Multiple baseline approach to predict the heart rate response to simulated diving in young adults

Subject of this study is the predictive value of baseline heart rate (HR) response to simulated diving. Twenty-seven male volunteers aged 20-25 performed apneic face immersion in cold water, while ECG was recorded. Both the initial HR increase and the following bradycardic response significantly correlated to resting HR. To optimally estimate the reference HR (mean HR or the longest 512-RR-interval-long time series or minimum of moving HR average at given lengths), we compared three different approaches, based on the best correlations between the evoked responses, HRV measures and resting baseline. Our data indicate lack of universal HR reference useful to predict resulting diving response. The longest RRi observed across preceding time window is apparently the best indicator of the diving bradycardic response, while the initial HR increase and time of voluntary apnea corresponds to the longtime HR average.