Coherent hemodynamics spectroscopy in a single step.

Coherent Hemodynamics Spectroscopy (CHS) is a technique based on inducing cerebral hemodynamic oscillations at multiple frequencies, measuring them with near-infrared spectroscopy (NIRS), and analyzing them with a hemodynamic model to obtain physiological information such as blood transit times in the microvasculature and the autoregulation cutoff frequency. We have previously demonstrated that such oscillations can be induced one frequency at a time. Here we demonstrate that CHS can be performed by a single inflation of two pneumatic thigh cuffs (duration: 2 min; pressure: 200 mmHg), whose sudden release produces a step response in systemic arterial blood pressure that lasts for ~20 s and induces cerebral hemodynamics that contain all the frequency information necessary for CHS. Following a validation study on simulated data, we performed measurements on human subjects with this new method based on a single occlusion/release of the thigh cuffs and with the previous method based on sequential sets of cyclic inflation/deflation one frequency at a time, and demonstrated that the two methods yield the same CHS spectra and the same physiological parameters (within measurement errors). The advantages of the new method presented here are that CHS spectra cover the entire bandwidth of the induced hemodynamic response, they are measured over ~20 s thus better satisfying the requirement of time invariance of physiological conditions, and they can be measured every ~2.5 min thus achieving finer temporal sampling in monitoring applications.

[1]  B. Levine,et al.  Transfer function analysis of dynamic cerebral autoregulation in humans. , 1998, American journal of physiology. Heart and circulatory physiology.

[2]  Nudleman Kl,et al.  Transcranial Doppler study. , 1991 .

[3]  Rune Aaslid,et al.  Asymmetric Dynamic Cerebral Autoregulatory Response to Cyclic Stimuli , 2007, Stroke.

[4]  Sergio Fantini,et al.  Reduced speed of microvascular blood flow in hemodialysis patients versus healthy controls: a coherent hemodynamics spectroscopy study , 2014, Journal of biomedical optics.

[5]  B. Mermillod,et al.  Is cerebral autoregulation impaired in Parkinson's disease? A transcranial Doppler study , 2007, Journal of the Neurological Sciences.

[6]  W. Kuschinsky,et al.  Lack of Capillary Recruitment in the Brains of Awake Rats during Hypercapnia , 1989, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[7]  R. Aaslid,et al.  Cerebral autoregulation dynamics in humans. , 1989, Stroke.

[8]  Sergio Fantini,et al.  Dynamic model for the tissue concentration and oxygen saturation of hemoglobin in relation to blood volume, flow velocity, and oxygen consumption: Implications for functional neuroimaging and coherent hemodynamics spectroscopy (CHS) , 2014, NeuroImage.

[9]  Tomaž Pogačnik,et al.  The Middle Cerebral Artery Flow Velocities during Head-Up Tilt Testing in Diabetic Patients with Autonomic Nervous System Dysfunction , 2003, Cerebrovascular Diseases.

[10]  Peter Berlit,et al.  Spontaneous blood pressure oscillations and cerebral autoregulation , 1998, Clinical Autonomic Research.

[11]  T B Kuo,et al.  Transfer Function Analysis of Cerebral Hemodynamics in Patients with Carotid Stenosis , 1999, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[12]  M. J. Blake,et al.  Dynamic cerebral autoregulation and beat to beat blood pressure control are impaired in acute ischaemic stroke , 2002, Journal of neurology, neurosurgery, and psychiatry.

[13]  O. Paulson,et al.  Capillary circulation in the brain. , 1992, Cerebrovascular and brain metabolism reviews.

[14]  Ronney B Panerai,et al.  Influence of controlled breathing patterns on cerebrovascular autoregulation and cardiac baroreceptor sensitivity. , 2004, Clinical science.

[15]  R. Hughson,et al.  Critical Analysis of Cerebrovascular Autoregulation During Repeated Head-Up Tilt , 2001, Stroke.

[16]  D. Ziegler,et al.  Impairment of cerebral autoregulation in diabetic patients with cardiovascular autonomic neuropathy and orthostatic hypotension , 2003, Diabetic medicine : a journal of the British Diabetic Association.

[17]  C. Patlak,et al.  Slightly altered permeability-surface area products imply some cerebral capillary recruitment during hypercapnia. , 1994, Microvascular research.

[18]  David W. Kaczka,et al.  The frequency response of cerebral autoregulation. , 2013, Journal of applied physiology.

[19]  Sergio Fantini,et al.  Validation of a novel hemodynamic model for coherent hemodynamics spectroscopy (CHS) and functional brain studies with fNIRS and fMRI , 2014, NeuroImage.

[20]  Rong Zhang,et al.  Dynamic cerebral autoregulation during repeated squat-stand maneuvers. , 2009, Journal of applied physiology.

[21]  A. Lagi,et al.  Cerebral Autoregulation in Orthostatic Hypotension: A Transcranial Doppler Study , 1994, Stroke.

[22]  Arno Villringer,et al.  The intravascular susceptibility effect and the underlying physiology of fMRI , 2012, NeuroImage.

[23]  T G Robinson,et al.  Continuous estimates of dynamic cerebral autoregulation during transient hypocapnia and hypercapnia. , 2010, Journal of applied physiology.

[24]  Sergio Fantini,et al.  A new hemodynamic model shows that temporal perturbations of cerebral blood flow and metabolic rate of oxygen cannot be measured individually using functional near-infrared spectroscopy , 2014, Physiological measurement.

[25]  A. Villringer,et al.  Capillary perfusion of the rat brain cortex. An in vivo confocal microscopy study. , 1994, Circulation research.

[26]  C Franzini,et al.  Brain Capillary Perfusion during Sleep , 1996, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[27]  J Timmer,et al.  Transfer function analysis for clinical evaluation of dynamic cerebral autoregulation—a comparison between spontaneous and respiratory-induced oscillations , 2003, Physiological measurement.

[28]  D. Newell,et al.  Comparison of static and dynamic cerebral autoregulation measurements. , 1995, Stroke.

[29]  C. Robertson,et al.  Dynamic autoregulatory response after severe head injury. , 2002, Journal of neurosurgery.

[30]  P. Berlit,et al.  Phase relationship between cerebral blood flow velocity and blood pressure. A clinical test of autoregulation. , 1995, Stroke.

[31]  Sergio Fantini,et al.  Practical steps for applying a new dynamic model to near-infrared spectroscopy measurements of hemodynamic oscillations and transient changes: implications for cerebrovascular and functional brain studies. , 2014, Academic radiology.

[32]  L Fattorini,et al.  Autonomic control of the cerebral circulation during normal and impaired peripheral circulatory control , 1999, Heart.

[33]  A P Blaber,et al.  Transfer function analysis of cerebral autoregulation dynamics in autonomic failure patients. , 1997, Stroke.

[34]  A. Lagi,et al.  Cerebral Autoregulation in Orthostatic Hypotension , 1994 .