Relevance of Arterial Blood Gas Values Obtained during Capnography

Abstract

The reliability of arterial blood gas values obtained during capnography (recording of expiratory CO₂-curve) was studied in a series of 40 patients with chronic lung diseases. Capnography did not result in systematic changes in Pao₂ and Paco₂ compared with an examination 10 minutes after capnography. The distribution of the blood gas changes did not differ significantly from that observed in a reference series with corresponding test arrangements without the use of capnography in a group of 22 patients. It is concluded that capnography does not exert marked influence on blood gas values. The dispersion observed seems to depend primarily on normal spontaneous variations of blood gases with time.

Key Words:

• Expiratory CO₂-curve
• hyperventilation
• hypoventilation
• respiratory gas exchange