From the Guidelines
Safe apnea time is approximately 8 minutes after pre-oxygenation with 100% oxygen for a healthy adult with normal lung function, as evidenced by the most recent and highest quality study 1.
Factors Affecting Safe Apnea Time
The safe apnea time varies significantly based on individual factors, including:
- Obesity: shorter safe apnea times, often only 2-5 minutes 1
- Pregnancy: shorter safe apnea times, especially during labor 1
- Respiratory diseases: shorter safe apnea times 1
- Critical illness, anemia, and increased oxygen consumption: further reduction of the safe apnea time window 1
Pre-oxygenation and Safe Apnea Time
Pre-oxygenation before procedures extends safe apnea time by replacing nitrogen in the lungs with oxygen, creating an oxygen reservoir 1.
Clinical Recommendations
Clinicians should always anticipate a shorter safe apnea time than theoretically calculated, especially in high-risk patients, and have backup airway plans ready during procedures requiring apnea, such as intubation or bronchoscopy 1.
Additional Considerations
High-flow nasal oxygen and apneic oxygenation techniques can also prolong the safe apnea time, especially in patients at risk of rapid arterial desaturation 1. The position of the patient during pre-oxygenation, such as a proclive position, can also impact the safe apnea time, with studies showing a benefit in obese patients and potentially in the general population 1.
From the Research
Definition of Safe Apnea Time
- Safe apnea time refers to the duration of time a patient can safely remain apneic (without breathing) before oxygen saturation levels drop to a critically low level, typically defined as 95% or lower [ 2 ].
- This concept is crucial in anesthesia and critical care, as it helps clinicians determine how long a patient can safely remain without ventilation during procedures like intubation.
Factors Influencing Safe Apnea Time
- Age, body weight, and height can influence safe apnea time, with younger children and those with lower body mass indexes being more susceptible to rapid oxygen desaturation [ 3 ].
- Preoxygenation techniques, such as high-flow nasal oxygenation, can significantly prolong safe apnea time in patients, including those with morbid obesity [ 2 ].
- The use of transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) has also been shown to provide effective preoxygenation and apneic oxygenation, minimizing the risk of hypoxia during emergency intubation [ 4 ].
Clinical Applications and Considerations
- In patients with obstructive sleep apnea, oxygen supplementation can be an effective treatment option for correcting nocturnal hypoxemia, especially for those who are not candidates for CPAP or surgical correction [ 5 ].
- High-flow nasal insufflation of oxygen (HFNI) has been compared to standard flow oxygen insufflation for apneic oxygenation in morbidly obese patients, with some studies finding no significant difference in the duration of safe apnea between the two methods [ 6 ].