Li Bassi Gianluigi, Marti Joan Daniel, Saucedo Lina, Rigol Montserrat, Roca Ignasi, Cabanas Maria, Muñoz Laura, Ranzani Otavio Tavares, Giunta Valeria, Luque Nestor, Esperatti Mariano, Gabarrus Albert, Fernandez Laia, Rinaudo Mariano, Ferrer Miguel, Ramirez Jose, Vila Jordi, Torres Antoni
1Department of Pulmonary and Critical Care Medicine, Division of Animal Experimentation, Hospital Clínic, Thorax Institute, Barcelona, Spain. 2Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain. 3Centro de Investigación Biomedica En Red-Enfermedades Respiratorias, Barcelona, Spain. 4Department of Cardiology, Hospital Clínic, Thorax Institute, Barcelona, Spain. 5Department of Clinical Microbiology, School of Medicine, and Barcelona Centre for International Health Research (CRESIB, Hospital Clínic, Universitat de Barcelona), Barcelona, Spain. 6Department of Pathology, Hospital Clínic, Barcelona, Spain. 7Pulmonary Intensive Care Unit, Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil. 8Department of Pneumology, Hospital Clínic, Thorax Institute, Office of Biostatistics, Barcelona, Spain. 9University of Barcelona, Barcelona, Spain.
Crit Care Med. 2014 Sep;42(9):e620-7. doi: 10.1097/CCM.0000000000000487.
In the semirecumbent position, gravity-dependent dissemination of pathogens has been implicated in the pathogenesis of ventilator-associated pneumonia. We compared the preventive effects of a ventilatory strategy, aimed at decreasing pulmonary aspiration and enhancing mucus clearance versus the Trendelenburg position.
Prospective randomized animal study.
Animal research facility, University of Barcelona, Spain.
Twenty-four Large White-Landrace pigs.
Pigs were intubated and on mechanical ventilation for 72 hours. Following surgical preparation, pigs were randomized to be positioned: 1) in semirecumbent/prone position, ventilated with a duty cycle (TITTOT) of 0.33 and without positive end-expiratory pressure (control); 2) as in the control group, positive end-expiratory pressure of 5 cm H2O and TITTOT to achieve a mean expiratory-inspiratory flow bias of 10 L/min (treatment); 3) in Trendelenburg/prone position and ventilated as in the control group (Trendelenburg). Following randomization, Pseudomonas aeruginosa was instilled into the oropharynx.
Mucus clearance rate was measured through fluoroscopic tracking of tracheal markers. Microspheres were instilled into the subglottic trachea to assess pulmonary aspiration. Ventilator-associated pneumonia was confirmed by histological/microbiological studies. The mean expiratory-inspiratory flow in the treatment, control, and Trendelenburg groups were 10.7 ± 1.7, 1.8 ± 3.7 and 4.3 ± 2.8 L/min, respectively (p < 0.001). Mucus clearance rate was 11.3 ± 9.9 mm/min in the Trendelenburg group versus 0.1 ± 1.0 in the control and 0.2 ± 1.0 in the treatment groups (p = 0.002). In the control group, we recovered 1.35% ± 1.24% of the instilled microspheres per gram of tracheal secretions, whereas 0.22% ± 0.25% and 0.97% ± 1.44% were recovered in the treatment and Trendelenburg groups, respectively (p = 0.031). Ventilator-associated pneumonia developed in 66.67%, 85.71%, and 0% of the animals in the control, treatment, and Trendelenburg groups (p < 0.001).
The Trendelenburg position predominates over expiratory flow bias and positive end-expiratory pressure in the prevention of gravity-dependent translocation of oropharyngeal pathogens and development of ventilator-associated pneumonia. These findings further substantiate the primary role of gravity in the pathogenesis of ventilator-associated pneumonia.
在半卧位时，病原体因重力作用而扩散被认为与呼吸机相关性肺炎的发病机制有关。我们比较了一种旨在减少肺误吸和增强黏液清除的通气策略与头低脚高位的预防效果。
前瞻性随机动物研究。
西班牙巴塞罗那大学动物研究设施。
24头大白-长白猪。
猪进行气管插管并机械通气72小时。在外科准备后，猪被随机分组安置：1）处于半卧位/俯卧位，以0.33的占空比（TITTOT）通气且无呼气末正压（对照组）；2）与对照组相同，但呼气末正压为5 cm H₂O且采用TITTOT以实现平均呼气-吸气流量偏转为10 L/min（治疗组）；3）处于头低脚高位/俯卧位并与对照组相同方式通气（头低脚高位组）。随机分组后，将铜绿假单胞菌滴入口咽部。
通过荧光透视追踪气管标志物来测量黏液清除率。将微球滴入声门下气管以评估肺误吸情况。通过组织学/微生物学研究确诊呼吸机相关性肺炎。治疗组、对照组和头低脚高位组的平均呼气-吸气流量分别为10.7±1.7、1.8±3.7和4.3±2.8 L/min（p<0.001）。头低脚高位组的黏液清除率为11.3±9.9 mm/min，而对照组为0.1±1.0，治疗组为0.2±1.0（p = 0.002）。在对照组中，每克气管分泌物中回收的滴入微球为1.35%±1.24%，而治疗组和头低脚高位组分别为0.22%±0.25%和0.97%±1.44%（p = 0.031）。对照组、治疗组和头低脚高位组动物发生呼吸机相关性肺炎的比例分别为66.67%、85.71%和0%（p<0.001）。
在预防口咽病原体因重力作用而移位及呼吸机相关性肺炎的发生方面，头低脚高位比呼气流量偏置和呼气末正压更具优势。这些发现进一步证实了重力在呼吸机相关性肺炎发病机制中的主要作用。
