airway clearance devices in cystic fibrosis

7/31/2019 Airway Clearance Devices in Cystic Fibrosis

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MINI-SYMPOSIUM: AIRWAY CLEARANCE IN CYSTIC FIBROSIS

Airway clearance devices in cystic fibrosis

John H. Marks*

Associate Professor, Department of Pediatrics and Human Development, Michigan State University College of

Human Medicine, East Lansing, and Associate Director, Pediatric Pulmonology and Cystic Fibrosis Center, Michigan

State University-Kalamazoo Center for Medical Studies, Kalamazoo, Michigan, USA

Management of the pulmonary complications of cystic

fibrosis (CF) involves airway clearance therapies (ACTs)

to remove obstructing secretions from the airways. To aid

airway clearance, aerosolized bronchodilators and muco-

lytics are also often used to dilate respiratory passages and

breakdown secretions; other articles in this symposium

discuss these. Conventional manual chest physiotherapy with gravity assisted drainage (CCPT) has long been the

‘gold’ standard method of airway clearance for patients with

CF.1 While CCPT has been shown to aid in clearance of

pulmonary secretions in CF patients, the time involved and

the need for assistance often leads to reduced adherence

to this form of therapy. Several independently administered

airway clearance devices have been shown to be effective

in aiding airway clearance in CF patients, including positive

expiratory pressure (PEP), the Flutter 1 device, the Aca-

pella1, the Cornet1, the intrapulmonary percussive venti-

lation device (IPV), the PercussiveNeb1, and the high

frequency chest wall oscillation devices. This paper will

describe each device, the mechanisms (known and pro-

posed) by which the devices aid airway clearance, and the

clinical evidence based on short- and long-term clinical trials that supports their use in patients with CF.

POSITIVE EXPIRATORY PRESSURE

The PEP device is the simplest and least expensive of the

airway clearance devices. The PEP mask was developed in

Denmark in the late 1970s as an alternative to CCPT. The

mask has a one-way inhalation valve and an expiratory

resistor. Exhalation through the resistor generates positive

pressure in the airways which can be measured with a

manometer or pressure indicator. Resistance orifices of

PAEDIATRIC RESPIRATORY REVIEWS (2007) 8, 17–23

KEYWORDS

airway clearance;

chest physical therapy;

cystic fibrosis;

high frequency chest wall

oscillation;

intrapulmonary

percussive ventilation;

positive expiratory

pressure

Summary Clearance of infected airway secretions is essential to preserve lung function

in patients with cystic fibrosis (CF). Although the value of regular airway clearance

treatments has been shown in many studies, adherence to the prescribed treatments is

not very good (see Making airway clearance successful, pp. 000–000). In the past the only

method available was conventional chest physiotherapy (CCPT; also known as manual

percussion and postural drainage). CCPT remains the ‘gold standard’ of airway clearance

methods and may be the best choice for some patients, such as infants and young

children. However, the many newer methods of airway clearance available now allow CF

patients and their families to choose the techniques and devices that best suits them.

Most of the newer airway clearance devices have been studied in comparison to standard

chest physiotherapy and most studies show no advantage of one method over another.

This review will describe newer airway clearance devices available for CF patients and

discuss evidence for the effectiveness of these devices compared to standard chest

physiotherapy.

ß 2007 Elsevier Ltd. All rights reserved.

* Tel.: +1 269 337 6467; Fax: +1 269 337 6474.

E-mail address: [email protected].

1526-0542/$ – see front matter ß 2007 Elsevier Ltd. All rights reserved.

doi:10.1016/j.prrv.2007.02.003

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different diameters can be chosen so that individual patients

can generate pressures of 10–20 cm H2O. The patient

inhales to mid-lung volumes and then exhales actively with

an inspiration to expiration ratio (I:E) of 1:3 or 1:4. After

about 10 PEP exhalations the patient does a series of huff

coughs, keeping the glottis open. The cycle is repeated

several times over about 20 min or until secretions are nolonger being expectorated. PEP can also be done with a

mouthpiece making sure the cheeks are well supported. A

resistor can also be utilized with a nebulizer so aerosolized

medications can be delivered during inspiration (Fig. 1).

Higher pressure PEP achieving pressures of 60–80 cm H2O

has also been advocated.2

The proposed mechanism of action of PEP is to stabilize

airways and improve aeration to obstructed distal lung units

through colla teral ventilation via pores of Kohn and canals

of Lambert.3 PEP has also been shown to improve the

distribution of ventilation and gas mixing in CF patients.4

Most studies assessing the effectiveness of PEP in CF

patients have demonstrated equivalence compared to tradi-

tional CCPT. One study (16 patients, 8 week crossover

design) showed more improvemen t in forced expiratory

volume in 1 s (FEV1) with CCPT.5 Another study (36

patients, 1 year parallel design) showed greater improve-

ment in FEV1 in the PEP group.6 Four evidence-based

reviews comparing PEP with CCPT and o ther airway clear-

ance methods were published in 2006.7–10 Three Cochrane

Database reviews concluded that there was essentially no

evidence that PEPwas betterthan CCPT or vice versa.There

were trendsthat showed patients preferredPEP over CCPT.

