Influence of overdistension/recruitment induced by high positive end-expiratory pressure on ventilation–perfusion matching assessed by electrical impedance tomography with saline bolus

Abstract Background High positive end-expiratory pressures (PEEP) may induce overdistension/recruitment and affect ventilation–perfusion matching (VQMatch) in mechanically ventilated patients. This study aimed to investigate the association between PEEP-induced lung overdistension/recruitment and VQMatch by electrical impedance tomography (EIT). Methods The study was conducted prospectively on 30 adult mechanically ventilated patients: 18/30 with ARDS and 12/30 with high risk for ARDS. EIT measurements were performed at zero end-expiratory pressures (ZEEP) and subsequently at high (12–15 cmH 2 O) PEEP. The number of overdistended pixels over the number of recruited pixels (O/R ratio) was calculated, and the patients were divided into low O/R (O/R ratio 8 s). DeadSpace % , Shunt % , and VQMatch % were calculated based on lung EIT perfusion and ventilation images. Results Increasing PEEP resulted in recruitment mainly in dorsal regions and overdistension mainly in ventral regions. ΔVQMatch % (VQMatch % at high PEEP minus that at ZEEP) was significantly correlated with recruited pixels ( r = 0.468, P = 0.009), overdistended pixels ( r = − 0.666, P 20% in response to high PEEP. Conclusions Change of ventilation–perfusion matching was associated with regional overdistention and recruitment induced by PEEP. A low O/R ratio induced by high PEEP might indicate a more homogeneous ventilation and improvement of VQMatch. Trial registration ClinicalTrials.gov, NCT04081155 . Registered on 9 September 2019—retrospectively registered.