604 - Perflubron and gas distribution in the lungs during weaning from total liquid ventilation in a newborn piglet model: A novel approach using X-ray CT imaging

Poster Number: 604
Publication Number: 604.1279

Background: We previously showed that lung aeration following transition from tidal liquid ventilation (TLV) to conventional mechanical ventilation (CMV) favors gravity-independent lung regions (figure 1).

Objective: The aim of this study was to evaluate whether positional changes during weaning from TLV affect regional distribution of residual Perflubron (PFOB) and gas, using X-ray computed tomography (CT).

Design/Methods: Seven term piglets (1.97 ± 0.15 kg) were intubated through tracheotomy under general anesthesia to receive 3 h of TLV using our TLV prototype in the supine position. Piglets were randomized either to the static (S, n = 4) or the returned (R, n = 3) groups for weaning prior to being disconnected from the TLV prototype. Weaning from TLV was done with CMV for 2 h. CT imaging was done during inspiratory and expiratory pauses at baseline (while on CMV), end of TLV, and 10, 30 and 120 min of weaning. After 10 min of weaning, animals in the R group were moved to the prone position for 20 min and replaced in the supine position at the 30th minute mark up until the end of the experiment. Using the 3D Slicer software, lungs were segmented in two (anterior and posterior) regions from which the mean radiodensity values in Hounsfield units (HU) were extracted. Throughout weaning from TLV, the proportion of gas and liquid in the anterior and posterior lung regions were interpolated from regional mean radiodensity measured during initial CMV and TLV, using a linear regression.

Results: While in the prone position, 2/3 animals from the R group have a transient increase in estimated PFOB content in the anterior region, concomitant with a decrease in the posterior region (figure 2) in all 3 animals, at end-expiration. The change to prone position significantly decreased the percentage of gaseous tidal volume distributed to the gravity-dependent region (R group: 19 ± 12% vs. S: 73 ± 12%, p = 0.03). In addition, the temporary positional change of the R group seems to result in an increased PFOB elimination at the end of weaning from TLV compared to the S group, especially in the anterior region (figure 3).

Conclusion(s): In conclusion, there is a transient effect of positional change on regional lung aeration and gaseous tidal volume distribution during weaning from total liquid ventilation. Further testing is needed to determine whether this effect leads to an increased PFOB elimination, as well as to assess the optimal duration and frequency of periods of prone positioning.