Re-evaluation of the cold face test in humans.

The cold face test has been found to be a simple clinical test to elicit the diving reflex, which assesses function of the sympathetic and parasympathetic nerve systems at the same time. However, there is no consensus about how the test should be performed without confounding the results by eliciting other reflexes, such as the oculocardiac reflex. The object of this study was to compare and standardize methods for performing the cold face test. Reproducibility of results was assessed. Groups of 6 to 11 subjects participated in each protocol. To act as a cold stimulus a bag filled with iced-water and having a wet surface was used. The effects of allowing breathing to continue, of different masses of the bag, and of avoiding ocular pressure by wearing diving goggles were investigated. Blood pressure and heart rate were measured beat to beat using an automatic blood pressure measuring device. The cold stimulus used in this study was too small to elicit the oculocardiac reflex: wearing diving goggles and different masses of the bag had no influence on the response. The prevention of breathing, however, tended to enhance the fall in heart rate during the cold stress. Reproducibility was highest when the subjects were habituated to the intensity of the stimulus. We recommend practising the test method in advance and performing it in a setting where the subject is unable to breathe.