Effect of Mild Hypercapnia and Skin Temperature on Physiological Responses during Face Immersion

The studies in this thesis were to assess if face cooling and CO2 combine in their influences on pulmonary ventilation and cardiovascular responses in humans. It was hypothesized that mild hypercapnia enhances these ventilatory and cardiovascular response to cold water face immersion. The first study resulted in significant elevations in pulmonary ventilation (p = 0.014), tidal volume (p = 0.008), inspiratory duty cycle (p = 0.013) and reductions in inspiratory flow (p = 0.051) during face immersions. The second study resulted in significant graded elevations in mean arterial blood pressure (p < 0.001), and reductions in the index of cerebral conductance in the middle cerebral artery (MCA) (p = 0.045) during face immersion. In conclusion, cold face immersion during mild hypercapnia increases ventilatory gasping and the blood pressure response while decreasing the conductance for cerebral blood flow to cerebral tissues supplied by the MCA.