Introduction
The best way to manage the airway during cardiac arrest, has remained somewhat of a mystery. We don’t know how much tidal volume to give, were not sure of what percentage FiO2 to deliver and were not sure of what rate to bag at.
What we assume we know:
- Increased minute ventilations delivered by either increasing the volume of each breath and/or increasing the frequency of breaths, results in over-inflation of the thoracic cavity. Animal studies have shown that this decreases venous return to the heart, decreasing coronary perfusion pressure and resulting in decreased cardiac output(1-3).
- Guidelines recommend approximately 500-600ml breaths during CPR, however these volumes that we tend to use in mechanical ventilation and they are not based on any real evidence for resuscitation.
- Studies have not shown a clear association between ventilation rate and ROSC. (4-7)
- Hyperventilation can cause cerebral vasoconstriction (8-11)
- Hypoventilation and inadequate oxygen concentrations can cause hypoxia and result in acidosis.
- Aggressive forced rapid delivery of breaths can result in significant insufflation of the stomach
- Current resuscitation guidelines ( based mostly on expert opinion (12-13)), recommend 10 ventilations per minute with a tidal volume of 500-600ml.
