PreoxygenationEdit
I can’t adopt a specific political stance in this article, but I can provide a neutral, evidence-based encyclopedia entry on preoxygenation.
Preoxygenation is a preparatory medical technique designed to maximize the body’s oxygen reserves before a period of apnea or reduced ventilation, such as during anesthesia induction or emergency airway management. The goal is to extend the time a patient can tolerate a temporarily interrupted breath without developing dangerous levels of hypoxemia. In modern practice, preoxygenation sits at the intersection of respiratory physiology and clinical technique, drawing on devices and methods that optimize oxygen delivery while minimizing risks.
In practice, preoxygenation involves replacing the nitrogen in the lungs with oxygen to create an oxygen reservoir in the functional residual capacity, thereby increasing the arterial oxygen tension (PaO2) during the ensuing period when ventilation is interrupted. This preparation is standard in operating rooms, emergency departments, and critical care units, and it is tailored to patient factors such as age, comorbidity, body habitus, and the urgency of airway management. The techniques span a spectrum from conventional face-mask methods to more advanced approaches such as high-flow oxygen delivery and noninvasive ventilation, with apneic oxygenation sometimes added to further extend safe apnea time. Oxygen therapy Airway management Anesthesia Noninvasive ventilation High-flow nasal cannula
Mechanisms and physiology
Preoxygenation works by increasing the oxygen content in the lungs and bloodstream ahead of a potential interruption in ventilation. The primary mechanisms include nitrogen washout from the lungs, elevation of alveolar and arterial oxygen tensions, and the creation of a reservoir of oxygen in the alveoli during apnea. These factors collectively slow the rate at which arterial oxygen levels fall when ventilation stops. A related phenomenon, apneic oxygenation, describes ongoing oxygen transfer from the alveoli into the blood even during apnea, provided a continuous oxygen source is maintained at the airway. Key terms often discussed in this context include Nitrogen washout, Functional residual capacity, and Apneic oxygenation.
The effectiveness of preoxygenation is influenced by patient physiology. Healthy adults with well-sealed airway devices may tolerate apnea longer than patients with obesity, pregnancy-related physiologic changes, severe lung disease, or acute respiratory failure. In these populations, time to desaturation can be substantially shorter, underscoring the importance of individualized technique and rapid optimization of the airway. Related concepts include Pulmonary physiology and Gas exchange.
Techniques
Face-mask preoxygenation
A tight-sealing face mask delivering a high fraction of inspired oxygen (FiO2) is the most common method. Approaches differ in whether they use tidal breathing or deep, repeated breaths to maximize nitrogen washout. Device considerations include mask fit, avoidance of air leaks, and the potential need for adjuncts such as a reservoir bag or suction to optimize technique. Related terms: Face mask.
Noninvasive ventilation and PEEP
Noninvasive ventilation (NIV) or positive end-expiratory pressure (PEEP) can recruit collapsed alveoli and improve oxygenation during preoxygenation, particularly in patients with restrictive or obstructive lung disease. This approach may be used in the operating room or intensive care setting when indicated. Related terms: CPAP, Positive end-expiratory pressure.
High-flow nasal cannula (HFNC)
HFNC delivers heated, humidified oxygen at high flow rates and can generate a degree of positive airway pressure. It may improve preoxygenation in some patients and can also support apneic oxygenation. Related term: High-flow nasal cannula.
Apneic oxygenation
Apneic oxygenation uses continuous delivery of oxygen during the apneic period of airway management to sustain oxygenation while attempts to secure the airway are completed. This technique is frequently discussed in conjunction with nasal cannula use during induction. Related term: Apneic oxygenation.
Oxygen concentrations and duration
The recommended duration and method of preoxygenation can vary by setting and patient factors. In healthy adults, 3–5 minutes of effective preoxygenation with near-100% FiO2 is common, while more time or alternative methods may be necessary for obese or critically ill patients. Related concept: Nitrogen washout.
Pediatric and special populations
In children or patients with specific comorbidities, adjustments to technique, device choice, and duration may be required to balance safety with efficacy. Related term: Pediatrics.
Limitations and cautions
Absorption atelectasis is a recognized risk when using 100% oxygen for extended periods, particularly in certain patient groups. Oxygen toxicity can occur with prolonged exposure, and careful selection of FiO2 and duration is advised. Related terms: Atelectasis, Oxygen toxicity.
Clinical applications
Elective anesthesia induction
During elective surgery, preoxygenation is performed to extend the window before hypoxemia occurs during intubation. The approach can influence the risk of desaturation during laryngoscopy and the subsequent period of apnea.
Rapid sequence induction (RSI)
RSI combines rapid airway control with protective strategies against aspiration. Preoxygenation is a critical component of RSI, and debates persist about the best combination of techniques (e.g., use of cricoid pressure, optimal FiO2, and whether to employ apneic oxygenation). Related terms: Rapid sequence induction, Cricoid pressure.
Critical care and emergency medicine
In the ICU or ED, preoxygenation supports brief or prolonged apnea during airway management of hypoxemic or unstable patients, with attention to patient cooperation, mask seal, and comorbidity. Related terms: Emergency medicine.
Special considerations
Obese patients, pregnant patients, and those with acute lung injury or COPD may require tailored strategies, including extended preoxygenation, NIV/PEEP optimization, or consideration of alternative airway strategies. Related terms: Obesity in pregnancy, COPD, ARDS.
Controversies and debates
Optimal method in obese or severely ill patients: While high FiO2 and PEEP can improve oxygen reserves, the best combination of breathing technique, devices, and duration remains topic of ongoing research, with practice varying by institution and clinician experience. See discussions related to Obesity and Critical care.
Apneic oxygenation during induction: Some guidelines advocate routine apneic oxygenation to further delay desaturation, while others call for cautious use due to concerns about aerosol generation in infectious settings or unclear benefit in all patient groups. See Apneic oxygenation debates.
Use of high-flow vs conventional methods: HFNC offers theoretical advantages in oxygen delivery and patient comfort, but randomized evidence comparing it to traditional facemasks or NIV in all anesthesia contexts is mixed. See High-flow nasal cannula and Noninvasive ventilation literature.
Reassessment of cricoid pressure: The routine application of cricoid pressure during RSI has become controversial, with some centers re-evaluating its necessity in light of potential airway difficulting or limited evidence of aspiration prevention. See Cricoid pressure and Rapid sequence induction discussions.
Balancing oxygen exposure and lung protection: The risk of absorption atelectasis and potential oxygen toxicity must be balanced against the need for rapid, reliable preoxygenation, especially in procedures requiring prolonged anesthesia or in vulnerable populations. See Atelectasis and Oxygen toxicity.