Autonomic cardiac regulation in obstructive sleep apnea syndrome: evidence from spontaneous baroreflex analysis during sleep
Objective. To assess spontaneous baroreceptor-heart rate reflex sensitivity during sleep in patients with obstructive sleep apnea syndrome, a condition associated with increased cardiovascular morbidity and mortality and characterized by marked sympathetic activation, which is believed to originate from hypoxic chemoreceptor stimulation, although little is known of other possible mechanisms such as baroreflex impairment. Design and methods. In 11 patients with severe obstructive sleep apnea syndrome (mean ± SD age 46.8 ± 8.1 years, apnea/hypopnea index 67.9 ± 19.1 h), who were normotensive or borderline hypertensive during wakefulness by clinic blood pressure measurements, finger blood pres…
Cardiovascular control and time domain granger causality: Insights from selective autonomic blockade
We studied causal relations among heart period (HP), systolic arterial pressure (SAP) and respiration (R) according to the definition of Granger causality in the time domain. Autonomic pharmacological challenges were used to alter the complexity of cardiovascular control. Atropine (AT), propranolol and clonidine (CL) were administered to block muscarinic receptors, β-adrenergic receptors and centrally sympathetic outflow, respectively. We found that: (i) at baseline, HP and SAP interacted in a closed loop with a dominant causal direction from HP to SAP; (ii) pharmacological blockades did not alter the bidirectional closed-loop interactions between HP and SAP, but AT reduced the dominance of…
Methodology and technology for peripheral and central blood pressure and blood pressure variability measurement: current status and future directions - Position statement of the European Society of Hypertension Working Group on blood pressure monitoring and cardiovascular variability
Office blood pressure measurement has been the basis for hypertension evaluation for almost a century. However, the evaluation of blood pressure out of the office using ambulatory or self-home monitoring is now strongly recommended for the accurate diagnosis in many, if not all, cases with suspected hypertension. Moreover, there is evidence that the variability of blood pressure might offer prognostic information that is independent of the average blood pressure level. Recently, advancement in technology has provided noninvasive evaluation of central (aortic) blood pressure, which might have attributes that are additive to the conventional brachial blood pressure measurement. This position …
Baroreflex control of heart rate during sleep in severe obstructive sleep apnoea: effects of acute CPAP
Baroreflex control of heart rate during sleep (baroreflex sensitivity; BRS) has been shown to be depressed in obstructive sleep apnoea (OSA), and improved after treatment with continuous positive airway pressure (CPAP). Whether CPAP also acutely affects BRS during sleep in uncomplicated severe OSA is still debatable. Blood pressure was monitored during nocturnal polysomnography in 18 patients at baseline and during first-time CPAP application. Spontaneous BRS was analysed by the sequence method, and estimated as the mean sequence slope. CPAP did not acutely affect mean blood pressure or heart rate but decreased cardiovascular variability during sleep. Mean BRS increased slightly during CPAP…
Signal processing procedures for the evaluation of the cardiovascular effects in the obstructive sleep apnea syndrome
A new index, the cross-power index (CPI), is proposed to quantify the severity of obstructive sleep apnea syndrome (OSAS) in terms of its cardiovascular effects. On the basis of the influences that recurring drops in oxygen saturation have on systolic blood pressure variability of OSAS patients, CPI is defined as the integral of the cross-spectrum modulus between systolic blood pressure and oxygen saturation. In a test group of 22 subjects, CPI correctly identified all 15 OSAS patients included in the pool. Moreover, evaluation of CPI in six OSAS patients sleeping with and without a CPAP (continuous positive airway pressure) device demonstrated that CPAP treatment substantially reduced the …
Assessing Complexity in Physiological Systems through Biomedical Signals Analysis
The idea that most physiological systems are complex has become increasingly popular in recent decades [...]