The American College of Chest Physicians Evidence-Based

Clinical Practice Guidelines on Nonpharmacologic Airway Clearance Therapies states, ‘In patients with CF, PEP is

recommended over conventional chest physiotherapy

because it is approximately as effective as chest physiother-

apy, and is inexpensive, safe, and can be self-administered’.10

OSCILLATORY DEVICES

Flutter 1

The Flutter 1 (Axcan Scandipharm, Birmingham, Alabama,

USA) is a small, handheld, mucus clearance device that

provides PEPtherapywith oral airwayoscillations.It is shaped

like a pipe with a hardened plastic mouthpiece at one end, aplastic, protective, perforated cover at the other end, and a

high-density stainless steelball resting in a plastic circularcone

on the inside (Fig. 2). The patient sits comfortably and inhales

to about 75% of inspiratory capacity, then exhales through

the Flutter keeping the stem parallel to the floor. During

exhalation, pressure from the airways is transmitted to the

Flutter causing the steel ball to bounce and roll up and down,

creating several opening and closing cycles with each breath

(Fig. 3). PEP develops in the range of 10–25 cm H2O at an

oscillatory frequency of about 15 Hz. Tilting the device

adjusts the frequency to achieve the greatest amount of

airway vibration (the individual’s pulmonary resonance fre-

quency). Several series of five to ten exhalations each

followed by one or two forceful exhalations and huff coughs

are done over 10–20 min.

The proposed mechanisms of action of the Flutter

include shearing of mucus from airway walls by oscillatory

action, stabilization of airways preventing airway collapse,

accelerating expiratory airflow to move mucus upward to

the trachea, and possibly by altering mucus quality, although

data for direct effec ts of thinning of airway secretions by any

AC device is scant.11

Evidence for effectiveness of the Flutter has been shown

in short- and long-term studies. Expectorated sputum

volume was greater after a 15 min session with the Flutter compared to sessions of CCPT or directed vigorous cough

(18 patients, three-way crossover over 2 weeks).12 Two

studies demonstrated no difference in effectiveness of

Flutter and CCPT during hospital treatment of an acute

18 J. H. MARKS

Figure 2 Top: Flutter device components showing the pipe

stem, cone with steel ball and perforated top. Bottom: the

Acapella device.

Figure 1 Pari PEP device (Pari Respiratory Equipment, Mid-

lothian, Virginia, USA) used with a Pari LC nebulizer. Resistance is

set by choosing one of the various orifices over the exhalation

port (inset). A pressure monitor is at right.



pulmonary exacerbation.13,14 One study showed the Flut-

ter was less effective than PEP (40 patients over 1 y ear) in

maintaining pulmonary function and clinical scores.15 These

conflicting studies point out the difficulty of drawing con-

clusions as to the efficacy of an AC device when a study is

small and often statistically underpowered.

Acapella1

The Acapella1 (Smiths Medical Inc, Carlsbad, California,

USA) is a handheld airway clearance device (Fig. 2) that

operates on the same principle as the Flutter, i.e. a valve

interrupting expiratory flow generating oscillating PEP.

Utilizing a counterweighted plug and magnet to achieve

valve closure, the Acapella is not gravity dependent like the

Flutter. The Acapella comes in three models, a low flow(<15 L/min), high flow (>15 L/min) and the Acapella

Choice. The high and low flow models have a dial to set

expiratory resistance while the Choice model has a

numeric dial to adjust frequency. All models can be used

with a mask or mouthpiece and can be used in line with a

nebulizer. While these attributes may offer the Acapella

some advantage over the Flutter, no long-term studies have

been done in CF patients. A bench study of the perfor-

mance characteristics of the two devices showed a slight

advantage for the Acapella, with more stable wave form

and a wider range of PEP at low air flow.16

RC-Cornet1

The RC Cornet1 (R. Cegla, Montabaur, Germany) consists

of a semi-circular tube containing a flexible latex-free hose

(Fig. 4). Expiration through the Cornet causes the hose to

flex,buckle and unbuckle, causing oscillating positivepressure

in the airways which fluctuates many times per second. The

mouthpiece can be adjusted to produce the optimal effect.

Operating principle and use are similar to the Flutter valve,

although the Cornet is not gravity dependent and can be

used in any position. Like the Flutter the Cornet cannot be

used in line with a nebulizer. No studies showing the long-

term effectiveness of the Cornet in CF patients are available

yet. The Cornet is available in Europe but not in the USA.

