Figure 1. Typical changes in arterial pressure and heart rate during the Valsalva manoeuvre in control and trimetaphan protocols.

The efficacy of ganglion blockade by trimetaphan was demonstrated not only by the absence of heart rate response, but also by the absence of BP recovery during phase II or BP overshoot during phase IV of the Valsalva manoeuvre. Arrows show the time points when Valsalva manoeuvre was started or stopped.