This document discusses acid-base balance and blood gas values. It notes that carbon dioxide (CO2) is the main acid and bicarbonate (HCO3) is the main alkali in the body. The lungs control PaCO2 and the kidneys control HCO3 to regulate acid-base balance. Normal blood gas values and interpretations for oxygenation, ventilation, and acid-base status are provided based on PaO2, PaCO2, pH, and HCO3 levels. Several blood gas results are presented and solicits the reader to comment on acid-base and oxygenation status for each.

1. Main Acid & Main Alkali
Main acid: CO2
Main alkali: HCO3
Main Organs controlling AB balance
Lungs: Through control of PaCO2
Kidneys: Through control of HCO3

2. Item Normal Value
pH 7.35-7.45
PaO2 80-100 mmHg
PaCO2 35-45 mmHg
HCO3 20-24 mEq/L

3. A)Oxygenation We can Not comment on
oxygenation in a venous
sample
PaO2 < 70 mmHg = Hypoxemia
PaO2 80-100 mmHg = Normal Oxygenation
PaO2 < 50 mmHg = Hypoxemic respiratory failure
PaO2 > 100 mmHg = Hyperoxygenation
-Oxygen therapy
-Air in the sample

4. PaCO2 35-45 mmHg = Normal Ventilation
PaCO2 < 35 mmHg = Hyperventilation
PaCO2 45-50 mmHg = Mild Hypoventilation
PaCO2 50-60 mmHg = Moderate Hypoventilation
PaCO2 > 60 mmHg = Severe Hypoventilation
A)Ventilation

5. pH < 7.35: Acidosis
pH > 7.45: Alkalosis
A)Acid-Base Balance

6. ↑↑ PaCO2 + ↑↑ HCO3: Respiratory acidosis
↑↑ PaCO2 + Normal HCO3: Respiratory acidosis
↓↓ HCO3 + ↓↓ PaCO2: Metabolic acidosis
Very low pH + Near normal HCO3 & PaCO2:
Mixed metabolic & respiratory acidosis
Very low pH + Normal HCO3 & PaCO2:
Mixed metabolic & respiratory acidosis
A)Acidosis

7. ↓↓ PaCO2 ± ↓↓ HCO3: Respiratory alkalosis
↑↑ HCO3 ± ↑↑ PaCO2: Metabolic alkalosis
A)Alkalosis

8. PaO2 : 50 mmHg
PaCO2 : 60 mmHg
pH : 7.25
Bicarbonate : 24 mEq/L
Comment on the following arterial blood gases

9. Comment on the following arterial blood gases
PaO2 : 90 mmHg
PaCO2 : 25 mmHg
pH : 7.1
Bicarbonate : 7 mEq/L

10. Comment on the following venous blood gases
PaO2 : 60 mmHg
PaCO2 : 28 mmHg
pH : 7.5
Bicarbonate : 20 mEq/L

11. Comment on the following arterial blood gases
PaO2 : 120 mmHg
PaCO2 : 40 mmHg
pH : 7.55
Bicarbonate : 32 mEq/L

12. Comment on the following arterial blood gases
PaO2 : 45 mmHg
PaCO2 : 40 mmHg
pH : 7.1
Bicarbonate : 20 mEq/L

13. PaO2 : 40 mmHg
PaCO2 : 72 mmHg
pH : 7.0
Bicarbonate : 26 mEq/L
Comment on the following arterial blood gases

14. Comment on the following arterial blood gases
PaO2 : 97 mmHg
PaCO2 : 23 mmHg
pH : 7.15
Bicarbonate : 9 mEq/L

15. Comment on the following venous blood gases
PaO2 : 60 mmHg
PaCO2 : 28 mmHg
pH : 7.52
Bicarbonate : 18 mEq/L

16. Comment on the following arterial blood gases
PaO2 : 120 mmHg
PaCO2 : 40 mmHg
pH : 7.58
Bicarbonate : 30 mEq/L

17. Comment on the following arterial blood gases
PaO2 : 48 mmHg
PaCO2 : 43 mmHg
pH : 7.1
Bicarbonate : 19 mEq/L