Intrapulmonary Percussive Ventilation

IPV-11

The IPV-11 (Percussionaire, Sand Point, Idaho, USA) is a

positive pressure ventilator device (Fig. 5) that delivers

small bursts of air through a mouthpiece at a rate of

200–300 cycles/min (2–5 Hz) using a sliding venturi to

cause rapid flow interruptions. It entrains an aerosol of

up to 20 ml of saline with or without a bronchodilator over

about 20 min. It delivers a positive pressure at the mouth of

10–30 cm H2O. The optimal effect achieved by pressure

and frequency is determined by direct observation of chest

movement and patient comfort. Oscillations occur mainly

during inhalation, but may occur throughout the respiratory

cycle. The pressure source can be either an oxygen cylinder

or an air compressor.The presumed mechanisms of action of the IPV include

bronchodilation from increased airway pressure and deliv-

ery of nebulized bronchodilator, prevention of airway

collapse, improved distribution of ventilation and stimula-

tion of cough.

Evidence to support the effectiveness of IPV treatment

in CF patients is limited. Three short-term studies and one

long-term study have been published. Two single interven-

tion studies established safety and demonstrated no dif-

ference in effects on pulmonary function and spu tum

production with IPV compared to CCPT and Flutter.17,18

A short-term study in hospitalized CF patients (24 subjects,

crossover design) demonstrated an increased sputum wet

weight after IPV compared to high frequency chest wall

oscillation.19 A 6-month study (16 CF patients, parallel

design) that compared daily IPV with standard bronchodi-

lator aerosol and CCPT showed no significant differences in

pulmonary function, number of hospitalizations, use of oral

or intravenous antibiotics and anthropometrics.20

PercussiveNeb1

The PercussiveNeb1 (P-Neb; Vortran Medical Technology

1, Sacramento, California, USA) is an oral intrapulmonary

AIRWAY CLEARANCE DEVICES 19

Figure 4 The RC-Cornet device.Figure 3 Oscillating up and down action of the steel ball in the

Flutter. (From Flutter 1 mucus clearance device, Instructions for

use, Axcan Scandipharm, Birmingham, Alabama, USA.)



percussive treatment device that incorporates a large

volume nebulizer (20 ml) for delivery of aerosolized med-

ication with oscillating positive pressure (Fig. 6). Oscillatory

frequency ranges from 6 to 30 Hz with airway pressures of

6–15 cm H2O. The P-Neb oscillates during both inhalation

and exhalation, enhancing aerosol delivery and maintaining

airway patency (Fig. 7). The pressure source is a high-

output compressor capable of delivering a gas flow >60 L/

min. Most of the flow is utilized to operate the modulator

piston that causes the oscillatory effect. The patient fills the

nebulizer reservoir with bronchodilator medication, starts

the compressor and occludes the mouthpiece until the

device begins to cycle. After placing the mouthpiece in the

mouth, the flow is adjusted to accommodate the patient’s

comfort and breathing pattern. Oscillating amplitude can be

adjusted from ‘soft’ to ‘hard’.Presumed mechanisms of action are similar to the IPV

and include bronchodilation, prevention of airway collapse

and shearing of mucus from airway walls, and possible

thinning of secretions by high expiratory percussive flow

(Fig. 8).

There are no published long-term studies of the P-Neb

in CF patients. A single intervention study of the precursor

device, the PercussiveTech HF, in CF patients showed it to

be safe and probably as effective as CCPT.21 A 6-month

study (16 CF patients, parallel design) comparing daily use

of the PercussiveTech HF with the Flutter showed no

differences in pulmonary function or days of hospital or

home intravenous antibiotic use.22

It should be noted that for all the oral positive

expiratory pressure devices, especially when used with

a mouthpiece, the cheeks should be kept flat and rigid

and a nose clip should be considered so that the pressure

and oscillations are primarily delivered to the lower

airways.

High frequency chest wall oscillation

There are two devices utilizing an inflatable vest con-

nected to an air-pulse generating compressor to deliver

20 J. H. MARKS

Figure 6 The PercussiveNeb device.

Figure 7 Mouth pressure and amplituderecording with PTHF

in two CF patients. Top: Pressure recorded shows oscillations at

approximately 10 Hz with an amplitude of 0–6 cm H2O during

inhalation and 8–14 cm H2O during exhalation. Bottom: There

are no oscillations during inhalation and lower amplitude and

frequency during exhalation. (Adapted with permission from

Marks et al.21)

Figure 5 The IPV-1 device.



high-frequency chest wall oscillation (HFCWO), The

Vest1 (Hill-Rom, St Paul, Minnesota) and the SmartVest1

(Electromed, New Prague, Minnesota) (Fig. 9). The air-

pulse generator rapidly inflates and deflates the vest,

gently compressing and releasing the chest wall several

times per second. Oscillation frequency can be adjusted

from 5 to 25 Hz with pressure to the vest ranging from 3 to 25 cm H2O. The chest wall oscillations are transmitted

to the airways creating mini-coughs. Treatment sessions

generally last 20 to 30 min and consist of short segments at

different frequencies separated by huff coughs. An exam-

ple would be 5 min sessions at 8, 10, 12, 15, 17 and 20 Hz.

