Hypovolemia and intermittent positive pressure ventilation are conditions that frequently characterize the state of critical illness, but their interaction and resulting cardioventilatory coupling is poorly understood even in healthy humans.

We explored heart rate variability, baroreflex activity, and their interaction in an experimental protocol involving twelve mildly hypovolemic healthy subjects during spontaneous breathing and noninvasive positive-pressure ventilation. In seven subjects, an echocardiographic assessment was also performed.

Correction of hypovolemia, raising cardiac preload, produced an increase in high-frequency spectral power density of heart rate, left low-frequency spectral power density unchanged but enhanced baroreflex sensitivity. Cardioventilatory coupling was affected by both central blood volume and ventilatory mode and was mainly entrained by the respiratory oscillation.

In conclusion, the autonomic nervous system and baroreflex have a significant role in compensating the hemodynamic perturbation due to changes of volemia and ventilatory-induced fluctuations of venous return. They exert an integrative function on the adaptive pattern of cardioventilatory coupling.

血容量不足和间歇性正压通气是危重疾病状态的常见特征，但即使在健康人中，它们的相互作用和由此产生的心脏换气耦合也知之甚少。

我们在一项涉及 12 名轻度低血容量健康受试者在自主呼吸和无创正压通气期间的实验方案中探索了心率变异性、压力反射活动及其相互作用。在七名受试者中，还进行了超声心动图评估。

纠正血容量不足，提高心脏前负荷，增加心率的高频频谱功率密度，保持低频频谱功率密度不变，但增强了压力反射敏感性。心脏通气耦合受中心血容量和通气模式的影响，主要受呼吸振荡的影响。

总之，自主神经系统和压力反射在补偿由于血容量变化和通气引起的静脉回流波动引起的血流动力学扰动方面具有重要作用。它们对心脏通气耦合的适应性模式发挥综合作用。