Week 1: Arterial blood gas analysis

Question 1

Arterial blood gas measures what levels? values that are calculated?

Answer 1

MEASURED
-PO2 -oxygen tension
-O2 sat
-PCO2
-pH
-COHb and metHb levels
CALCULATED
-HCO3-
-base excess
-oxygen saturation

Question 2

Normal values for ABG

Answer 2

pH: 7.4
paCO2 40 mmHg
PaO2 97 mmHg
HCO3 24 mEq/L
SaO2 97%
A-a grad: 5-20 mmHg

Question 3

Indications for ABG

Answer 3

1. assess blood oxygenation
2. assess ventilation
3. determine acid-base status
4. determin carboxyhemoglobin or methemoglobin levels

Question 4

Arterial oxygen content

Answer 4

CaO2=(Hb)(SaO2)(1.34)+(PaO2)(0.003)

• dissolved O2 measured with clark electrode
• oxygen sat measured by co-oximetry
• calculated oxygen sat won’t be accurate if COHb or MetHb is present

Question 5

co-oximetry vs pulse oximetry

Answer 5

• Co-ox-fractional oxyhemoglobin: O2Hb/(O2Hb+RHb+COHb+MetHb)
• pulse ox: O2Hb/(O2Hb+RHb)
• RHb=reduced hemoglobin, deoxyHb

Question 6

Minute ventilation

Answer 6

MV=RR X TV

Question 7

measure of ventilation of lungs

Answer 7

-most accurate measure is arterial CO2 tension (PaCO2 mmHg) and pH
-PaCO2=(VCO2*0.863)/VA
VCO2=CO2 production
VA=alveolar ventilation