Extubation generates lung volume inhomogeneity in preterm infants

Abstract

Objective: To evaluate the feasibility of EIT to describe the regional tidal ventilation (VT) and change in end-expiratory lung volume (EELV) patterns in preterm infants during the process of extubation from invasive to non-invasive respiratory support. Design: Prospective observational study Setting: Single-centre tertiary neonatal intensive care unit Patients: Preterm infants born <32 weeks gestation who were being extubated to nasal continuous positive airway pressure (nCPAP) as per clinician discretion. Interventions: Electrical Impedance Tomography measurements were taken in supine infants during elective extubation from synchronised positive pressure ventilation (SIPPV) before extubation, during and then at 2 and 20 minutes after commencing nCPAP. Extubation and pressure settings were determined by clinicians. Main outcome measures: Global and regional {Delta}EELV and {Delta}VT were measured. Heart rate, respiratory rate and oxygen saturation were measured throughout. Results: Thirty infants of median (range) 2 (1, 21) days were extubated to a median (range) CPAP 7 (6, 8) cmH2O. SpO2/FiO2 ratio was mean (95% CI) 50 (35, 65) lower 20 minutes after nCPAP compared with SIPPV. EELV was lower at all points after extubation compared to SIPPV, and EELV loss was primarily in the ventral lung (p=0.04). VT was increased immediately after extubation, especially in the central and ventral regions of the lung, but the application of nCPAP returned VT to pre-extubation patterns. Conclusions: Lung behaviour during the transition from invasive positive pressure ventilation to nCPAP at moderate distending pressures is variable and associated with lung volume loss in the ventral lung.