Effect of an individualized lung protective ventilation on lung strain and stress in children undergoing laparoscopy: an observational cohort study

Exaggerated lung strain and stress could damage lungs in anesthetized children. We hypothesized that the association of capnoperitoneum and lung collapse in anesthetized children increases lung strain-stress. Our primary aim was to describe the impact of capnoperitoneum on lung strain-stress and the effects of an individualized protective ventilation during laparoscopic surgery in children.We performed an observational cohort study in healthy children aged 3-7 years scheduled for laparoscopic surgery in a community hospital. All received standard protective ventilation with 5 cmH2O of positive end-expiratory pressure (PEEP). Children were evaluated before capnoperitoneum (pre-CP), during capnoperitoneum (CP) prior and after lung recruitment and optimized PEEP [PEEP adjusted to get end-expiratory transpulmonary pressure of zero = CP-PEEPopt], and after capnoperitoneum with optimized PEEP (post-CP). The presence of lung collapse was evaluated by lung ultrasound, positive Air-Test (SpO2 ≤96% breathing 21% O2 for 5 minutes), and negative end-expiratory transpulmonary pressure. Lung strain was calculated as tidal volume/end-expiratory lung volume measured by capnodynamics, and lung stress as the end-inspiratory transpulmonary pressure.We studied twenty children. At pre-CP, mean lung strain was 0.20±0.07 (95%CI 0.17-0.23) and stress was 5.68±2.83 (95%CI 4.44-6.92) cmH2O. During CP, eighteen patients presented lung collapse and strain (0.29±0.13, 95%CI 0.23-0.35; p<0.001) and stress (5.92±3.18, 95%CI 4.53-7.31 cmH2O; p=0.374) increased compared to pre-CP. During CP-PEEPopt, children presenting lung collapse were recruited and optimized PEEP was 8.3±2.2 (95% CI 7.3-9.3) cmH2O. Strain returned to pre-CP values (0.20±0.07, 95%CI 0.17-0.22; p=0.318) but lung stress increased (7.29±2.67, 95% CI 6.12-8.46) cmH2O (p=0.020). At post-CP strain decreased (0.18±0.04, 95% CI 0.16-0.20; p=0.090) but stress remained higher (7.25±3.01, 95% CI 5.92-8.57 cmH2O; p=0.024) compared to pre-CP.Capnoperitoneum increased lung strain in healthy children undergoing laparoscopy. Lung recruitment and optimized PEEP during capnoperitoneum decreased lung strain but slightly increased lung stress. This little rise in pulmonary stress was maintained within safe, lung protective and clinically acceptable limits.