No abstract

Spontaneous and provoked nonrespiratory arousals can be accompanied by a patterned hemodynamic response. To investigate whether a patterned response is also elicited by respiratory arousals, we compared nonrespiratory arousals (NRA) to respiratory arousals (RA) induced by airway occlusion during non-rapid eye movement sleep. We monitored mean arterial blood pressure (MAP), heart rate, iliac and renal blood flow, and sleep stage in 7 pigs during natural sleep. Iliac and renal vascular resistance were calculated. Airway occlusions were obtained by manually inflating a chronically implanted tracheal balloon during sleep. The balloon was quickly deflated as soon as electroencephalogram arousal occurred. As previously reported, NRA generally elicited iliac vasodilation, renal vasoconstriction, little change in MAP, and tachycardia. In contrast, RA generally elicited iliac and renal vasoconstriction, an increase in MAP and tachycardia. The frequent occurrence of iliac vasoconstriction and arterial pressure elevation following RA but not NRA suggests that sleep state change alone does not account for the hemodynamic response to airway occlusion during sleep.

To determine the effects of nonventilatory CO₂ transfer on breathing pattern, we monitored breathing in 7 patients with renal failure undergoing hemodialysis. A respiratory inductance plethysmograph was used to record ventilation before and during dialysis. The duration of inspiration (T_I), the duration of each breath (T_Tot) and the duty cycle (T_I/T_Tot) did not differ for the pre-dialysis and the dialysis periods. In contrast, for each patient the mean tidal volume (V_T) fell significantly during dialysis (p < 0.05), accounting for the reduction in minute ventilation (p < 0.005). The mean inspiratory flow rate (V_T/T_I) also fell (p < 0.01), demonstrating that nonventilatory CO₂ loss via the dialysis bath is associated with reduced respiratory drive.