Arterial blood gas. By Mrs. Amala Rajan Reader Medical Nursing Dept. “Life is a struggle, not against sin, not against the Money Power, not against malicious animal magnetism, but against hydrogen ions." H.L. MENCKEN. What is an ABG. Arterial Blood Gas
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Mrs. Amala Rajan
Medical Nursing Dept
Arterial Blood Gas
Drawn from artery- radial, brachial, femoral
It is an invasive procedure.
Caution must be taken with patient on anticoagulants.
Arterial blood gas analysis is an essential part of diagnosing and managing the patient’s oxygenation status, ventilation failure and acid base balance.
PCO2 Partial pressure CO2
PO2 Partial pressure O2
BE Base excess
SaO2 Oxygen Saturation
H2O + CO2 H2CO3 HCO3 + H+
pH: Measurement of acidity or alkalinity, based on the hydrogen (H+)
7.35 – 7.45
Pao2 The partial pressure oxygen that is dissolved in arterial blood.
80-100 mm Hg.
PCO2: The amount of carbon dioxide dissolved in arterial blood.
35– 45 mmHg
: The calculated value of the amount of bicarbonate in the blood
22 – 26 mmol/L
The base excess indicates the amount of excess or insufficient
level of bicarbonate. -2 to +2mEq/L
(A negative base excess indicates a base deficit in blood)
SaO2:The arterial oxygen saturation.
Assess pao2 < 80 mm Hg - Hypoxemia
For a resp. disturbance : acute, chronic
= 0.3 X body weight X BE
= 0.3 X 50 X10 = 150 mM
AG = (Na+ + K+) – (cl- + Hco3-)
Step 5 cont…
Determine if there is a compensatory mechanism working to try to correct the pH.
ie: if have primary respiratory acidosis will have increased PaCO2 and decreased pH. Compensation occurs when the kidneys retain HCO3.
80 7.2060 7.30407.4030 7.5020 7.60
(ON 21% O2)
(ON VENTILATOR) 60 – 90