From the Guidelines
To address a low ETCO2 level in the prehospital field, ventilation should be adjusted to achieve normocapnia, equivalent to an end-tidal CO2 of 4.0–4.5 kPa, as abnormal end-tidal CO2 is associated with increased mortality 1. When encountering a low ETCO2 level, it is crucial to first identify and treat the underlying cause while ensuring adequate ventilation.
- Check equipment for proper function and connection to rule out technical issues that can cause false readings.
- Assess the patient's airway patency and breathing quality, providing supplemental oxygen as needed, and consider using lower oxygen flows for stable patients, titrated against oxygen saturations to conserve supplies during transfer 1.
- For intubated patients, verify tube placement and adjust ventilation parameters—aim for a respiratory rate of 10-12 breaths per minute and tidal volumes of 6-8 mL/kg. Common causes of low ETCO2 include hypoventilation, hypoperfusion, hypothermia, and pulmonary embolism.
- For hypoperfusion, consider administering IV fluids and vasopressors if needed, while also ensuring that lung-protective ventilation strategies are used, but reduction or removal of positive end-expiratory pressure may be necessary in hypovolaemic patients 1. It is essential to document all interventions and ETCO2 trends, as these provide valuable information for receiving facility staff.
- ETCO2 monitoring serves as an early warning system for respiratory and circulatory compromise, making it a valuable tool for guiding interventions in the prehospital setting 1.
From the Research
Addressing Low ETCO2 Levels in the Pre-Hospital Field
To address a low ETCO2 level in the pre-hospital field, consider the following:
- Low ETCO2 values are associated with increased need for transfusion, operative intervention, and death in trauma patients 2, 3, 4
- A low initial pre-hospital ETCO2 measurement may predict poor outcomes in adult asthmatic patients, including intubation, ICU admission, and death 5
- ETCO2 levels can differentiate between cardiac and obstructive causes of dyspnea, with lower levels predicting congestive heart failure 6
Key Findings
- Optimal cutoff for low ETCO2 varies by study, but values ≤ 27-30 mmHg are associated with poor outcomes 2, 3, 4
- Low ETCO2 is associated with increased odds of mortality, in-hospital complications, and blood transfusion requirement in trauma patients 3
- Pre-hospital ETCO2 measurement has prognostic value in acute trauma, with an area under the ROC curve of 0.84 for predicting mortality 4
Considerations for Pre-Hospital Care
- Use ETCO2 measurements as an adjunct to traditional vital signs to predict mortality and poor outcomes in trauma patients 4
- Consider low ETCO2 levels when differentiating between cardiac and obstructive causes of dyspnea 6
- Be aware of the potential for low ETCO2 levels to predict poor outcomes in adult asthmatic patients 5