Both pH and CO 2 are measured from arterial blood gas (ABG) samples. As HCO 3-, CO 2 influences blood pH direct CO 2 measurement indicates ventilatory effectiveness.

Depending on blood pH at any given time, CO 2 converts either to carbonic acid (H 2CO 3, an acid) or to bicarbonate (HCO 3-, a base).ĬO 2 exists in three primary states in the blood: as HCO 3– (70%), bound to hemoglobin (20%), and dissolved in the plasma (10%). CO 2 plays an important role in acid–base buffering. Cells take in oxygen and glucose and release water, carbon dioxide, and energy. The science behind the techniqueĬO 2 is a byproduct of cellular metabolism. Keep in mind that ETco 2 findings are interpreted within the context of physical and other traditional assessment methods.

Although ETco 2 is used in non-intubated patients, here we focus on its use in patients with endotracheal intubation. This article explains these concepts, discusses ETco 2 waveforms, and describes the assessment capabilities of this monitoring method.

To fully optimize its use, clinicians must understand certain basic principles. Although the principles underlying ETco 2 monitoring have been known for many years, recent technological advances have made the technique feasible for routine clinical application. Wherever ETco 2 monitoring is used, it can enhance patient safety-as long as bedside clinicians understand the interplay among ventilation, perfusion, and CO 2 production.

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High dead space ventilation