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Patient factors that can affect efficacy and efficiency of preoxygenation

Patient factors that can affect efficacy and efficiency of preoxygenation
Patient factor Effect on preoxygenation
Efficacy* Efficiency
Obesity:
  • Reduced FRC
  • Atelectasis
  • Tidal volume may fall within closing capacity
↓ ↓
Pregnancy:
  • Reduced FRC
  • Atelectasis
  • Increased oxygen consumption
↓ ↓
Very young age:
  • Reduced FRC
  • Increased oxygen consumption
Faster preoxygenation ↓↓Δ
Older adults:
  • Reduced oxygen consumption
  • Reduced lung function
Slower, less effective preoxygenation ↓
Critically ill; varies:
  • Increased oxygen consumption
  • Anemia
  • Acidemia
  • Cardiopulmonary disease
Slower, less effective preoxygenation ↓↓
FRC: functional residual capacity.
* Efficacy refers to achieving end tidal oxygen >90%.
¶ Efficiency refers to prolongation of safe apnea time (ie, time during apnea until oxygen saturation falls to 90%).
Δ Children desaturate faster than adults during apnea; the younger the child the more rapidly he/she desaturates.
Graphic 120162 Version 1.0