Detail explanation of ABG and different ways to understand ABG analysis

1. ABG ANALYSIS
ANIKA DAHAL
LECTURER

2. INTRODUCTION
 An arterial blood gas measurement provides
valuable information about the blood pH and
the partial pressures of arterial carbon
dioxide (PaCO2) and oxygen (PaO2).
 Most analysers calculate serum bicarbonate
(HCO3
-) and the base excess. Some
analysers also measure electrolytes,
haemoglobin, glucose, lactate, and other
analytes.

3.  Arterial blood gas is a blood test that is
performed using blood from an artery. It
involves puncturing an artery with a thin
needle and syringe and drawing a small
volume of blood

4.  The relatively low incidence of major
complications, its ability to be performed at
bed side, and its rapid analysis make it an
important tool to direct and redirect the
treatment of the patient esp in patient who
are critically ill to determine gas exchange
levels in the blood related to respiratory,
metabolic and renal function.

5. DEFINITION
 It is a procedure to measure the partial
pressure of oxygen and carbondioxide
(CO2) gases and the pH (Hydrogen ion
concentration) in arterial blood.

6. PURPOSE
 To evaluate the acid base level in the blood
 To diagnose and evaluate respiratory disease
 To assess the integrity of the ventilator
control system
 To evaluate the efficiency of pulmonary
gaseous exchange
 To monitor the respiratory therapy

7. INDICATION
 Critically ill or deteriorate unexpectedly—for
example, because of sepsis or multiorgan
failure
 Uncontrolled diabetes mellitus
 Identification of metabolic, respiratory and
acid base disorder

8.  Assessment of the response to
therapeutic interventions such as
mechanical ventilation in a patient with
respiratory failure
 The significance change in ventilator
mode or FiO2
 Any sign of respiratory distress
 After the extubation

9. CONTRAINDICATION
 Local infection or distorted anatomy at
the potential puncture site
 Severe coagulopathy
 Anticoagulation therapy with warfarin,
heparin and derivatives

10. EQUIPMENT
 Disposable syringe, 2ml with swab.
needle no. 22/23
 Heparin injection
 Methylated spirit swab
 Ice pack

11. PRECAUTION
 Syringe should be heparinized before
sample is collected; clotting should be
avoided
 The syringe should be free from air both
before and after sample is collected
 For transportation the syringe should be
capped, place on ice pack, and immediately
sent for the laboratory analysis

13. PROCEDURE
1. Explain the procedure to the patient
2. Take the vital signs
Hyperthermia and hypothermia influence 02 release
from hemoglobin.
2 . Wash hands
3. Assemble equipments on bed side
4. Put on gloves
5. Assemble needle to syringe
a. keep needle sterile
b. eject excess heparin and air bubbles, if using syringe
with liquid heparin.

14. 6. Palpate the radial ,brachial or femoral artery
Select Site
 Palpate the right and left radials arterial
pulse and visualize the course of the artery
 Pick strongest pulse
a. Radial artery is always the first choice and
should be used because of it provides
collateral circulation
- if radial pulse weak on right, move to left
- if pulse on left weak, then try brachial
Note: If puncturing the radial artery,perform
allen test to determine if collateral circulation
is present

15. ALLEN TEST

16. ALLEN TEST

17. POSITIVE RESULTS

18. b. Brachial used as alternative site
c. Femoral is the last choice in normal
situations
7. For the radial site ,place a small towel roll
under the patient’s wrist

19. 9.The needle is at a 45 to 60 degree angle
to the skin surface and is advanced in to
the artery .
1o. once the artery is punctured ,arterial
pressure will push up the hub of the
syringe and a pulsating flow of blood will
fill the syringe

22. 10. After blood is obtained ,withdraw the
needle and apply firm pressure over the
puncture with a dry sponge
11. Remove air bubbles from syringe and
needle use safety syringe system for
closure
12. Place the capped syringe in the
container of ice

23. 13. Maintain firm pressure on the puncture
site for 5 minutes
14. If the patient is on anticoagulant
medication ,apply direct pressure over
puncture site for 10-15 minute and then
apply a firm pressure dressing

24. POST PUNCTURE

25. COMPONENTS OF THE ABG
 Pao2 =The partial pressure of oxygen that is dissolved
in arterial blood 80-100 mm Hg.
 HCO3- = The calculated value of the amount of
bicarbonate in the blood 22 – 26 mmol/L
 PCO2= The amount of carbon dioxide dissolved in
arterial blood 35– 45 mmHg
 pH= Measurement of acidity or alkalinity, based on the
hydrogen (H+) 7.35 – 7.45
 SAO2 =The arterial oxygen saturation >95%

26. NORMAL ARTERIAL AND VENOUS BLOOD GAS
VALUES
Parameter Arterial Venous
pH 7.35-7.45 7.35-7.45
Paco2 35-45mmhg 40-45mmhg
Bicarbonate(HCO3) 22-26 mEq/L( MMOL/L) 22-26 mEq
pao2 80-100 mmhg 40-50 mmhg
Oxygen saturation 96-100% 60-85%

27. ACID BASE DISORDER
 Respiratory acidosis
 Respiratory alkalosis
 Metabolic acidosis
 Metabolic alkalosis

28. DEFINITIONS
 Metabolic acidosis
Metabolic acidosis is a clinical disturbance
characterized by a low pH (increased H+
concentration) and a low plasma bicarbonate
concentration. It can be produced by a gain of
hydrogen ion or a loss of bicarbonate
• Metabolic alkalosis
Metabolic alkalosis is a clinical disturbance
characterized by a high pH (decreased H+
concentration) and a high plasma bicarbonate
concentration. It can be produced by a gain of
bicarbonate or a loss of H+

