Effect of High-Frequency Chest Wall Oscillation on the Central and Peripheral Distribution of Aerosolized Diethylene Triamine Penta-acetic Acid as Compared to Standard Chest Physiotherapy in Cystic Fibrosis: Discussion

We were unable to detect any decremental effect of combined HFCWO and aerosol treatment in the C/P ratio. In addition, no significant correlation was found between the C/P ratio and the level of lung function in the HFCWO group.
Virtually all CF patients require daily aerosolized medications during the course of their disease. Maximizing the administration of these medications and ensuring appropriate delivery of antibiotics to the site of infection are the goals of aerosol therapy. Many factors influence whether an aerosolized particle deposits centrally or peripherally, including particle size, inspiratory flow rate, and lung volume. More specifically, in patients with CF, bronchos-pasm, abnormal secretions, and airway collapse contribute significantly to the impaction of airway particles centrally.
We were concerned that HFCWO, by its restrictive effect on the chest wall, may limit inspiration, a major factor determining aerosol deposition. Superimposed oscillatory airflow, compressive pulses, and high peak expiratory airflow also may affect distribution of aerosolized medication. These effects may be exaggerated in patients with more severe airway disease or hyperinflation. In our study, the difference in aerosol deposition was not significant (NS) between the two groups, suggesting that concurrent administration of HFCWO and aerosol therapy does not significantly alter the deposition of the aerosol particles. Although our sample size was small, based on these results we would not expect to see either a decrease in the effectiveness of aerosolized medications or an increase in untoward side effects when these medications are used in conjunction with HFCWO therapy. review
We further expected to find an inverse correlation between lung function and peripheral deposition. Studies have demonstrated that as FEV1 decreases, central deposition increases. Bronchocon-striction results in smaller airway diameter and airway collapse on exhalation, and both result in enhanced central deposition. In a study evaluating the deposition of aerosolized gentamicin in 13 patients with CF, Ilowite et al found a relatively strong correlation between FEV1 percentage of predicted and C/P ratio. However, the range of lung function was quite broad, with FEV1 from 16 to 172% of predicted and four patients with FEV1 > 100% of predicted. Mean FEV1 was 73.8 ± 48.1% of predicted. Eliminating patients with FEV1 > 80% of predicted would have yielded a significantly less conclusive correlation between level of FEV1 and C/P ratio. Similar results were found in an evaluation of the factors related to aerosol deposition of recombinant human deoxyribonuclease in 15 CF patients, but again the range of FEV1 was broad, from 63.7 to 135% of predicted and mean of 86.9%.

This entry was posted in Cystic Fibrosis and tagged aerosol, airway clearance, central to peripheral deposition ratio, chest physiotherapy, cystic fibrosis, high-frequency chest wall oscillation, pulmonary, Xe.