Effect of different lung recruitment strategies and airway device on oscillatory mechanics in children under general anaesthesia

BACKGROUND Atelectasis has been reported in 68 to 100% of children undergoing general anaesthesia, a phenomenon that persists into the recovery period. Children receiving recruitment manoeuvres have less atelectasis and fewer episodes of oxygen desaturation during emergence. The optimal type of recruitment manoeuvre is unclear and may be influenced by the airway device chosen. OBJECTIVE We aimed to investigate the different effects on lung mechanics as assessed by the forced oscillation technique (FOT) utilising different recruitment strategies: repeated inflations vs. one sustained inflation and different airway devices, a supraglottic airway device vs. a cuffed tracheal tube. DESIGN Pragmatic enrolment with randomisation to the recruitment strategy. SETTING We conducted this single-centre trial between February 2020 and March 2022. PARTICIPANTS Seventy healthy patients (53 boys) aged between 2 and 16 years undergoing general anaesthesia were included. INTERVENTIONS Forced oscillations (5 Hz) were superimposed on the ventilator waveform using a customised system connected to the anaesthesia machine. Pressure and flow were measured at the inlet of the airway device and used to compute respiratory system resistance and reactance. Measurements were taken before and after recruitment, and again at the end of surgery. MAIN OUTCOME MEASURES The primary endpoint measured is the change in respiratory reactance. RESULTS Statistical analysis (linear model with recruitment strategy and airway device as factors) did not show any significant difference in resistance and reactance between before and after recruitment. Baseline reactance was the strongest predictor for a change in reactance after recruitment: prerecruitment Xrs decreased by mean (standard error) of 0.25 (0.068) cmH 2 O s l −1 per 1 cmH 2 O −1 s l −1 increase in baseline Xrs ( P < 0.001). After correcting for baseline reactance, the change in reactance after recruitment was significantly lower for sustained inflation compared with repeated inflation by mean (standard error) 0.25 (0.101) cmH 2 O ( P = 0.0166). CONCLUSION Although there was no significant difference between airway devices, this study demonstrated more effective recruitment via repeated inflations than sustained inflation in anaesthetised children. TRIAL REGISTRATION Australian New Zealand Clinical Trials Registry: ACTRN12619001434189.