# Efficiency of 80% vs. 100% Oxygen for Preoxygenation: A Randomized Study on Duration of Apnoea Without Desaturation

## TL;DR

This study compares using 80% versus 100% oxygen for preoxygenation before surgery, finding that 80% oxygen may be feasible but with a shorter time before oxygen levels drop.

## Contribution

The study evaluates the clinical feasibility of using 80% oxygen for preoxygenation as an alternative to 100% oxygen.

## Key findings

- DAWD was numerically shorter with 80% oxygen (345 s) compared to 100% oxygen (430 s), though not statistically significant.
- No significant differences were found in time to adequate preoxygenation or additional warning time from ORi™.
- The study suggests 80% oxygen may be feasible but highlights the need for larger trials to confirm safety and clinical relevance.

## Abstract

Background/Objectives: Preoxygenation with 100% oxygen is commonly used but poses risks such as hyperoxia and atelectasis. Using 80% oxygen may reduce these effects but shortens duration of apnoea without desaturation (DAWD). This study compared preoxygenation efficiency between 80% and 100% oxygen and evaluated changes in the Oxygen Reserve Index™ (ORi™). Methods: Patients undergoing elective laparoscopic cholecystectomy were randomized to preoxygenation with 80% or 100% oxygen. Adequate preoxygenation was defined as a ≤10% difference between fraction of inspired oxygen and end-tidal oxygen (EtCO2). The primary outcome was DAWD, the interval from apnoea onset to peripheral oxygen saturation (SpO2) of 93%. Secondary outcomes included time to adequate preoxygenation and additional warning time from ORi™ zero to SpO2 97%. Results: Thirty patients were randomised to 80% (n = 15) or 100% oxygen (n = 15) oxygen groups. One patient in the 100% group was excluded due to spontaneous breathing before SpO2 93%, leaving 29 for DAWD analysis. DAWD was 345 ± 136 s (80%) and 430 ± 163 s (100%) with a mean difference of 86 s (p = 0.135). No significant differences were observed in tie to adequate preoxygenation or additional warning time. Conclusions: Preoxygenation with 80% oxygen resulted in a numerically shorter DAWD compared with 100% oxygen, without a significant difference in ORi™. These findings may suggest the potential feasibility of using 80% oxygen for preoxygenation. However, given the limited sample size and uncertain clinical relevance, further large-scale studies are warranted to clarify the safety and clinical implications of lower oxygen concentration during anaesthesia induction.