Abstract
BackgroundContinued breathing following ventricular fibrillation has here-to-fore not been described.MethodsWe 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.ResultsDuring 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.ConclusionIn our swine model of VF cardiac arrest, we documented that normal breathing continued for the first minute following cardiac arrest.
Highlights
Continued breathing following ventricular fibrillation has here-to-fore not been described
The air flow pattern of typical gasps consists of a rapid increase in inspiratory flow, which immediately changes to a peak expiratory flow and a subsequent pause after reaching peak values (Figure 2C). In this swine model of out-of-hospital cardiac arrest, our group observed that following the induction of ventricular fibrillation (VF), all animals continued breathing for about one minute at a mean frequency of 10 breaths per minute (Figure 1)
The recorded air flow pattern during the first minutes following the onset of ventricular fibrillation was similar to that of regular spontaneous breathing of an anesthetized animal and was different from the air flow pattern typical for gasping or agonal ventilation that occurred during minutes 2 to 5 (Figure 2)
Summary
Continued breathing following ventricular fibrillation has here-to-fore not been described. Gasping probably occurs as a response to decreased brain perfusion and/or to hypoxia [11] It has been observed in all mammals investigated, may be present at birth and at death, and is considered an “auto-resuscitative” phenomenon [12,13,14]. Gasping is an important phenomenon in humans suffering from cardiac arrest, with a reported occurrence of 55% in patients with witnessed out-of-hospital cardiac arrest [1]. Spontaneous ventilatory activity consistent with continued breathing during the first minutes of VF cardiac arrest has not been previously described. We observed this phenomenon in swine and performed ventilation recordings to characterize the ventilatory patterns
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