A ventilation strategy during general anaesthesia to reduce postoperative atelectasis

Abstract

Background. Atelectasis is common during and after general anaesthesia. We hypothesized that a ventilation strategy, without recruitment manoeuvres, using a combination of continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) and a reduced end-expiratory oxygen fraction (F_ETO₂) before ending mask ventilation with CPAP after extubation would reduce the area of postoperative atelectasis.

Methods. Thirty patients were randomized into three groups. During induction and emergence, inspiratory oxygen fractions (F_IO₂) were 1.0 in the control group and 1.0 or 0.8 in the intervention groups. No CPAP/PEEP was used in the control group, whereas CPAP/PEEP of 6 cmH₂O was used in the intervention groups. After extubation, F_IO₂ was set to 0.30 in the intervention groups and CPAP was applied, aiming at F_ETO₂ < 0.30. Atelectasis was studied by computed tomography 25 min postoperatively.

Results. The median area of atelectasis was 5.2 cm² (range 1.6–12.2 cm²) and 8.5 cm² (3–23.1 cm²) in the groups given F_IO₂ 1.0 with or without CPAP/PEEP, respectively. After correction for body mass index the difference between medians (2.9 cm²) was statistically significant (confidence interval 0.2–7.6 cm², p = 0.04). In the group given F_IO₂ 0.8, in which seven patients were ex- or current smokers, the median area of atelectasis was 8.2 cm² (1.8–14.7 cm²).

Conclusion. Compared with conventional ventilation, after correction for obesity, this ventilation strategy reduced the area of postoperative atelectasis in one of the intervention groups but not in the other group, which included a higher proportion of smokers.

Key words::

• Atelectasis
• CPAP
• general anaesthesia
• oxygen fraction
• PEEP
• ventilation strategy

Acknowledgements

We would like to thank Anders Nydahl, MD, PhD, Chief of Staff and Lena Lundgren, CRNA, Department of Anaesthesiology and Intensive Care, University Hospital, Örebro, Sweden for their support and skilful assistance.

Declaration of interest: This study was financially supported by intramural departmental funding (both Departments of Anaesthesiology), and from the Centre for Clinical Research. The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.