Maintaining healthy lungs: the role of airway clearance therapy. (EP Guide To Every Body Part 4).

Good respiratory health is impossible without efficient clearance of airway secretions. Normal airway clearance is accomplished by two major mechanisms: the mucociliary clearance system (MCS) and the ability to cough. An impaired MCS is linked to poor lung health in a broad range of diseases and disabilities. Because at-risk individuals are prone to recurrent episodes of respiratory inflammation, infection and, eventually, irreversible lung damage, improvement of mucociliary clearance is a vital treatment goal--a goal that can be accomplished with an individualized bronchial hygiene plan that includes effective airway clearance therapy.

AIRWAY CLEARANCE THERAPY: WHO NEEDS IT?

For several decades, airway clearance therapy has been a fundamental component in the treatment of children with primary diseases affecting the mucociliary clearance system (MCS). In conditions including cystic fibrosis (CF), primary ciliary dyskenesia syndrome and bronchiectasis, excess mucus production and/or inability to clear it are major features of the illness; for that reason, the rationale for improving mucociliary clearance has been intuitive. Currently, physicians recognize that uncleared secretions are implicated as the starting place for serious respiratory illness in children with a spectrum of illnesses and disabilities. (See "Respiratory Compromise and the Child with Special Healthcare Needs" Exceptional Parent, May 2001).

Impairment of the MCS can occur as a result of any event or dysfunction that disrupts normal airway clearance mechanisms. Excess, often sticky mucus may accumulate in the airways in conditions as varied as cerebral palsy, muscular dystrophy, and immunodeficiency disorders. Retained secretions are a universal problem in children with artifical airways or those who depend on assisted ventilation. As a consequence of uncleared mucus, breathing becomes hard work. More energy and effort are required to get vital oxygen. Although precipitating causes are diverse--aspiration, dysphagia, gastroesophageal reflux, weakness of respiratory muscles, breathing problems associated with skeletal deformity, ineffective cough function, and immobility--consequences are the same: vulnerable individuals are caught up in the vicious cycle of recurrent, ever-worsening episodes of inflammation, pulmonary infection, lung damage, increased production of excess mucus, and airway obstruction. Airway clearance therapy is indicated for anyone whose pulmonary health is threatened by the adverse effects of retained airway mucus.

EARLY HISTORY

Physicians have long recognized a cause and effect relationship between uncleared airway secretions and acute and chronic pulmonary complications. By the early 1900s, the link between trapped bronchial secretions and airway obstruction, airway resistance, poor exchange of oxygen and carbon dioxide, and episodes of severe, frequently fatal respiratory infection was well understood. Yet, despite a firm therapeutic basis for removing excess airway secretions, useful methods were unavailable. Inadequate knowledge of the mechanisms of the MCS precluded the development of practical techniques. Doctors were limited to approaches based on trial and error or anecdote.

EARLY STRATEGIES

In medical texts dating from the turn of the twentieth century, doctors were advised to try a variety of techniques aimed at stimulating the cough or gag reflexes to bring up accumulated mucus. A pediatric journal dated 1903 urged physicians to encourage deep breathing and coughing by snapping the soles of a child's feet with a rubber band. Another journal from the same period advised pouring whiskey into a child's throat, a method certain to cause violent coughing. Other sources suggested chest massage, tickling the glottis with feathers, and placing a finger into the pharynx to induce a gagging response. Needless to say, none of these methods have endured to find a place in modern practice.

CPT: THE "PIONEER" OF AIRWAY CLEARANCE THERAPIES

As the health consequences of poor mucociliary clearance became increasing clear, physicians and caregivers were motivated to search for ways to clear airway mucus. Unlike their "horse and buggy" predecessors, they began to look for solutions based upon scientific principles of anatomy, physiology, and physics. Gradually, contributions from a variety of sources resulted in the development of an unstandardized but logically sound method consisting of various combinations of breathing techniques: positioning to achieve drainage using the force of gravity, manual percussion, squeezing or thrusting of the chest wall, and sometimes shaking, or vibration, of the thorax. Variations of this general method became known by terms including bronchial drainage (BD), percussion and postural drainage (P&PD), and chest physical therapy/chest physiotherapy (CPT).

Forms of CPT have been used in the management of airway clearance disorders since the early 1900s; in 1901, a report of the beneficial effects of "bronchial drainage" first appeared in the medical literature. By the end of World War I, doctors used CPT routinely to treat a variety of infectious lung diseases, especially tuberculosis. In England in the 1930s and in the United States a decade later, the use of special breathing exercises was introduced for use after chest surgery.

Although CPT represented a significant therapeutic advance, it was extremely unreliable. Lacking practical guidelines for its effective use, practitioners had to guess, improvise, and simply hope for the best.

THE "KETCHUP BOTTLE" THEORY

The development and "fine-tuning" of CPT represents a milestone in the management of respiratory complications. In the 1950s, two American physicians described their successful use in post-surgical patients of a rationally sequenced version of CPT. Their method, sometimes called the "ketchup bottle" technique, consisted of a well-defined combination of breathing exercises, chest percussion (the systematic, sequential striking of areas of the chest wall with the hand), and postural drainage. Their theory was based upon certain principles of physics known to all who have struggled to pour ketchup from the traditional glass bottle. One may shake, pound on, or dangle the bottle ineffectually over a plate, or one may get good results by tapping the bottle strategically while positioning it just so and waiting ever so patiently for the ketchup to flow. Extremely patient individuals know that it is possible, using a sequential combination of these techniques, to eventually empty the ketchup bottle so completely that it appears to have gone through a dishwasher. Theoretically, the same results may be obtained treating mucus-filled lungs.

