1. The Siggaard-Andersen acid-base chart
Radiometer Medical ApS, Åkandevej 21, DK-2700 Brønshøj, Tel: ,

2. The Siggaard-Andersen Acid-Base Chart
Illustrating
pCO2 pH
standard base excess,
SBE, cBase(ecf)
Tool for fast interpretation of acid-base status
illustrates metabolic and respiratory conditions
differentiates between acute and chronic cases
gives a reading of SBE
Developed by Ole Siggaard-Andersen in the 1960s.

3. Use of the Siggaard-Andersen Chart
Acid-base balance is maintained by
respiratory regulation
metabolic regulation
Difficult to establish the underlying cause for a disturbance
SBE indicates the metabolic acid-base status
is practically unaffected by respiratory changes
indicates the level of “missing buffer capacity”
Slopes have been experimentally determined by CO2 inhalation or hyperventilation

4. Acute resp. alkalosis
Acute resp. acidosis
Acute metab. acidosis
Chronic metab. alkalosis
Chronic resp. alkalosis
Chronic metab. acidosis
Chronic resp. acidosis

5. Case: 56-year-old man
A 56-year-old man was admitted to hospital because of dyspnea and cyanosis
A BG sample is drawn

6. Chronic hypercapnia with an acute exacerbation
pO mmHg
pCO mmHg
sO %
Exacerbation= forværring
Emphysema= pathological accumulation of air
Fibrosis= formation of fibrous tissue
Chronic hypercapnia with an acute exacerbation
A chest X-ray revealed emphysema and fibrosis

7. Patient
result

8. Treatment
On suspicion of pulmonary infection antibiotic treatment was started and supplemental oxygen was administered by one liter per minute nasally
Because of the chronic hypercapnia, oxygen treatment might cause risk of further deterioration due to hypoventilation
The second arterial blood gas results were collected 30 minutes after start of oxygen treatment:

9. pO mmHg
pCO mmHg
sO %
Slight improvement

10. Patient
result

11. Treatment The oxygen supply was increased to two liters per minute
Another 30 minutes later the third blood gas status was measured:

12. pO mmHg
pCO mmHg
sO %
This revealed that the oxygen therapy had caused hypoventilation and acute hypercapnia

13. Patient
result

14. Treatment
The oxygen flow was therefore decreased to one liter per minute again
During the next hours the arterial blood gas status gradually improved
Six hours after admission, the patient’s blood gas status turned out to be:

15. pO mmHg
pCO mmHg
sO %

16. Patient
result

17. Conclusion - Acid-Base Chart
This case shows the importance of fast and correct interpretation of the acid-base status
If the chronic component of the initial arterial blood gas status had been misjudged, the patient would have been given more supplemental oxygen, and this could have caused severe hypoventilation or even respiratory arrest

18. Radiometer Medical ApS, Åkandevej 21, DK-2700 Brønshøj, Tel: +45 38 27 38 27, www.radiometer.com