Peer-Reviewed Clinical Trials Investigating Efficacy
Studies
- Prospective randomized controlled trial (RCT)
- Arens et al. 1994
- Prospective randomized
- Scherer et al. 1998
- Crossover trials
- Kluft et al. 1996
- Braggion et al. 1995
- Hansen and Warwick 1990
- Retrospective/prospective non-randomized trial
- Giarraffa 2006
- Warwick and Hansen 1991
Key Outcomes/Measurements
There are three general categories of outcomes examined in studies of High Frequency Chest Wall Oscillation (HFCWO): mucus clearance, pulmonary function tests, and general indicators. (See Reported Outcomes for details.)
The amount of mucus in the lungs is a function of both initial secretion into the lungs and of the ability of the mucociliary apparatus to transport it from the lungs into the central airways, from which it is cleared by expectoration or swallowing. Transport of mucus depends upon several factors, including airflow (or variations in airflow, as generated by coughing), gravity, ciliary function, and mucus viscosity. The total amount of mucus measured in each of the six studies varies considerably, in part because some mucus may be coughed up, some swallowed, and some diluted with saliva. Other variables may include severity of illness, efficiency of previous Airway Clearance Therapy, and rigor of quantitative collection and measurement methods.
Pulmonary function tests (PFTs) are more direct measures of lung health; results reflect, among other things, the infection/inflammation status of the lungs. Because cystic fibrosis is a disease characterized by progressive decline in pulmonary function, and because many of the cystic fibrosis subjects were hospitalized for infectious exacerbations of their illnesses, interpretation of PFT outcomes is limited by a variety of confounding variables. In one study blood oxygen saturation was used as an outcome measure; because that outcome measure is relatively insensitive to therapy-induced change, its use has been criticized. In one study, a number of general clinical health outcomes were measured. Because effective airway clearance has a direct impact of general health and well being, such measures are of interest.
Reported Outcomes
- Mucus Clearance
- The amount of mucus coughed up by the patient in a fixed period of time, measured by volume, wet weight, or dry weight.
- VC
- Vital capacity; the amount of air that can be inhaled and exhaled
- FVC
- Forced vital capacity
- FEV1
- Forced expiratory volume in the first second of exhalation
- FEV 25-75
- Forced expiratory volume from the 25th to 75th percentile of total expiration capacity
- RV
- Residual volume; a measure of trapped air
- RV/TLC
- Residual volume over total lung capacity, the amount of trapped air normalized to total lung capacity
- Nitrogen washout rate
- A measure of pulmonary gas exchange
- Clinical tests/measurements
- Weight gain
- Respiratory rate
- Blood oxygen saturation
- White blood cell count/ microliter
- Neutrophil count/microliter
Study Results
Arens R, Gozal D, Omlin K, Vega J, Boyd K, Keens T, Woo M. Comparison of high-frequency chest compression1 and conventional chest physiotherapy in hospitalized patients with cystic fibrosis. Am J Respir Crit Care Med 1994; 150: 1154-1157. |
|
| Population |
50 CF patients hospitalized for acute exacerbations (32M, 14 F) |
|---|---|
| Treatment |
HFCC (mean age 22.9 + 2.0) CPT (mean age 18.0 + 1.3) Randomly assigned to: HFCC (n=25) 3x/day for 4-6 min at 6 frequencies CPT (n=25) 3x/day with percussion and postural drainage |
| Outcome |
Both HFCC and CPT groups showed significant improvements in pulmonary function and clinical status; no statistical difference between groups Mean percentage change in VC, FEV1, FEF 25-75, RV, RV/TLC, and SP3N2 improved significantly w/o differences between groups 24 hr sputum weight:
|
| Morbidity/Mortality |
Neither method was associated with significant adverse effects
|
| Comments |
22 patients (88%) in the HFCC group expressed satisfaction with method and requested HFCC be used for treatment of future exacerbations. Patients receiving concomitant therapy Investigation limited to short-term efficacy |
Table 1 Summary
Fifty cystic fibrosis patients hospitalized for acute pulmonary exacerbations were randomized to receive either "conventional" chest physiotherapy or high-frequency chest compression. Both groups, after 7 and 14 days of treatment, demonstrated significant, statistically similar improvements in both pulmonary function and clinical status.
