Increased hypoxic blood pressure response in patients with amyotrophic lateral sclerosis

There is evidence of impaired cardiovascular autonomic control and reduced baroreflex sensitivity in patients with amyotrophic lateral sclerosis (ALS). A compromised baroreflex-chemoreflex interaction might result in inadequate responses to chemoreflex activation with progressive hypercapnia and hypoxia and contribute to early fatalities. This study was performed to assess cardiovascular and ventilatory responses to hypercapnic and hypoxic stimulation in ALS patients with impaired baroreflex function.

In 15 ALS patients with previously demonstrated baroreflex dysfunction and in 15 age-matched controls, we compared electrocardiographic RR-interval (RRI), systolic blood pressure (SBP) and minute ventilation (VE) during normal ventilation and during selective progressive hypoxia and hypercapnia.

Ventilatory and RRI responses to hypoxic and hypercapnic stimulation as well as SBP responses to hypercapnia did not differ between patients and controls. In contrast, hypoxia induced a significant SBP increase in patients only.

The normal ventilatory and RRI responses to chemoreflex activation suggest intact afferent chemoreflex function. The hypertensive response to hypoxia might be due to a compromised interaction with the baroreflex. Avoiding hypoxic episodes might reduce the risk of cardiovascular crisis in ALS patients.