EBQ:End-Tidal CO2 Monitoring

incomplete Journal Club Article

Burton J. et al.. "Does end-tidal carbon dioxide monitoring detect respiratory events prior to current sedation monitoring practices?". Acad Emerg Med. 2006. 13(5):500-4.
PubMed Full text PDF

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