Decreased cardiac response to isoproterenol infusion in acute and chronic hypoxia

9 human subjects

Isoproterenol infusion at increasing doses (0.0, 0.02, 0.04, and 0.06 micrograms.kg-1.min-1) during acute hypoxia (2 days at 4,350 m), prolonged hypoxia (13 days between 850 and 4,800 m), and chronic hypoxia (21 days at 4,800 m)

Isoproterenol infusion at sea level

Increase in heart rate (chronotropic response)surrogate