What are the benefits and risks of using high flow oxygen in anesthesia?

Benefits and Risks of High Flow Oxygen in Anesthesia

High flow oxygen in anesthesia should be used selectively based on patient risk factors, with flow rates kept to a minimum necessary to maintain adequate oxygenation, as excessive use can lead to both respiratory complications and increased risk of aerosol generation. 1

Benefits of High Flow Oxygen

• High flow nasal oxygen (HFNO) can significantly prolong safe apnea time during intubation procedures, providing an extended window for securing the airway in difficult situations 1
• In morbidly obese patients, HFNO can increase safe apnea time by approximately 76 seconds (40%) compared to conventional oxygenation methods 2
• HFNO maintains higher minimum oxygen saturation levels during the peri-intubation period, reducing the risk of critical desaturation events 2
• HFNO can transform difficult airway management from a hurried, potentially traumatic procedure to a smoother event within an extended safe apnoeic window 1
• When used for apneic oxygenation, HFNO can prevent arterial oxygen desaturation in patients with anticipated difficult intubation, with studies showing a median apnea time of 14 minutes without SpO₂ dropping below 90% 1

Risks and Concerns

• High flow oxygen therapy can generate aerosols and exhaled air jets that may travel significant distances, with potential implications for infection control 1
  • Nasal cannula with 5 L/min flow can project exhaled air up to 1 meter caudally 1
  • Higher flows create greater dispersion distances, raising concerns during infectious disease outbreaks 1
• Excessive oxygen administration can lead to absorption atelectasis (lung collapse) and shunt, as oxygen is rapidly absorbed behind closed airways 3
• Atelectasis caused by high oxygen concentrations may become a focus for infection and potentially lead to post-operative pneumonia 3
• The use of 100% oxygen for pre-oxygenation consistently causes atelectasis and should be followed by recruitment maneuvers to re-expand collapsed alveoli 3
• High flow oxygen through nasal cannulae should be avoided when there is concern about aerosol generation and transmission of respiratory infections 1

Recommendations for Clinical Practice

• For pre-oxygenation in patients without anticipated difficult airways, consider using 80% oxygen rather than 100% to reduce atelectasis formation, though this reduces safe apnea time from approximately 7 to 5 minutes 3
• When high flow oxygen is necessary, implement the following precautions for infection control 1:
  • Keep oxygen flow to the minimum required to maintain arterial oxygen saturation
  • Preferably maintain flow rates below 5 L/min to reduce aerosolization risk
  • Consider placing a surgical facemask over oxygen delivery devices to limit droplet dispersion
• For patients at high risk of rapid desaturation (obese, critically ill), combining apneic oxygenation techniques with mandatory pre-oxygenation is recommended to prevent arterial oxygen desaturation 1
• In difficult airway scenarios, high flow nasal oxygen at 30-70 L/min can significantly extend safe apnea time compared to conventional face mask pre-oxygenation 1
• For morbidly obese patients, consider HFNO at 60 L/min during the apneic period after induction to maintain higher oxygen saturation levels 2

Special Considerations

• In patients with cervical spine injuries, high flow nasal oxygen should be used with caution, particularly in those with suspected or confirmed base of skull fractures due to risk of pneumocephalus 1
• For patients with COVID-19 or other respiratory infections, minimize oxygen flow rates to reduce aerosol generation while maintaining adequate saturation 1
• In pediatric anesthesia, there is growing recognition of the need to limit excessive oxygen use, with a trend toward titrating FiO₂ intraoperatively based on pulse oximetry values rather than using fixed high concentrations 4
• The goal of anesthetic management should be to deliver a patient with no atelectasis to the post-operative ward, which may require moderate use of oxygen combined with strategies to maintain functional residual capacity 3

Common Pitfalls to Avoid

• Assuming that higher oxygen concentrations are always better - unnecessary high FiO₂ can cause atelectasis and potential oxygen toxicity 3, 5
• Failing to perform recruitment maneuvers after pre-oxygenation with 100% oxygen, which is necessary to reverse atelectasis 3
• Using high flow nasal oxygen without considering the infection control implications in patients with respiratory infections 1
• Neglecting to titrate oxygen flow rates to the minimum required for adequate oxygenation 1
• Overlooking the potential for pneumocephalus when using HFNO in patients with base of skull fractures 1