Partial airway occlusion during sleep and waking in the dog

Airflow was impeded for four consecutive hours in nine adult dogs in order to ascertain whether the sleeping pattern would be altered and whether the respiratory responses would differ according to the stage of sleep or waking. Partial airway occlusion (PAO) was induced by reducing the diameter of a tracheostomy tube by an average of 58% (i.e. to a final airway diameter of ca 3mm). This had the effect, during sleep, of significantly decreasing the respiratory rate by 21%, decreasing the minute volume by 31% and increasing PACO2 by 5 Torr (0.67 kPa) as compared to sleep in which respiration was unimpeded. There appeared to be no difference between REM sleep and Non-REM sleep in terms of the respiratory responses to the imposed stress. In the case of the waking state, the PAO did not elicit any statistically significant alteration of the respiratory parameters although there was a suggestion that the direction of change for each parameter was the same as in sleep. While respiration during sleep was unquestionably affected when the dogs were required to breathe through a plug with a very narrow opening, the gross sleep pattern remained unchanged.