逻辑关系有问题吗？

Modes of proportional ventilation readily available in clinical practice on dedicated ventilators are neurally adjusted ventilatory assist (NAVA) [3], and proportional assist ventilation with load-adjustable gain factors (PAV+) [2]. Their physiological effects are very similar, but they differ in the signal used to control the ventilator. NAVA delivers inspiratory assist in proportion to the diaphragm electrical activity (EAdi), which closely reflects central respiratory drive and is measured via a dedicated nasogastric (feeding) tube with embedded electrodes [3]. PAV+ delivers assist in proportion to the instantaneous flow and volume generated by the patient’s inspiratory effort or muscular pressure (Pmus), which is estimated from semi-continuous automatic measurements of respiratory mechanics applying the equation of motion of the respiratory system [10, 11]. As patients tailor the amount of assist themselves, proportional modes simplify the implementation of assisted mechanical ventilation [12]. An important barrier to wide implementation of those modes, however, is the unfamiliarity with the settings and functioning, which differ from conventional modes. Real-time monitoring of respiratory drive (EAdi time course during NAVA) and patient effort (semi-continuous estimation of Pmus in PAV+) is also available in proportional modes and allows quantification of the physiological response to changes in ventilatory assist. Although proportional modes have been increasingly used, setting inspiratory assist levels remains a challenge at the bedside as it cannot be based on usual parameters such as tidal volumes and PaCO2 targets [13, 14]. Moreover, safe targets for respiratory effort may vary among patients, depending on the severity of lung injury and diaphragm function [15–17]. The uncertainty regarding titration of inspiratory support with NAVA and PAV+ might be one of the reasons why there is still limited data showing improved clinical outcomes when using proportional modes as compared to conventional modes [18, 19], but clinical benefits of NAVA compared to PSV were recently demonstrated in difficult-to-wean patients [20, 21]. At the same time, despite having very complex physiological consequences, PSV maintains an appearance of simplicity and is the most frequently used partially supported mode of ventilation [22].

临床上现有的专用的呼吸机比例通气模式有神经调节辅助通气（NAVA）和负荷可调增益因子比例辅助通气（PAV+）。它们的生理效应非常相似，但它们用来控制呼吸机的信号方式不同。NAVA提供与膈肌电活动（EADI）成比例的吸气辅助通气，EADI与中枢呼吸驱动密切相关，并通过嵌入电极的专用鼻胃（喂食）管进行测量。PAV+提供的通气辅助与患者吸气努力或吸气肌肉压力（Pmus）产生的瞬时流速和容量成比例，Pmus是通过应用呼吸系统运动方程对呼吸力学进行半连续自动测量而估计的。当患者自己决定辅助量时，比例模式简化了辅助机械通气的实施。然而，广泛实施这些模式的一个重要障碍是医师不熟悉这种与传统模式不同的设置和功能。实时监测呼吸驱动（NAVA期间的EADI时间进程）和患者努力（在PAV+时Pmus的半连续估计）的也可采用成比例模式，并允许对通气辅助改变的生理反应进行量化。虽然比例模式已经越来越多地被使用，但在床边设置吸气辅助水平仍然是一个挑战，因为它不能基于潮气量和PaCO2等目标来设置常见参数。此外，根据肺损伤的严重程度和膈肌功能，呼吸努力的安全目标可能因患者不同而不同。与常规模式相比，使用NAVA和PAV+的吸气支持滴定时不设定固定值可能是虽然数据有限但仍然显示与传统模式相比临床结果有所改善的原因之一，但最近在困难脱机的患者中证明了NAVA较PSV相比更大的临床益处。同时，尽管PSV有非常复杂的生理后果，但它保持了简单的外观，也是最常使用的部分支持通气模式。

The uncertainty regarding titration of inspiratory support with NAVA and PAV+ might be one of the reasons why there is still limited data showing improved clinical outcomes when using proportional modes as compared to conventional modes [18, 19], but clinical benefits of NAVA compared to PSV were recently demonstrated in difficult-to-wean patients。我怎么感觉这句话的逻辑关系是顺下来的，没有转折的意味

与常规模式相比，使用NAVA和PAV+的吸气支持滴定时不设定固定值可能是虽然数据有限但仍然显示与传统模式相比临床结果有所改善的原因之一，但最近在困难脱机的患者中证明了NAVA较PSV相比更大的临床益处。