In: Bronchiolitis3 Apr 2014
Air trapping was found more frequently in patients with BO (10/11, 91%) compared to patients without BO (2/10, 20%) (p<0.002). With a sensitivity of 91%, specificity of 80%, and an accuracy of 86% for BO, air trapping was a better indicator of BO than either bronchiectasis or mosaic pattern of lung attenuation (Fig 2). Air trapping was identified in two patients with BO who had normal baseline FEY, values (BOS stage 0) (Tables 2 and 3). Oxygen therapy
In the eight patients with a mosaic pattern, the areas of low attenuation were confirmed on expiratory images to represent regions of air trapping. Expiratory images detected the presence of air trapping in four additional patients and upgraded the extent of air trapping identified on inspiratory images by at least one category in all patients. Although the use of narrow window settings increased conspicuity of air trapping (Fig 3) in 10 of 12 (83%) affected patients and upgraded the extent of air trapping by one grade in 2 patients, detection of the presence or absence of air trapping was not affected in any patient (Tables 2 and 3). In both of the two patients without BO who had air trapping identified on expiratory HRCT, the extent of air trapping was scored as 2. No correlation (p>0.05) existed between the air trapping score on expiratory IIRCT and clinical stage of BOS in the 11 patients with BO (Tables 2 and 3).
BO is currently the major determinant of longterm outcome in patients undergoing heart-lung and lung transplantation. BO developing after lung transplantation is believed to be caused by immunologically mediated and/or ischemic injury to the epithelial cells of the airways; cytomegalovirus disease has also been identified as a risk factor. Although affected patients experience variable rates of functional decline, untreated BO is likely a progressive process with a 5-year mean survival of 37% at our institution. Early diagnosis of BO with administration of immunosuppressive therapy prior to the development of clinical symptoms may improve long-term outcome.
FlGURE 2. A 53-year-old heart-lung transplant recipient with BO. Top: HRCT scan at level of inferior pulmonary veins obtained at suspended full inspiration shows neither evidence of bronchiectasis nor mosaic pattern of lung attenuation. Bottom: corresponding HRCT scan obtained at suspended full expiration shows persisting areas of hypoattenuation consistent with air trapping most prominently affecting the lower lobes (arrows).
Figure 3. A 40-year-old heart-lung transplant recipient with BO. Top: HRCT scan obtained during suspended full expiration and displayed at standard (level —700, width 1,500) window settings shows regions of hypoattenuation and hypovascularity (arrows). Bottom: identical HRCT image displayed at narrow (level —700, width 1,000) window settings increases conspicuity of the regions of air trapping (arrows).
Table 2—Correlation of CT Air Trapping Scores With BOS Stage in Patients With BO
|Case No./Age, yr||TransplantProcedure||StandardWindow||NarrowWindow||FEV1, % Baseline Value||BOSStage|
Table 3—Pulmonary Function Values at Time of CT in Patients With BO
|Case No.||FVC, L||FVC, % Predicted||FEV1 L||FEV1 % Predicted||fef25_75, l||fef25_75, %Predicted|
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