Application of Vagal Stimulation by Cold Face Mask in Exposure and Response Prevention for Obsessive Compulsive Disorder

1. Background

Obsessive Compulsive Disorder (OCD) is a condition associated with recurrent intrusive distressing thoughts, images and urges compelling the person to perform neutralizing acts or thoughts to the extent of significantly interfering with their daily activities. The symptoms of OCD are associated with both subjective and objective signs of distress. Psychophysiological studies of OCD and other anxiety disorders often report abnormal sympathovagal balance with decreased parasympathetic or vagal tone and increased sympathetic tone (Hoehn-Saric et al 1995, Broderick et al 2013, Kawano et al 2012, Pittig et al 2013, Buhlmann et al 2007, Blechert et al 2007, Friedman and Thayer 1998).

The first line treatment of OCD is Cognitive Behaviour Therapy (CBT) which includes Exposure and Response Prevention (ERP) when the patient tests out their fears without responding by compulsive act (NICE Clinical Guideline 31). ERP treatment itself is often associated with significant subjective distress (Kellner et al 2012) with dropout rates up to 20% and only minimal improvement in another 20% of patients (Foa 2010). Various modalities of treatment reducing the subjective and physiological distress have been used in treatment of anxiety disorders and symptoms (Streeter et al 2012, Miu et al 2009, Gorman et al 2000) and similar approach could increase the rates of improvement and adherence to ERP treatment in OCD. Most of the attempts to reduce distress in anxiety focus on re-establishing the sympathovagal balance by enhancing the vagal or parasympathetic tone and it has been suggested that this can reduce the mobilization behaviours of fight or flight response and improve emotion regulation (Austin et al 2007). Disgust is an emotion implicated to have significant role on anxiety disorders such as OCD with contamination fears (Moretz and McKay 2008). It has been shown to have only limited response to exposure therapy (Olatunji et al 2009) and can be associated with increased avoidance and reduced compliance with exposures (Olatunji et al 2007) possibly contributing to poorer treatment outcome. Disgust can be associated with changes in sympathovagal balance (Ottaviani et al 2013) but the effect of manoeuvres affecting this balance has not been tested.

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).

The physiological response during diving reflex can be measured by recording standard physiological measures such as heart rate, blood pressure or skin conductance. Heart rate and its interpretation in terms of heart rate variability is becoming more frequently utilized to evaluate the balance between sympathetic and parasympathetic nervous system. Most frequently used is the frequency domain approach which allows differentiating specific frequency bands. The low frequency (LF) band groups the variability between 0.05-0.15Hz and is believed to represent the sympathetic cardiac control with slower unmyelinated nerve fibres while the high frequency (HF) band including frequencies between 0.15-0.4Hz reflects the parasympathetic or vagal control with faster myelinated nerve fibres (Berntson et al 1997). 2. Aims of the study