The decluttering of the respiratory tract

‍Integration work presented at the Faculty of Medicine of the University of Montreal in order to obtain the master's degree and health sciences — Physiotherapy

For several years, new methods of decluttering secretions have emerged in order to facilitate the daily life of individuals suffering from cystic fibrosis (CF). These new modalities include several devices that are easy and quick to use in addition to allowing the autonomy of the user. Among the principles behind these devices are positive exhalation pressure (PEP), oscillating positive exhalation pressure (PEPO) and high-frequency chest vibration (VTHF).

Positive Expiratory Pressure

PEP is a therapy used by individuals with CF to clear secretions from the respiratory tract. Since the majority of PEP devices are easy to use, they can be used from the age of three or four 1, 2. Normally, this modality does not require the presence of a third person, but young children often require supervision. PEP uses a portable device that is relatively inexpensive. Indeed, a PEP device costs an average of $25 to $60 3, 4. Several models are available, for example: the PEP mask, the PariPEP®, the TheraPEP® and the Threshold PEP®. All of these models are based on the same basic principle, but each has its own components and characteristics of use. Among these devices, there are, in general, two categories: low-pressure devices and high-pressure devices.

PEP at low pressure can be performed during the acute phases of the disease 5. However, since PEP creates exhalation resistance, its use is not recommended in subjects with severe dyspnoea 6 and is contraindicated in the presence of undrained pneumothorax 7. As high-pressure PEP therapy creates greater exhalation resistance, it could be difficult to perform or poorly tolerated in the acute phases of the disease 8. In addition, high-pressure PEEP is contraindicated in the case of cardiac disorders, hemoptysis, asthma, pneumothorax or following lung surgery 7.

Exhaling through the PEP device creates exhalation resistance that creates positive airway pressure. This makes it possible to increase intrapulmonary pressure and to avoid dynamic airway compression 3, 13. PEP therefore reduces hyperinflation and improves air flow at the end of expiration 3. In addition, the increase in intrapulmonary pressure allows air to seep between the wall of the respiratory tract and the mucus in order to facilitate the movement and elimination of the latter.

Oscillating positive expiratory pressure

PEPO is one of the therapies that allows the decluttering of the respiratory tract in cases of damage to the pulmonary system. Like PEP devices, PEPO devices are easy to use and can be used by individuals over the age of three 9. Normally, this modality is done independently, but young children often require supervision. In addition, PEPO devices are portable and inexpensive with prices ranging between $35 and $100. Several device models are available. Among others, we find Flutter®, Acapella®, Acapella®, Cornet® and Quake®. Although all these devices use the PEPO principle, each has its own particularities. PEPO may be poorly tolerated in the acute phases of the disease 10. In addition, if the patient does not master the technique well, he may experience dizziness caused by hyperventilation11. As PEPO devices increase intrapulmonary pressure, they may contribute to the development or worsening of pneumothorax 12. This is why this modality is contraindicated in patients in the presence of the latter, but also in patients with hemoptysis or right heart failure 13, 14.

The Flutter®, the best known PEPO device, is a portable pipe-shaped device composed of a mouthpiece and a perforated lid. Inside the device, there is a stainless steel ball that rests in a conical plastic receptacle 15. The vibrations are induced by the ball which, due to exhaled air and the force of gravity, oscillates vertically 13. When the ball goes down, it settles in the cone and blocks the passage of air and when it rises, it creates an opening that allows air to pass through. These oscillations of the ball cause fluctuations in the resistance to the expiratory flow, which induces PEP and the vibration of the respiratory tract. To optimize the latter, the inclination of the device must be adjusted in order to obtain a frequency similar to the resonance frequency of the lungs. However, as the Flutter® mechanism depends on gravity, the device can only be tilted very slightly. By tilting the device slightly downwards, you get a smaller oscillation frequency or a greater frequency if it is tilted up.

The Acapella® device is a portable device that uses a magnet and a counterbalanced valve to produce PEPO. When the patient exhales through the device, it is the valve that induces PEPO by blocking the passage of air intermittently 16. At the end of the device, a button can be used to adjust the distance between the magnet and the valve in order to adjust the frequency, amplitude and pressure 16. Unlike Flutter®, the Acapella® mechanism is not influenced by gravity. It can therefore be used in several positions 17, 18.

The Cornet® is a device composed of a semicircular plastic tube containing a flexible hose. One end of the tube is formed by a mouthpiece while at the other end, there is a roller that allows you to adjust the flow, the pressure and the frequency of the oscillations. When using Cornet®, PEPO is produced thanks to the movements of the flexible hose. During exhalation, this pipe fills with air and bends in some places due to the stress of the semicircular plastic tube.

The Quake® is a device composed of a mouthpiece and a crank. During expiration, the user can manually manage the frequency of the oscillations by turning the crank to the desired speed. A slow rotation of the crank induces low frequency oscillations while a fast rotation induces high frequency oscillations. Thus, Quake® is recommended for patients who have significant lung damage and who are unable to generate sufficient exhalation flow to use the previous devices19.

