIC
ALKALOSIS
N
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14. COMPENSATION
 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
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15. RESPIRATORY ACIDOSIS
PHASE PH PACO2 HCO3 REASON
UNCOMPENSATED --------- There is no response from
the kidneys yet to acidosis
the HCO3 will remain
normal
PARTIALLY
COMPENSATED
The kidneys start to
respond to the acidosis by
increasing the amount of
circulating HCO3
FULLY
COMPENSATED
N PH return to normal
PaCO2 & HCO3 levels are
still high to correct acidosis
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16. RESPIRATORY ALKALOSIS
PHASE PH PACO2 HCO3 REASON
UNCOMPENSATED --------- There is no response from
the kidneys yet to acidosis
the HCO3 will remain
normal
PARTIALLY
COMPENSATED
The kidneys start to
respond to the alkalosis by
decreasing the amount of
circulating HCO3
FULLY
COMPENSATED
N PH return to normal
PaCO2 & HCO3 levels are
still low to correct alkalosis
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17. METABOLIC ACIDOSIS
PHASE PH PACO2 HCO3 REASON
UNCOMPENSATED -------- There is no response from
the lungs yet to acidosis the
PaCO2 will remain normal
PARTIALLY
COMPENSATED
The lungs start to respond
to the acidosis by
decreasing the amount of
circulating PaCO2
FULLY
COMPENSATED
N PH return to normal
PaCO2 & HCO3 levels are
still low to correct acidosis
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18. METABOLIC ALKALOSIS
PHASE PH PACO2 HCO3 REASON
UNCOMPENSATED -------- There is no response from
the lungs yet to alkalosis
the PaCO2 will remain
normal
PARTIALLY
COMPENSATED
The lungs start to respond
to the alkalosis by
increasing the amount of
circulating PaCO2
FULLY
COMPENSATED
N PH return to normal
PaCO2 & HCO3 levels are
still high to correct
alkalosis 09-04-2024 18

19. CLINICAL SIGNS
 Respiratory acidosis: chronic pulmonary dysfunction and CNS depression , neuro
muscular diseases
 Respiratory alkalosis.: Paraesthesia, Severe hyperventilation may lead to hyperactive
reflexes, tetanic convulsions
 Metabolic acidosis: increases in minute ventilation, dyspnoea, increases tidal volume,
neuro symp like lethargy and coma
 Metabolic alkalosis: hypoventilation
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20. SUMMARY
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21. REFERENCES
 ESSENTIALS OF CARDIOPULMONARY PHYSICAL THERAPY, 3RD ED;
ELLEN HILLEGAS.
 EGAN’S FUNDAMENTALS OF RESPIRATORY CARE, 10TH ED
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