Radioaerosol assessment of lung improvement in cystic fibrosis patients treated for acute pulmonary exacerbations

Small airway deposition of dornase alfa during exacerbations in cystic fibrosis; a randomized controlled clinical trial

INTRODUCTION

Small airway obstruction is important in the pathophysiology of cystic fibrosis (CF) lung disease. Additionally, many CF patients lose lung function in the long term as a result of respiratory tract exacerbations (RTEs). No trials have been performed to optimize mucolytic therapy during a RTE. We investigated whether specifically targeting dornase alfa to the small airways improves small airway obstruction during RTEs.

METHODS

In a multi-center, double-blind, randomized controlled trial CF patients hospitalized for a RTE and on maintenance treatment with dornase alfa were switched to a smart nebulizer. Patients were randomized to small airway deposition (n = 19) or large airway deposition (n = 19) of dornase alfa for at least 7 days. Primary endpoint was forced expiratory flow at 75% of forced vital capacity (FEF75 ).

MAIN RESULTS

Spirometry parameters improved significantly during admission, but the difference in mean change in FEF75 between treatment groups was not significant: 0.7 SD, P = 0.30. FEF25-75 , FEV1 , nocturnal oxygen saturation and diary symptom scores also did not differ between groups.

CONCLUSIONS

This study did not detect a difference if inhaled dornase alfa was targeted to small versus large airways during a RTE. However, the 95% confidence interval for the change in FEF75 was wide. Further studies are needed to improve the effectiveness of RTE treatment in CF.

Nebulized antibiotics in cystic fibrosis

Nebulization is a useful administration route in cystic fibrosis (CF) as it delivers antibiotics directly to the endobronchial site of infection and is associated with decreased toxicity because of limited systemic absorption. It is assumed that the concentration of antibiotics in bronchial secretions should be as high as 10 times the minimum inhibiting concentration to allow penetration of antibiotics into biofilms, suppress inhibitory factors and promote bactericidal effectiveness. However, effective aerosol delivery is compromised by nebulizers with limited capacity to produce particles of a size in the respirable range. Three antibiotics are commonly used for inhalation: tobramycin, amikacin and colistin (colomycin). Placebo-controlled studies evaluating antibiotic aerosol maintenance in stable patients chronically infected with Pseudomonas aeruginosa indicate a significant improvement of lung function and a reduction of the number of hospital admissions for an acute exacerbation of CF. TOBI is a recently marketed preservative- and sulfate-free formula of tobramycin, specially designed for diffusion in the bronchioles and optimal tolerance. A wide-scope study involving 520 patients compared TOBI (300 mg twice daily; n = 258) with placebo (n = 262) for three 28-day cycles with each cycle separated by a 28-day period of no treatment. Respiratory function was significantly improved as early as in the second week and remained so for the rest of the trial even during periods without aerosol treatment. There was also a parallel decrease in the relative risk of hospitalization, the number of days of hospitalization and the number of days on intravenous antipyocyanic treatment. Toxicity studies carried out so far have shown no renal or ototoxicity with nebulized tobramycin. Introduction or selection of resistant bacteria is relatively rare but remains a matter of concern. Aerosol maintenance treatment with an appropriate antibiotic in a high enough dosage can be recommended for patients with CF who are chronically infected with P. aeruginosa.

Regional mucociliary clearance in patients with cystic fibrosis

This paper reports on a large retrospective analysis of mucociliary clearance (MCC) studies in a group of 59 patients with cystic fibrosis (CF) and 17 age-matched healthy subjects. As many of the CF patients were studied on multiple occasions, a total of 184 patient studies are presented. MCC was measured using a radioaerosol and gamma camera technique. In addition to whole lung clearance, MCC was measured from the central, intermediate, peripheral, basal, mid and apical regions of the lung. MCC was markedly decreased in the CF patient group. Not only was whole lung clearance (14.2 +/- 1.4% vs. 28.0 +/- 3.7%) impaired, but also clearance from the central (19.1 +/- 1.9% vs. 35.6 +/- 4.3%), intermediate (10.7 +/- 1.6% vs. 25.5 +/- 3.7%), apical (12.4 +/- 2.6% vs. 31.6 +/- 4.6%) and mid (14.0 +/- 1.9% vs. 30.4 +/- 4.0%) regions. Attempts were made to identify factors that may have influenced MCC in both the normal subjects and CF patients. Age, gender, body mass index, patient genotype, penetration index, spontaneous cough, and various lung function parameters were entered into a stepwise multiple regression model, but none of the factors proved to be statistically important in determining MCC. Both intrasubject repeatability and intersubject variability estimates are presented for the patients and normal subjects that had multiple studies. The values were found to be remarkably similar for both CF patients and normal subjects and for both intra- and intersubject repeatability. With marked deviation from normal ranges and good repeatability, the measurement of MCC in CF patients would seem to be a valuable outcome measure for clinical trials involving new pharmaceuticals and physical therapy designed to improve removal of secretions from the airways.

