Estimation of Autonomic Nervous System Modulation by Pulse Plethysmographic Analysis

Study Overview
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Brief Summary
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Novel pulse plethysmography-derived indexes has been proposed as a tool to measure autonomic nervous system modulation in anaesthetized and awake patients, but nowadays a physiologic validation is lacking. We aim to examine the effects of sympathetic stimulation on pulse plethysmographic amplitude (PPGA), autonomic nervous system state (ANSS) and autonomic nervous system state index (ANSSi).

Detailed Description
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It has been supposed that indexes derived from pulse plethysmographic analysis -the autonomic nervous system state (ANSS) and ANSS index (ANSSi)- may be useful tools to measure the autonomic nervous system (ANS) activity but, to date, physiologic experimental evidences are lacking. Traditionally,it is widely accepted that ANS modulation and the baro-reflex control can be non-invasively studied through heart rate variability (HRV) and systolic variability analyses. The aim of this study is to assess if PPGA-derived indexes are able to detect changes of ANS system modulation directed to heart and vessels. Changes in position of patients lead to changes in the balance of the ANS. One of the most used manoeuver to stimulate ANS is head-up tilt (HUT). Tilt causes pooling of blood toward lower body and reduces the venous return to the heart. These activation of ANS leads to an increase of heart rate and peripheral vascular resistance aiming to maintain arterial pressure near to the level preceding the challenge (baro-reflex control). Methods: we study the effects of sympathetic stimulation on ANSS and ANSSi induced with two different tilt at 45 and 90 degrees angles. We compare the ANSS and ANSSi with HRV analysis and baro-reflex control analysis. We plan to study 7 volunteers to detect a difference of 30 (standard deviation of 15) between the mean of ANSS and ANSSi at baseline and during tilt, with a power of 80% and alfa error of 5%.

Conditions
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Autonomic Nervous System Modulation

Intervention / Treatment
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* Other: Tilt test


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: adult healthy humans (american society of anesthesiologists class I) age between 25 and 35 years old no assumption of any drug, beverages containing caffeine or alcohol during the previous 24 hours fasting 3 hours before the study protocol Exclusion Criteria: american society of anesthesiologists class >1 age <25 or >35 years pregnancy accidental discover of non sinus cardiac rhythm or ectopic beats >5%

Ages Eligible for Study
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Minimum Age: 25 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: all patients<br>tilt | Other: Tilt test<br>* The experiment protocol consists of a sequence of passive postural changes gained with a tilt table, each of them lasting 10 minutes. The sequence consists of: (i) baseline recording in supine position; (ii) tilt at 45 degrees angle; (iii) recovery period in supine position; (iv) tilt at 90 degrees angle and (v) recovery in supine position.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| to measure the degree of correlation of ANSS and ANSSi with LF/HF and baroreflex sensitivity and their agreement in response to an orthostatic sympathetic load |  | 1 week | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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pulse plethysmography, autonomic nervous system, heart rate variability, baro-reflex