Marinakis Giorgos, Paraschos Michael, Patrani Maria, Tsoutsouras Theodoros, Vassiliou Miltos
Dept of Critical Care Medicine, General Hospital of Athens, "Korgialenio - Benakio" Hellenic Red Cross, Athens, Greece.
Pulmonology Dept, Ioannina Medical School, Ioannina, Greece.
ERJ Open Res. 2021 Jan 25;7(1). doi: 10.1183/23120541.00264-2020. eCollection 2021 Jan.
Expiratory flow limitation (EFL) is common among patients in the intensive care unit under mechanical ventilation (MV) and may have significant clinical consequences. In the present study, we examine the possibility of non-interventional detection of EFL during experimental MV.
Eight artificially ventilated New Zealand rabbits were included in the experiments. EFL was induced during MV by application of negative expiratory pressure (-5, -8 and -10 hPa) and detected by the negative expiratory pressure technique. Airway pressure ( ) and gas flow () were digitally recorded and processed off-line for the evaluation of respiratory mechanics. The method is based on the computation and monitoring of instantaneous respiratory resistance (t). The resistive pressure ( (t)) is calculated by subtracting from its elastic component and the end-expiratory pressure, as assessed by linear regression. Then, (t) is computed as the instant ratio (t)/(t).
Two completely different patterns of expiratory (t) separate the cases with EFL from those without EFL. Small and random fluctuations are noticed when EFL is absent, whereas the onset of EFL is accompanied by an abrupt and continuous rise in (t), towards the end of expiration. Thus, EFL is not only detected but may also be quantified from the volume still to be expired at the time EFL occurs.
The proposed technique is a simple, accurate and non-interventional tool for EFL monitoring during MV.
呼气流量受限（EFL）在接受机械通气（MV）的重症监护病房患者中很常见，可能会产生重大临床后果。在本研究中，我们探讨了在实验性机械通气期间非介入性检测呼气流量受限的可能性。
八只人工通气的新西兰兔被纳入实验。在机械通气期间通过施加呼气负压（-5、-8和-10 hPa）诱导呼气流量受限，并采用呼气负压技术进行检测。气道压力（）和气体流量（）进行数字记录，并离线处理以评估呼吸力学。该方法基于瞬时呼吸阻力（t）的计算和监测。通过从 中减去其弹性成分和呼气末压力（通过线性回归评估）来计算阻力压力（（t））。然后，将（t）计算为瞬时比值（t）/（t）。
两种完全不同的呼气（t）模式将存在呼气流量受限的情况与不存在呼气流量受限的情况区分开来。当不存在呼气流量受限时，会出现小的随机波动，而呼气流量受限开始时，在呼气末期（t）会突然持续上升。因此，不仅可以检测到呼气流量受限，还可以根据呼气流量受限发生时仍有待呼出的气量对其进行量化。
所提出的技术是一种用于机械通气期间呼气流量受限监测的简单、准确且非介入性的工具。