High frequency chest vibrations

VTHF is also called high-frequency chest wall oscillation, high-frequency chest wall compression, or, more commonly, the vest. Like the two previous modalities, VTHF does not require the active participation of the subject. Thus, it can be used from the age of two or three. VTHF uses equipment costing several thousand dollars and can be done independently. Created by Hansen and Warwick in 1990, several models are now available on the market: The Vest®, the Smartvest® and InCourage®.

VTHF therapy uses an inflatable jacket and a compressed air generator. The latter sends air, intermittently, into the jacket so that it can be inflated and deflated. Thus, both when inhaling and exhaling, high-frequency mechanical oscillations are transmitted to the chest wall. These oscillations cause, as with PEPO devices, the vibration of the respiratory tract, which makes it possible to loosen the mucus and mobilize it towards the upper airways. In addition, the chest compression produced by the air-filled jacket makes it possible to improve respiratory flow at small lung volumes and to increase the efficiency of mucociliary transport by inducing a force similar to cough. A nebulizer may be attached to the device in order to administer a hypertonic solution to the patient during treatment.

The other devices

There are a multitude of devices that can help clear the airways and improve lung function. Unfortunately, some of them are less well known, less used, or less studied. Novelty, specificity to specific clienteles, an effectiveness already demonstrated with other clienteles, or an already impressive and difficult choice of methods of de-congestion of the respiratory tract are some factors that may explain the lack of evidence on the use of certain devices with CF patients.

The Frequencer® is a device equipped with a transducer that emits, at frequencies varying from 25 to 40 Hz, mechanical sine waves as well as acoustic vibrations. These mechanical and acoustic stimulations cause the respiratory tract 20 to vibrate, which makes it possible to detach mucus from the walls and mobilize it towards the upper respiratory tract in order to be eliminated.

The CoughAssist® is a device that facilitates the release of secretions from the respiratory tract in patients with an ineffective cough. The device gradually exerts positive pressure on the respiratory tract allowing a deep breath. This positive pressure changes suddenly into negative pressure, which allows rapid exhalation, stimulates cough and promotes the elimination of secretions 21.

Effectiveness of airway decluttering devices

Several studies have been carried out in order to determine whether PEP, PEPO, and VTHF are effective and/or superior airway de-congestion modalities to other modalities. The variables analyzed to assess effectiveness are numerous, but the most used variable is lung function. The latter can be assessed by forced vital capacity (FVC), maximum exhalation volume in one second (FEV1), and mean exhalation flow (DEM). Other frequently used variables are the amount of secretion, the duration or number of hospitalizations, the saturation of hemoglobin with oxygen (SpO2), and side effects.

In the majority of studies, the results of FEV1, DEM and CVF did not show a significant difference in effectiveness between the methods of decluttering the airways.

The quantity of expectorated secretions following the use of an airway decluttering modality is a variable often used to assess the effectiveness of treatment. However, it is important to keep in mind that the reliability of this measure is questionable. In fact, the quantity of secretions can vary greatly since they can contain a variable quantity of saliva or be swallowed. By examining expectorated secretions, a single study revealed a variation between two methods of decluttering the respiratory tract. In fact, App et al. noted a significant reduction in the viscoelasticity of secretions following treatment sessions with Flutter® compared to autogenous drainage 22.

The number of hospital admissions following pulmonary deterioration may also vary depending on the mode of release of secretions chosen. In the study by McIlwaine et al., there was no significant difference in the number of hospital admissions between the group using the PD with percussion and the group using a PEP device.23 However, another study by McIlwaine et al., by comparing PEP with Flutter® over a period of one year, demonstrated a significant difference in the number of hospital admissions caused by lung deterioration. In fact, in the PEP group, five participants had to be hospitalized compared to 18 in the Flutter® 24 group.

Conclusion

Methods for releasing secretions with devices are easy to use, fast, portable and allow more autonomy than conventional methods. The three main types of devices presented are the PEP, the PEPO and the VTHF seem to be safe. However, no clear conclusions can be drawn about the effectiveness and superiority of a device over other treatment modalities. Considering that the majority of the studies presented are cross-studies evaluating short-term effects, it would be relevant to have long-term randomized clinical trials in order to give more credibility to the results. In addition, as Flutter® is the best known PEPO device, it is the most used in studies, but very little data is available on other devices in the same class such as the Acapella®, the Cornet® and the Quake®. The novelty of these devices could explain the lack or absence of literature, 25 but it would be interesting if these devices were also studied.

Rachel Brosseau Master's director

And

Amélie Côté

Florence Charbonneau-Dufresne

Annick Circé

Léa Charbonneau Corbeil

Montreal (Quebec) Canada

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23. McIlwaine PM, Wong LT, Peacock D, Davidson AG. Long-term comparative trial of conventional postural drainage and percussion versus positive fibrillatory pressure physiotherapy in the treatment of cystic fibrosis. The Journal of Pediatrics. 1997; 131 (4) :570-4.

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25. Morrison L, Agnew J. Oscillating devices for airway clearance in people with cystic fibrosis. The Cochrane database of systematic reviews. 2009 (1) :CD006842.

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