Davis K, Branson R D, Campbell R S, Porembka D T
Department of Surgery, University of Cincinnati Medical Center, OH 45267-0558, USA.
J Trauma. 1996 Nov;41(5):808-14. doi: 10.1097/00005373-199611000-00007.
To examine the hypothesis that a decelerating inspiratory flow waveform is responsible for improvements in gas exchange during pressure control ventilation for acute lung injury.
Prospective, controlled, crossover study.
Twenty-five patients with acute lung injury requiring mechanical ventilation with a positive-end expiratory pressure > or = 10 cm H2O, ventilator frequency of > or = 8 bpm, inspired oxygen concentration of > or = 0.50, peak inspiratory pressure > or = 40 cm H2O, and requiring sedation and paralysis were studied. Patients were ventilated at a tidal volume of 10 mliters/kg, respiratory frequency was set to maintain a pH > 7.30 and PaCO2 < 50 mm Hg, and positive end-expiratory pressure (PEEP) set to maintain Pao2 > 70 mm Hg or Sao2 > 93% with an Fio2 < or = 0.50. In random sequence, ventilator mode was changed from volume control with a square flow waveform, pressure control ventilation with a decelerating flow waveform, or volume control ventilation with a decelerating flow waveform. Tidal volume, minute ventilation, and airway pressures were continuously measured at the proximal airway. After 2 hours of ventilation in each mode, arterial and mixed venous blood gases were drawn and cardiac output determined by thermodilution. Dead space to tidal volume ratio was determined from mixed expired gas concentrations and Paco2. During volume control ventilation with a square flow waveform, Pao2 was decreased (75 +/- 11 mm Hg vs. 85 +/- 9 mm Hg and 89 +/- 12 mm Hg), p < 0.05, and peak inspiratory pressure was increased (50 +/- 9 cm H2O vs. 42 +/- 7 cm H2O and 39 +/- 9 cm H2O) p < 0.05 compared to volume control with a decelerating flow waveform and pressure control ventilation. Mean airway pressure was also lower with volume control with a square flow waveform (17 +/- 4 cm H2O vs. 20 +/- 4 cm H2O and 21 +/- 3 cm H2O) compared to volume control with a decelerating flow waveform and pressure control ventilation. There were no differences in hemodynamic parameters.
Both pressure control ventilation and volume control ventilation with a decelerating flow waveform provided better oxygenation at a lower peak inspiratory pressure and higher mean airway pressure compared to volume control ventilation with a square flow waveform. The results of our study suggest that the reported advantages of pressure control ventilation over volume control ventilation with a square flow waveform can be accomplished with volume control ventilation with a decelerating flow waveform.
检验以下假设，即吸气气流波形减速是压力控制通气治疗急性肺损伤时气体交换改善的原因。
前瞻性、对照、交叉研究。
对25例急性肺损伤患者进行研究，这些患者需要机械通气，呼气末正压≥10 cmH₂O，通气频率≥8次/分钟，吸入氧浓度≥0.50，吸气峰压≥40 cmH₂O，且需要镇静和肌松。患者以10 ml/kg的潮气量进行通气，呼吸频率设定为维持pH>7.30且PaCO₂<50 mmHg，呼气末正压（PEEP）设定为在Fio₂≤0.50时维持Pao₂>70 mmHg或Sao₂>93%。按照随机顺序，通气模式从方波气流波形的容量控制、减速气流波形的压力控制通气或减速气流波形的容量控制通气进行切换。在近端气道连续测量潮气量、分钟通气量和气道压力。每种模式通气2小时后，采集动脉血和混合静脉血血气样本，并通过热稀释法测定心输出量。根据混合呼出气体浓度和Paco₂确定死腔与潮气量之比。在方波气流波形容量控制通气期间，与减速气流波形容量控制通气和压力控制通气相比，Pao₂降低（75±11 mmHg对85±9 mmHg和89±12 mmHg），p<0.05，吸气峰压升高（50±9 cmH₂O对42±7 cmH₂O和39±9 cmH₂O），p<0.05。方波气流波形容量控制通气的平均气道压也低于减速气流波形容量控制通气和压力控制通气（17±4 cmH₂O对20±4 cmH₂O和21±3 cmH₂O）。血流动力学参数无差异。
与方波气流波形容量控制通气相比，减速气流波形的压力控制通气和容量控制通气在较低的吸气峰压和较高的平均气道压下能提供更好的氧合。我们的研究结果表明，压力控制通气相对于方波气流波形容量控制通气所报道的优势，可通过减速气流波形容量控制通气实现。