Table 1 Comments
Despite the impossibility of controlling for certain variables among sick patients, it is significant that with consistent, continuous, carefully controlled CPT or HFCC, important improvements in both pulmonary functions and clinical status were obtained. Results suggest the role of Airway Clearance Therapy in decelerating the rate of pulmonary decline in CF patients. Twenty-two (22) patients (88%) in the HFCC group expressed satisfaction with method and requested HFCC be used for treatment of future exacerbations.
|
Scherer TA, Barandun J, Martinez E, Wanner A, Rubin EM. Effect of high frequency oral airway and chest wall oscillation and conventional chest physiotherapy on expectoration in patients with stable cystic fibrosis. Chest 1998; 113(4): 1019-1027 |
|
| Population |
14 CF patients over age 12 with stable disease recruited at CF center |
|---|---|
| Treatment |
Each patient received two modes of oral airway oscillation (1. frequency 8 Hz; inspiratory to expiratory [I: E] ratio 9:1; 2. frequency 14 Hz; I: E ratio 8:1), two modes of chest wall oscillation (1. frequency 3 Hz; I: E ratio 4:1; 2. frequency 16 Hz; I: E ratio 1:1, alternating with frequency 1.5 Hz, I: E ratio 6:1), and CPT (clapping, vibration, postural drainage, and encouraged coughing) One treatment per study day with 2 or more days between study days |
| Outcome | Comparable results were obtained with each modality with respect to weight of expectorated sputum, pulmonary function scores, and oxygen saturation values. All treatments were well tolerated |
| Morbidity/Mortality |
3 patients developed streaky hemoptysis during treatments; 2 with oral airway oscillation and 1 with HFCWO. |
| Comments |
7 patients found oral airway oscillation uncomfortable Small population sample with variable disease progression Patients received concomitant therapy Investigation limited to short-term efficacy |
Table 2 Summary
In a prospective randomized short-term trial including 14 stable CF patients, a study to compare the effects of oral high-frequency airway oscillation, HFCWO, and CPT showed that all three modalities have statistically equivalent effects augmenting sputum expectoration without changing PFTs or oxygen saturation.
Table 2 Comments
Although the short-term duration of this study precludes inferences, some patients expressed comments and preferences suggesting that oral high-frequency oscillation therapy is uncomfortable. Treatment discomfort is strongly associated with non-adherence. Study authors suggested that self-administered airway clearance modalities might have cost advantages.
|
Kluft J, Beker L, Castagnino M, Gaiser J, Chaney H, Fink R. A comparison of bronchial drainage treatments in cystic fibrosis. Pediatr Pulmonol 1996; 22: 271-274. |
|
| Population |
29 consecutive CF patients hospitalized for acute pulmonary exacerbations |
|---|---|
| Treatment |
Four day study; patients randomly assigned to 2 days each of HFCC and CPT for 30 minutes, 3x/day |
| Outcome |
Treatment with HFCC yielded significantly more sputum (both wet [p=0.001] and dry [p=0.01]) than CPT |
| Morbidity/Mortality |
No adverse events observed |
| Comments |
Results suggest that HFCC is at least as effective as CPT in clearing secretions during acute CF exacerbations Patients supervised by same therapist Patients receiving concomitant therapy Investigation limited to short-term only |
Table 3 Summary
A prospective, randomized controlled, crossover study of 29 CF patients hospitalized with acute pulmonary exacerbations were allocated to treatment with HFCC and CPT for 2 days each over a 4-day period. Pulmonary function tests were not included as a measure of efficacy because the effect of continued antibiotic therapy could not be separated from the experimental therapy. Sputum weight was used as a clinical index of mucus clearance. Sputum clearance, determined by both wet and dry weight, both during and after treatment, was increased significantly in the HFCC group compared to the CPT group.
Table 3 Comments
This study suggests that HFCC is at least as effective as CPT in clearing secretions from the airways of CF patients; because, in this study, CPT was administered with a standard of rigor not practiced consistently in the outpatient setting, research results may understate the efficacy of HFCC.
|
Braggion C, Cappelletti L, Cornacchia M, Zanolla L, Mastella G. Short-term effects of three chest physiotherapy regimens in patients hospitalized for pulmonary exacerbations of cystic fibrosis: a cross-over randomized study. Pediatr Pulmonol 1995:19; 16-22. |
|
| Population |
16 CF patients hospitalized for acute exacerbations (8M, 8F (mean age 20.3 + 4 years). |
|---|---|
| Treatment |
Three CPT regimens (postural drainage, positive expiratory pressure, and HFCC) and one control treatment administered in random sequence |
| Outcome |
All three methods resulted in increased sputum production; differences among modalities was not statistically significant Lung function endpoints were statistically similar following all three methods and control; No significant changes in mean percentage of predicted values for FEV1, FVC, or FEF 25-75. |
| Morbidity/Mortality |
No adverse event Small population sample |
| Comments |
Patients supervised by therapist Patients receiving concomitant therapy Investigation limited to short-term efficacy |
Table 4 Summary
In this study, Braggion et al. compared the short-term efficacy of three physiotherapy modalities including postural drainage (PD), positive expiratory pressure (PEP) therapy, and high-frequency chest compression (HFCC) in 16 patients hospitalized for acute exacerbations of CF. Utilizing a prospective, randomized, controlled crossover design, subjects experienced a control session and randomized 2-day trials of each of the three therapeutic regimens cited above. Endpoint measures included wet and dry weight assays of expectorated sputum and measures of FEV1, FVC, and FEF. Results of sputum volume studies and lung function scores were statistically similar for all three physiotherapy regimens. None of the modalities demonstrated superior efficacy in the short-term treatment of patients hospitalized for acute pulmonary complications of CF.
