This document provides information on interpreting arterial blood gas (ABG) results, including: 1. It evaluates oxygenation by examining pO2 and SaO2 levels, ventilation by looking at pCO2 levels and production vs elimination of CO2, and acid-base balance by analyzing pH, HCO3, and BE levels. 2. Normal ranges are provided for interpreting pH, pCO2, HCO3, and BE levels to determine if the patient has respiratory or metabolic acidosis or alkalosis. 3. The document describes how to assess for compensation by seeing if other parameters have changed to correct acid-base imbalances and restore the pH to a normal range.

1. ABG
DR ASHOK KUMAR BADAMALI

2. Lecture
• Evaluation of oxygenation
• Evaluation of Ventilation
• Evaluation of acid base balance
• ABG analysis

3. Test Result Unit ref
PH 7.44 7.35 7.45
pCO2 26mmHg mmHg 34 45
pO2 73 mmHg 75 100
O2 (HB%) 95.1 95 100
HCO3 18.2 Meq/L 23 27
BE -5.2 Meq/L -2.4 2.3
FiO2

4. Evaluation of Oxygenation
• Po2 should be >60 mmHg/ tor
• SaO2 >90%
• SpO2 may or may not corelate SaO2
• Haemoglobin
• FiO2 – fraction of inspired oxygen

5. Hypoxemia
• Low oxygen in blood
• Pao2 < 60 mmHg
• SaO2 < 90%

6. Test name Results Units Ref
FiO2 35%
pH 7.4
PCo2 26
PO2 73
HCO3 18.2
BE -5.4
O2 % 95.4

7. Evaluation of Ventilation
(CO2 elimination)
• Co2 Production vs Elimination
• Tidal volume
• Respiratory rate
• Metabolic rate
• Fever
• Seizure

8. Hyperventilating
Test name Results Units Ref
FiO2 35%
pH 7.4
PCo2 26
PO2 73
HCO3 18.2
BE -5.4
O2 % 95.4

9. Interpretation of ABG
• Normal ranges
• Po2 ≥ 60
• PCO2 35-45
• HCO3 22-26
• pH - 7.35- 7.45
• BE (-2) – (+2)
• Sao2 ≥ 90%

10. Base excess / deficit
• Reflects metabolic balance of the bicarbonate
• Deficit = loss of base
may be a problem or a correction
Excess = Gain of base
may be a problem or a correction

11. Approach to Interpretation of ABG
• Acid –Base Status (pH)
• Respiratory status ( PCO2)
• Metabolic status ( HCO3)
• Degree of Compentation

12. Acid –Base Status (pH)
• > 7.45 - Alkaline
• < 7.35 - Acidic
• 7.35-7.45 - WNL

13. Respiratory status
• PCO2 < 35 mmHg – Respiratory Alkalosis
• PCO2 >45 mmHg – Respiratory Acidosis
• 35-45 WNL

14. Metabolic status
• HCO3 > 26 metabolic alkalosis
• HCO3 < 22 metabolic acidosis
• 22-26 WNL
• BE (-2) base deficit
• > 2 is base excess

15. compensation
• Uncompensated – the other parameter within
the normal range and has not changed to fix
the problem
• Partial Compensation– The other parameter is
outside the normal range & pH is not within
7.35 -7.45
• Full compensation – other parameter is
outside normal range & pH is 7.35-7.45

16. Evaluating ABG
• Evaluate oxygenation
• Is the pH acid /alkaline
• Which direction CO2 move the pH
• Which direction HCO3 move the pH
• Name the disorder
• Is there compentaion
• Patrial / complete

17. Interpret ABG
• pH 7.39 - acid
• PCO2 -50 - acid
• HCO3 -29 fully compensated
• PO2 – 65 respiratory acidosis
• BE- + 4.7
• HB- 8
• FiO2 -21
• SaO2 -90% - No hypoxemia

18. • pH- 7.22
• pCO2- 50
• HCO3- 20
• PO2 -200
• BE- (-8)
• SaO2 100%
• HB-15
• FiO2 - 1