EBQ:ED Preoxygenation

Under Review Journal Club Article

Weingart, S. et al. "Preoxygenation and Prevention of Desaturation During Emergency Airway Management". Annals of Emergency Medicine. 2012. 59(=3):165-75.
PubMed PDF

Clinical Question

Reviews preoxygenation and peri-intubation oxygenation techniques to minimize the risk of critical hypoxia and introduces a risk-stratification approach to emergency tracheal intubation.

Major Points

• Prior to intubation, physicians should aim to achieve an 02 saturation of 100%
• Increasing oxygen storage requires denitrogenation of the residual capacity of the lungs
• Preoxygenation can extend the duration of time until a patient reaches O₂ saturation of 88-90%. This is know as the “safe apnea” period.

• Desaturation after Paralysis with succinylcholine in adults (<90% O₂ saturation)
  • 8.7 min in healthy patient (70kg)
  • 5.5 minutes in moderately ill patient
  • 3.7 minutes in healthy child (10kg)
  • 3.1minutes in obese patient. (127kg)

Design

This was a review of methods and approaches to preparing for intubation of patients with varying levels of risk of hypoxia from critical care, emergency medicine, and anesthesia literature.

Conclusion

• Preoxygenation and apneic oxygenation are crucial in emergency airway management especially prior to rapid sequence intubation in order to prevent desaturation and prolong the time to desaturation, known as the safe apenic period.
• Since standard BVMs cannot deliver PEEP, in patients with shunt physiology (i.e. pneumonia, pulmonary edema) a PEEP valve attached to the BVM or non-invavisve positive pressure ventilation (i.e. CPAP,BIPAP) should be utilized

Preoxygenation Times:

1. 3 minutes of tidal volume breathing with a high FiO2 source (15L nasal cannula + 100% non rebreather on patient at the same time)

OR

1. 8 vital capacity breaths (maximal inhalation and maximal exhalation) with a high FiO2 source

Oxygen Sources for Preoxygenation:

1. Standard nonrebreather at 15L/minute will deliver 60 – 70% FiO2
2. The FiO₂ can be increased to ≥90% with flow rates > 30L/min

OR

1. Consider adding a nasal cannula increased >10L/min or as tolerated by patient along with nonrebreather mask

• Positive pressure ventilation should be given to patients unable to achieve oxygen saturations of >93 – 95% with 3 minutes of high FiO₂
• Positive pressure ventilation should be given to patients already apneic due to respiratory failure

====Patient Positioning

Review Questions

1 What do they recommend while awaiting the onset of muscle relaxation for a patient who is hypoxemic (<90% SpO2)?

	NRB and nasal oxygen at 15L/min
	NRB, CPAP or BVM with peep and nasal oxygen at 15L/min
	CPAP or BVM with peep and nasal oxygen at 15L/min

2 What is the recommendation for passive oxygenation in low risk (>96% or above SpO2) intubation patients?

	It is always indicated
	It may not be necessary but could extend safe apnea in the event of repeated intubation attempts.
	It could increase the risk of adverse events due to complications from equipment confusion