Cardiovascular response to static apneas

While holding one's breath the human body experiences complex but meaningful changes of different cardiovascular parameters. During the so-called static apnea compensatory mechanisms of mechanical and neuronal nature are involved. Two types of apnea have been investigated and compared while blood pressure, vascular constriction, and heart rate have been estimated in parallel. One type of voluntary apnea AP_I began after the end of inspiration, whereas the other type AP_E after the end of expiration. Nine young and healthy subjects were recruited for the study. In both cases of AP_I and AP_E an increasing systolic blood pressure was observed (118±5% in type AP_I at the end of apnea relative to preceding baseline versus 115±5% in type AP_E). A more dominant vascular constriction was seen in AP_E (46±8% versus 71±11%). A slightly decreasing heart rate was observed during the apneic period, with stronger changes given in AP_I (90±7% versus 98±8%). Duration of voluntary apneas was shorter in AP_E (0.9±0.6min versus 1.2±0.6min). The study has shown that apneas AP_E of higher severity level have a less distinct diving reflex and are accompanied by stronger changes in blood pressure and heart rate.