Objective: To investigate from literature how recruitment manoeuvres are being performed and from this information to deduce directions on how to recruit in order to find a standardized and optimal method of lung volume recruitment as a starting point for future clinical trials. Search strategy:We identified the most relevant English language publications on lung recruitment by search- ing the Medline database. We limited our search to human adult studies. Thirty-four studies were selected. Summary of findings:Only a limited number of studies on the use of lung recruitment manoeuvres were available, and only a few patients with diverse follow-up periods were included, the most common category being ALI/ARDS patients. There was some small indication for the superiority of recruitment manoeuvres in patients with extra-pulmonary and early ARDS. CPAP followed by pressure-controlled ventilation was most commonly used during lung recruitment. Maximum airway recruitment pressures are on average 45-50 cmH2O but may be as high as 80 cmH2O. Recruitment duration varied between 3.3 seconds and one hour; muscle paralysis was often used. Adjustment of PEEP was not standard practice after recruitment. Improvements in blood oxygenation and respiratory mechanics most commonly defined successful recruitment and their deterioration was cited as a reason to repeat recruitment. Recruitment was found to be most com- monly terminated due to haemodynamic instability or barotraumas. The majority of trials studying recruitment manoeuvres favour these procedures. Conclusions: The categories of patient who profited most from recruitment were those with ALI/ARDS, post-cardiac surgery patients and patients with lung collapse after endotracheal suctioning. We believe the use of the PaO2/FiO2-ratio (P/F-ratio) is at present the method that best combines practicality with sensitivity in defining the state of openness of a lung. Limiting peak inspi- ratory recruitment pressures may prevent recruitment of the most severely affected alveoli. Opening pressures should be applied for about 10-15 seconds. Use of pressure-controlled time-cycled modes of mechanical ventilation is preferable to volume-cycled modes of mechanical ventilation and CPAP when performing recruitment. PEEP can prevent collapse of open and perfused alveoli but PEEP itself does not recruit collapsed alveoli because recruitment is an inspiratory phenomenon. Defining the right PEEP level by finding the clos- ing pressure of the alveolar system should always be part of a recruitment protocol. If during ventilation renewed alveolar collapse of alveoli occurs, a fall in P/F-ratio indicates that a re-opening manoeuvre has to be performed.
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