Today our topic of discussion is Arterial Blood Gas Analysis.
Arterial Blood Gas Analysis
ARTERIAL BLOOD GAS ANALYSIS
The term arterial blood gas (ABG) is used to refer to a collection of parameters that reflect an individual’s ability to maintain an internal environment that allows normal cell function. Arterial blood gases are measured to give an indication of adequacy of ventilation and sufficiency oxygen.
They also indicate the body’s ability to maintain a balance between acids and alkalis known as the acid-base status. This is mainly controlled by respiratory and renal mechanisms (Fig. 30.19).
Definition
Arterial blood gas analysis is done by performing an arterial puncture thereby blood sample is collected for analysis.
Components of ABG.
- ABG includes measurements of hydrogen ion concentration or pH, base excess (BE) Bicarbonate (SBC) and partial pressure of oxygen and carbon dioxide, PaO, and PaCO,.
- Base excess is a measurement that estimates the degree of metabolic acidosis. It refers to the amount of base (alkali) that is needed to restore to a normal 7.4. Negative base excess is referred to as a base deficit (acid surplus)
- Bicarbonate is measured by means of standard bicarbonate measurement Lungs excrete acid in the form of CO, tension or partial pressure in arterial blood (PaCO) which reflects the alveolar ventilation and measure of acid excretion
- The partial pressure of oxygen in the blood (PaO) is not used for acid measurements but reflects the oxygenation of the blood..
Purpose
- To assess the acid-base status
- To assess the degree of oxygenation of blood and adequacy of alveolar ventilation
- To obtain details of ventilatory status
- To provide active medical and nursing interventions
- ABG determinations are used in the management of clients on mechanical ventilators and during the weaning process from the ventilator.
Normal Values
- PH:7.35-7.45
- PCO:35-45 mm Hg
- PHCO: 21-28 mEq/L PO: 80-100 mm Hg
- Sa0-95-100%,
Indication
- Chronic and restrictive pulmonary disease
- Acute respiratory failure
- Acid-base disturbances
- Pulmonary emboli
- Sleep disorders
- Central nervous system dysfunctions
- Cardiovascular disorders such as congestive heart failure, shunts and intracardiac atrial or ventricular shunts or both.
Interfering Factors
- Noncompliance with proper collection procedure,including air bubbles in syringe and hemolysis of sample
- Low hemoglobin level
- With continuous intra-arterial blood gas monitoring colt formation at sensor tip, sensor lying against arterial wall and transition periods, when a change in FiO
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