We analyzed the spontaneous ventilatory activity during the first several minutes of ventricular fibrillation (VF) in our isoflurane anesthesized swine model of out-of-hospital cardiac arrest. The frequency and type of ventilatory activity was monitored by pneumotachometer and main stream infrared capnometer and analyzed in 61 swine during the first 3 to 6 minutes of untreated VF.
During the first minute of VF, the air flow pattern in all 61 swine was similar to those recorded during regular spontaneous breathing during anesthesia and was clearly different from the patterns of gasping. The average rate of continued breathing during the first minute of untreated VF was 10 breaths per minute. During the second minute of untreated VF, spontaneous breathing activity either stopped or became typical of gasping. During minutes 2 to 5 of untreated VF, most animals exhibited very slow spontaneous ventilatory activity with a pattern typical of gasping; and the pattern of gasping was crescendo-decrescendo, as has been previously reported. In the absence of therapy, all ventilatory activity stopped 6 minutes after VF cardiac arrest.
The significance of this observation is as follows:
If you find someone “down” don't be too quick to dismiss cardiac arrest just because they appear to be “breathing.”
This observation provides yet another explanation for why, in primary cardiac arrest, compression only CPR, as well as delayed intubation, is associated with better outcomes.
At this meeting (which I will be blogging about in more detail soon) Ewy made the anecdotal observation that in human resuscitation good compressions, good enough to at least perfuse the medula oblongata, may prolong the duration of spontaneous gasping.