1. Julie Perkins RRT-NPS LPCH Respiratory Care
ABG Interpretation
Julie Perkins RRT-NPS
LPCH Respiratory Care

2. pH Normal pH is 7.35-7.45 Value <7.35 is acidotic
Value >7.45 is alkalotic
Acidosis & Alkalosis can be caused by a problem with the respiratory system or a metabolic cause
Can also have combined respiratory/metabolic states

3. Is it Respiratory or Metabolic?
Respiratory Acidosis
Respiratory Alkalosis
Metabolic Acidosis
Metabolic Alkalosis
Increased pCO2 >50
Decreased pCO2<30
Decreased HCO3 <18
Increased HCO3 >30

4. Compensated or Uncompensated—what does this mean?
Evaluate pH—is it normal? Yes
Next evaluate pCO2 & HCO3
pH normal + increased pCO2 + increased HCO3 = compensated respiratory acidosis
pH normal + decreased HCO3 + decreased pCO2 = compensated metabolic acidosis

5. Compensated vs. Uncompensated
Is pH normal? No
Acidotic vs. Alkalotic
Respiratory vs. Metabolic
pH< pCO2>50 + normal HCO3 = uncompensated respiratory acidosis
pH< HCO3<18 + normal pCO2 = uncompensated metabolic acidosis
pH> pCO2<30 + normal HCO3 = uncompensated respiratory alkalosis
pH> HCO3>30 + normal pCO2 = uncompensated metabolic alkalosis

6. Causes of Acidosis Respiratory Metabolic Hypoventilation
Impaired gas exchange
Metabolic
Ketoacidosis
Diabetes
Renal Tubular Acidosis
Renal Failure
Lactic Acidosis
Decreased perfusion
Severe hypoxemia

7. Causes of Alkalosis Respiratory Metabolic Hyperventilation due to:
Hypoxemia
Metabolic acidosis
Neurologic
Lesions
Trauma
Infection
Metabolic
Hypokalemia
Gastric suction or vomiting
Hypochloremia
HYPOKALEMIA—kidneys hold on to K+ and excrete H+ causing increase blood base
GASTRIC SX/VOMIT--loss of HCL
HYPOCHLOREMIA—CL- depleted so HCO3- increased to maintain electrical balance

8. Assessing Oxygenation
Normal value for arterial blood gas mmHg
Normal value for venous blood gas 40mmHg
Normal SaO2
Arterial: 97%
Venous: 75%

9. Important points for assessing tissue oxygenation
This is the O2 that’s really available at the tissue level.
Is the THb normal?
Low THb means the ability of the blood to carry the O2 to the tissues is decreased
Is perfusion normal?
Low perfusion means the blood isn’t even getting to the tissues

10. Let’s Practice

11. 12 year old diabetic presents with Kussmaul breathing
pH :
pCO2: mmHg
pO2: mmHg
HCO3: mEq/L
BE: mEq/L
Severe partly compensated metabolic acidosis without hypoxemia due to ketoacidosis

12. 17 year old w/severe kyphoscoliosis, admitted for pneumonia
pCO2: mmHg
pO2: mmHg
HCO3: 14 mEq/L
BE : mEq/L
Compensated respiratory alkalosis due to chronic hyperventilation secondary to hypoxia

13. pH: 7.51 pCO2: 25 mmHg pO2 35 mmHg HCO3: 22 mEq/L BE: -2 mEq/L
9 year old w/hx of asthma, audibly wheezing x 1 week, has not slept in 2 nights; presents sitting up and using accessory muscles to breath w/audible wheezes
pH:
pCO2: mmHg
pO mmHg
HCO3: mEq/L
BE: mEq/L
Uncompensated respiratory alkalosis with severe hypoxia due to asthma exacerbation

14. 7 year old post op presenting with chills, fever and hypotension
pH:
pCO2: mmHg
pO2: mmHg
HCO3: mEq/L
BE: mEq/L
Uncompensated metabolic acidosis due to low perfusion state and hypoxia causing increased lactic acid