Capnometry

What Is Capnometry?

Capnometry is the measurement of exhaled carbon dioxide expressed as a numeric end-tidal CO2 (ETCO2) value, without necessarily including a graphical waveform display. Technically, capnometry refers to the number alone, while capnography refers to the number plus the continuous waveform — in practice, most modern EMS monitors provide both together, so the terms are often used interchangeably in the field, but understanding the distinction matters because a numeric-only capnometer (without waveform) gives less diagnostic information than full waveform capnography, since it can't show the shape changes that indicate bronchospasm, rebreathing, or a developing airway problem. Normal ETCO2 is roughly 35–45 mmHg, with values outside that range prompting further assessment of ventilation, perfusion, or metabolic status.

Why Capnometry Matters on the Fireground

Knowing whether your service's equipment provides numeric-only capnometry or full waveform capnography affects what you can rely on it for — a numeric value alone can flag a problem (like a sudden drop in ETCO2) but can't help you distinguish the cause the way a waveform shape can. EMS protocols increasingly specify 'waveform capnography' precisely because the numeric value by itself doesn't provide the same level of confirmation and ongoing reassurance for advanced airway placement.

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. Confirm whether your monitoring equipment provides numeric ETCO2 only or full waveform capnography, and understand its limitations accordingly.
2. Record the initial ETCO2 value immediately after airway placement or sensor attachment as a baseline.
3. Treat any sudden or unexplained change in the ETCO2 number as a prompt for immediate reassessment of the airway and ventilation status.
4. Use waveform capnography when available, as it provides additional diagnostic detail beyond the numeric value alone.
5. Document ETCO2 values at regular intervals and correlate them with the patient's clinical presentation.

Common Context & Application

Referenced whenever EMS providers discuss or document ETCO2 values during airway management, ventilation assessment, or cardiac arrest care — most modern EMS monitors provide full waveform capnography, making the numeric-only distinction more of a technical and protocol-language issue than a common equipment limitation today.

Frequently Asked Questions about Capnometry