Recruitment manoeuvres dislodge mucus towards the distal airways in an experimental model of severe pneumonia

Abstract Background Recruitment manoeuvres (RM) generate a transient increase in trans-pulmonary pressure that could open collapsed alveoli. RM might generate very high inspiratory airflows. We evaluated whether RM 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 RM 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 RM. The effects of each RM on gas exchange were assessed 15 min after the intervention. Results Before RM, mucus always cleared towards the glottis. Conversely, mucus was displaced towards the distal airways in 28.6% ES applications and 50% of all other RMs ( P =0.053). Median mucus velocity was 1.26 mm min −1 [0.48–3.89] before each RM, 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 PaO 2 failed to improve after RM, mucus was displaced towards the distal airways in 68.7% of the cases, compared with 31.2% RM associated with improved PaO 2 (odds ratio: 4.76 (95% confidence interval: 1.13–19.97). Conclusions RM dislodge mucus distally, irrespective of airflow generated by different RM. Further investigation in humans is warranted to corroborate these pre clinical findings, as there may be limited benefits associated with lung recruitment in pneumonia.