Sleep does not affect the cardiovascular response to alveolar hypoxia in lambs

We investigated the effect of sleep on the cardiovascular response to alveolar hypoxia in seven lambs aged 17 to 21 days. Each lamb had previously been anesthetized and instrumented for measurements of electrocorticogram, electro-oculogram, nuchal and diaphragm electromyograms, pulmonary blood flow (electromagnetic flow transducer), aortic and pulmonic blood pressures. The lambs were allowed to recover from surgery at least three days before they were studied. Measurements were made during a 1-min control period and during an experimental period of alveolar hypoxia (FIO2 0.10) during quiet wakefulness, quiet sleep and active sleep. Alveolar hypoxia produced similar increases in cardiac output, heart rate, mean aortic and pulmonic blood pressures and a similar decrease in systemic vascular resistance during the three behavioral states. These data provide evidence that sleep does not affect the integrated cardiovascular response to arterial chemoreceptor stimulation in lambs.