Table 4 Comments
Although no significant improvements in lung function occurred with short-term use of any of the three airway clearance modalities under study, results suggest that with consistent, regimented use, the performance of each method may be equivalent.
|
Hansen LG, Warwick WJ. High-frequency chest compression system to aid in clearance of mucus from the lungs. Biomed Instrum Technol 1990; July/August: 289-294. |
|
| Population |
5 CF patients. |
|---|---|
| Treatment |
30 sessions of HFCC per patient @ 12-16 Hz. 30 sessions of standard CPT per patient. All sessions of equal (unspecified) duration. |
| Outcome |
Total volume of mucus cleared per day: Mean volume of mucus cleared with HFCC: 3.3cc/session. Mean volume of mucus cleared with CPT:1.8 cc/session. Treatment with HFCC yielded significantly more sputum (p<0.001) than CPT. |
| Morbidity/Mortality |
No adverse events observed. |
| Comments |
All treatments administered by registered respiratory therapists. Patients unanimously preferred HFCC to CPT. Small patient sample. |
Table 5 Summary
In a crossover study to compare the volume of mucus cleared using HFCC and CPT, five CF patients were administered 30 sessions each of HFCC and CPT. Treatments sessions matched for time of day were administered by a registered respiratory therapist (RRT). Total volume of expectorated sputum was collected. Results showed that a statistically significant greater volume of mucus was cleared using HFCC.
Table 5 Comments
This small-scale study suggests that HFCC is more effective than standard CPT in clearing secretions from the airways of CF patients. Because, in this study, CPT was administered with a standard of rigor not practiced consistently in the outpatient setting, research results may overstate the efficacy of CPT. All participating patients preferred HFCC to CPT.
|
Warwick W, Hansen L. The long-term effect of high-frequency chest compression therapy on pulmonary complications of cystic fibrosis. Pediatr Pulmonol 1991; 11: 265-271. |
|
| Population |
16 CF patients (aged 14-47); 8 with mild disease (FEV1>70% of predicted); 3 with moderate disease (FEV1 36%-70% of predicted); and 3 with severe disease (FEV1<36% of predicted). |
|---|---|
| Treatment |
Daily HFCC for 30-minute sessions of 5-minute periods at different frequencies; therapy time ranged from 30-240 minutes for a mean of 21.6 months (range=7-26 months). Results compared with pre-HFCC CPT administered 1-4x/day for a mean of 23.2 months (range= 14-27 months). Coughing and huffing techniques also employed. |
| Outcome |
FVC and FEV1 improved in all 8 patients with mild disease (p=0.0003 and p=0.008, respectively). FVC and FEV1 improved in 7/8 (87.5%) of patients with moderate to severe disease (p= 0.1804 and p= 0.0229, respectively). The percent predicted FVC slope increased during HFCC from pre-HFCC (p=0.001). FVC and FEV1 slopes improved in younger patients (p=0.0004 and p=0.00a, respectively) but only FEV1 (p=0.0509) improved in older patients. For FVC, p=0.0947. |
| Morbidity/Mortality |
No treatment-associated adverse events observed. |
| Comments |
4/16 patients died during study period 94% of patients' regression line slopes became more positive during self-administered HFCC therapy as compared to slopes calculated from pulmonary function scores obtained before HFCC was substituted for CPT. The only published long-term study. |
Table 6 Summary
Sixteen CF patients were treated prospectively with HFCC for a mean of 21.6 months. Their PFTs were compared with retrospectively obtained values recorded during treatment with CPT for a mean interval of 23.2 months. Evaluating regression line slopes, both FEV1 and FVC improved after HFCWO in 94% of patients, regardless of disease severity or age. When classified according to disease severity, FEV1, but not FVC, improved in patients with moderate to severe disease while both indices improved in patients with mild disease. Similar results were obtained contrasting older with younger patients.
Table 6 Comments
This long-term study demonstrates significant, sustained improvements in pulmonary function among CF patients receiving consistent HFCWO Airway Clearance Therapy. In the treatment of CF, goals include preservation of lung function and mitigation of disease progression. Because CF is a progressive disease, it is impressive that patients receiving HFCWO therapy obtained not only stability in PFT scores, but in most cases, meaningful improvement.
- In some studies, HFCWO is referred to as: external chest wall oscillation (ECWO), high-frequency chest compression (HFCC), high-frequency chest wall compression (HFCWC) or high-frequency transthoracic ventilation (HFTV).