Breathing during sleep and wakefulness in the cat

Abstract

Adult cats were equipped with standard electrodes and skull-bolts for chronic sleep recordings with head-restraint. Respiration was monitored with a pneumotachograph connected to a tube which was inserted into the trachea through a chronic fistula. Episodes of breathing in wakefulness (W), nonrapid eye movement (NREM) and rapid eye movement (REM) sleep were recorded and digitized for computer analysis. The combined means and standard errors of the mean for frequency of breathing (f), peak inspiratory airflow rate (PF), tidal volume (V t) and minute-volume ( e) were as follows, (1) In NREM, f was lower (25.5 ± 0.35/min) than in W (37.5 ± 1.5) and REM (41.8 ± 1.9). Changes in f across states resulted from changes in both the lengths of inspiration (T i) and expiration (T e). The ratio T i/T i+T k progressively increased from W to NREM and from NREM to REM. (2) PF decreased from W (4.324 liter/min) to NREM (3.03 ± 0.04) and REM (2.572 ± 0.05). There was a strong positive correlation between PF and V t. (3) V t was larger in NREM (35.1 ± 0.43 ml) than in W (33.2 ± 0.73) or REM (24.4 ± 0.63). V T and f were positively correlated on a breath-by-breath basis. (4) V e decreased in sleep (W = 1081 ± 25 ml; NREM = 883 ± 9.9: REM = 806 ± 19). Cats were also studied with dead spaces added to the pneumotachograph. Ventilation parameters increased, but the effects of state on breathing, as determined without added dead space, were confirmed.