Lutchen K R, Yang K, Kaczka D W, Suki B
Department of Biomedical Engineering, Boston University, Massachusetts 02215.
J Appl Physiol (1985). 1993 Jul;75(1):478-88. doi: 10.1152/jappl.1993.75.1.478.
We present a broad-band optimal ventilator waveform (OVW), the concept of which was to create a computer-driven ventilator waveform containing increased energy at specific frequencies (f). Values of f were chosen such that nonlinear harmonic distortion and intermodulation were minimized. The phases at each f were then optimized such that the resulting flow waveform delivered sufficient volume to maintain gas exchange while minimizing peak-to-peak airway opening pressure. Simulations with a linear anatomically consistent branching airway model and a nonlinear viscoelastic model showed that respiratory resistance (Rrs) and elastance (Ers) estimates at 0.1-2 Hz from the OVW are far superior to those from a standard step ventilator waveform (SVW) during healthy and obstructed conditions and that the OVW reduces the influences of harmonic interactions. Using a servo-controlled oscillator, we applied individual sine waves, an OVW containing energy at 0.15625-2.4 Hz, and an SVW to healthy humans and one symptomatic asthmatic subject before and after bronchodilation. The OVW was markedly superior to the SVW and always provided smooth estimates of Rrs and Ers. Before bronchodilation in the asthmatic subject Rrs was highly elevated and Ers was markedly increased with f; after bronchodilation the level of Rrs and the f dependence of Ers decreased. Although based on results from only one asthmatic subject, these data suggest a dominant influence of airway constriction and lung inhomogeneities during asthmatic bronchoconstriction that is alleviated by bronchodilators. These and other results indicate that the OVW approach has high potential for simultaneously probing f and amplitude dependence in the mechanical properties of clinical subjects during physiological breathing conditions and perhaps during dynamic bronchoconstriction.
我们提出了一种宽带最优通气波形（OVW），其概念是创建一种计算机驱动的通气波形，该波形在特定频率（f）下包含增加的能量。选择f的值，以使非线性谐波失真和互调最小化。然后优化每个f处的相位，使得产生的流量波形输送足够的容积以维持气体交换，同时使峰峰值气道开口压力最小化。使用线性解剖学一致的分支气道模型和非线性粘弹性模型进行的模拟表明，在健康和阻塞状态下，从OVW估计的0.1 - 2Hz的呼吸阻力（Rrs）和弹性（Ers）远优于标准阶跃通气波形（SVW），并且OVW减少了谐波相互作用的影响。我们使用伺服控制振荡器，在支气管扩张前后，将单个正弦波、包含0.15625 - 2.4Hz能量的OVW和SVW应用于健康人和一名有症状的哮喘患者。OVW明显优于SVW，并且始终能提供对Rrs和Ers的平滑估计。在哮喘患者支气管扩张前，Rrs显著升高，并且Ers随f显著增加；支气管扩张后，Rrs水平以及Ers对f的依赖性降低。尽管仅基于一名哮喘患者的结果，但这些数据表明在哮喘性支气管收缩期间气道收缩和肺不均匀性的主要影响，而支气管扩张剂可减轻这种影响。这些以及其他结果表明，OVW方法在生理呼吸条件下以及可能在动态支气管收缩期间同时探测临床受试者机械特性中f和幅度依赖性方面具有很大潜力。
