Arterial blood gas

The blood gas analysis (short BGA, sometimes under the eponym Astrup by Poul Bjørn Dahl Astrup known ) is a method for measuring the gas distribution (partial pressure ) of O2 ( oxygen), CO2 ( carbon dioxide ), and the pH and acid - base balance in the blood.

The BGA goes back to the need for monitoring and control of ventilation parameters and was developed in the sixties in their basic form. The blood gas analysis has become an important part of clinical diagnostics. Over the years, came to the classical acid -base balance add more analytes and calculated parameters: hemoglobin, hemoglobin derivatives, bicarbonate, glucose, lactate, electrolytes, etc.

Meanwhile, the blood gas analysis of the monitoring of many patients with respiratory disorders and lack of oxygen used (such as in chronic obstructive pulmonary disease or cystic fibrosis ). In the ICU, in the Operations or anesthesia department and in the emergency room of a hospital blood gas analysis is usually " bedside " - bedside performed ( in the immediate patient vicinity ). Preference for arterial whole blood is used from an artery or arterialized capillary blood for example from the hyperämisierten earlobe. Venous blood is suitable for assessing breathable specific values ​​only with restrictions and is mainly used in the assessment of metabolic components of its use.

Standard values ​​(arterial ) in adults

  • PO2 = 75-97 mm Hg or 10 to 12.9 kPa ( depending on age)
  • SaO2 = 95-99 % (oxygen saturation)
  • PCO2 = 35-45 mm Hg and 4.6 to 6.0 kPa ( carbon dioxide partial pressure ); less: hypocapnia; more: hypercapnia
  • HCO3 (act ) = 21-26 mmol / l (current bicarbonate )
  • HCO3 (std) = 23-27 mmol / l ( standard bicarbonate )
  • BE (base deficit base excess or base excess ) = 0 mEq / l ( -2 to 3 mmol / l)

Standard values ​​(newborns / infants / children)

PH = 7.38 to 7.45 (Infant 4-12 months)

PCO2 = 29-61 mmHg ( 4.0 to 8.0 kPa ) ( Newborn 1st day)

PCO2 = 26-43 mmHg ( 3.5 to 5.7 kPa ) ( Newborn 10 - 90 days)

PCO2 = 27-40 mmHg ( 3.6 to 5.3 kPa) (Infant 4-12 months)

PO2 = 16-35 mmHg ( 2.2 to 4.7 kPa ) ( umbilical vein )

PO2 = 70-85 mmHg ( 9.3 to 11.4 kPa ) ( Newborn 10 - 90 days)

Interpretation

A pH below 7.35 corresponds to an acidity (acidosis ), a pH above 7.45 a Untersäuerung or alkalosis. If the change is primarily caused by a change in pCO2, one speaks of a ( breathing -related ) respiratory disorder. Carbon dioxide is a " volatile acid" represents an increase of pCO2 ( hypoventilation ) consequently leads to a respiratory acidosis, a decrease ( hyperventilation) to respiratory alkalosis.

Bicarbonate is the corresponding base. Disorders in which the primary bicarbonate concentration is changed, it's called metabolic ( metabolic ) disorders. A lowering of the bicarbonate is characteristic of a metabolic acidosis, an increase of metabolic alkalosis. After a sprint as the lactate concentration may rise by itself possibly adjusting oxygen deficiency. Lactic acid dissociates completely, the protons are buffered by bicarbonate ions, whose concentration decreases. The buffering is not complete, it comes to metabolic acidosis, which is a common disorder in acid -base balance.

Mechanical ventilation Horowitz index
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