Davidson Shaun, Pretty Chris, Pironet Antoine, Desaive Thomas, Janssen Nathalie, Lambermont Bernard, Morimont Philippe, Chase J Geoffrey
Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand.
GIGA-Cardiovascular Sciences, University of Liège, Liège, Belgium.
PLoS One. 2017 Apr 27;12(4):e0176302. doi: 10.1371/journal.pone.0176302. eCollection 2017.
This paper develops a means of more easily and less invasively estimating ventricular dead space volume (Vd), an important, but difficult to measure physiological parameter. Vd represents a subject and condition dependent portion of measured ventricular volume that is not actively participating in ventricular function. It is employed in models based on the time varying elastance concept, which see widespread use in haemodynamic studies, and may have direct diagnostic use. The proposed method involves linear extrapolation of a Frank-Starling curve (stroke volume vs end-diastolic volume) and its end-systolic equivalent (stroke volume vs end-systolic volume), developed across normal clinical procedures such as recruitment manoeuvres, to their point of intersection with the y-axis (where stroke volume is 0) to determine Vd. To demonstrate the broad applicability of the method, it was validated across a cohort of six sedated and anaesthetised male Pietrain pigs, encompassing a variety of cardiac states from healthy baseline behaviour to circulatory failure due to septic shock induced by endotoxin infusion. Linear extrapolation of the curves was supported by strong linear correlation coefficients of R = 0.78 and R = 0.80 average for pre- and post- endotoxin infusion respectively, as well as good agreement between the two linearly extrapolated y-intercepts (Vd) for each subject (no more than 7.8% variation). Method validity was further supported by the physiologically reasonable Vd values produced, equivalent to 44.3-53.1% and 49.3-82.6% of baseline end-systolic volume before and after endotoxin infusion respectively. This method has the potential to allow Vd to be estimated without a particularly demanding, specialised protocol in an experimental environment. Further, due to the common use of both mechanical ventilation and recruitment manoeuvres in intensive care, this method, subject to the availability of multi-beat echocardiography, has the potential to allow for estimation of Vd in a clinical environment.
本文提出了一种更简便、侵入性更小的方法来估算心室死腔容积（Vd），这是一个重要但难以测量的生理参数。Vd代表测量心室容积中不积极参与心室功能的、与个体和状况相关的部分。它被用于基于时变弹性概念的模型中，该模型在血流动力学研究中广泛应用，并且可能具有直接诊断用途。所提出的方法涉及对Frank-Starling曲线（每搏输出量与舒张末期容积）及其收缩末期等效曲线（每搏输出量与收缩末期容积）进行线性外推，这些曲线是在诸如肺复张手法等正常临床操作过程中生成的，将它们外推至与y轴的交点（每搏输出量为0处）以确定Vd。为了证明该方法的广泛适用性，在一组六只经镇静和麻醉的雄性皮特兰猪中进行了验证，涵盖了从健康基线状态到因内毒素输注引起的脓毒性休克导致循环衰竭的各种心脏状态。曲线的线性外推得到了强有力的线性相关系数支持，内毒素输注前和后平均分别为R = 0.78和R = 0.80，并且每个受试者的两个线性外推y轴截距（Vd）之间具有良好的一致性（变化不超过7.8%）。所产生的生理上合理的Vd值进一步支持了方法的有效性，内毒素输注前和后分别相当于基线收缩末期容积的44.3 - 53.1%和49.3 - 82.6%。该方法有可能在实验环境中无需特别苛刻的专门方案就能估算Vd。此外，由于重症监护中机械通气和肺复张手法都很常用，在具备多搏超声心动图的情况下，该方法有可能在临床环境中估算Vd。
