Difference between revisions of "Blood Gas Analysis"
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(New page: {{unfinished}} ==Introduction== Blood gas analysis is the gold standard for evaluating gas exchange in a patient. Analysers measure the pH, partial pressures of oxygen and carbon dioxide ...) |
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==Introduction== | ==Introduction== | ||
Blood gas analysis is the gold standard for evaluating gas exchange in a patient. Analysers measure the pH, partial pressures of oxygen and carbon dioxide of the sample directly as well as calculating other parameters such as haemoglobin saturation and plasma bicarbonate. It provides details on oxygenation, ventilation and acid-base status of the patient. Samples used are usually heparinised and can be arterial or venous, but this should be considered when interpreting results. | Blood gas analysis is the gold standard for evaluating gas exchange in a patient. Analysers measure the pH, partial pressures of oxygen and carbon dioxide of the sample directly as well as calculating other parameters such as haemoglobin saturation and plasma bicarbonate. It provides details on oxygenation, ventilation and acid-base status of the patient. Samples used are usually heparinised and can be arterial or venous, but this should be considered when interpreting results. | ||
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*Increases indicate an alkalaemia. | *Increases indicate an alkalaemia. | ||
*Decreases indicate an acidemia. | *Decreases indicate an acidemia. | ||
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==Oxygen== | ==Oxygen== | ||
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*Increases indicate a metabolic alkalosis. | *Increases indicate a metabolic alkalosis. | ||
*Decreases indicate a metabolic acidosis. | *Decreases indicate a metabolic acidosis. | ||
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Revision as of 16:25, 9 April 2009
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This article is still under construction. |
Introduction
Blood gas analysis is the gold standard for evaluating gas exchange in a patient. Analysers measure the pH, partial pressures of oxygen and carbon dioxide of the sample directly as well as calculating other parameters such as haemoglobin saturation and plasma bicarbonate. It provides details on oxygenation, ventilation and acid-base status of the patient. Samples used are usually heparinised and can be arterial or venous, but this should be considered when interpreting results.
pH
- Direct measurement
- Normal values - 7.35 -7.45
- Increases indicate an alkalaemia.
- Decreases indicate an acidemia.
Oxygen
Partial Pressure
- Direct measurement
- Assuming the inspired oxygen fraction is 21%, normal values are 80-100mmHg (10.7-13.3kPa)
- Increases may be due to increases in fractional inspired oxygen or atmospheric pressure.
- Decreases indicate hypoxaemia if below 60mmHg (8kPa)
Saturation
- Calculated value.
- Normal values - 95-100%
- Decreases indicate hypoxaemia if below 90%
Carbon Dioxide
Partial Pressure
- Direct measurement
- Normal values - 35-45mmHg
- Increases indicate a respiratory acidosis.
- Decreases indicate a respiratory alkalosis.
Plasma Bicarbonate
- Calculated value.
- Normal values - 22-26 mmol/l
- Increases indicate a metabolic alkalosis.
- Decreases indicate a metabolic acidosis.