Preoxygenation Techniques for Critically Ill Patients
Standard Preoxygenation Technique
- Position all patients with head elevation of 25-30° before starting preoxygenation to increase functional residual capacity and extend safe apnea time by approximately 30% 1, 4, 5
- Use tight-fitting face mask with 100% oxygen at 10-15 L/min for 3 minutes to achieve end-tidal oxygen concentration >90% 5
- Ensure mask seal is adequate, as absence of capnograph trace indicates significant leak 5
- Achieve end-tidal oxygen concentration (FeO₂) >90% as the accepted standard for effective preoxygenation 1, 2, 3
Alternative Techniques Based on Clinical Scenario
- For hypoxemic patients, use non-invasive positive pressure ventilation (NIPPV) with CPAP 5-10 cmH₂O and pressure support to decrease critical desaturation during RSI 5, 6, 7
- High-flow nasal oxygen (HFNO) is an acceptable alternative, but evidence shows it may be slightly inferior to NIPPV for preventing desaturation 6, 7
- For agitated/uncooperative patients, use medication-assisted preoxygenation (delayed sequence intubation) with ketamine to achieve dissociative state and allow patient to tolerate face mask, NIPPV, or HFNO 8, 6, 7
- For obstetric emergencies, shorten preoxygenation time to 2 minutes due to decreased FRC, and consider NIV with PEEP to achieve FeO₂ >90% more rapidly 1, 4
Techniques to Avoid
- Do not use vital capacity maneuvers, as they are inferior to 3-minute spontaneous ventilation 1, 4
- Avoid positive pressure ventilation in normoxemic patients, as it is associated with lower intubation success and increased aspiration risk
Critical Pitfalls to Avoid
- Failure to position patient head-up is the most common error, which extends safe apnea time by 30% 1, 4
- Inadequate mask seal negates preoxygenation efforts, so check for capnograph waveform 5
- Preoxygenating flat supine in obese patients reduces tolerance to apnea to as little as 2.5 minutes 1, 4