Gravity predominates over ventilatory pattern in the prevention of ventilator-associated pneumonia

Gianluigi Li Bassi, Joan Daniel Marti, Lina Saucedo, Montserrat Rigol, Ignasi Roca, Maria Cabanas, Laura Muñoz, Otavio Tavares Ranzani, Valeria Giunta, Nestor Luque, Mariano Esperatti, Albert Gabarrus, Laia Fernandez, Mariano Rinaudo, Miguel Ferrer, Jose Ramirez, Jordi Vila, Antoni Torres

Research output: Contribution to journalArticlepeer-review


OBJECTIVE:: 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. DESIGN:: Prospective randomized animal study. SETTING:: Animal research facility, University of Barcelona, Spain. SUBJECTS:: Twenty-four Large White-Landrace pigs. INTERVENTIONS:: 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 5cm H2O and TITTOT to achieve a mean expiratory-inspiratory flow bias of 10L/min (treatment); 3) in Trendelenburg/prone position and ventilated as in the control group (Trendelenburg). Following randomization, Pseudomonas aeruginosa was instilled into the oropharynx. MEASUREMENTS AND MAIN RESULTS:: 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±2.8L/min, respectively (p <0.001). Mucus clearance rate was 11.3±9.9mm/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). CONCLUSIONS:: 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.

Original languageEnglish
JournalCritical Care Medicine
Issue number9
Publication statusPublished - 2014


  • mechanical ventilation
  • mucus clearance
  • semirecumbent position
  • ventilator-associated pneumonia

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine


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