EBQ:End-Tidal CO2 Monitoring
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Clinical Question
Can end-tidal carbon dioxide (ETCO₂) monitoring during emergency department procedural sedation and analgesia (PSA) detect acute respiratory events earlier than standard monitoring methods (e.g., SpO₂, clinical observation)?
Conclusion
ETCO₂ monitoring identified the majority of acute respiratory events during PSA, and in 70% of these cases, abnormalities were detected before clinical recognition via SpO₂ or observed hypoventilation. ETCO₂ monitoring offers earlier detection of respiratory compromise than current standard practices.
Major Points
33% of PSA encounters included acute respiratory events.
85% of those with respiratory events had abnormal ETCO₂ findings.
In 70% of events, abnormal ETCO₂ was recorded before observed clinical signs.
Many ETCO₂ abnormalities were not associated with interventions, suggesting possible transient or clinically insignificant episodes.
Use of capnography may enhance detection of early hypoventilation or apnea and improve patient safety during PSA.
Study Design
- Prospective, observational case series using a convenience sample.
- Single-center, 500-bed tertiary hospital emergency department.
- Blinded design: Clinical staff were blinded to ETCO₂ readings; a study investigator monitored and recorded data.
- Institutional review board-approved with interim safety analyses performed after every 30 patients.
Population
- 59 patients undergoing 60 PSA encounters (1 patient had 2 separate sedations during the same ED visit).
- Procedures included joint dislocations, cardioversions, wound closures, and fracture reductions.
Patient Demographics
- Median age: 38 years (range: 1–89)
- 58% male
- Most common PSA medication: Propofol (68%)
Inclusion Criteria
- Adults and children receiving PSA in the ED
Exclusion Criteria
- Inability to provide informed consent
- No investigator available for enrollment
Interventions
- Standard PSA monitoring: SpO₂, heart rate, respiratory rate, cardiac rhythm, and BP.
- Study intervention: Continuous ETCO₂ monitoring via nasal cannula with integrated CO₂ sampling and oxygen delivery (2 L/min).
- Clinical team blinded to ETCO₂ data.
Outcomes
Primary Outcome
Detection of acute respiratory events, including:
- SpO₂ < 92%
- Increased oxygen requirements
- Use of airway adjuncts or bag-valve mask
- Patient repositioning
- Physical/verbal stimulation
- Reversal agent administration
Secondary Outcomes
Abnormal ETCO₂ defined as:
- Change of ≥10 mmHg from baseline
- Absolute value <30 mmHg or >50 mmHg
Subgroup analysis
Of the 20 respiratory events:
- 17 (85%) had abnormal ETCO₂ findings
- 14 (70%) showed ETCO₂ abnormalities before SpO₂ or clinical observation changes
- In 44% of cases with abnormal ETCO₂, no other clinical interventions were performed
Criticisms & Further Discussion
- No continuous waveform data recorded; data points logged every 30 seconds
- Sampling bias possible: higher than expected rate of respiratory events (33% vs. anticipated 15%)—may reflect sicker patients or deeper sedation
- Some abnormal ETCO₂ findings were transient and not clinically significant
- Study terminated early for ethical and safety reasons—planned for 250 patients but stopped after 60
Funding
Medtronic Emergency Response Systems loaned the LIFEPAK 12 monitors for the study