Ellenberger C, Pelosi P, de Abreu MG, Wrigge H, Diaper J, Hagerman A, Adam Y, Schultz MJ, Licker M, Probese investigators otPVN, Clinical Trial Network of the European Society of A, Intensive C: Distribution of ventilation and oxygenation in surgical obese patients ventilated with high versus low positive end-expiratory pressure: A substudy of a randomised controlled trial. Eur J Anaesthesiol 2022; 39: 875-884- Outcomes Research Consortium

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Ellenberger C, Pelosi P, de Abreu MG, Wrigge H, Diaper J, Hagerman A, Adam Y, Schultz MJ, Licker M, Probese investigators otPVN, Clinical Trial Network of the European Society of A, Intensive C: Distribution of ventilation and oxygenation in surgical obese patients ventilated with high versus low positive end-expiratory pressure: A substudy of a randomised controlled trial. Eur J Anaesthesiol 2022; 39: 875-884

September 12, 2022

BACKGROUND:
Intra-operative ventilation using low/physi- ological tidal volume and positive end-expiratory pressure (PEEP) with periodic alveolar recruitment manoeuvres (ARMs) is recommended in obese surgery patients.

OBJECTIVES
To investigate the effects of PEEP levels and ARMs on ventilation distribution, oxygenation, haemody- namic parameters and cerebral oximetry.

DESIGN
A substudy of a randomised controlled trial.

SETTING
Tertiary medical centre in Geneva, Switzerland, between 2015 and 2018.

PATIENTS
One hundred and sixty-two patients with a BMI at least 35 kg per square metre undergoing elective open or laparoscopic surgery lasting at least 120 min.

INTERVENTION
Patients were randomised to PEEP of 4 cmH2 O (n ¼ 79) or PEEP of 12 cmH2 O with hourly ARMs (n ¼ 83).

MAIN OUTCOME MEASURES
The primary endpoint was the fraction of ventilation in the dependent lung as measured by electrical impedance tomography. Secondary endpoints were the oxygen saturation index (SaO2 /FIO 2 ratio), respira- tory and haemodynamic parameters, and cerebral tissue oximetry.

RESUL
TS Compared with low PEEP, high PEEP was asso- ciated with smaller intra-operative decreases in dependent lung ventilation [-11.2%; 95% confidence interval (CI) -8.7 to -13.7 vs. -13.9%; 95% CI -11.7 to -16.5; P ¼ 0.029], oxygen saturation index (-49.6%; 95% CI -48.0 to -51.3 vs. -51.3%; 95% CI -49.6 to -53.1; P < 0.001) and a lower driving pressure (-6.3 cmH2 O; 95% CI -5.7 to -7.0). Haemodynamic parameters did not differ between the groups, except at the end of ARMs when arterial pressure and cardiac index decreased on average by -13.7 mmHg (95% CI -12.5 to -14.9) and by -0.54 l min -1 m -2 (95% CI -0.49 to -0.59) along with increased cerebral tissue oximetry (3.0 and 3.2% on left and right front brain, respectively). CONCLUSION In obese patients undergoing abdominal surgery, intra-operative PEEP of 12 cmH 2 O with periodic ARMs, compared with intra-operative PEEP of 4 cmH2 O without ARMs, slightly redistributed ventilation to dependent lung zones with minor improvements in peripheral and cere- bral oxygenation.

TRIAL REGISTRATION
NCT02148692, https://clinicaltrials. gov/ct2