High-Flow Nasal Oxygen is Safer Than Low-Flow for Sedated Endoscopy
High-flow nasal oxygen (HFNO) significantly reduces hypoxemia during sedated endoscopy compared to conventional low-flow oxygen delivery and should be the preferred oxygenation method for these procedures. The evidence demonstrates a dramatic reduction in desaturation events—from 33.5% with standard oxygen to 9.4% with HFNO in at-risk patients 1, and from 8.4% to 0% in routine gastroscopy patients 2.
Primary Evidence Supporting HFNO
The most compelling recent evidence comes from high-quality randomized controlled trials:
The 2021 ODEPHI trial enrolled 379 at-risk patients (age >60, cardiac/respiratory disease, ASA >1, obesity, or sleep apnea) undergoing GI endoscopy under deep sedation. HFNO (70 L/min, FiO2 0.50) reduced SpO2 ≤92% events by an absolute 23.4% compared to standard oxygen (6 L/min via nasal cannula/mask), with prolonged desaturation reduced from 14.9% to 7.3% 1.
The 2019 multicenter trial of 1,994 patients undergoing gastroscopy with propofol sedation demonstrated HFNO (30-60 L/min) completely eliminated hypoxemia (75% ≤ SpO2 < 90%) compared to 8.4% incidence with standard nasal cannula at 2 L/min, and eliminated severe hypoxemia (0.6% to 0%) 2.
The 2024 elderly patient trial showed HFNO (60 L/min, FiO2 0.6) reduced hypoxemia from 22.6% to 3.2% in patients ≥65 years, with higher minimum SpO2 values and shorter recovery times 3.
Guideline Recommendations and Context
Current guidelines provide important context but were written before the strongest HFNO evidence emerged:
The 2017 BTS guidelines recommend oxygen delivery at ≥2 L/min via nasal cannulae during endoscopy to maintain SpO2 >90%, but emphasize oxygen should only be given to correct hypoxemia, not routinely, particularly in patients at risk of hypercapnia 4.
The 2007 AGA guidelines note that while supplemental oxygen reduces desaturation magnitude, there is "little evidence that this practice reduces significant cardiopulmonary complications" and warn that oxygen may delay recognition of apnea and respiratory failure 4.
The 2020 Difficult Airway Society guidelines recommend HFNO as the technique of choice for procedural oxygenation when available, noting reported desaturation rates of 12-16% with low-flow oxygen versus 0-1.5% with HFNO 4.
Physiological Advantages of HFNO
HFNO provides multiple mechanisms that explain its superior safety profile:
- Delivers warm, humidified oxygen at flows up to 60-70 L/min, exceeding patient inspiratory flow rates 5, 6
- Provides modest positive end-expiratory pressure (PEEP effect) 5, 6
- Reduces anatomical dead space through washout effect 5, 6
- Improves pulmonary compliance and reduces work of breathing 5
- Maintains better patient comfort compared to masks 4, 5
Meta-Analysis Confirmation
A 2023 systematic review and meta-analysis of 3,294 patients confirmed HFNO's superiority:
- 77% reduction in desaturation events (OR 0.23) 7
- 89% reduction in procedural interruptions (OR 0.11) 7
- Higher nadir SpO2 levels during procedures (mean difference 3.16%) 7
- 37% reduction in overall sedation-related adverse events (OR 0.63) 7
Critical Implementation Points
For standard-risk patients undergoing routine endoscopy:
For high-risk patients (elderly, obese, cardiopulmonary disease, ASA >1):
For patients at risk of hypercapnia (COPD, chronic CO2 retention):
- Exercise caution with any supplemental oxygen 4
- Target lower SpO2 88-92% 4
- Consider transcutaneous CO2 monitoring 4
- The concern about oxygen masking respiratory failure applies to both low-flow and HFNO 4
Common Pitfalls to Avoid
Do not rely on low-flow oxygen in high-risk patients. The evidence clearly shows unacceptable desaturation rates of 22-33% with conventional oxygen in at-risk populations 1, 3.
Do not assume oxygen prevents complications without monitoring. Continuous pulse oximetry is mandatory regardless of oxygen delivery method 4. Oxygen may delay recognition of hypoventilation, so clinical assessment and consideration of capnography remain essential 4.
Do not use HFNO as a substitute for airway management. If significant desaturation occurs despite HFNO, escalate to airway interventions rather than simply increasing oxygen flow 4.
Minimal adverse events with HFNO. The only HFNO-specific adverse event reported was mild nasal dryness/discomfort in 1.7% of patients, which resolved within 30 minutes 2.
Equipment and Training Considerations
While HFNO requires additional equipment compared to standard nasal cannulae, the dramatic reduction in hypoxemic events (from 8-33% down to 0-9%) justifies the investment 1, 2, 3. The cost-effectiveness is enhanced by reduced procedural complications and interruptions 5.