System identification of closed-loop cardiovascular control mechanisms: diabetic autonomic neuropathy.

Authors:
  • TMThomas J. Mullen
    Thomas J. Mullen
  • RCRichard J. Cohen
    Richard J. Cohen
  • XCXiaoxiao Chen
    Xiaoxiao Chen
  • JSJavier A. Sala-Mercado
    Javier A. Sala-Mercado
  • RHRobert L. Hammond
    Robert L. Hammond
  • MIMasashi Ichinose
    Masashi Ichinose
  • SSSoroor Soltani
    Soroor Soltani
  • DODonal S. O'Leary
    Donal S. O'Leary
  • RBRobert J. Brychta
    Robert J. Brychta

Abstract
We applied cardiovascular system identification (CSI) to characterize closed-loop cardiovascular regulation in patients with diabetic autonomic neuropathy (DAN). The CSI method quantitatively analyzes beat-to-beat fluctuations in noninvasively measured heart rate, arterial blood pressure (ABP), and instantaneous lung volume (ILV) to characterize four physiological coupling mechanisms, two of which are autonomically mediated (the heart rate baroreflex and the coupling of respiration, measured in terms of ILV, to heart rate) and two of which are mechanically mediated (the coupling of ventricular contraction to the generation of the ABP wavelet and the coupling of respiration to ABP). We studied 37 control and 60 diabetic subjects who were classified as having minimal, moderate, or severe DAN on the basis of standard autonomic tests. The autonomically mediated couplings progressively decreased with increasing severity of DAN, whereas the mechanically mediated couplings were essentially unchanged. CSI identified differences between the minimal DAN and control groups, which were indistinguishable based on the standard autonomic tests. CSI may provide a powerful tool for assessing DAN.

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