29. RESPIRATORY ACIDOSIS
 Respiratory acidosis is a clinical disorder
in which the pH is less than 7.35 and the
PaCO2 is greater than 42 mm Hg.
 It may be either acute or chronic.
 Respiratory acidosis is always due to
inadequate excretion of CO2 with
inadequate ventilation, resulting in
elevated plasma CO2 levels and thus
elevated carbonic acid (H2CO3) levels

30. RESPIRATORY ALKALOSIS
 Respiratory alkalosis is a clinical condition in
which the arterial pH is greater than 7.45
and the PaCO2 is less than 38 mm Hg.
 As with respiratory acidosis, acute and
chronic conditions can occur.
 Respiratory alkalosis is always due to
hyperventilation, which causes excessive
“blowing off” of CO2 and, hence, a decrease
in the plasma carbonic acid concentration.

32. INTERPRETATIONS
1.Blood Ph(7.35-7.45)
-high indicates alkalosis
-Low indicates acidosis
2.Paco2(35-45mmhg)
>45mmhg-respiratory acidosis
<45mmhg-respiratory alkalosis

33. 3.Pao2 (80-100 mmhg)
The partial pressure of o2 that is dissolved in arterial
blood
4.Hco3 (22-26meq/lit)
The calculated value of the amount of bicarbonate in
the blood stream.
5.Base excess (-2 to +2meq/l)
>+3= metabolic alkalosis
<-3=metabolic acidosis
6.Sao2(95%-100%)

35. INTERPRETATION BY TIC
TAC TOE METHOD

36. 1. Know the normal values
 Know the normal and abnormal ABG values
when you review the lab reports. They’re
fairly easy to remember: for pH, the
normal value is 7.35 to 7.45; 35-45
for paCO2; and 22-26 for HCO3.

37. 2. Determine if pH is under acidosis or
alkalosis
 Next thing to do is to determine the
acidity or alkalinity of the blood through
the value of pH. The pH level of a healthy
human should be between 7.35 to 7.45.
The human body is constantly striving to
keep pH in balance.
 pH level below 7.35 is acidosis
pH level above 7.45 is alkalosis

39. 3. Determine if acid-base is respiratory
or metabolic
 Next thing you need to determine is
whether the acid base is Respiratory or
Metabolic.
 paCO2 = Respiratory
HCO3 = Metabolic

40. 4. Remember ROME
 Still, it all boils down to mnemonics. The
mnemonic RO-ME.
Respiratory Opposite
 When pH is up, PaCO2 is down = Alkalosis
When pH is down, PaCO2 is up = Acidosis
Metabolic Equal
 When pH is up, HCO3 is up = Alkalosis
When pH is down, HCO3 is down = Acidosis

41. 5. Tic-Tac-Toe
 And yes, ABG problems can be solved
work using the tic-tac-toe method. All you
have to do is make a blank chart similar to
this:

43. 6. Mark the Chart
 Using the lab result values, mark them on
your tic-tac-toe. Let’s begin with this sample
problem:
 pH: 7.26, paCO2: 32, HCO3: 18
 Using the normal values reference chart in
the first step, determine where the values
should be under in the tic-tac-toe.

44.  In the given example, the solution is as
follows:
 pH of 7.26 is LOW = ACID so place pH
under Acid
paCO2 of 32 is LOW = BASE so place
paCO2 under Base
HCO3 of 18 is LOW = ACID so place HCO3
under Acid

46. 7. Match it up
 In this step, determine at which column
matches up with the pH. In the given
example, HCO3 goes with pH. HCO3 is
considered Metabolic (shown in step 3),
and both are under Acid, so this example
implies Metabolic Acidosis.

48. 8. Determine compensation
 The last step is to determine if the ABG
is Compensated, Partially Compensated, or
Uncompensated. Here’s the trick:

49.  If pH is NORMAL, PaCO2 and HCO3 are both
ABNORMAL = Compensated
 If pH is ABNORMAL, PaCO2 and HCO3 are
both ABNORMAL = Partially Compensated
If pH is ABNORMAL, PaCO2 or HCO3 is
ABNORMAL = Uncompensated
 Therefore this ABG is METABOLIC
ACIDOSIS, PARTIALLY COMPENSATED .

50.  By applying the steps above, interpret the
following ABGs:
 pH:7.44, PaCO2: 30, HCO3: 21
 pH is NORMAL = NORMAL so place pH under
Normal
PaCO2 is LOW = BASE so place PaCO2 under
Base
HCO3 is LOW = ACID so place HCO3 under
Acid

51.  *Since the acidity of the blood is determined by
the value of the pH, determine whether the normal
pH is SLIGHTLY ACIDIC or SLIGHTLY BASIC.
In this example, pH is NORMAL but SLIGHTLY
BASIC therefore it is ALKALOSIS.
 In this case PaCO2 goes with pH. PaCO2 is
considered Respiratory (shown in step 3), and both
are under Basic, so this example implies
Respiratory Alkalosis. The HCO3 is also abnormal.
 When pH is NORMAL and PaCO2 and HCO3 are
both ABNORMAL, it indicates FULL
COMPENSATION.

53. THANK YOU