Lung recruitment

There has been considerable interest in recent years in the concept of lung recruitment. The rationale is that re-opening of collapsed alveoli results in improved gas exchange, with resulting reductions in airway pressures and FIO2. Timing is crucial as collapsed alveoli are more likely to be recruitable in the early stages of respiratory failure.

It appears that benefit is more likely in extra-pulmonary causes of ARDS rather than in cases of direct pulmonary pathology such as pneumonia. Some animal studies suggest that recruitment procedures may even be potentially injurious in the latter situation.

Consideration should be given to lung recruitment soon after intubation of patients with severe respiratory failure, and procedures causing de-recruitment, e.g. endotracheal suction, airway disconnection.

Recruitment techniques

• Several techniques are used to recruit collapsed alveoli, e.g. applying 40cmH2O PEEP for 40s with no ventilator breaths; delivering a few

large-volume, ventilator-delivered breaths; or by using a combination of varying levels of PEEP and increasing pressure-delivered breaths to

obtain optimal gas exchange.

• Although anecdotal successes are reported, with occasionally dramatic improvements in lung compliance and gas exchange, no comparative

trials have been performed and outcomes have not been assessed prospectively. Haemodynamic compromise may occur during the procedure though this usually recovers on cessation.