Effectiveness of treatment with high-frequency chest wall oscillation in patients with bronchiectasis

Bronchiectasis is defined as an irreversible dilatation and destruction of the bronchi [1] with a reduction in clearance of secrections (and particularly in the expiratory airflow) [2]. This disease can lead to recurrent lower respiratory tract infections and worsening pulmonary function, with increased morbidity and mortality [2–5]. The incidence and the prevalence of bronchiectasis is not known, but its diagnosis has increased mainly due to the more frequent use of high-resolution computed tomography [2, 6]. Bronchiectasis is usually associated with chronic cough, increasing secretions, and recurrent airway and pulmonary infections [6]. The fundamental aspects in these patients are the colonizations and infection of the bronchial mucous by potentially pathogenic microorganisms such as Pseudomonas Aeruginosa, Burkholderia cepacia and others. This chronic process results in the destruction and dilatation of the bronchial tree that is the characteristic of the disease [7]. The goals of bronchiectasis treatment are to reduce the number of exacerbations and infections and to improve patient quality of life by reducing airway inflammation and mobilizing secretions [6, 8, 9]. Therapies showing to be effective in cystic fibrosis are often provided to patients with bronchiectasis,without definitive evidence of benefit. In recent years, there has been increased interest in validating and developing new therapies for patients without cystic fibrosis [10]. These include inhaled antibiotics (tobramycin, aztreonam, ciprofloxacin, colistin, amikacin) [10], hyperosmolar agents (hypertonic saline solution, dry powder mannitol) [10, 11], anti-inflammatory agents (macrolides, corticosteroids) [7, 12], bronchodilators (salbutamol) [13],chest physiotherapy, physical exercise and nutritional treatment [7, 14–16]. In the field of chest physiotherapy several secretion management techniques have been proposed: they include modified postural drainage [17], assisted cough [17], active cycle of breathing techniques [17, 18], oscillatory positive-expiratory pressure devices [17, 18] and intrapulmonary percussive ventilation [6]. Although the mucous clearance is recommended in bronchiectasis, there are no definitive studies or guidelines on the preference or superiority of one technique versus the others [6, 19]. High frequency chest wall oscillation (HFCWO) is widely used in the USA where is considered standard care in cystic fibrosis (CF) [20, 21]. It has recently been introduced to UK and Europe and has been used in several other pulmonary diseases, different from CF like chronic obstructive pulmonary disease [22] or exacerbations of chronic obstructive pulmonary disease or bronchial asthma [23]. To our knowledge there have been no trials of HFCWO in patients with non-CF bronchiectasis. The aim of the study was to compare the efficacy, the safety of HFCWO with our standard traditional chest physiotherapy (CPT) in patients with non-CF bronchiectasis.

The exclusion criteria were cystic fibrosis, tracheostomy, non-invasive ventilation, inability to perform forced expiratory maneuvers, recent episode of significant hemoptysis, or pneumothorax in the six months preceding enrollment. The drop-out criteria were withdrawal of patient consent, severe clinical worsening, chest radiograph changes and occurrence of any of the exclusion criteria.

The study was carried out according to the rules of the declaration of Helsinki and approved by Ethics committee of ASL 4 Chiavarese all patients provided written informed consent before beginning the study. The study was registered as Chi CTR-TRC-12002134 at http://www.chictr.org.

Protocol

Every patient was assigned following a computed randomized list to High frequency chest wall oscillation (HFCWO) or to chest physiotherapy (CPT) or to medical therapy only (control group) (Figure 1). CPT secretion clearance sessions lasted 45 minutes per session; HFCWO lasted 30 minutes per session. Both treatments were given twice daily (morning and late afternoon).The duration of each treatment was fifteen days: the treatment was administered five days per week. High frequency chest wall oscillation (HFCWO). HFCWO was provided with the Vest® Airway Clearance System (Hill-Rom, Batesville, Indiana, USA).The Vest system consists of an inflatable vest, which is worn over the torso and an air pulse generator that delivers the oscillating air pulses to the vest via a connecting air hose. The patient was in upright sitting position and the Vest air pulse generator was set to an optimum oscillating frequency of 13–15 Hz based on individual patient tolerance and a pressure setting of 2–5 cm H2O to achieve a tight but comfortable snug fit [22]. Every session lasted 30 minutes and every patient had a treatment twice per day (morning and late afternoon). Chest Physiotherapy (CPT) consisted of a group of respiratory physiotherapy techniques like, slow expiratory with glottis opened in lateral position (ELTGOL) [24], positive expiratory pressure (PEP) mask [25] or PEP bottle [26] and vibratory positive expiratory pressure therapy system [27] (Acapella choice, Smiths Medical, England). Every session lasted 45 minutes and every patient had a treatment twice per day (morning and late afternoon).

Techniques for augmenting the normal muco-ciliary and cough clearance mechanisms of the lungs are not new, but in recent years several techniques have been developed which are effective and comfortable; these techniques can be used without an assistant in the majority of adolescents and adults [35]. HFCWO has been one of the most studied techniques in the more recent years and it has been used in many circumstances such as thoracic trauma [36], neuromuscular diseases, chronic obstructive pulmonary disease [22, 23, 37, 38], bronchial asthma [23], and cystic fibrosis [38–47]. In chronic obstructive pulmonary diseases HFCWO produces improvements in gas mixing and homogenization of alveolar ventilation for previously closed or under ventilated lung units [37, 44]. HFCWO has been shown to decrease functional residual capacity (FRC) in subject with obstructive lung disease [37, 39]:this could explain the improvement of FVC we have observed. Moreover, high frequency chest wall oscillation delivers an intermittent flow of air into the jacket which rapidly compresses and releases the chest wall at a variety of frequencies. An oscillation in airflow within the airways is achieved. HFCWO has been shown to augment central and peripheral mucus clearance [21]. Only one study reported an improvement in FEV1 in the longer term using [46], and few trials have compared HFCWO with traditional chest physiotherapy in cystic fibrotic (CF) patients with favorable results for HFCWO [21, 41, 46]. The effects of HFCWO on sputum production as well as lung function is in dispute. Compared with PEP, there was no difference in either lung function or sputum production [41, 47]. When compared with oscillating PEP, one study showed a benefit in terms of sputum production but did not show differences in lung function [34, 41, 48]. A recently published study on hypersecretive COPD with recurrent exacerbations showed that the treatment with HFCWO led to improvement in lung function, quality of life, and reduction of symptoms, but not in sputum production [22]. An important limitation of most HFCWO studies is the short number of days of treatment. This makes it difficult to evaluate some outcomes like lung function or quality of life, which need much more time to change. None of the previous studies investigated sputum cellularity and its changes after airways clearance treatment. If we consider already published definitions used in the analysis of sputum cellularity (32, 33, 49) all the patients enrolled in the two groups (HFCWO and CPT) presented at starting a total cell count suggesting in all the patient the absence of infection. The reduction of percentage of neutrophils and the increase of percentage of macrophage could suggest a modulation of HFCWO in inflammatory cells (greater than CPT), but these data must be validated with further studies. The significance of this observation is not known.

Our study showed that HFCWO produced an improvement in several lung function parameters compared to traditional chest physiotherapy. Long-term study are needed, not only to establish the effectiveness of different airways clearance devices or techniques and their cost-effectiveness, but especially to establish their acceptability in order to long-term home use.