Grasso Francesco, Engelberts Doreen, Helm Emma, Frndova Helena, Jarvis Steven, Talakoub Omid, McKerlie Colin, Babyn Paul, Post Martin, Kavanagh Brian P
Department of Critical Care Medicine, Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada.
Am J Respir Crit Care Med. 2008 Feb 15;177(4):412-8. doi: 10.1164/rccm.200707-1004OC. Epub 2007 Dec 13.
Conventional positive-pressure ventilation delivers pressure to the airways; in contrast, negative pressure is delivered globally to the chest and abdomen.
To test the hypothesis that ventilation with negative pressure results in better oxygenation and less injury than with positive pressure.
Anesthetized, surfactant-depleted rabbits were ventilated for 2.5 hours in pairs (positive or negative). Tidal volume was 12 ml . kg(-1), normocapnia was maintained by adjusting respiratory rate, and Fi(O(2)) was 1.0.
Lung injury was assessed with histologic scoring, perfusion using thermodilution (global perfusion), and injected intravascular microspheres (regional perfusion); and dynamic computed tomography was used to determine inflation patterns. Negative pressure was associated with a higher Pa(O(2)), a lower Pa-Pet(CO(2)) gradient (despite identical minute ventilation), and less lung injury. Lung perfusion (global and regional) was similar with positive and negative pressure. Positive end-expiratory pressure applied to the airway was more efficiently transmitted to the pleural space than comparable levels of negative end-expiratory pressure applied to the chest wall; however, the oxygenation associated with any level of end-expiratory lung volume was greater when achieved by negative versus positive pressure. Dynamic computed tomography suggested that lung distension achieved with negative pressure is characterized by greater proportions of normally aerated lung (with less atelectasis) during inspiration and at end-expiration.
Negative-pressure ventilation results in superior oxygenation that is unrelated to lung perfusion and may be explained by more effective inflation of lung volume during both inspiration and expiration.
传统的正压通气是将压力施加于气道；相比之下，负压是整体施加于胸部和腹部。
检验负压通气比正压通气能带来更好的氧合且损伤更小这一假设。
对麻醉且缺乏表面活性物质的兔子进行配对通气2.5小时（正压或负压）。潮气量为12 ml·kg⁻¹，通过调整呼吸频率维持正常碳酸血症，吸入氧分数为1.0。
采用组织学评分评估肺损伤，用热稀释法（整体灌注）和注入血管内微球（局部灌注）评估灌注情况；并使用动态计算机断层扫描确定充气模式。负压通气与更高的动脉血氧分压、更低的动脉 - 呼气末二氧化碳分压梯度（尽管分钟通气量相同）以及更少的肺损伤相关。正压和负压通气时的肺灌注（整体和局部）相似。施加于气道的呼气末正压比施加于胸壁的同等水平的呼气末负压更有效地传递至胸膜腔；然而，与任何呼气末肺容积水平相关的氧合在负压通气时比正压通气时更高。动态计算机断层扫描显示，负压通气实现的肺扩张特点是在吸气和呼气末正常充气肺的比例更高（肺不张更少）。
负压通气导致更好的氧合，这与肺灌注无关，可能是由于在吸气和呼气过程中肺容积的充气更有效。
