Vagal tonus can be increased with specific procedures called vagal manoeuvres. These include the diving reflex, Valsalva manoeuvre, pressure on the eyeball and carotid sinus massage, with the diving reflex being one of the most effective (Arnold 1999). The diving reflex is a phylogenetically ancient physiological phenomenon believed to facilitate survival after immersion in cold water through bradycardia and peripheral vasoconstriction redistributing blood flow to vital organs (Gooden 1994). The combined bradycardia and vasoconstriction effect indicates on complex sympathovagal activation and the bradycardia itself is believed to be due to central vagal activation (Stemper et al 2002). The natural trigger for diving reflex includes change in body position, apnoea and sensation of cold and wet surface on the face and a cold sensation on the face is sufficient to induce the vagal response. This is believed to be transmitted by the ophthalmic branch of the trigeminal nerve and can be achieved by using cold compressions or cold face gel masks (Khurana et al. 1980).