Optimal positive end-expiratory pressure to prevent anaesthesia-induced atelectasis in infants: A prospective, randomised, double-blind trial.
Background and Objectives
Anaesthesia related atelectasis is common in paediatrics. This study’s main aim was to measure the effects of positive end-expiratory pressure (PEEP) on alveolar recruitment in children by using lung ultrasound measurements. In addition, PEEP effects on the cardiovascular system (CVS) were measured using oesophageal Doppler US (CardioQ doppler system) and on the respiratory system by measuring ventilator derived parameters e.g., lung compliance.
Design
Prospective, randomised, double blind trial in single centre university hospital.
May 2019– March 2020.
Methods
“Normal” ASA 1-2 infants, 6-12 months old undergoing simple elective surgery.
Standard GA with neuromuscular blockade. Preoxygenation with 100% O2. Intubated and ventilated with tidal volume target (6ml/kg) PCV mode.
Children receive either +3, +6 or +9 cmH2O PEEP.
Lung US was performed in 12 areas as a baseline following intubation and before PEEP was applied and then repeated at the end of surgery before extubation.
CVS parameters were measured firstly following intubation and institution of +3cmH2O PEEP and then repeated 5 minutes after application of each PEEP setting.
Primary outcome: Lung US Score (LUS) at end of surgery
Secondary outcomes: Various respiratory parameters e.g., dynamic compliance, cardiac index, arterial pressure, before/after PEEP.
Results
N=90 (30 x3 groups).
LUS was increased (indicating atelectasis) in all groups equally in the first measurements, before PEEP. LUS values were consistently higher (worse) in posterior regions.
At the end of surgery, LUS (total score and sub types of measurement) were strongly significantly different between groups: PEEP +3cmH20 > +6/+9cmH2O.
Dynamic compliance was significantly higher in +9cmH2O PEEP group > +3/+6 cmH2O PEEP groups.
CVS parameters: There were no differences in mean arterial pressure (MAP) or heart rate between groups, before or after PEEP. However cardiac index, and by inference stroke volume, fell significantly (in a statistical sense) at PEEP +9cmH2O compared to at PEEP +3 and +6 cmH2O.
Conclusions/Comments
Both +6cmH2O and +9cmH2O PEEP significantly reduced anaesthesia related atelectasis as inferred by LUS and dynamic compliance with no clinically significant haemodynamic changes in this age group of healthy infants. Since high levels of PEEP can be associated with complications, a level of +6cmH2O PEEP may be a safer and equally effective setting.
It has yet to be shown whether such findings and suggested recommendations apply to children of other ages and conditions.
It is also worth considering whether the standard use of preoxygenation with 100% O2 in this study may have contributed to the presence of “pre-existing” atelectasis (as judged by raised LUS) in all groups at baseline measurement. The authors do not mention whether PEEP (and if so, at what level) was employed during preoxygenation. It is also unclear to me whether any PEEP and/or manual ventilation was provided between preoxygenation and induction and intubation. This may have had significant effects on the extent of atelectasis at baseline. These potential issues influence how directly applicable the findings are to real-practice anaesthesia.
Reviewed by H. Hack
