Effect of chest wall oscillation on mucus clearance: comparison of two vibrators

Criteria for enhancing mucus transport: a systematic scoping review

Background

Uncertainty exists regarding the physiological basis of physiotherapy strategies to facilitate mucus clearance. The aim of this review was to describe the physiological factors and intrinsic conditions that facilitate airway mucus transport.

Method

A scoping review was performed. A systematic literature search of six databases was executed. Eligibility criteria were applied by two researchers to reach the aim of the review. Papers were identified independently by two reviewers on title, abstract and full-text level. Any discrepancies were discussed with a third reviewer.

Results

The search identified 35 papers published between 1975 and 2015. These differed significantly in terms of outcome measures, measurement techniques and methodologies and included animal studies, laboratory investigations, and the use of small human samples. Nine key factors influencing mucus transport were identified. These include: temperature and humidity, bronchial perfusion, ATP, forced expiratory technique and cough, generation of oscillation, ventilation patterns/airflow, epithelial differences, mucus properties and positioning.

Conclusion

This review provides a framework for factors/conditions influencing mucus transport. Existing physiotherapy strategies for augmentation of airway mucus clearance can now be evaluated against the framework and new modalities informed.

Electronic supplementary material

The online version of this article (10.1186/s40248-018-0127-6) contains supplementary material, which is available to authorized users.

Role of mechanical stress in regulating airway surface hydration and mucus clearance rates

Effective clearance of mucus is a critical innate airway defense mechanism, and under appropriate conditions, can be stimulated to enhance clearance of inhaled pathogens. It has become increasingly clear that extracellular nucleotides (ATP and UTP) and nucleosides (adenosine) are important regulators of mucus clearance in the airways as a result of their ability to stimulate fluid secretion, mucus hydration, and cilia beat frequency (CBF). One ubiquitous mechanism to stimulate ATP release is through external mechanical stress. This article addresses the role of physiologically relevant mechanical forces in the lung and their effects on regulating mucociliary clearance (MCC). The effects of mechanical forces on the stimulating ATP release, fluid secretion, CBF, and MCC are discussed. Also discussed is evidence suggesting that airway hydration and stimulation of MCC by stress-mediated ATP release may play a role in several therapeutic strategies directed at improving mucus clearance in patients with obstructive lung diseases, including cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD).

Hemodynamic and ventilatory effects of manual respiratory physiotherapy techniques of chest clapping, vibration, and shaking in an animal model

Chest clapping, vibration, and shaking were studied in 10 physiotherapists who applied these techniques on an anesthetized animal model. Hemodynamic variables (such as heart rate, blood pressure, pulmonary artery pressure, and right atrial pressure) were measured during the application of these techniques to verify claims of adverse events. In addition, expired tidal volume and peak expiratory flow rate were measured to ascertain effects of these techniques. Physiotherapists in this study applied chest clapping at a rate of 6.2 +/- 0.9 Hz, vibration at 10.5 +/- 2.3 Hz, and shaking at 6.2 +/- 2.3 Hz. With the use of these rates, esophageal pressure swings of 8.8 +/- 5.0, 0.7 +/- 0.3, and 1.4 +/- 0.7 mmHg resulted from clapping, vibration, and shaking respectively. Variability in rates and "forces" generated by these techniques was <20% in average coefficients of variation. In addition, clinical experience accounted for 76% of the variance in vibration rate (P = 0.001). Cardiopulmonary physiotherapy experience and layers of towel used explained approximately 79% of the variance in clapping force (P = 0.004), whereas age and clinical experience explained >80% of variance in shaking force (P = 0.003). Application of these techniques by physiotherapists was found to have no significant effects on hemodynamic and most ventilatory variables in this study. From this study, we conclude that chest clapping, vibration, and shaking 1). can be consistently performed by physiotherapists; 2). are significantly related to physiotherapists' characteristics, particularly clinical experience; and 3). caused no significant hemodynamic effects.

Effect of high-frequency oral airway and chest wall oscillation and conventional chest physical therapy on expectoration in patients with stable cystic fibrosis

STUDY OBJECTIVE

To compare the effect of high-frequency oral airway oscillation, high-frequency chest wall oscillation, and conventional chest physical therapy (CPT) on weight of expectorated sputum, pulmonary function, and oxygen saturation in outpatients with stable cystic fibrosis (CF).

DESIGN

Prospective randomized trial.

SETTING

Pediatric pulmonary division of a tertiary care center.

PATIENTS

Fourteen outpatients with stable CF recruited from the CF center.

INTERVENTIONS

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) were applied during the first 20 min of 4 consecutive hours.

MEASUREMENTS AND RESULTS

Sputum was collected on an hourly basis for a total of 6 consecutive hours. During the first and the last hour, patients collected sputum without having any treatment and underwent pulmonary function tests (PFTs). Oxygen saturation was measured at 30-min intervals during hours 1 to 6. For the first 20 min of the second to the fifth hour, patients received one of the treatments. To assess the effect of the intervention, the weight of expectorated sputum during hours 2 to 6 was averaged and expressed as percentage of the weight expectorated during the first hour (baseline). For the five treatment modalities, mean sputum dry and wet weights ranged between 122% and 185% of baseline. There was no statistically significant difference among the treatment modalities. As measured by sputum wet weight, all oscillatory devices tended to be less effective than CPT (p=0.15). As measured by dry weight, oral airway oscillation at 8 Hz with an I:E ratio of 9:1 and CPT tended to be more effective than the other treatment modalities (p=0.57). None of the treatment modalities had an effect on PFTs and oxygen saturation and all were well tolerated.

CONCLUSION

In outpatients with stable CF, high-frequency oscillation applied via the airway opening or via the chest wall and CPT have comparable augmenting effects on expectorated sputum weight without changing PFTs or oxygen saturation. In contrast to CPT, high-frequency oral airway and chest wall oscillations are self-administered, thereby containing health-care expenses.