Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, Hugstetter Strasse 55, 79106 Freiburg, Germany.
Physiol Meas. 2020 May 7;41(4):045005. doi: 10.1088/1361-6579/ab83e6.
Flow-controlled expiration (FLEX) and flow-controlled ventilation (FCV) imply a linearized expiration, and were suggested as new approaches for lung-protective ventilation, especially in the case of an inhomogeneous lung. We hypothesized that a linearized expiration homogenizes the pressure distribution between compartments during expiration, compared to volume-controlled (VCV) and pressure-controlled (PCV) ventilation.
We investigated the expiratory pressure decays in a physical model of an inhomogeneous respiratory system. The model contained four compartments of which two had a high (25 ml cmHO) and two a low compliance (10 ml cmHO). These were combined with either a high (6.5 cmHO s l) or low resistance (2.8 cmHO s l), respectively. The model was ventilated in all modes at various tidal volumes and peak pressures, and we determined in each compartment the expiratory time at which the pressure declined to 50% (t) of the end-inspiratory pressure, and the maximal differences of t (Δt) and pressure (Δp) between all compartments.
During FLEX and FCV, t was 6- to 7-fold higher compared to VCV and PCV (all P < 0.001). During VCV and PCV, Δt was higher (128 ± 18 ms) compared to FLEX and FCV (49 ± 19 ms; all P < 0.001). Δp reached up to 3.8 ± 0.2 cmHO during VCV and PCV, but only 0.6 ± 0.1 cmHO during FLEX and FCV (P < 0.001).
FLEX and FCV provide a more homogeneous expiratory pressure distribution between compartments with different mechanical properties compared with VCV and PCV. This may reduce shear stress within inhomogeneous lung tissue.
流量控制呼气（FLEX）和流量控制通气（FCV）意味着呼气的线性化，被建议作为肺保护性通气的新方法，特别是在肺部不均匀的情况下。我们假设与容量控制（VCV）和压力控制（PCV）通气相比，线性化呼气使各腔室之间的压力分布在呼气过程中均匀化。
我们在不均匀呼吸系统的物理模型中研究了呼气压力衰减。该模型包含四个腔室，其中两个具有较高的顺应性（25mlcmHO），两个具有较低的顺应性（10mlcmHO）。它们分别与较高（6.5cmHOSL）或较低阻力（2.8cmHOSL）相结合。该模型在各种潮气量和峰压下以所有模式进行通气，我们在每个腔室中确定了压力下降到终吸气压的 50%（t）的呼气时间，以及所有腔室之间 t（Δt）和压力（Δp）的最大差异。
在 FLEX 和 FCV 期间，t 比 VCV 和 PCV 高 6-7 倍（所有 P <0.001）。在 VCV 和 PCV 期间，Δt 较高（128±18ms），与 FLEX 和 FCV 相比（49±19ms；所有 P <0.001）。在 VCV 和 PCV 期间，Δp 达到 3.8±0.2cmHO，但在 FLEX 和 FCV 期间仅为 0.6±0.1cmHO（P<0.001）。
与 VCV 和 PCV 相比，FLEX 和 FCV 可在具有不同机械特性的腔室之间提供更均匀的呼气压力分布。这可能会减少不均匀肺组织内的剪切力。
