(taken by Henbest & Baker)
Developing of an automated VALSALVA experiment with tidal volume and pressure control.
The Valsalva maneuver is a common test of the autonomic nervous system in humans. Valsalva maneuver consist of straining against a closed glottis for a limited time. The straining will induce an abrupt transient increase of intrathoracic and intraabdominal pressures which will provoke changes in arterial blood pressure. The response to the Valsalva maneuver can be divided into four classical phases. Immediately after the onset of straining the arterial blood pressure will increase and the heart rate will slow (Phase I). During straining the arterial blood pressure will fall close to the initial level, and the heart rate will speed up (Phase II). During release of straining the blood pressure will drop and the heart rate will accelerate further (Phase III). In the terminal phase (Phase IV) the blood pressure will reach a level above initial value (overshoot) and the heart rate will decrease. This response will give us information about both branches of the autonomic nervous system the sympathetic and vagal.
The pressure, duration and the phase of the begin of straining in the respiratory cycle can influence a response during the Valsalva maneuver. It is highly probable that the breathing pattern before and after the Valsalva maneuver will change the response too. Therefore a control of the breathing pattern before and after a Valsalva maneuver, the timing of straining, and the pressure level during straining is very important. The aim of this project is to develop an automatic VASALVA device with tidal volume and strain pressure control, which can be used at the Clinical Research Center.
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Smith, S. A., T. J. Stallard, and M. M. Salih. Can sinoaortic baroreceptor heart rate reflex sensitivity determined from phase IV of the Valsalva manoeuvre? Cardiovasc. Res. 21: 422-427, 1987.