Amato M B, Barbas C S, Bonassa J, Saldiva P H, Zin W A, de Carvalho C R
Respiratory Intensive Care Unit, Hospital das Clínicas, Universidade de São Paulo, Brazil.
Chest. 1992 Oct;102(4):1225-34. doi: 10.1378/chest.102.4.1225.
This study reports the preliminary clinical evaluation of a new mode of ventilation--volume-assured pressure support ventilation (VAPSV)--which incorporates inspiratory pressure support (PSV) with conventional volume-assisted cycles (VAV). This combination optimizes the inspiratory flow during assisted/controlled cycles, reducing the patient's respiratory burden commonly observed during VAV. Different from conventional PSV, VAPSV assures precise control of tidal volume (VT) in unstable patients. Eight patients with acute respiratory failure (ARF) were submitted to assisted ventilation under VAV and VAPSV. Patient's ventilatory workload (evaluated through the pressure-time product, mechanical work per liter of ventilation, and work per minute) and patient's ventilatory drive (occlusion pressure--P0.1) were significantly reduced during VAPSV. This "relief" was more evident among the most distressed patients (p < 0.001), allowing a reduction of more than 60 percent in muscle load, without the need of increasing peak tracheal pressure. Mean inspiratory flow (VT/TI), VT, and effective dynamic compliance were significantly increased during VAPSV, whereas the effective inspiratory impedance decreased. These mechanical advantages of VAPSV allowed a reduction of intrinsic PEEP, whenever it was present. Blood gas values were similar in both periods. We concluded that VAPSV is a promising form of ventilatory support. At the same time that it was able to safely assure a minimum preset VT, VAPSV reduced patient workload and improved synchrony between the patient and the ventilator during ARF.
本研究报告了一种新的通气模式——容量保证压力支持通气（VAPSV）的初步临床评估，该模式将吸气压力支持（PSV）与传统的容量辅助通气周期（VAV）相结合。这种结合优化了辅助/控制通气周期中的吸气流量，减轻了VAV期间常见的患者呼吸负担。与传统PSV不同，VAPSV可确保对不稳定患者的潮气量（VT）进行精确控制。八名急性呼吸衰竭（ARF）患者接受了VAV和VAPSV模式下的辅助通气。在VAPSV期间，患者的通气负荷（通过压力-时间乘积、每升通气的机械功和每分钟功评估）和通气驱动（阻断压力——P0.1）显著降低。这种“缓解”在病情最严重的患者中更为明显（p<0.001），无需增加气管峰值压力即可使肌肉负荷降低60%以上。VAPSV期间，平均吸气流量（VT/TI）、VT和有效动态顺应性显著增加，而有效吸气阻抗降低。VAPSV的这些机械优势可降低内源性PEEP（如果存在）。两个阶段的血气值相似。我们得出结论，VAPSV是一种有前景的通气支持形式。在能够安全保证最低预设VT的同时，VAPSV减轻了患者的负荷，并改善了ARF期间患者与呼吸机之间的同步性。
