Cold Pressor Test

The human being can perceive different degrees of thermal sensation. For distinguished cold sensation, Cold receptors are located under the skin at discrete separated spots. The Extreme degree of cold may provoke a stimulation of pain receptors and fibers (1). Thus a painful cold sensation can develop a psychological state that triggers the response in the sympathetic nervous system and release norepinephrine. Extensive sympathetic discharge excites the cardiovascular systems that produce pressor response, i.e, arteriolar constriction, increase heart rate, increase stroke volume, increase cardiac output and blood pressure (2). Hence, to assess the sympathetic activity in a subject, simple vasomotor test called the cold pressor test was done.

Endothelial dysfunction of peripheral vasculature is an important feature of atherogenesis (8). Egashira K et al (9) concluded that the rise in heart rate and systolic blood pressure in cold stress is due to sympathetic stimulation. Moreover, serum thyroid stimulating hormone (TSH) levels have been found to be inversely correlated with endothelium-dependent dilatation (7). Taddei S, et al (10) assessed that in subclinical hypothyroid patients the endothelial dysfunction is caused by reducing nitric oxide (NO) availability. Nitric oxide is a signaling molecule that raising cGMP levels to relaxes vascular smooth muscle

Sympathetic nervous activity during cold stress increases cardiac output to increase capillary filtration rate in muscle tissue to the supplying the nutrients and oxygen to the muscular tissue and also allow for increase muscle to contract. Heart rate and blood pressure will be measured in the cold pressor test is to determine the level of stress response in the body. It is based on the reflex pathway where the afferent limb is somatic fibers where as the efferent limb is sympathetic fibers .The cold pressor test is an ethical and efficient way to affect the sympathetic response