Assessing the utility of bradypnea and hypoventilation as predictors of hypoxemia during procedural sedation

Abstract

Background: Procedural sedation and analgesia (PSA) is commonly performed in emergency departments (EDs) but is associated with respiratory complications such as hypoventilation and hypoxemia. Capnography is effective in detecting respiratory depression, however, it remains unclear that how reliably hypoventilation and bradypnea can predict hypoxemia in the Japanese ED setting. We aimed to describe the frequency of hypoventilation and bradypnea events preceding hypoxia and the time lag between these episodes.

Methods: This study was a prospective observational study at two Japanese EDs from July to October 2021, and was a sub-analysis of the Japanese Procedural Sedation and Analgesia Registry with additional physiologic monitoring data. Second-by-second time-stamped physiologic data were extracted using a dedicated viewer system.

Results: We included 13 patients with a median age of 62 years (IQR 49-75). Sedative agents included propofol (n=5), midazolam (n=4), and thiopental (n=4). Hypoxemia occurred in six of 13 patients (46.2%). All patients experienced bradypnea prior to hypoxemia, with a median time lag of 93 seconds (IQR 42.5-106). Hypoventilation was observed in only one patient (7.7%), who also experienced hypoxemia.

Conclusions: Hypoxemia occurred in almost half of patients but hypoventilation occurred only one patient. Bradypnea consistently preceded hypoxemia and may serve as a more sensitive early warning sign. Respiratory monitoring during PSA should focus on respiratory rate rather than end-tidal CO₂ values, to enhance early detection of respiratory failure and patient safety in the ED settings.