Normal end-tidal CO2 is about 35 to 45 mmHg with a square waveform.
Before you read
Test yourself first: 5 questions
Question 1 of 5
A patient in severe diabetic ketoacidosis was breathing deeply at 34 a minute before intubation. After intubation the crew ventilates at 10 a minute. The main danger is that the:
Answer: A. Deep, rapid breathing was the patient's compensation for a severe metabolic acidosis, blowing off carbon dioxide to hold the pH up. Ventilating at a standard rate removes that compensation, carbon dioxide climbs and the pH can crash into arrest. Post-intubation ventilation has to match the patient's pre-intubation minute volume, guided by capnography.
Question 2 of 5
How does flexing an intubated patient's head forward affect the tube's position?
Answer: A. The tube tip follows the chin: flexion drives it deeper, risking mainstem intubation, and extension pulls it upward, risking dislodgement above the cords. Tape anchors the tube at the lips, not at the tip, which is why placement is reconfirmed after every move. Deep tubes usually enter the right mainstem, not the left.
Question 3 of 5
Immediately after intubation there is no capnography waveform, the abdomen is distending and the saturation is falling. You should:
Answer: A. No waveform with a distending abdomen is an esophageal tube until proven otherwise, and the safe move is to take it out and oxygenate by a route you know works before considering another attempt. Withdrawing slightly is the correction for a tube that is too deep, which is a different problem with breath sounds on one side and a waveform still present.
Question 4 of 5
A restaurant patron is clutching her throat. She can produce a weak, ineffective cough and a faint high-pitched noise when she inhales, and her lips are turning blue. You should:
Answer: A. A strong cough moves air and should be encouraged, but a weak, ineffective cough with high-pitched inspiratory noise and cyanosis means air exchange is poor, and that is managed exactly like a complete obstruction: five back blows, then five abdominal thrusts, repeated. Watching and encouraging a cough is right only when air exchange is good. Blind finger sweeps can push the object deeper.
Question 5 of 5
A choking adult in late pregnancy suddenly cannot speak, cough or move air. You should deliver:
Answer: A. The gravid uterus fills the upper abdomen, so there is no safe space to compress and the same thrust would reach the uterus rather than the diaphragm. The 2025 AHA sequence is five back blows followed by five thrusts — and in late pregnancy, or a patient too large to encircle, chest thrusts replace the abdominal ones. A blind sweep pushes the object deeper and is never indicated.
Keep the streak going with more questions like these, each with a full rationale.
What is capnography deep dive?
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 to remember
- 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.
Field priorities
- 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.
Coaching the patient
- Pulse oximetry lags; capnography changes with the very next breath.
Red flags: act now
- 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
Capnography Deep Dive: 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.
