The effect of pain on changes in heart rate during the Valsalva manoeuvre.

The presence of pain may influence autonomic function in patients with painful neurological or cardiovascular disorders. The aim of the present study was to determine whether pain influences cardiac baroreflexes during the Valsalva manoeuvre. Eighteen healthy subjects immersed their hand twice at each temperature in 30 degrees C water and painfully hot (47 degrees C) and cold water (12 degrees C and 7 degrees C) for 2.5 minutes, followed by 5 minute rest periods. During 50% of the immersions, subjects performed the Valsalva manoeuvre (40 mmHg for 30 seconds) starting one minute after their hand entered the water. Pain ratings and heart rate were greater during the 7 degrees C and 47 degrees C immersions than during the 12 degrees C and 30 degrees C immersions. Pain-induced increases in heart rate did not influence peak tachycardia during phase II or III of the Valsalva manoeuvre or peak bradycardia during phase IV, but opposed bradycardia during the post-strain recovery period. Further studies are needed to establish whether pain influences indices of autonomic function during clinical assessment.