5 Capnography and Respiratory Monitoring Free Online FlashCards

What does capnography measure?

It continuously measures carbon dioxide in exhaled gas. The trace can also reflect changes in pulmonary blood flow and CO₂ production.

What is a common stable-adult EtCO₂ range, and how does it compare with PaCO₂?

In a stable adult, EtCO₂ is often about $35\text{–}45\ \text{mm Hg}$, usually a few mm Hg below PaCO₂. The difference can widen when ventilation–perfusion matching or pulmonary perfusion is abnormal.

What does Phase I of a typical capnogram represent?

Phase I is the near-zero baseline, representing inspired gas and gas from the conducting airways.

What can a rising EtCO₂ indicate?

A rise may indicate hypoventilation, reduced minute ventilation, increased CO₂ production, or improved pulmonary blood flow.

What does a slanted “shark-fin” plateau suggest?

A slanted, “shark-fin” plateau suggests expiratory airflow obstruction, such as bronchospasm or obstructive lung disease. The waveform alone does not establish the cause.

What capnography finding strongly supports tracheal tube placement?

A sustained exhaled-CO₂ waveform over successive breaths strongly supports tracheal placement. Continue monitoring because a correctly placed tube can later become displaced or obstructed.

Why can normal oxygen saturation fail to rule out hypoventilation?

Supplemental oxygen can maintain oxygen saturation while CO₂ rises, so a normal saturation does not rule out hypoventilation.

How do a capnogram and EtCO₂ differ?

A capnogram is the waveform showing exhaled CO₂ over time. EtCO₂ is the CO₂ value at the end of exhalation.

What causes the Phase II upstroke?

Phase II is the rapid upstroke as exhaled gas mixes with CO₂-rich alveolar gas.

What does Phase III show, and where is EtCO₂ read?

Phase III is the alveolar plateau, where gas is predominantly alveolar. EtCO₂ is measured at the end of this phase.

What causes the inspiratory downstroke?

The inspiratory downstroke occurs as fresh inspired gas rapidly returns the trace toward baseline.

What can a falling EtCO₂ indicate?

A fall may indicate hyperventilation, reduced pulmonary perfusion, increased dead-space ventilation, or a sampling problem.