Banner M J, Kirby R R, Gabrielli A, Blanch P B, Layon A J
University of Florida College of Medicine, Department of Anesthesiology, Gainesville.
Chest. 1994 Dec;106(6):1835-42. doi: 10.1378/chest.106.6.1835.
To evaluate the clinical feasibility of using real-time measurements of work of breathing obtained at the bedside with a portable, commercially available respiratory monitor as an objective and quantifiable guideline for appropriately setting pressure support ventilation (PSV) to partially and totally unload the respiratory muscles in patients with respiratory failure.
In vivo measurements of work of breathing were performed on a consecutive series of patients after applying incremental levels of PSV.
University teaching hospital in a surgical ICU.
Thirty adults (18 men and 12 women, ages 20 to 77 years) who had acute respiratory failure were studied. All patients had an endotracheal or a tracheostomy tube in place and were breathing spontaneously, receiving continuous positive airway pressure and PSV.
Intraesophageal pressure (indirect measurement of intrapleural pressure) was measured with an esophageal balloon catheter positioned in the mid- to lower-third of the esophagus. Tidal volume was obtained by positioning a flow sensor between the "Y" piece of the breathing circuit and the endotracheal or tracheostomy tube. Airway pressure was measured from a catheter attached to the flow sensor. Data from these measurements were directed to the respiratory monitor (CP-100, Bicore Monitoring Systems) which calculates work of breathing performed by the patient using the Campbell diagram. Work of breathing performed by the ventilator to inflate the respiratory system was calculated by the monitor by integrating the change in airway pressure and tidal volume. Initially, the level of PSV was set to 0 cm H2O and work measurements were obtained. Pressure support ventilation was then increased until the work performed by the patient decreased to a range of 0.3 to 0.6 J/L, which corresponds to a normal range for physiologic work of breathing (ie, partial respiratory muscle unloading), and then until the work decreased to 0 J/L (ie, total respiratory muscle unloading).
Work performed by the patient varied inversely (r = -0.83; p < 0.001) and work performed by the ventilator varied directly with the level of PSV (r = 0.94; p < 0.001). Work performed by the patient was 1.5 +/- 0.3 J/L at zero pressure support ventilation and decreased significantly to 0.50 +/- 0.1 J/L (p < 0.05) as the level of PSV was increased to 18 +/- 7 cm H2O. The respiratory muscles were partially unloaded under these conditions. Patient work decreased to 0 J/L and ventilator work increased when the muscles were totally unloaded at a PSV level of 31 +/- 8 cm H2O.
We propose an objective and goal-oriented clinical approach for using PSV by directly measuring the work of breathing performed by the patient with an easy to operate, bedside respiratory monitor and then applying pressure support ventilation to decrease the work to appropriate levels. Partially or totally shifting the workload from the respiratory muscles to the ventilator is appropriate under specific clinical conditions.
评估使用便携式、市售呼吸监测仪在床边实时测量呼吸功作为客观且可量化的指导原则，以适当设置压力支持通气（PSV）来部分或完全减轻呼吸衰竭患者呼吸肌负荷的临床可行性。
在应用递增水平的PSV后，对一系列连续的患者进行呼吸功的体内测量。
外科重症监护病房的大学教学医院。
研究了30名患有急性呼吸衰竭的成年人（18名男性和12名女性，年龄20至77岁）。所有患者均有气管内插管或气管造口管，且自主呼吸，接受持续气道正压通气和PSV。
使用置于食管中下段的食管气囊导管测量食管内压力（间接测量胸腔内压力）。通过将流量传感器置于呼吸回路的“Y”形接头与气管内插管或气管造口管之间来获取潮气量。从连接到流量传感器的导管测量气道压力。这些测量数据被传输到呼吸监测仪（CP - 100，Bicore监测系统），该监测仪使用坎贝尔图计算患者的呼吸功。监测仪通过整合气道压力和潮气量的变化来计算呼吸机使呼吸系统充气所做的功。最初，PSV水平设置为0 cm H₂O并获取功的测量值。然后增加压力支持通气，直到患者所做的功降至0.3至0.6 J/L的范围，这对应于呼吸生理功的正常范围（即部分呼吸肌卸载），然后直到功降至0 J/L（即完全呼吸肌卸载）。
患者所做之功呈反比变化（r = -0.83；p < 0.001），呼吸机所做之功与PSV水平呈正比变化（r = 0.94；p < 0.001）。在零压力支持通气时，患者所做之功为1.5±0.3 J/L，并随着PSV水平增加至18±7 cm H₂O而显著降至0.50±0.1 J/L（p < 0.05）。在这些条件下呼吸肌得到部分卸载。当在PSV水平为31±8 cm H₂O时呼吸肌完全卸载时，患者所做之功降至0 J/L，呼吸机所做之功增加。
我们提出一种客观且以目标为导向使用PSV的临床方法，即通过使用易于操作的床边呼吸监测仪直接测量患者的呼吸功，然后应用压力支持通气将功降至适当水平。在特定临床条件下，将工作负荷部分或完全从呼吸肌转移到呼吸机是合适的。
