Atelectasis – a partial collapse or incomplete inflation of the lung – affects almost all subjects undergoing general anesthesia, impairing oxygenation even in patients with normal lungs. In fact, atelectasis is the primary cause of hypoxemia during general anesthesia. Preventing atelectasis is thus critical to ensuring the well-being of patients undergoing anesthesia. Recruitment maneuvers – which involve temporarily increasing airway pressure with mechanical ventilation in order to open up collapsed alveoli – are an important method of reducing the incidence of atelectasis and “recruiting” more of the lung to function properly [1].  

A systematic review of the literature from 2015 demonstrated that lung recruitment maneuvers followed by positive end-expiratory pressure should be carried out after the induction of general anesthesia to reduce atelectasis. Ideally, these should be used both routinely and in the presence of dropping oxygen saturation levels when feasible [2]. Such alveolar recruitment maneuvers allow the anesthesia provider to reduce the fraction of inspired oxygen while maintaining a higher oxygen saturation. Overall, alveolar recruitment maneuvers were found to clearly reduce postoperative pulmonary complications and improve patient outcomes. 

In infants in particular, a 2016 study similarly revealed that ultrasound-guided lung recruitment maneuvers combined with positive end-expiratory pressure helped minimize the incidence of anesthesia-induced atelectasis [3]. This is particularly important in light of the fact that positive end-expiratory pressure alone was revealed to be insufficient to eliminate atelectasis. In addition, interestingly, the younger the patient, the more prone they were to developing atelectasis. 

Research from 2019 has further confirmed that alveolar recruitment maneuvers help minimize atelectasis when integrated with intraoperative lung protective ventilation. Specifically, such interventions tend to result in decreased respiratory resistance and increased lung compliance during mechanical ventilation [4].  

Most recently, these findings were validated by a 2022 study which sought to assess the impact of recruitment maneuvers plus positive end-expiratory pressure on the incidence of atelectasis in adult women undergoing gynecologic surgery [5]. Overall, their results confirmed that the combination of recruitment maneuvers and positive end-expiratory pressure could reduce the incidence of atelectasis in patients with healthy lungs 15 min after arrival at the post-anesthesia care unit.  

Various studies have been carried out seeking to develop best practices for this technique. A 2019 research project aimed at developing recommendations for lung protection for surgical patients at an international consensus development conference identified that a dedicated score should be used to evaluate preoperative pulmonary risk. Thereafter, mechanical ventilation that is tuned to the individual may improve a patient’s breathing mechanics and respiratory function, as such helping to prevent postoperative pulmonary complications. To this end, data demonstrated that when recruitment maneuvers are carried out, the lowest effective pressure and the shortest effective time or fewest number of breaths should be used [6]. 

Lung recruitment maneuvers are essential to minimizing the incidence of atelectasis during general anesthesia. However, further targeted research is required to continue to develop and specify best practices in order to best harness the benefits of lung recruitment maneuvers in the context of general anesthesia.  

References 

1. Brismar, B. et al. Pulmonary densities during anesthesia with muscular relaxation – A proposal of atelectasis. Anesthesiology (1985). doi:10.1097/00000542-198504000-00009
2. 2. Lung Recruitment Maneuver – Physiopedia. Available at: https://www.physio-pedia.com/Lung_Recruitment_Maneuver.
3. 2. Hartland, B. L., Newell, T. J. & Damico, N. Alveolar recruitment maneuvers under general anesthesia: A systematic review of the literature. Respiratory Care (2015). doi:10.4187/respcare.03488
4. 3. Song, I. K. et al. Effects of an alveolar recruitment manoeuvre guided by lung ultrasound on anaesthesia-induced atelectasis in infants: a randomised, controlled trial. Anaesthesia (2017). doi:10.1111/anae.13713
5. 4. Nakahira, J., Nakano, S. & Minami, T. Evaluation of alveolar recruitment maneuver on respiratory resistance during general anesthesia: a prospective observational study. BMC Anesthesiol. (2020). doi:10.1186/s12871-020-01182-9
6. 5. Liu, Y. et al. The effect of ultrasound-guided lung recruitment maneuvers on atelectasis in lung-healthy patients undergoing laparoscopic gynecologic surgery: a randomized controlled trial. BMC Anesthesiol. 22, 1–9 (2022). doi: 10.1186/s12871-022-01742-1.
7. 6. Young, C. C. et al. Lung-protective ventilation for the surgical patient: international expert panel-based consensus recommendations. British Journal of Anaesthesia (2019). doi:10.1016/j.bja.2019.08.017