👤 By the CinnaEMS Content Team🕐 Updated 2026-09-28🏷️ Airway, Respiration & Ventilation🔖 Free to read, print, and share
Also known as: ETCO2 · end-tidal CO2 · waveform capnography · capnogram · shark fin · hypoventilation · tube confirmation
💡
Use this quick-reference guide to recognise, treat and hand over Capnography Deep Dive on the NREMT and on the call. Keep it handy during review and on exam day!
🩺
📒 The 1-minute cheat sheet
📌 Normal
35–45 mmHg
Square waveform
📌 Shapes
Shark fin = bronchospasm
Flat = tube misplaced
Rising = hypoventilation
📌 Cpr
Low = poor compressions
Sudden rise = ROSC
📌 Use
Guide rate in head injury
Low in sepsis = poor perfusion
📚 Capnography Deep Dive — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what changes the plan, and what to hand over.
Waveform capnography reports ventilation, perfusion and metabolism in one number and one shape. Beyond confirming a tube, it shows the quality of CPR, signals return of circulation, and reveals bronchospasm and hypoventilation before the pulse oximeter changes.
🔑
Key points
Understand these first
Normal end-tidal CO2 is about 35 to 45 mmHg with a square waveform.
Shark-fin waveform means bronchospasm (asthma or COPD) — slow, obstructed exhalation.
Rising end-tidal CO2 means hypoventilation; falling means hyperventilation or poor perfusion.
During CPR, a persistently low end-tidal CO2 signals poor-quality compressions.
A sudden sustained rise in end-tidal CO2 during CPR suggests return of spontaneous circulation.
✅
Treatment priorities
What to do, in order
Keep waveform capnography attached for every advanced airway, including during transport.
Use end-tidal CO2 to guide ventilation rate in head injury and avoid hyperventilation.
Treat a sudden loss of waveform as a displaced tube until proven otherwise.
🚩
Red flags — report now
Escalate immediately
Flat line after intubation
Very low end-tidal CO2 with a septic or shocked patient
Rising end-tidal CO2 in a sedated or opioid patient
🗣️
Patient teaching
What patients must know
Pulse oximetry lags; capnography changes with the very next breath.
❓ Capnography Deep Dive: NREMT FAQs
What are the priority actions for Capnography Deep Dive in the field?
Keep waveform capnography attached for every advanced airway, including during transport. Use end-tidal CO2 to guide ventilation rate in head injury and avoid hyperventilation. Treat a sudden loss of waveform as a displaced tube until proven otherwise.
What findings in Capnography Deep Dive change your plan or your transport decision?
Flat line after intubation. Very low end-tidal CO2 with a septic or shocked patient. Rising end-tidal CO2 in a sedated or opioid patient.
What do I need to know about Capnography Deep Dive for the NREMT?
Normal end-tidal CO2 is about 35 to 45 mmHg with a square waveform. Shark-fin waveform means bronchospasm (asthma or COPD) — slow, obstructed exhalation. Rising end-tidal CO2 means hypoventilation; falling means hyperventilation or poor perfusion. During CPR, a persistently low end-tidal CO2 signals poor-quality compressions.
What should the crew communicate or document for Capnography Deep Dive?
Pulse oximetry lags; capnography changes with the very next breath.
✨
Quick Tip
Normal end-tidal CO2 is about 35 to 45 mmHg with a square waveform.