Neonatal Pulmonology 1: Lung Development, Control of Breathing
Christophe Morin, M.Sc. (he/him/his)
Université de Sherbrooke
Universite de Sherbrooke Faculte de Medecine et des Sciences de la Sante
Sherbrooke, Quebec, Canada
Based on our previous results in term lambs, total liquid ventilation (TLV) using perfluorocarbons could decrease ventilation heterogeneity in the extremely premature babies during the immediate transition to extrauterine life.
We aimed to assess tidal volume distribution and regional ventilation delays during TLV using electrical impedance tomography (EIT) for the first 30 min of extrauterine life.
Ten extremely premature lambs (118-120 days, term 147) were born through cesarean section and randomized to receive 6 h of TLV (n = 7) or CMV (n = 3) in the supine position. Neither drainage of lung liquid nor lung aeration was performed before TLV initiation. An EIT electrode belt was placed around the thorax to measure a proxy of tidal volume. EIT recordings were performed during TLV or CMV 10 min after umbilical cord clamping (T10) and at 30 min (T30). Regional tidal volume (VT) distribution was measured in the anterior and posterior half lung regions as a % of total thoracic impedance change. In addition, an anterior (posterior) region ventilation delay was computed as the time to reach 40% of the global maximal change in impedance minus the time to reach 40% of the regional—anterior/posterior—change.
During TLV, VT was mostly distributed in the anterior region, similarly to CMV (table 1). No difference in VT distribution could be detected between T10 and T30 min post-clamping during TLV (table 1). However, there was a significant regional ventilation delay between the posterior and the anterior regions during TLV (table 2). Posterior region received the dense fluid earlier. Such a difference was not apparent in the 3 CMV lambs.
In conclusion, tidal volume mostly distributes in the anterior half of the lungs during the first 30 min of extrauterine life in TLV, when initiated in the absence of lung liquid drainage or aeration. The apparent similar distribution of VT in TLV and CMV, which needs to be confirmed, does not necessarily mean that the underlying mechanisms—distended region with poor compliance vs. atelectasis—are similar. The early, but low volume, filling of the posterior lung region during TLV could mean this region is in a state closer to the upper inflexion point of the pressure-volume curve at the beginning of inspiration. CT-scan imaging studies are under way to complement EIT data on ventilation heterogeneity during TLV.