Analysis of the phrenic neurogram during hypoxia and recovery in the piglet

We investigate the patterns of the phrenic neurogram during severe hypoxia and recovery from hypoxia in the piglet. We have used the matching pursuit (MP) method to examine the effects of maturation on breathing patterns in both time and frequency domains. The phrenic neurogram in piglets was recorded during eupnea (normal breathing), severe hypoxia and recovery from hypoxia in 8 piglets (3-35 days). During the first 6 days of postnatal age, most circular structured components, representing the burst type breathing activities, were present during eupnea, hypoxia and recovery from hypoxia. But the hypoxia significantly reduced the duration of the phrenic neurogram. The duration was restored after 10 min post recovery. However as maturation proceeds, both continuous and burst type neural activities were present at the late phase of the phrenic neurogram during eupnea. Similarly, during hypoxia, the duration of phrenic neurograms was smaller than those of eupnea, and breathing patterns consisted of circular structured components. The reoxygenation restored the continuous structured components at both early and late phases of phrenic neurogram after 20-30 min post reoxygenation.