The aim of the study is to evaluate the effect of a simple vagal manoeuvre, that is a cold face gel mask application, on subjective measures of Anxiety, Disgust, Strength of belief in obsession, Strength of urge to carry out the compulsion, Strength of belief in Theory A/B and an increase in Feeling of being supported, Readiness to face the fear during the ERP treatment of OCD by using a single-case series experimental design and to explore the relationship between subjective measures and sympathovagal balance measured by heart rate variability. Our hypothesis is that: