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References: Tantucci et al, 2001

Tantucci C, Bottini P, Fiorani C, Dottorini ML, Santeusanio F, Provinciali L, Sorbini CA, Casucci G

Cerebrovascular reactivity and hypercapnic respiratory drive in diabetic autonomic neuropathy

J Appl Physiol 2001, 90: p. 889896.

Clinica di 1Semeiotica e Metodologia Medica and Neurologia e Neuroriabilitazione, University of Ancona, and Dipartimento di Medicina Interna e Scienze Endocrino-Metaboliche, University of Perugia, Italy

Because abnormalities in cerebrovascular reactivity (CVR) in subjects with long-term diabetes could partly be ascribed to autonomic neuropathy and related to central chemosensitivity, CVR and the respiratory drive output during progressive hypercapnia were studied in 15 diabetic patients without (DAN2) and 30 with autonomic neuropathy (DAN1), of whom 15 had postural hypotension (PH) (DAN1PH1) and 15 did not (DAN1PH2), and in 15 control (C) subjects. During CO2 rebreathing, changes in occlusion pressure and minute ventilation were assessed, and seven subjects in each group had simultaneous measurements of the middle cerebral artery mean blood velocity (MCAV) by transcranial Doppler. The respiratory output to CO2 was greater in DAN1PH1 than in DAN1PH2 and DAN2 (P , 0.01), whereas a reduced chemosensitivity was found in DAN1PH2 (P , 0.05 vs. C). MCAV increased linearly with the end-tidal PCO2 (PETCO2) in DAN1PH2 but less than in C and DAN2 (P , 0.01). In contrast, DAN1PH1 showed an exponential increment in MCAVwith PETCO2 mainly .55 Torr. Thus CVR was lower in DAN1 than in C at PETCO2 ,55 Torr (P , 0.01), whereas it was greater in DAN1PH1 than in DAN1PH2 (P , 0.01) and DAN2 (P , 0.05) at PETCO2 .55 Torr. CVR and occlusion pressure during hypercapnia were correlated only in DAN1 (r 5 0.91, P , 0.001). We conclude that, in diabetic patients with autonomic neuropathy, CVR to CO2 is reduced or increased according to the severity of dysautonomy and intensity of stimulus and appears to modulate the hypercapnic respiratory drive.

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