Controlled breathing maneuver is being widely applied for cardiovascular autonomic control evaluation and cardiac vagal activation through reduction of breathing rate (BR). However. this maneuver presented contradictory results depending on the protocol and the chosen BR. These variations may be related to the individual intrinsic profile baseline sympathetic tonus. https://www.roneverhart.com/Lindell-Audio-LIN76-Vintage-Limiting-Amplifier-p14154/