Arousal response from sleep to tracheal obstruction in lambs during postnatal maturation

Experiments were carried out to investigate the arousal response from sleep to tracheal obstruction in lambs during postnatal maturation. Ten fetal sheep were instrumented with electrodes for sleep staging and a tracheotomy was done. After spontaneous vaginal delivery, serial experiments were carried out on the lambs at five postnatal ages: 18-48 h and 4, 6, 11, and 18 d. During an experiment, a 5F balloon-tipped catheter was inserted into the tracheostomy tube so that tracheal obstruction could be produced by inflating the balloon. Measurements were made in quiet sleep and active sleep during control periods of tidal respiration and during experimental periods of tracheal obstruction. Neither sleep state nor age influenced control arterial Hb oxygen saturation (SaO2). SaO2 decreased significantly before arousal during tracheal obstruction in quiet sleep at 18-48 h and in active sleep at all ages. The SaO2 at arousal was always lower in active sleep than in quiet sleep. Overall, however, there were no significant effects of age on the change in SaO2 before arousal in either quiet sleep or active sleep. The time to arousal during tracheal obstruction increased between 18-48 h and 6 d of postnatal life in active sleep but not in quite sleep. Our data provide evidence that the arousal response to tracheal obstruction is functional by 18 h of postnatal life in lambs. The increase in time to arousal after tracheal obstruction in active sleep most likely results from state-specific changes in the factors governing oxygen supply and demand.