Banner M J, Kirby R R, Blanch P B, Layon A J
Department of Anesthesiology, University of Florida, Gainesville.
Crit Care Med. 1993 Sep;21(9):1333-8. doi: 10.1097/00003246-199309000-00017.
To apply pressure-support ventilation with the goal of decreasing the imposed work of the breathing apparatus (endotracheal tube, breathing circuit tubing, and the ventilator's demand-flow system) to zero and to evaluate a clinical method of measuring the imposed work of breathing.
A prospective evaluation of adult and pediatric patients receiving mechanical ventilatory support.
A surgical and a pediatric intensive care unit in a university hospital.
Fifteen patients (11 adult and four pediatric), who were diagnosed with acute respiratory failure from various etiologies, and who were intubated and spontaneously breathing, received continuous positive airway pressure and pressure-support ventilation.
Imposed work of the breathing apparatus was calculated by integrating pressure measured at the tracheal end of the endotracheal tube from a narrow air-filled catheter and the change in volume from a miniature pneumotachograph (flow sensor) positioned between the "Y" piece of the breathing circuit and the endotracheal tube. Pressure and volume signals were directed to a computerized, portable respiratory monitor (Bicore Monitoring Systems) that provides real-time display of the pressure-volume (work) loops and calculation of the imposed work. Imposed work was measured at 0 cm H2O pressure-support ventilation, and then incremental levels of pressure-support ventilation were applied until the imposed work decreased to zero. Imposed work decreased in a quadratic fashion after incremental levels of pressure-support ventilation (r = -.83 [r2 = .69]; p < .001). At pressure-support ventilation level of 0 cm H2O, the imposed work was 0.60 +/- 0.17 joule/L. At mean pressure-support ventilation levels of 13.5 +/- 4.8 cm H2O, imposed work decreased to 0 joule/L.
Ideally, the imposed work of the breathing apparatus should be zero to decrease the afterload on the ventilatory muscles and, thus, the patient's work of breathing. Eliminating the imposed work is achieved using appropriate levels of pressure-support ventilation. We describe an easily applied, practical method of measuring imposed work using a commercially available, portable, bedside respiratory monitor. We recommend that all patients diagnosed with respiratory failure and compromised pulmonary mechanics and who are intubated and breathing spontaneously, receive at least a minimal level of pressure-support ventilation that results in zero breathing apparatus-imposed work of breathing.
应用压力支持通气，目标是将呼吸设备（气管内导管、呼吸回路管道和呼吸机的按需流量系统）所施加的功降至零，并评估一种测量呼吸设备所做功的临床方法。
对接受机械通气支持的成人和儿科患者进行前瞻性评估。
一所大学医院的外科重症监护病房和儿科重症监护病房。
15例患者（11例成人和4例儿科患者），因各种病因被诊断为急性呼吸衰竭，已插管且自主呼吸，接受持续气道正压通气和压力支持通气。
通过对细充气管在气管内导管气管端测得的压力与置于呼吸回路“Y”形接头和气管内导管之间的微型呼吸流速仪（流量传感器）的容积变化进行积分，计算呼吸设备所施加的功。压力和容积信号被传输至一台计算机化的便携式呼吸监测仪（Bicore监测系统），该监测仪可实时显示压力-容积（功）环并计算所施加的功。在压力支持通气为0 cmH₂O时测量所施加的功，然后逐渐增加压力支持通气水平，直至所施加的功降至零。在逐渐增加压力支持通气水平后，所施加的功呈二次方下降（r = -0.83[r² = 0.69]；p < 0.001）。在压力支持通气水平为0 cmH₂O时，所施加的功为0.60±0.17焦耳/升。在平均压力支持通气水平为13.5±4.8 cmH₂O时，所施加的功降至0焦耳/升。
理想情况下，呼吸设备所施加的功应为零，以减轻通气肌肉的后负荷，从而减轻患者的呼吸功。通过适当水平的压力支持通气可消除所施加的功。我们描述了一种使用市售便携式床边呼吸监测仪测量所施加功的简便实用方法。我们建议，所有被诊断为呼吸衰竭且肺力学受损、已插管且自主呼吸的患者，至少接受能使呼吸设备所施加的呼吸功为零的最低水平压力支持通气。
