Respiratory Care Arterial Blood Gas Interpretation Reference Egans

Respiratory Care Arterial Blood Gas Interpretation Reference – Egan’s Fundamentals of Respiratory Care 8 th Edition

Normal Values for ABG n n n p. H = 7. 40 p. CO 2 = 40 mm. Hg p. O 2 = 90 mm. Hg Bicarb = 24 m. Eq/L Base Excess = 0 m. Eq/L Sa. O 2 = >90%

Normal Ranges n n n p. H = 7. 35 – 7. 45 p. CO 2 = 35 - 45 mm. Hg p. O 2* = 80 – 100 mm. Hg Bicarb = 22 - 26 m. Eq/L Base Excess = 0 + 2 m. Eq/L Sa. O 2 = 90 – 100% *Normal p. O 2 levels decrease naturally due to age. One mm. HG for each year over 60 is considered normal.

5 “types” of classification n n Respiratory acidosis Respiratory alkalosis Metabolic acidosis Metabolic alkalosis Mixed state (both respiratory and metabolic involvement)

Interpreting an ABG Divided into 2 basic steps n n n Interpretation of the acid-base status Interpretation of the oxygenation status

Acid-Base Classification n n Inspect the p. H (acidemia, alkalemia, or normal) Inspect the p. CO 2 (respiratory component) Inspect the HCO 3 - (metabolic component) Check for compensation

Step 1 n Categorize the p. H n < 7. 35 = acidosis n > 7. 45 = alkalosis

Step 2 n Determine respiratory involvement n n n p. CO 2 is the indicator of respiratory involvement Determine if p. CO 2 could have caused the abnormality by itself If p. CO 2 is normal, probably metabolic

Step 3 n Determine Metabolic Involvement n n n HCO 3 - is the indicator of metabolic involvement Determine if HCO 3 - could have caused the abnormality by itself If HCO 3 - is normal, probably respiratory

Step 4 n Assess for compensation n n The system NOT responsible for the imbalance usually attempts to return the p. H to normal 3 levels n Compensated (chronic) n Uncompensated (acute) n Partially Compensated

Step 4 continued n In cases in which compensation has occurred (but the p. H is still above/below 7. 40) the component which would cause the change is generally the primary cause

Oxygenation Status – p. O 2/Sa. O 2 n n n p. O 2 < 80 = mild hypoxemia p. O 2 < 60 = moderate hypoxemia p. O 2 < 40 = severe hypoxemia Sa. O 2 represents the degree to which the hemoglobin is saturated with O 2. 40 -50 -60 70 -80 -90 theory n p. O 2 to saturation match

Quick guide ↑ → ↓

Respiratory Acidosis Uncompensated Partially Compensated p. H ↓ ↓ N p. CO 2 ↑ ↑ ↑ HCO 3 - N ↑ ↑

Respiratory Acidosis Example Uncompensated Partially Compensated 7. 18 ↓ 7. 31 ↓ 7. 38 N p. CO 2 75 ↑ HCO 3 - 24 N 30 ↑ 35 ↑ p. H

Respiratory Alkalosis Uncompensated Partially Compensated p. H ↑ ↑ N p. CO 2 ↓ ↓ ↓ HCO 3 - N ↓ ↓

Respiratory Alkalosis Example Uncompensated Partially Compensated 7. 52 ↑ 7. 47 ↑ 7. 42 N p. CO 2 25 ↓ HCO 3 - 24 N 21 ↓ 18 ↓ p. H

Metabolic Acidosis Uncompensated Partially Compensated p. H ↓ ↓ N p. CO 2 N ↓ ↓ HCO 3 - ↓ ↓ ↓

Metabolic Acidosis Example Uncompensated p. H Partially Compensated 7. 09 ↓ 7. 29 ↓ 7. 38 N p. CO 2 40 N 20 ↓ 18 ↓ HCO 3 - 15 ↓

Metabolic Alkalosis Uncompensated Partially Compensated p. H ↑ ↑ N p. CO 2 N ↑ ↑ HCO 3 - ↑ ↑ ↑

Metabolic Alkalosis Example Uncompensated p. H Partially Compensated 7. 55 ↑ 7. 48 ↑ 7. 42 N p. CO 2 40 N 47 ↑ 55 ↑ HCO 3 - 35 ↑

Let’s Do a Few

? ? ? n n n p. H p. CO 2 p. O 2 HCO 3 Sa. O 2 7. 40 41 85 24 95

? ? ? n n n p. H p. CO 2 p. O 2 HCO 3 Sa. O 2 7. 29 57 64 24 91

? ? ? n n n p. H p. CO 2 p. O 2 HCO 3 Sa. O 2 7. 11 18 116 15 99

? ? ? n n n p. H p. CO 2 p. O 2 HCO 3 Sa. O 2 7. 39 62 79 35 95

? ? ? n n n p. H p. CO 2 p. O 2 HCO 3 Sa. O 2 7. 36 71 55 32 90

? ? ? n n n p. H p. CO 2 p. O 2 HCO 3 Sa. O 2 7. 58 15 101 24 98

? ? ? n n n p. H p. CO 2 p. O 2 HCO 3 Sa. O 2 7. 55 40 85 34 97

? ? ? n n n p. H p. CO 2 p. O 2 HCO 3 Sa. O 2 7. 25 65 80 19 97