PREOXYGENATION: COULD SAFETY MEASURE BE MADE LESS DANGEROUS?

Area of Science:

• Anesthesiology
• Respiratory Physiology
• Critical Care Medicine

Background:

• Preoxygenation with 100% oxygen can cause absorption atelectasis, increasing pulmonary complication risks.
• Optimizing preoxygenation strategies is crucial for patient safety during anesthesia.

Purpose of the Study:

• To evaluate the impact of decreased fraction of inspired oxygen (FiO₂) during preoxygenation on safe apnea time.
• To assess the feasibility of preventing atelectasis using reduced FiO₂.
• To identify predictors for difficult facemask ventilation.

Main Methods:

• Randomized controlled trial in elective surgery patients comparing preoxygenation with FiO₂ 100%, 70%, 60%, 60% + PEEP 5 mbar, and 50%.
• Measurement of safe apnea time (time to SpO₂ 95%) and SpO₂ fall patterns.
• Development and validation of a prognostic model for difficult facemask ventilation using bedside tests.

Main Results:

• FiO₂ 70% reduced safe apnea time by half; FiO₂ 50% reduced it by over threefold.
• Rapid SpO₂ desaturation (to 90% in <1 min) was observed with FiO₂ 70%, contrasting with FiO₂ 100% (200s).
• A prognostic model for difficult facemask ventilation demonstrated 97.5% reliability for negative prognosis.

Conclusions:

• Preoxygenation with reduced FiO₂ (50-60%) may prevent absorption atelectasis.
• This strategy is potentially safe only in patients with a reliable prognosis for easy facemask ventilation.
• Careful patient selection is paramount when using lower FiO₂ during preoxygenation to mitigate risks associated with difficult airway management.