# Oxygen reserve index monitoring reduced the incidence of low pulse oxygen saturation during deep sedation for hysteroscopy: a prospective randomized controlled trial

## TL;DR

Using oxygen reserve index monitoring during hysteroscopy sedation significantly reduced the risk of low oxygen levels compared to standard methods.

## Contribution

This study shows that ORI monitoring improves oxygenation outcomes during hysteroscopy under deep sedation.

## Key findings

- ORI monitoring reduced low SpO2 incidence by 41% compared to non-ORI groups.
- Nasopharyngeal airway caused more sore throat and airway injury than face mask.
- Assist ventilation duration was shorter in ORI monitoring groups.

## Abstract

Low pulse oxygen saturation (SpO2) during deep sedation for hysteroscopy was common, which was a barrier for sedation performance. This randomized controlled trial tested whether oxygen reserve index (ORI) monitoring could reduce the incidence of low SpO2 during deep sedation for hysteroscopy.

Based on whether ORI monitoring was adopted or not, and the oxygen supply methods during procedure [through face mask (FM) or nasopharyngeal airway (NPA)], four hundred participants underwent hysteroscopy under deep sedation were randomly divided into ORI+FM group, ORI+NPA group, non-ORI+FM group, and non-ORI+NPA group in a 1:1:1:1 ratio. Assist ventilation was performed when ORI dropped to zero in ORI monitoring groups, it was performed when SpO2 dropped to 98% in non-ORI monitoring groups. The incidence of low SpO2, which defined as SpO2 less than 95% during procedure, was compared.

Compared to non-ORI monitoring groups, the incidence of low SpO2 was lower (18% (95%CI: 0.103–0.257) and 21.4% (95%CI: 0.132–0.297) vs. 70.4% (95%CI: 0.612–0.796) and 51.5% (95%CI: 0.415–0.615), P < 0.001), average duration of assist ventilation (18 [0–35] and 15 [0–33] s vs. 36 [16–55] and 27 [0–53] s, P < 0.001) and time-weighted average duration of assist ventilation (0.016 [0–0.021] and 0.008 [0–0.016] vs. 0.022 [0.011–0.027] and 0.015 [0–0.025], P < 0.001) were shorter, the lowest SpO2 value during procedure was higher (98 [96–99] and 97 [96–99] vs. 93 [91–97] and 94 [92–99], P < 0.001) in ORI monitoring groups (data ordered as ORI+FM, ORI+NPA, non-ORI+FM, and non-ORI+NPA group). The absolute risk reduction between ORI monitoring groups and non-ORI monitoring groups was 0.41 (41%) (95%CI: 0.322–0.498), the NTT was 3. Compared to FM, NPA could induce mild to moderate sore throat and mild airway injury.

During deep sedation for hysteroscopy, ORI monitoring and the altered clinician behavior from it may related to the reducing of the incidence of low SpO2 and ensure oxygenation in low-to-moderate risk outpatients.

https://clinicaltrials.gov/search?term=NCT05701839, identifier NCT05701839.