Role of breathing and respiratory support in initiating preterm lung injury at birth

Background: Although synchronisation of positive pressure ventilation (PPV) inflations with breathing is common in the NICU, the lung protective mechanisms have never been characterised. Objective: To determine the role of synchronous and asynchronous breathing, and apnoea during PPV on early lung injury in preterm lambs. Design/Methods: 126-129d preterm lambs randomly received 1) synchronised PPV, 2) asynchronous ventilation using untriggered PPV or PPV during apnoea for 90 min from birth (11-17/group). All other aspects of support were standardised using a lung protective strategy. At 90 min lung tissue and bronchoalveolar fluid was taken for histology and proteomic analysis. Results: Breathing created faster rates of pressure, flow and volume change during inflations. Synchronisation resulted in lower inflating pressures and better dynamic compliance (both p< 0.0001). Lung protein was 1.4-1.6-fold higher in the asynchronous group than synchronous or apnoea groups (p=0.0025). Lung protein expression differed dependent on breathing pattern and gravity-dependency (Figure 1). Conclusion: At birth, breathing itself creates unique injury events related to the complex interactions between negative and positive pressure changes. Asynchrony is especially harmful, and our findings suggest that the entity of 'patient self-inflicted lung injury' identified in ARDS maybe important in preterm lung disease.