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Background Recruitment manoeuvres generate a transient increase in trans-pulmonary pressure that could open collapsed alveoli. Recruitment manoeuvres might generate very high inspiratory airflows. We evaluated whether recruitment manoeuvres could displace respiratory secretions towards the distal airways and impair gas exchange in a porcine model of bacterial pneumonia. Methods We conducted a prospective randomised study in 10 mechanically ventilated pigs. Pneumonia was produced by direct intra-bronchial introduction of Pseudomonas aeruginosa. Four recruitment manoeuvres were applied randomly: extended sigh (ES), maximal recruitment strategy (MRS), sudden increase in driving pressure and PEEP (SI-PEEP), and sustained inflation (SI). Mucus transport was assessed by fluoroscopic tracking of radiopaque disks before and during each recruitment manoeuvre. The effects of each RM on gas exchange were assessed 15 min after the intervention. Results Before recruitment manoeuvres, mucus always cleared towards the glottis. Conversely, mucus was displaced towards the distal airways in 28.6% ES applications and 50% of all other recruitment manoeuvres (P=0.053). Median mucus velocity was 1.26 mm min−1 [0.48–3.89] before each recruitment manoeuvre, but was reversed (P=0.007) during ES [0.10 mm min−1 [-0.04–1.00]], MRS [0.10 mm min−1 [-0.4–0.48]], SI-PEEP [0.02 mm min−1 [-0.14–0.34]], and SI [0.10 mm min−1 [-0.63–0.75]]. When PaO2 failed to improve after recruitment manoeuvre, mucus was displaced towards the distal airways in 68.7% of the cases, compared with 31.2% recruitment manoeuvres associated with improved PaO2 (odds ratio: 4.76 (95% confidence interval: 1.13–19.97). Conclusions Recruitment manoeuvres dislodge mucus distally, irrespective of airflow generated by different recruitment manoeuvres. Further investigation in humans is warranted to corroborate these pre clinical findings, as there may be limited benefits associated with lung recruitment in pneumonia.

Background Tracheal tube biofilm develops during mechanical ventilation. We compared a novel closed-suctioning system vs standard closed-suctioning system in the prevention of tracheal tube biofilm. Methods Eighteen pigs, on mechanical ventilation for 76 h, with P. aeruginosa pneumonia were randomized to be tracheally suctioned via the KIMVENT* closed-suctioning system (control group) or a novel closed-suctioning system (treatment group), designed to remove tracheal tube biofilm through saline jets and an inflatable balloon. Upon autopsy, two tracheal tube hemi-sections were dissected for confocal and scanning electron microscopy. Biofilm area, maximal and minimal thickness were computed. Biofilm stage was assessed. Results Sixteen animals were included in the final analysis. In the treatment and control group, the mean (sd) pulmonary burden was 3.34 (1.28) and 4.17 (1.09) log cfu gr−1, respectively (P=0.18). Tracheal tube P. aeruginosa colonization was 5.6 (4.9–6.3) and 6.2 (5.6–6.9) cfu ml−1 (median and interquartile range) in the treatment and control group, respectively (P=0.23). In the treatment group, median biofilm area was 3.65 (3.22–4.21) log10 μm2 compared with 4.49 (4.27–4.52) log10 μm2 in the control group (P=0.031). In the treatment and control groups, the maximal biofilm thickness was 48.3 (26.7–71.2) µm (median and interquartile range) and 88.8 (43.8–125.7) µm, respectively. The minimal thickness in the treatment and control group was 0.6 (0–4.0) µm and 23.7 (5.3–27.8) µm (P=0.040) (P=0.017). Earlier stages of biofilm development were found in the treatment group (P Conclusions The novel CSS reduces biofilm accumulation within the tracheal tube. A clinical trial is required to confirm these findings and the impact on major outcomes.