Estimation of Autonomic Nervous System Modulation by Pulse Plethysmographic Analysis

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%.

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%