Human face-only immersion in cold water reduces maximal apnoeic times and stimulates ventilation

Abstract

In two studies, the cold shock and diving responses were investigated after human face immersion without prior hyperventilation to explore the mechanism(s) accounting for reductions in maximal apnoeic times (ATmax) at low water temperatures. In study 1, ATmax, heart rate (HR) and cutaneous blood cell velocity were measured in 13 non-apnoea-trained males during apnoeic face immersion in 0, 10, 20 and 33°C water and room air (AIR). In study 2, six males were measured during non-apnoeic face immersion in 0, 10 and 33°C water for ventilation (V̇E), respiratory exchange ratio (RER), HR and oxygen consumption (V̇O2), as well for end-tidal partial pressures of oxygen (PET, O2) and carbon dioxide (P ET, CO2). Results indicated that the ATmax of 30.7 s (s.d. 7.1 s) at 0°C (P < 0.001) and 48.2 s (s.d. 16.0 s) at 10°C (P < 0.05) were significantly shorter than that of ∼58 s in AIR or 33°C. During apnoea at 0, 10, 20 and 33°C, both the deceleration of HR (P < 0.05) and peripheral vasoconstriction (P < 0.05), as well as the peak HR at 0°C (P = 0.002) were significantly greater than in AIR. At 0°C in comparison with 33°C, non-apnoeic face immersions gave peaks in V̇E (P = 0.039), RER (P = 0.025), PET, O2 (P = 0.032) and HR (P = 0.011), as well as lower minimum values for PET, CO2 (P = 0.033) and HR (P = 0.002). With V̇2 as the covariate, ANCOVA showed that V̇E remained significantly greater (P = 0.003) at lower water temperatures. In conclusion, during face immersion at 10°C and below, there is a non-metabolic, neurally mediated cold shock-like response that shortens apnoea, stimulates ventilation and predominates over the oxygen conserving effects of the dive response. © 2007 The Authors.