Eastwood P R, Hillman D R
Dept of Pulmonary Physiology, Sir Charles Gairdner Hospital, Nedlands, Western Australia.
Eur Respir J. 1995 Mar;8(3):463-6. doi: 10.1183/09031936.95.08030463.
Threshold loading is a method of incrementally loading the inspiratory muscles, which requires development of an adjustable threshold pressure (Pth) before air will flow. In the ideal device, flow is independent of pressure once Pth is exceeded. A "weighted plunger" apparatus is commonly used, but devices described previously perform unreliably at high inspiratory load. We have modified this apparatus using the diaphragm and valve seating from a threshold valve used to deliver positive airway pressure (AMBU 10, AMBU International, Denmark) to yield improved pressure-flow characteristics. With this device, there was a linear relationship between Pth and weight on the plunger (r = 0.998), and flow was largely independent of pressure once Pth was exceeded: pressure developed at an inspiratory flow of 1.3 +/- 0.1 l.s-1 was 13.6 +/- 7.0% below Pth. Our modified weighted plunger apparatus allows consistent and reliable threshold loading of inspiratory muscles, even at high inspiratory loads.
阈负荷是一种对吸气肌进行递增负荷的方法，该方法要求在气流流动之前先设定一个可调节的阈压力（Pth）。在理想的装置中，一旦超过Pth，气流就与压力无关。通常使用“加重活塞”装置，但先前描述的装置在高吸气负荷下表现不可靠。我们使用了一个用于输送气道正压的阈门（丹麦AMBU国际公司的AMBU 10）的隔膜和阀座对该装置进行了改进，以获得更好的压力-气流特性。使用该装置时，Pth与活塞上的重量之间呈线性关系（r = 0.998），一旦超过Pth，气流在很大程度上与压力无关：在吸气流量为1.3 +/- 0.1 l.s-1时产生的压力比Pth低13.6 +/- 7.0%。我们改进的加重活塞装置即使在高吸气负荷下也能对吸气肌进行一致且可靠的阈负荷训练。
