What are the recommended ventilator settings for a six dial strategy during Cardiopulmonary Resuscitation (CPR)?

Six-Dial Ventilator Strategy During CPR

When using a mechanical ventilator during CPR with an advanced airway in place, set the ventilator to volume control mode with: PEEP 0 cmH₂O, tidal volume 8 mL/kg, respiratory rate 10 breaths/minute, maximum peak inspiratory pressure alarm at 60 cmH₂O, trigger OFF, and I:E ratio of 1:5. 1

Rationale for Mechanical Ventilation During CPR

• Mechanical ventilators can be equally efficacious as bag-valve resuscitators during CPR, with the advantage of reducing human error and freeing the airway manager to focus on other resuscitation tasks in busy emergency departments with less trained personnel. 1
• However, a critical caveat exists: modern mechanical ventilators may erroneously sense chest compressions as spontaneous respiratory efforts, triggering additional breaths and causing dangerous hyperventilation that decreases venous return and cardiac output. 2

The Six Ventilator Settings Explained

1. PEEP: 0 cmH₂O

• Zero PEEP allows maximal venous return to the heart during chest compressions, which is critical since positive intrathoracic pressure already impedes venous return during CPR. 1
• Positive-pressure ventilation significantly lowers cardiac output during both spontaneous circulation and CPR, making minimization of intrathoracic pressure essential. 3

2. Tidal Volume: 8 mL/kg with FiO₂ 100%

• A tidal volume of 8 mL/kg provides adequate oxygenation during the reduced metabolic state of cardiac arrest. 1
• This is slightly higher than the 6-7 mL/kg (500-600 mL) recommended by AHA guidelines for manual ventilation, accounting for potential volume loss during chest compressions. 3
• The goal is to produce visible chest rise without excessive volume that would increase intrathoracic pressure. 3
• 100% FiO₂ is appropriate during cardiac arrest to optimize arterial oxyhemoglobin content and oxygen delivery. 4

3. Respiratory Rate: 10 Breaths/Minute

• A rate of 10 breaths per minute (one breath every 6 seconds) aligns with AHA guidelines for ventilation with an advanced airway during CPR. 1, 4
• This rate is specifically recommended to be less than 12 breaths per minute to minimize the impact of positive-pressure ventilation on blood flow. 3
• Hyperventilation (rates exceeding 12 breaths/minute) is common during resuscitation and decreases venous return, diminishes cardiac output, and worsens survival. 3, 2, 5

4. Maximum Peak Inspiratory Pressure (Pmax): 60 cmH₂O

• Setting the Pmax alarm at 60 cmH₂O allows adequate tidal volume delivery during the mechanical interference of chest compressions. 1
• Chest compressions alter lung compliance, and higher pressures may be necessary to achieve visible chest rise during active compressions. 3
• Studies have documented peak inspiratory pressures during manual CPR ventilation ranging from 46-106 cmH₂O, with median values around 60 cmH₂O. 5

5. Trigger: OFF

• The trigger function must be switched OFF to prevent the ventilator from misinterpreting chest recoil during compressions as spontaneous respiratory efforts. 1
• Modern ventilators erroneously sense chest compressions as patient triggers, delivering excessive respiratory rates that are detrimental to outcomes. 2
• This is perhaps the most critical setting to prevent iatrogenic hyperventilation during CPR. 2

6. I:E Ratio: 1:5

• An inspiratory-to-expiratory ratio of 1:5 provides adequate inspiratory time of approximately 1 second per breath (as recommended by AHA guidelines) while maximizing expiratory time. 1, 3
• This ratio minimizes mean airway pressure and allows adequate time for venous return between breaths. 1
• Each rescue breath should be delivered over 1 second to avoid excessive intrathoracic pressure. 3

Critical Pitfalls to Avoid

• Hyperventilation is the most common error: Studies consistently show respiratory rates of 21-37 breaths/minute during actual resuscitations, far exceeding the recommended 10 breaths/minute. 5
• Excessive ventilation decreases survival: High ventilation rates increase intrathoracic pressure, decrease venous return, diminish cardiac output, and worsen outcomes. 3, 4, 2
• Persistently high airway pressures are detrimental: Airway pressure remaining positive for >95% of the respiratory cycle (as documented in clinical practice) severely impairs blood flow during CPR. 5
• Gastric insufflation and aspiration risk: Positive-pressure ventilation in an unprotected airway may cause gastric insufflation and aspiration of gastric contents, though this risk is reduced with proper tidal volumes. 3

Alternative Consideration: Manual Ventilation

• Some experts argue that manual ventilation with volume-marked resuscitation bags or self-inflating bags should be used instead of mechanical ventilators during CPR, specifically because modern ventilators cannot reliably avoid being triggered by chest compressions. 2
• If a patient on mechanical ventilation develops cardiac arrest, one approach is to disconnect from the ventilator and ventilate manually to ensure proper synchronization with compressions. 2
• However, the six-dial strategy addresses this concern by turning OFF the trigger function, making mechanical ventilation a viable option when properly configured. 1

Monitoring During CPR

• Objective measurement of both ventilation frequency and delivered tidal volume should be performed during CPR to ensure adherence to guidelines. 6
• Capnography and thoracic impedance pneumography are appealing monitoring methods due to widespread availability, though modifications may be needed for optimal use during CPR. 6
• Real-time monitoring of CPR quality parameters has been transformative to resuscitation practice and should be incorporated into every resuscitation. 3