Transcutaneous gas monitoring is a useful tool to detect respiratory depression during bronchoscopy performed under propofol sedation

Background: Bronchoscopy is a relatively invasive procedure where patients are often sedated. However, adequate sedation is not always achieved. Propofol is often used for difficult-to-sedate patients undergoing bronchoscopy despite a potential risk of respiratory depression. Transcutaneous carbon dioxide (tcpCO₂) monitoring, introduced recently, is recognized as a convenient surrogate method for continuous monitoring of the partial pressure of arterial carbon dioxide (PaCO₂). This study examined the safety of switching to propofol during bronchoscopy by using transcutaneous carbon dioxide monitoring.

Methods: Patients in whom transcutaneous gas monitoring had been performed during bronchoscopy were included in this study. The participants were divided into two groups: 1) the midazolam + fentanyl group (MF group), and 2) the group in which midazolam was switched to propofol owing to inadequate sedation obtained with midazolam + fentanyl (MFP group). We retrospectively analyzed the transcutaneous gas measurement data collected in patients under propofol sedation for bronchoscopy.

Results: This study included 61 (MF, n = 41; MFP, n = 20) patients. The duration of elevated tcpCO₂ (>50 mm Hg) was greater in the MFP group (MF 8.5 min vs. MFP 22.1 min, p = 0.042).

Conclusion: Switching midazolam to propofol during bronchoscopy was significantly associated with a higher risk of elevated tcpCO₂, which is indicative of respiratory depression. Therefore, continuous tcpCO₂ monitoring is required to ensure the safety of patients under propofol sedation for bronchoscopy.