The Trouble With Ventilation

Every time a breath is given to the patient, the intra-thoracic pressure in the chest increases. This increase in intra-thoracic pressure halts the return flow of blood to the heart. For this reason, even if a patient is intubated in the resuscitation bay in an ED, one breath every ten to 20 seconds would be more than adequate to support life until return of spontaneous circulation.

Breaths every two to five seconds are DETRIMENTAL to patients who do not have spontaneous circulation. One breath every two seconds means there is positive pressure in the chest (and no return blood) half the time CPR is being performed! Providing ventilations requires a calm provider who is consciously providing breaths to the patient MUCH less often than with any other type of patient.

It is also imperative that rescue breaths are given during the recoil phase of chest compressions so the person providing oxygen is not working against the person performing chest compressions.

Interesting side-note: In the hospital setting, some physicians attach a ventilator to the bag-valve mask and set the machine to deliver one breath every 15 seconds, eliminating the human temptation to over-breathe during CPR.  Over-ventilating a patient is enough to negate all your hard work in CPR, but it's easy to prevent if you keep it in mind.