Ventilation Rate During CPR Should Not Be Adjusted Based on End-Tidal CO2
Providers should maintain a fixed ventilation rate of 8-10 breaths per minute (1 breath every 6-8 seconds) during CPR with an advanced airway, regardless of end-tidal CO2 values. 1, 2
Fixed Ventilation Rate Recommendation
The most recent international consensus guidelines establish that ventilation during CPR should follow a standardized approach rather than being titrated to end-tidal CO2 levels:
- Maintain 8-10 breaths per minute when an advanced airway is in place, delivered asynchronously without pausing chest compressions 1, 2
- Use tidal volumes of 500-600 mL (6-7 mL/kg) to produce visible chest rise 1
- Avoid exceeding 12 breaths per minute as hyperventilation increases intrathoracic pressure, decreases venous return, and diminishes cardiac output and survival 1, 2
Why End-Tidal CO2 Should Not Guide Ventilation Rate
End-tidal CO2 during CPR serves as a marker of CPR quality and perfusion, not as a target for ventilation adjustment:
- During cardiac arrest, CO2 delivery to the lungs is dramatically reduced (cardiac output is only 25-33% of normal), so lower minute ventilation maintains adequate gas exchange 1
- End-tidal CO2 values during CPR primarily reflect the effectiveness of chest compressions and cardiac output, not ventilation adequacy 3, 4
- A sudden increase in end-tidal CO2 indicates return of spontaneous circulation (ROSC), not a need for ventilation changes 3, 4
- Research demonstrates that increasing ventilation rates from 10 to 20 breaths per minute does not improve CO2 washout, acidemia, or ROSC rates 5
The Harm of Excessive Ventilation
Hyperventilation is a common and dangerous error during CPR:
- Clinical studies show providers frequently deliver 21-26 breaths per minute (median), far exceeding the recommended 10 breaths per minute 6
- Excessive ventilation increases intrathoracic pressure, decreases venous return to the heart, and diminishes cardiac output—directly harming survival 1
- High airway pressures (often >60 cmH2O in practice) maintained for >95% of the respiratory cycle further impede blood flow 6
- Even clinically plausible hyperventilation (up to 10-fold higher minute volumes) reduces end-tidal CO2 without improving hemodynamics, demonstrating that low end-tidal CO2 during CPR does not indicate inadequate ventilation 7
Proper Use of End-Tidal CO2 During CPR
End-tidal CO2 monitoring provides valuable information, but not for adjusting ventilation rate:
- Values <10 mmHg during CPR suggest inadequate chest compression quality or poor cardiac output—improve compressions, not ventilation 3, 4
- Sudden increase to >40 mmHg indicates ROSC and is often the first clinical sign of return of circulation 3, 4
- Persistently low values despite good CPR technique may predict poor outcomes but should not trigger increased ventilation 4
Critical Pitfalls to Avoid
- Do not increase ventilation rate in response to low end-tidal CO2 values during CPR—this worsens outcomes 1, 2
- Do not hyperventilate in an attempt to "normalize" blood gases—metabolic demands are reduced during arrest 1
- Focus on compression quality when end-tidal CO2 is low, not on increasing ventilation 3, 4
- Monitor delivered ventilation rates with capnography or other feedback devices, as providers commonly hyperventilate without realizing it 2, 6
Mechanical Ventilator Settings During CPR
When using a mechanical ventilator during CPR, the American Heart Association recommends fixed settings 2:
- Respiratory rate: 10 breaths per minute
- Tidal volume: 8 mL/kg ideal body weight (accounting for volume loss during compressions)
- FiO2: 100%
- PEEP: 0 mmHg (to maximize venous return)
- I:E ratio: 1:5 (to minimize mean airway pressure)