Keeping the frequency set at 12 Hz for the entire treat-

ment is a simpler option. Nebulized bronchodilator can be

taken before or during a vest treatment session. Vests

come in different sizes to accommodate children and

adults.

The proposed mechanism of action of HFCWO is

enhancement of mucus transport in three essential ways:

by altering the rheologic properties of mucus, by creating a

cough-like expiratory airflow bias that shears mucus from

the airway walls, and by enhancing ciliary beat frequency, allof which help move mucus toward central airways.23

HFCWO has also been shown to improve distribution

of ventilation.24 One study found that patients with mod-

erate or severe airway obstruction may benefit from lower

vest pressures at frequencies of 10–15 Hz to minimize

decrease in end-expiratory lung volume and maximize

oscillatory flow.25

There is evidence to support the use of HFCWO in CF

patients based on several studies looking at acute and long-

term effects. When comparing HFCWO to oscil lating PEP

and CCPT, the acute effect, as assessed by sputum pro-

duction, showed no difference or superiority of HFCWO

using a vest device compared to CCPT and IPV.26

HFCWO using the Hayek Oscillator (Breasy Medical

Equipment Ltd, London, UK), a rigid cuirass ventilator,

and oscillating PEP using two similar oral airway oscillating

devices (Sensormedics, Yorba Linda, California, USA)

demonstrated, ‘comparable augmenting effects on expec-

torated sputum weight’ with no effect on pulmonary

function.27 Therapy during hospitalization for a pulmonary

exacerbation showed no differences in outcomes with

HFCWO compared to CCPT or PEP as assessed by

sputum production and pulmonary function.28,29 A

short-term crossover trial comparing HFCWO to CCPT

and oscillating PEP found no differences in pulmonary function or clinical score between therapies. Patients

tended to prefer HFCWO.30 A long-term study (16

patients, 22 months with historical controls) showed a

significant decrease in the rate of decline in pulmonary

function during the HFCWO treatment period compared

to standard CPT.31

The Hayek Oscillator was compared to active cycle

of breathing technique (ACBT) in a 2-day crossover

study; HFCWO was found to be less effective than

ACBT.32 No long-term studies using this device have been

published.

CONCLUSION

Several devices have been developed to enhance airway

clearance in CF patients. With the exception of the PEP

valve, these devices all involve airway oscillation, either

orally or via chest wall vibration. The advantage of these

devices is that they can be used by patients independently

without the need for an assistant or caregiver. Most of

these devices have been studied in either short- or long-

term comparisons with CCPT. The studies are generally

underpowered and it is not clear which outcome mea-

surements are most useful for comparing various clear-


Figure 9 The SmartVest1 showing the compressor unit and

vest. (Adapted from SmartVest1 product information, Electro-

med, New Prague, Minnesota, USA.)

Figure 8 Diagram of exhalation without PEP or oscillations

(upper figure) and with oscillatory PEP (lower figure). (Adapted

from PercussiveNeb1 User’s Guide, Vortran Medical Technology

1, Sacramento, California, USA.)



ance techniques. Short-term studies, especially those

measuring sputum production, are not helpful in demon-

strating equivalence of any airway clearance methods. In

spite of a lack of adequately powered, long-term trials,

two Cochrane evidence-based reviews conclude that

there is evidence that CCPT is generally at least as

effective as these airway clearance devices.

8,9

The ACCPEvidence-Based Clinical Practice Guidelines states, ‘In

patients with CF, devices designed to oscillate gas in

the airway, either directly or by compressing the chest

wall, can be considered as an alternative to chest phy-

siotherapy’.10

Evidence in these reviews also suggests that

these self-administered therapy devices may be preferred

by CF patients, which may lead to increased adherence to

treatment.

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22 J. H. MARKS

PRACTICE POINTS

Airway clearance devices as alternatives to CCPTallow CF patients to choose the therapy that best

fits their lifestyle and allows greatest independence

Airway clearance devices are preferred by many

patients compared to CCPT and may result in

better adherence.

PEP may be more effective for airway clearance

than CCPT.

Oscillating positive expiratory pressure devices

and HFCWO appear to be at least as effective

as CCPT.



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31. Warwick W, Hansen L. The long-term effect of high-frequency chest

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32. Phillips GE, Pike SE, Jaffe A, Bush A. Comparison of active cycle of

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airway clearance devices in cystic fibrosis

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