Images obtained after nebulization of aerosolized DTPA were transposed onto the Xe images. An ROI was drawn around the stomach to identify gastric radioactivity. Figure 1 shows a representative study. The amount of this activity compared to overall counts was small; however, the stomach images were removed before the data were analyzed. The C/P ratio of each lung determined by the pixel counts in those regions was obtained. Differences in regional volume were corrected by dividing C/P aerosol deposition ratio by the C/P ratio for Xe gas distribution. A C/P ratio < 1 demonstrates more peripheral deposition, whereas a C/P ratio > 1 indicates more central deposition.
Spirometry and C/P ratios after SCPT were compared with the data found during concomitant HFCWO by a paired Student t test (p < 0.05 considered significant). C/P ratios in both groups were also correlated with severity of airway obstruction using linear regression.
Ten patients (7 men and 3 women) met the criteria for inclusion and exclusion, and all were able to complete both arms of the study. Mean age of the patients was 27 ± 6.2 years (± SD), with a range of 18 to 48 years. No significant difference was found in FEV1 or FVC obtained prior to the nuclear studies in the respective treatment groups. Baseline characteristics are documented in Table 1.
The mean C/P ratios comparing both lungs showed no statistical difference whether aerosol administration occurred during HFCWO (1.45 ± 0.32) or after SCPT (1.46 ± 0.28). In addition, no difference was found in the C/P ratios between the SCPT and HFCWO groups involving the right and left lungs (Table 2). so
The effect of lung function on aerosol distribution was evaluated in each group by comparing FEV1 and FVC percentage of predicted with the C/P ratio using linear regression. We were unable to document an increase in central deposition in patients with worse spirometry results. Correlation coefficients appear in Table 3. We evaluated the effect of HFCWO on aerosol distribution by comparing the result of concomitant administration of therapy with deposition after SCPT using patients as their own control. We used a protocol that maintained the standard practices at our center for patients receiving ACT and aerosolized medications at home, including the nebulizer, compressor, and breathing techniques commonly recommended.
Figure 1. Xe and DTPA images in a patient with CF. Note the ROIs drawn over central and total areas. ROIs are then transferred from the 133Xe to DTPA images.
Table 1—Baseline Characteristics of Study Group
|Age, yr||27 ± 6.2 (18-48)|
|Male/female gender, No.||7/3|
|FEVj||1.7 ± 0.45 (0.92-2.33)|
|FEVb % predicted!||47 ± 13 (25-69)|
|FVC||2.66 ± 0.785 (1.32-3.94)|
|FVC, % predicted!||60 ± 16 (30-83)|
|FEF25-75||1.008 ± 0.43 (0.49-1.9)|
|Maximum FEF||5.57 ± 1.73 (2.88-9.08)|
Table 2—Mean C/P Ratios in HFCWO and SCPT Groups
|Variables||FollowingSCPT||Concurrently With HFCWO||p Value|
|Both lungs||1.46 ± 0.28||1.45 ± 0.32||NS|
|Right lung||1.85 ± 0.63||1.74 ± 0.43||NS|
|Left lung||1.21 ± 0.35||1.25 ± 0.29||NS|
Table 3—Correlation (r) of C/P Ratio and Each Treatment Group With Level of Obstruction as Determined by FEV1 and FVC
|Groups||FEV1 % Predicted||FVC % Predicted|