Autonomic, Cardiovascular, and Respiratory Responses to Hyperglycemic Stimulus in Healthy Subjects

Abstract

In ten healthy subjects we assessed the effects of hyperglycemia, provoked by the ingestion of 75 g of glucose on: R-R intervals (RR), systolic pressure (SP), diastolic pressure (DP), respiratory frequency (RF) and tidal volume (V T) 5-min time series; the time course of their low-frequency (LF RR , LF SP , LF DP), high-frequency (HF RR , HF DP , HF Res) powers and their central frequencies (cfLF DP , cfHF RR , cfHF DP), computed by a time-frequency distribution; baroreflex (BRS) and respiratory sinus arrhythmia sensitivities (RSAS), obtained by alpha index and their coherences (cBRS and cRSAS) by cross timefrequency analysis. In relation to control, in hyperglycemia (peak of 143±12 mg/100 ml, p<0.001)1min epoch mean values of: LF RR , LF DP , HF RR , HF Res , BRS, cBRS, RR, DP and V T decreased (p<0.03); cfLF DP , cfHF RR , RSAS, cRSAS and RF increased (p<0.04); and LF SP and SP were similar. Our findings outline an integrative dynamic response to hyperglycemia characterized by: vagal activity inhibition associated to RR shortening; sympathetic outflow inhibition associated to reduced DP, which, via baroreflex with reduced sensitivity and input-output coupling degree, reinforces the vagal reduction; and respiratory activity modification associated to V T decrease, RF increase and improved respiratory modulation of cardiovascular function.