Published ahead of print on October 24, 2002, doi:10.1164/rccm.200207-677OC Am. J. Respir. Crit. Care Med., Volume 167, Number 2, January 2003, 141-149 A more recent version of this article appeared on January 15, 2003
Submitted on July 9, 2002 RESPIRATORY AND CEREBROVASCULAR RESPONSES TO HYPOXIA AND HYPERCAPNIA IN FAMILIAL DYSAUTONOMIALuciano Bernardi1*,1 IRCCS S. Matteo and Dipartimento Medicina Interna, University of Pavia, Clinica Medica 2, Pavia, Italy, 2 New York University School of Medicine, New York University Medical Center, New York, NY, USA; University of Erlangen Nuernberg, Department of Neurology, Erlangen, Germany, 3 University of Erlangen Nuernberg, Department of Neurology, Erlangen, Germany, 4 New York University School of Medicine, New York University Medical Center, New York, NY, USA * To whom correspondence should be addressed. E-mail: lbern1ps{at}unipv.it.
Although cardio-respiratory complications contribute to the high morbidity/mortality of familial dysautonomia (FD), the mechanisms remain unclear. We evaluated the respiratory, cardiovascular and cerebrovascular control by monitoring ventilation, end-tidal carbon dioxide (CO2-et) oxygen saturation (SaO2), RR interval, blood pressure (BP) and mid-cerebral artery flow velocity (MCFV) during progressive isocapnic hypoxia, progressive hyperoxic hypercapnia and during recovery from moderate hyperventilation (to simulate changes leading to respiratory arrest) in 22 FD subjects and 23 matched controls. At baseline, FD had normal ventilation, higher CO2-et, lower SaO2, lower RR interval, higher BP. MCFV was also higher but depended on the higher baseline CO2-et. While hyperoxic hypercapnia induced normal cardiovascular and ventilatory responses, during progressive hypoxia ventilation increase was blunted, RR interval and blood pressure showed paradox decreases, and MCFV failed to increase. Hyperventilation induced a longer hypocapnia-induced apneic period (51.5±9.9 vs. 11.2±5.5 sec, p<0.008) with profound desaturation (to 75.8±3.5%), marked BP decrease and RR interval increase. FD subjects develop central depression in response to even moderate hypoxia with lack of expected change in cerebral circulation, leading to hypotension, bradycardia, hypoventilation and potentially respiratory arrest. Higher resting blood pressure delays occurrence of syncope during hypoxia. Therapeutic measures preventing hypoxia/hypocapnia may correct cardiovascular accidents in FD. Key words: Familial Dysautonomia Hypoxia Hypotension Chemoreceptors Autonomic nervous system
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