Positive Expiratory Pressure Changes Aerosol Distribution in Patients With Cystic Fibrosis

HYPOTHESIS: We hypothesized that aerosol distribution in the lungs of patients with cystic fibrosis changes with positive expiratory pressure (PEP).

METHODS: Eight patients were randomized to one of 2 conditions. On one study day, patients inhaled saline aerosol containing ^99mtechnetium generated by a Pari LC Plus nebulizer and exhaled through a Pari PEP device. On another day, the same patients exhaled through a low-resistance Pari filter (no PEP). Afterwards, they underwent gamma-camera lung imaging. Images were analyzed for lung deposition fraction, expressed as a percent of the initial nebulizer activity, and deposition pattern, expressed in terms of inner-outer and apical-basal ratios.

RESULTS: Lung deposition fraction was significantly lower with the Pari PEP device; the mean ± SD deposition fraction was 6.10 ± 3.05% (median 6.20%) with PEP, compared to 10.76 ± 4.52% (median 10.32%) (p = 0.0078) without PEP. The inner-outer ratio was 2.01 ± 0.69 (median 2.23) with PEP, which was significantly lower than without PEP (2.76 ± 1.33, median 2.55) (p = 0.004). The apical-basal ratio was 0.82 ± 0.31 (median 0.80) with PEP, which was not significantly different from no PEP (1.00 ± 0.49, median 0.90).

CONCLUSION: These results indicate that less aerosol is deposited in the lungs of patients with cystic fibrosis when the Pari LC Plus nebulizer is used with the Pari PEP device, as described in these experiments. Nevertheless, aerosol administration with this nebulizer and PEP device also results in a proportional redistribution of aerosol to the peripheral airways, compared to nebulization without the PEP device. The clinical relevance of this subtle redistribution of aerosol in cystic fibrosis patients will probably depend on the drug administered and disease severity.