Effect of a short course of rhDNase on cough and mucociliary clearance in patients with cystic fibrosis

The aim of the study was to measure the effect of a short course of recombinant human deoxyribonuclease I (rhDNase) on ciliary and cough clearance in a group of cystic fibrosis patients, using a radioaerosol and gamma camera technique. Patients were initially randomized to receive either rhDNase (2.5 mg qd) or placebo. Following the measurement of baseline clearance, patients were given a 7-day course of either rhDNase or placebo. The patient then returned on the seventh day for follow-up clearance measurements. This was followed by a 2-week washout period before the whole process was repeated with the alternative inhalation solution. On each of the study days, mucociliary clearance was initially measured for a period of 60 min (IC). This was followed by cough clearance (CC) measurements for 30 min, during which patients were requested to cough a total of 120 times. Post-cough clearance (PCC) was then measured for a further 60 min. Thirteen patients completed the study. Patients' age ranged between 18-38 years, and they had baseline values of FEV(1) of 27-103% of predicted values. Following completion of the course of rhDNase, there was a mean percent increase from baseline of 7.5% for FEV(1) and 5.4% for FVC% (P = 0. 03). There was a small, nonsignificant increase in IC (6.2 +/- 3.6%) on the rhDNase arm compared with the placebo arm (-2.3 +/- 2.9%), P = 0.1. No changes were seen in either CC (1.0 +/- 3.2% [rhDNase] vs. 1.9 +/- 2.4% [placebo], P = 0.9) or PCC (-0.7 +/- 1.5% [rhDNase] vs. 0.9 +/- 1.7% [placebo], P = 0.3). Patients who achieved a 10% or greater improvement in FEV(1) (n = 5) in response to rhDNase did not show any greater change in clearance than nonresponders. In conclusion, we were unable to demonstrate any improvements in either ciliary or cough clearance in response to a short course of rhDNase. The mechanism of action of this drug in vivo remains uncertain.

Improvement of nebulised antibiotic delivery in cystic fibrosis

AIM

To investigate deposition patterns and to assess the delivery rate of two nebuliser systems in children with cystic fibrosis (CF).

METHODS

Thirty three children with CF on regular treatment with nebulised antibiotics had radioisotope scans performed using technetium-99m labelled aerosol antibiotic generated by a Ventstream nebuliser (median mass diameter (MMD), 3.3 microm; delivery rate, 0. 075 ml/min) under conditions similar to their routine home practice. The inhomogeneity of the images was scored on a 1-10 rating scale (a low score indicating even distribution of the antibiotic), and stomach deposition was measured as a percentage of overall deposition. Twenty patients had a repeat scan using an Optimist nebuliser (MMD, 1.8 microm; delivery rate, 0.02 ml/min).

RESULTS

The mean inhomogeneity scores were 5.4 in the Ventstream group and 3. 5 in the Optimist group. Mean stomach deposition was 17.3% in the 33 patients using the Ventstream nebuliser. There was an inverse relation between height and stomach deposition (r = 0.69). In the 20 patients who had both nebulisers, the mean percentages of stomach deposition for the Ventstream and Optimist nebulisers were 11.8% and 1.6%, respectively. The Ventstream nebuliser delivered antibiotic at an average 2.8 times faster rate than the Optimist nebuliser.

IMPLICATIONS

A smaller particle size results in a more homogenous distribution of the antibiotic in the lungs with decreased stomach deposition. This should not be seen as a recommendation to use the Optimist nebuliser because more antibiotic was delivered to most parts of the lung with the Ventstream because of its increased delivery rate.

Outcome measures for clinical trials in cystic fibrosis. Summary of a Cystic Fibrosis Foundation consensus conference

The CFF Consensus Conference concluded with a summary of those outcome measures that would be most useful in studies of patients 6 years of age and older and those measures that would be most useful in studies of the younger population (< 6 years of age) (Table). These measures were further divided into biologic markers most appropriate for initial (phase I and phase II) clinical trials and those especially useful in large, multicenter (phase III) pivotal trials. There is an ongoing need to improve the accuracy and validity of currently available measures of biologic activity and clinical efficacy in CF, especially in the younger population. The conference participants recommended that the following eight issues be addressed as soon as possible: (1) definition of pulmonary exacerbation, (2) broadly applicable methods of testing pulmonary function in small children (ideally a single test for all ages), (3) a comprehensive severity-of-disease score for young children, (4) reliable methods of quantifying chest x-ray and CT scan changes in young patients, (5) simple, inexpensive measures of lung inflammation, (6) a centralized, uniform approach to the establishment of data monitoring committees, (7) a quality of well-being scale for small children, and (8) reliable, reproducible aerosol delivery systems with defined characteristics. In addition, participants recommended that better methods be developed for assessing patients' adherence to research protocols.

Evolution of pulmonary function during an acute exacerbation in hospitalized patients with cystic fibrosis

Few objective criteria have been validated for serial clinical monitoring in patients with cystic fibrosis (CF) during pulmonary exacerbations. While pulmonary function tests (PFT) are often used to monitor clinical improvement, it is not known which test correlates most closely with clinical improvement. To answer this, we measured routine PFT in 58 patients with CF before, during, and at discharge after 2-3 week hospital admission in 71 episodes of pulmonary exacerbation. Patients with CF were discharged based on clinical, radiological, and laboratory criteria. In general, all PFTs improved at midadmission and improved further by discharge, at which time forced expiratory volume in 1 second (FEV1), forced expiratory flow between 25% and 75% of forced vital capacity (FEF25-75), vital capacity (VC), maximal voluntary ventilation (MVV), and oxygen saturation by pulse oximetry (SPO2) increased. The residual volume to total capacity ratio (RV/TLC) and the slope of phase 3 in the single breath N2 washout curve (SP3 N2) decreased. The change in SP3 N2 was significantly greater than in any other PFT (P < 0.01 vs. VC and FEV1; P < 0.02 vs. RV and P < 0.001 vs. SPO2). A calculated optimal cut-off value for SP3 N2 improvement was significantly more sensitive in identifying patient improvement at discharge than any other pulmonary function test (P = 0.005). We speculate that clinical improvement in patients with CF is closely linked to improved distribution of ventilation.