Capnography & Monitoring
Capnography is on every NREMT AEMT and Paramedic exam and increasingly on the EMT exam. The four common waveforms cover about 90% of the questions.
AEMT · Paramedic
Normal waveform and values
A rectangular waveform with a sharp upstroke, flat alveolar plateau, and sharp downstroke. Normal ETCO₂ 35–45 mmHg.
Bronchospasm — the shark fin
The alveolar plateau curves upward instead of flattening. Asthma and COPD exacerbations. Watch it normalize as bronchodilators work.
Low ETCO₂ with tachypnea
A metabolic acidosis — DKA, sepsis, salicylate toxicity. The patient is blowing off CO₂ to compensate. Kussmaul respirations in numeric form.
Cardiac arrest and ROSC
During CPR, ETCO₂ under 10 mmHg predicts poor outcome. A sudden jump from 15 to 40+ mmHg strongly suggests ROSC — confirm at the next rhythm check.
Frequently asked
- What does an ETCO₂ of zero mean?
- Displaced tube, disconnected circuit, or arrest. Troubleshoot in that order.
- Is capnography required for supraglottic airways?
- Yes — modern guidelines call for continuous waveform capnography on any advanced airway, not just endotracheal tubes.
Test yourself
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