Voluntary Respiratory Control and Cerebral Blood Flow Velocity upon Ice-Water Immersion

Abstract

Even without prior cold-water experience, subjects were able to suppress reflex hyperventilation following ice-water immersion, maintaining the cerebral blood flow velocity at a level not associated with impaired consciousness. This study implies that those susceptible to accidental cold-water immersion could benefit from education in cold-shock response and the possibility of reducing the ventilatory response voluntarily.

“Float first and kick for your life”: Psychophysiological basis for safety behaviour on accidental short-term cold water immersion

“…We make the important addition of a suitable resting cold-water control (i.e., CWI-Rest) and a true thermoneutral resting control (i.e., TN-Rest) in unhabituated persons reflecting the majority of the population. The magnitude of the reduction in MCAv in our resting trial was also similar (i.e., ~6% cf 7%) to that of Mantoni et al [17] who studied resting ice water immersion. However, the present study observed a variation that was larger (SD = 9% cf 4%) and more so during leg only exercise (16%).…”

“…The inter-individual range in the first two minutes of immersion was also large with a peak reduction of ~23% seen in the CWI-Rest condition and ~35% in the CWI-Kick condition. It may be that those participants who show the greatest reduction in MCAv are most vulnerable to the symptoms of the CSR [17]. These individuals should be targeted for additional protection against the cold if they are at daily risk of accidental water entry.…”

“…Consequently, the reduction in brain blood flow, specifically mid-cerebral artery velocity (MCAv), that is ordinarily seen on CWI [17] was lessened. In resting tests, which were not included in the studies of Croft et al [15] and Button et al [16], it has been documented that MCAv could fall by 21 [4]% and in extreme cases as much as 68%.…”

“…In resting tests, which were not included in the studies of Croft et al [15] and Button et al [16], it has been documented that MCAv could fall by 21 [4]% and in extreme cases as much as 68%. This drop was linked to subjective sensations of dizziness and light-headedness and could increase the risk of fainting on immersion [17].…”

Human Physiology in an Aquatic Environment

“…Rapid immersion in cold (0 • C) water results in an immediate increase in HR, respiratory rate, and tidal volume. The hyperventilation leads to decreases in ETCO 2 and cerebral vasoconstriction reflected by a decline of middle cerebral artery velocity and is sufficient to cause disorientation and loss of consciousness (236).…”