呼吸影响心功能的力学原理——力学模型的超声心动图研究

Mechanical principle of the respiration-driven variation of cardiac function--Echocardiographic study of themechanical models

目的利用超声心动图技术观察呼吸影响心功能力学模型受模拟胸压变化影响的规律，揭示呼吸影响心功能的力学原理。方法模型1用来观察呼吸性胸压变化（respiratory intrathoracic pressurechange．RIPC）对体静脉回流系统（systemic venous return system, SVR）及肺静脉回流系统（pulmonary venous return system,PVR）的不同影响。模型2（即室间隔摆动的等效力学模型）用来观察RIPC对室间隔运动的影响。结果模型1说明RIPC对模拟SVR和PVR的影响完全不同．它改变了模拟右心的容积但其内压不变，对左心则相反。模型2说明了RIPC与模拟室间隔之间存在相对应的压力一位置关系。结论由于两个静脉回流系统相对于胸腔的解剖位置不同，导致RIPC对左右心内压力产生不同影响，进而产生了跨室间隔的压力差，使其随呼吸左右摆动。交替性地改变两侧心室短径及充盈，影响心功能。

Objective To reveal the exact mechanical principle of the respiration-driven variation of cardiac function by observing the effect of respiratory /ntrathoraeic pressure change （RIPC） on the mechanical models using echocardiography. Methods Model 1 was designed to observe the influence of RIPC on systemic and pulmonary venous return systems （SVR and PVR） respectively. Model 2. as an equivalent mechanical model of septal swing,was used to study the influence of RIPC on the motion of the interventricular septum （IVS）. Results Model I demonstrated that the simulated RIPC had totally different influences on the simulated SVR and PVR. It increased the volume of the simulated right ventricle when tlle internal pressure was kept constant （8.16 cm H20）, while it had the opposite effect on PVR. Model 2 demonstrated that there was a corresponding relationship between RIPC and the position of the simulated IVS which might be called pressure-position relationship. Conclusions The different anatomical arrangement of the two venous return systems leads to a different effect of RIPC on right and left ventricles, and thus generates a pressure gradient across IVS that tends to shift IVS left- and right-wards with respiration. The swing of the IVS changes the short axis diameters of the ventricles, thus their fillings and then their functions reciprocally.