Department of Anaesthesia 2041, Rigshospitalet, Blegdamsvej 9, Copenhagen, Denmark.
Acta Anaesthesiol Scand. 2009 Nov;53(10):1324-8. doi: 10.1111/j.1399-6576.2009.02062.x. Epub 2009 Jul 22.
Cardiac function curves are widely accepted to apply to humans but are not established for the entire range of filling of the heart that can be elicited during head-up (HUT) and head-down tilt (HDT), taken to represent minimal and maximal physiological filling of the heart, respectively. With the supine resting position as a reference, we assessed stroke volume (SV), cardiac output (CO) and filling of the heart during graded tilt to evaluate whether SV and CO are maintained during an assumed maximal physiological filling of the heart elicited by 90 degrees HDT in healthy resting humans.
In 26 subjects, central blood volume was manipulated with graded tilt from 60 degrees HUT to 90 degrees HDT. We measured SV, CO (Finometer) and cardiac filling by echocardiography of the left ventricular end-diastolic volume (LVEDV; n=12).
From supine rest to 60 degrees HUT, SV and CO decreased 23 ml [confidence intervals (CI): 16-30; P<0.001; 23%] and 0.9 l/min (0.4-1.4; P<0.0001; 14%), respectively, but neither SV nor CO changed during HDT up to 70 degrees . However, during 90 degrees HDT, SV decreased 12 ml (CI: 6-19; P<0.0001; 12%), with an increase of 21 ml (9-33; P=0.002; 16%) in LVEDV because HR increased 3 bpm and CO decreased 0.5 l/min (ns).
This study confirmed that SV and CO are maximal in resting, supine, healthy humans and decrease during HUT. However, 90 degrees HDT was associated with increased LVEDV and induced a reduction in SV.
心脏功能曲线被广泛认为适用于人类，但不适用于在头高位（HUT）和头低位倾斜（HDT）期间引起的整个心脏充盈范围，分别代表心脏的最小和最大生理充盈。以仰卧休息位为参考，我们评估了在逐渐倾斜时的每搏输出量（SV）、心输出量（CO）和心脏充盈，以评估在健康休息的人类中，90 度 HDT 引起的假设最大生理充盈时 SV 和 CO 是否得到维持。
在 26 名受试者中，通过从 60 度 HUT 到 90 度 HDT 的逐渐倾斜来操纵中心血容量。我们通过左心室舒张末期容积（LVEDV；n=12）的超声心动图测量 SV、CO（Finometer）和心脏充盈。
从仰卧休息位到 60 度 HUT，SV 和 CO 分别下降了 23ml[置信区间（CI）：16-30；P<0.001；23%]和 0.9l/min（0.4-1.4；P<0.0001；14%），但在 HDT 期间，SV 并没有变化，直到 70 度。然而，在 90 度 HDT 时，SV 下降了 12ml（CI：6-19；P<0.0001；12%），LVEDV 增加了 21ml（9-33；P=0.002；16%），因为 HR 增加了 3 次/分钟，CO 下降了 0.5l/min（无统计学意义）。
本研究证实，SV 和 CO 在仰卧休息的健康人群中达到最大值，并在 HUT 时下降。然而，90 度 HDT 与 LVEDV 增加有关，并导致 SV 减少。
