What does an end‑tidal CO₂ value greater than 8 kPa (≈60 mm Hg) during intubation indicate?

End-Tidal CO₂ >8 kPa (60 mmHg) During Intubation: Clinical Significance

An end-tidal CO₂ value greater than 8 kPa (approximately 60 mmHg) during intubation confirms successful tracheal tube placement in the airway and indicates adequate pulmonary blood flow, though it does not rule out right mainstem bronchus intubation.

Primary Indication: Confirmation of Tracheal Tube Position

The detection of exhaled CO₂ is the gold standard for confirming endotracheal tube placement. According to the 2010 AHA Pediatric Advanced Life Support Guidelines, exhaled CO₂ detection (capnography or colorimetry) is recommended as confirmation of tracheal tube position for patients with a perfusing cardiac rhythm in all settings (Class I, LOE C) 1. The 2025 European Resuscitation Council guidelines reinforce this, stating that correct placement of the tracheal tube must be confirmed with waveform capnography 2.

Key Clinical Interpretation:

• Presence of CO₂ (>8 kPa/60 mmHg): Confirms the tube is in the airway (trachea or bronchus), NOT the esophagus
• Color change or capnography waveform: Indicates airway placement but does NOT exclude right mainstem bronchus intubation 1
• Absence of CO₂: May indicate either esophageal intubation OR very low pulmonary blood flow (especially during cardiac arrest) 1

Context-Dependent Interpretation

During Cardiac Arrest vs. Perfusing Rhythm

The interpretation differs critically based on circulatory status:

In patients with perfusing rhythm:

• End-tidal CO₂ >8 kPa reliably confirms tracheal placement
• Absence of CO₂ strongly suggests esophageal intubation

During cardiac arrest:

• If exhaled CO₂ is NOT detected, confirm tube position with direct laryngoscopy (Class IIa, LOE C) because the absence of CO₂ may reflect very low pulmonary blood flow rather than tube misplacement 1
• Research shows that end-tidal CO₂ values <10 mmHg during CPR are associated with poor outcomes, while values >10 mmHg predict better survival 3, 4, 5

Prognostic Value

Beyond tube confirmation, end-tidal CO₂ values carry significant prognostic information:

• Values >20 mmHg at intubation: Independent predictor of survival to hospital admission and discharge with good neurological outcome 6
• Sudden increase >10 mmHg during CPR: May indicate return of spontaneous circulation (ROSC) 3
• Values <10 mmHg during cardiac arrest: Associated with poor survival; all but one patient with values <10 mmHg died before discharge in one study 4

Common Pitfalls and Caveats

False Negatives (No CO₂ Despite Correct Placement):

The following conditions can impair CO₂ detection even with correct tracheal placement 1:

• Cardiac arrest with very low pulmonary blood flow (most common)
• IV bolus of epinephrine (transiently reduces pulmonary blood flow)
• Severe airway obstruction (status asthmaticus)
• Pulmonary edema
• Large glottic air leak (dilutes CO₂ concentration)

False Positives (Misleading Readings):

• Contamination with gastric contents or acidic drugs (e.g., endotracheal epinephrine) may cause a consistent color rather than breath-to-breath change 1

Post-Intubation Management

After confirming placement with end-tidal CO₂ >8 kPa:

1. Target normocapnia: Aim for PaCO₂ of 4.7–6.0 kPa (35-45 mmHg) in post-cardiac arrest patients 2
2. Avoid hypoxemia: PaO₂ should be maintained >8 kPa (60 mmHg) 2
3. Reconfirm tube position: Check after securing the tube, during transport, and each time the patient is moved 1
4. Obtain chest x-ray: To verify the tube is not in a bronchus and identify proper position in the midtrachea 1

Clinical Algorithm

Step 1: Intubate and immediately attach capnography

Step 2: Ventilate and observe for CO₂ detection

• If CO₂ detected (>8 kPa/60 mmHg): Tube is in airway → Proceed to Step 3
• If NO CO₂ detected:
  • If perfusing rhythm → Likely esophageal → Remove and reintubate
  • If cardiac arrest → Confirm with direct laryngoscopy (may be correct placement with poor flow)

Step 3: Confirm bilateral breath sounds and chest rise

Step 4: Secure tube and obtain chest x-ray to exclude bronchial intubation

Step 5: Monitor end-tidal CO₂ continuously throughout care