Capnography

What Is Capnography?

Capnography is the measurement and display of carbon dioxide in a patient's exhaled breath, most commonly expressed as end-tidal CO2 (ETCO2) in mmHg. There are two main technologies: mainstream capnography, where the sensor sits directly in the ventilation circuit near the airway, and sidestream capnography, where a small sample of exhaled gas is drawn through tubing to a remote sensor — sidestream is more common in EMS because it works with a nasal cannula on non-intubated patients, not just advanced airways. Capnography is also distinct from the simpler colorimetric CO2 detector, a disposable device that changes color in the presence of CO2 to give a quick yes/no confirmation of airway placement but provides no numeric value, no waveform, and no continuous monitoring — colorimetric devices are a useful backup but don't replace true waveform capnography for ongoing patient monitoring.

Why Capnography Matters on the Fireground

Understanding the difference between colorimetric CO2 detection and true waveform capnography matters because many EMS protocols and quality assurance reviews specifically require continuous waveform capnography, not just a one-time color change, for confirming and monitoring advanced airway placement. Knowing which technology and device your service carries — and its limitations — prevents over-relying on a basic color-change indicator when continuous quantitative monitoring is what's actually needed.

Relevant NFPA Standards

• AHA Guidelines: Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
• NFPA 455: Standard for Emergency Medical Services (EMS)

Field Procedures & Tactical Steps

1. Select the appropriate capnography setup — mainstream for intubated patients on a ventilator circuit, or sidestream with a nasal cannula adapter for spontaneously breathing patients.
2. Confirm the device is functioning and calibrated per manufacturer instructions before patient use.
3. Apply continuous waveform capnography whenever an advanced airway is placed, rather than relying solely on a one-time colorimetric check.
4. Monitor ETCO2 values and waveform shape throughout patient care, adjusting ventilation or treatment based on trends.
5. Document capnography readings at regular intervals and at any significant clinical change for the patient care report.

Common Context & Application

Used across nearly every EMS call involving airway management, ventilation, or respiratory monitoring — sidestream capnography via nasal cannula has become increasingly common even on non-intubated patients in respiratory distress, overdose, or procedural sedation calls.

Frequently Asked Questions about Capnography