Acute increases in blood pressure cause arousal from sleep in lambs.

We did experiments to determine whether or not acute increases in blood pressure would cause arousal from sleep. Nine lambs were studied 3-4 days after a balloon-tipped catheter was inserted via the femoral artery into the descending aorta and electrodes for the following recordings were implanted: electrocorticogram, electro-oculogram, electrocardiogram and diaphragm electromyogram. Balloon inflation increased mean arterial blood pressure 27.9 +/- 6.3 mm Hg (mean +/- 1 S.D.) during quiet sleep (QS) and 24.4 +/- 8.9 mm Hg during active sleep (AS). Behavioral arousal occurred from both sleep states but was significantly (P less than 0.05) delayed during active sleep (21.3 +/- 6.7 s) compared to quiet sleep (10.0 +/- 3.3 s). This occurred despite there being a greater percent change in R-R interval for a percent change in mean blood pressure during active sleep (2.68 +/- 1.08) than during quiet sleep (1.55 +/- 0.62). The increases in blood pressure did not produce any significant changes in respiratory rate of integrated diaphragm activity. Thus, acute increases in blood pressure are capable of causing arousal from sleep. This finding should be considered when one discusses the possible mechanisms of arousal from sleep during rapidly developing hypoxemia.