The Science Journal of the American Association for Respiratory Care

2009 OPEN FORUM Abstracts

SEMI-QUANTITATIVE TRACKING OF INTRA-AIRWAY FLUIDS BY COMPUTED TOMOGRAPHY

Jeronimo Graf2, Alex B. Adams2, Joseph Tashjian1, David Dries2, John Marini2; 1Radiology, Regions Hospital, St. Paul, MN; 2Pulmonary Research, Regions Hospital, St. Paul, MN

Background: Airway secretions are a source of complications for patients with acute and chronic lung diseases, yet lack of techniques to quantitatively track secretions hampers research into clinical measures to reduce their pathologic consequences. Methods: In a preserved swine lung model we tracked a contrasted mucus simulant (CMS) using sequential computed tomography (CT). Known drivers of secretion movement - gravity and ventilation - were tested. Ten ml of CMS were unilaterally introduced (1ml/min) into the airways of 12 lung sets. After instillation, 6 lung sets were maintained prone and 6 were rotated 180∞. Subsequently, all were mechanically ventilated for 10 minutes. CTs were obtained before infusion, after infusion, and after ventilation/rotation. For CT analysis, the lungs were partitioned into 8 sub-cuboids using anatomic landmarks. The volumes of two CT number ranges representing CMS and poor aeration/collapse were computed in every sub-cuboid for each CT acquisition. Volume differences between study time points were used to quantify changes. Results: CMS and poor aeration/collapse volume change distributed gravitationally after infusion. After ventilation without rotation, the CMS and poor aeration/collapse volumes remained within the originally injected sub-cuboid, though the poor aeration/collapse volume expanded (27.3±6.1 to 50.5±7.4 ml, p<0.05). After ventilation+rotation there was a reduction in the CMS and poor/aeration collapse volumes in the originally injected sub-cuboid (14.4±1.7 to 4.4±0.6 ml, p<0.05 and 18.3±3.8 to 11.9±2.7 ml, p<0.05 respectively) accompanied by increases in the gravitationally opposite subcuboid (1.7±0.2 to 11.1±1.1 ml, p<0.05 and 0.8±0.5 to 40.6±3.5 ml, p<0.05 respectively).Conclusion: Movement of fluids within the bronchial tree can be semi-quantitatively tracked with analysis of sequential CT acquisitions. In this isolated swine lung model, gravity had an important and brisk effect on movement of a viscous fluid, while ventilation tended to embed it peripherally. Implications for Translation into Practice: Positioning of a patient with pneumonia can have a direct influence on propagation. Sponsored Research - None

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