Pattern of autoresuscitation in spontaneously breathing anesthetized adult rats

Exposure to an acute bout of severe hypoxia in Mammals results in a stereotyped respiratory response, comprising an initial brief hyperventilation, followed by respiratory arrest. Eupnea can be rescued by an endogenous process termed “autoresuscitation”, whereby gasping breaths are generated in an attempt to reoxygenate the animal, and if successful a normal breathing is restored. In examining the respiratory response during autoresuscitations from anoxic anoxia in 20 intact, spontaneously breathing, anesthetized, tracheostomized, adult male rats, we documented a pattern that is unique from that previously described in neonatal or adult animals. Resuscitating breaths did not occur as low frequency or sporadic ‘gasps’, but rather typically arose in one or more discrete groups of breaths that formed an augmenting pattern.The number of groups of resuscitating breaths ranged from 1 to 4 (avg = 1.6 ± 0.7), with the total number of resuscitating breaths varying between 2 and 18 (avg = 7.1 ± 4.3) before eupneic breathing was restored. The tidal volume of resuscitating breaths was extremely variable even within a single group of resuscitating breaths, ranging from barely detectable, to 13 mL. This pattern of autoresuscitation as documented in the 20 animals studied all led to a total of 80 successful restorations of eupneic breathing (4/4 attempts per animal). Our observations demonstrate that successful autoresuscitation from anoxia‐induced respiratory arrest in adult rats does not follow a pattern described previously in literature, and employs resuscitating breaths different from the classical description of gasps.