The human body, however, is more complicated than a ketchup bottle; intricate mechanisms interact to maintain its functional integrity. As a result, no matter how beautifully a treatment model can be demonstrated in laboratory apparatus (in vitro), finding ways to make it work in a living person (in vivo) is never so simple. For a number of reasons, the effective use of CPT is especially difficult.

CPT: TECHNICAL CHALLENGES

CPT is an airway clearance technique based on the theory that percussion of various areas of the chest and back transmits shock waves through the chest wall, loosening secretions in the airways. If the patient is strategically positioned, the loosened secretions will then drain into the upper airways, where they can be cleared using coughing and huffing techniques. To accomplish this effectively, a trained caregiver must:

* Place the recipient in a position that facilitates secretion drainage from the lobe about to be percussed.

* Hold his or her hands in a slightly cupped position in order to trap air between the hand and the patient's chest wall

* Administer vigorous percussion to one segment of the lung for five to ten minutes.

* Encourage the recipient to employ coughing and huffing techniques that involve holding the breath, emitting deep, hollow coughs, taking slow breaths through the nose, coughing again, and then expectorating.

* Repeat the procedure until each segment of the lung lobe is percussed, with the patient assuming a position appropriate for drainage of secretions from the segment receiving percussion.

To administer a complete treatment, most textbooks specify a sequence of 12 repetitions.

Although expertly administered CPT is effective, its disadvantages are many:

* CPT is technique-dependent; success depends upon skill and reliability of caregiver

* CPT is labor-intensive; caregiver must possess strength and endurance sufficient to percuss chest effectively and to position patient

* Optimal results require mental and physical cooperation: mentally impaired, physically uncooperative, or severely spastic patients present technical challenges

* CPT requires physical tolerance; contraindications arising from anatomical deformity-especially bony prominences-transient hypoxemia associated with postural drainage, predisposition to gastroesophageal reflux, inability to perform breathing techniques, etc., precludes its use

* Technology-dependent patients may be unable to tolerate positioning

* CPT is associated with poor treatment adherence

* CPT is costly if professionally administered

* CPT is time consuming; treatments may require 30-45 minutes three or more times daily

For more than 50 years, CPT was essentially the only form of airway clearance therapy available. Over that time, its value as an effective treatment became progressively clearer. Most notably, when CPT became "standard of care" for children with CF, their general health improved and average life expectancies rose dramatically. Nevertheless, even though the lung health of children with impaired mucociliary clearance depends upon routine airway clearance treatment, because of the technical difficulties and "burden of care" associated with CPT, it is, for most families, an impractical and unrealistic treatment for airway clearance problems.

NECESSITY: THE MOTHER OF INVENTION

Ideally, an airway clearance therapy should be effective, efficient, comfortable for the user, and easy to administer. It should clear mucus thoroughly and improve lung function without decreasing oxygenation or aggravating the reflux of stomach acids. Importantly, it should be designed to permit independent use. Because CPT meets few of these criteria, the incentive to "build a better mouse trap" has been strong. As evidence for the medical necessity of effective airway clearance mounted, so too did physician and consumer demand for better, more reliable techniques. In response, respiratory physiologists and biomedical engineers began to exercise their ingenuity.

MODERN MODALITIES 

In rapid succession, an array of innovative techniques, technologies, and devices emerged. Among them, the best known include breathing exercise techniques; for example, the forced exhalation technique (FET) uses variant forms of alternate periods of breathing control, thoracic expansion exercises, and huff-coughing. Other techniques and devices include Autogenic drainage (AD), mechanical percussors for use with traditional CPT, the Flutter[R] valve, and positive expiratory pressure (PEP); intrapulmonary percussive ventilation (IPV) represents a variant form of PEP. The Emerson In-Exsufflator[TM] provides cough assistance. Finally, The Vest[TM] Airway Clearance System administers a therapy based upon the physical principles of high-frequency chest wall oscillation (HFCWO).

CHOOSING AN AIRWAY CLEARANCE METHOD

For children at risk for serious respiratory illness, parents should seek careful evaluation of their MCS function; those found to have clinically significant problems should receive routine or intermittent airway clearance support. Because therapeutic results depend upon using a method adapted to individual and family circumstances, the importance of making an informed choice cannot be overstated.

ASSESSMENT OF TREATMENT OPTIONS

Parents want treatments that will help their child achieve optimal health and quality of life goals. To make appropriate choices, they require accurate information, including a clear description of the theory and technique of available airway clearance methods. Additionally, parents need information to help them rule out modalities likely to be unsuitable based on their child's particular physical or mental limitations and upon the psychological, social and economic circumstances of the entire family. Useful decision-making criteria include:

* Goals of physician and patient

* Effectiveness of the technique

* Clinical effectiveness

* Medical contraindications

* Ease of teaching/learning

* Ease of complying with the technique

* Fatigue or work required (patient and caregiver)

* Need for equipment/skilled caregivers

* Patient's ability to tolerate technique

* Patient's ability to perform the technique based on disease type and severity

* Patient's age, motivation, cognitive ability, concentration level, and caregiver situation

* Costs (direct and indirect)

HFCWO: A TECHNIQUE-INDEPENDENT AIRWAY CLEARANCE TECHNOLOGY

HFCWO was first adapted for use as an airway clearance therapy in the late 1980s by physicians specializing in the care of children with CF. Because effective CPT depends entirely on the skill, patience, and physical strength of the caregiver, and because its daily use imposed an unrealistic burden of care upon both the children and their families, these doctors desired a technique-independent treatment that would provide consistently effective, yet more efficient treatment. An emerging technology called HFCWO had shown excellent mucus-clearing ability in numerous laboratory studies. With the assistance of biotechnological engineers, these doctors created a device capable of meeting those criteria.

TREATMENT ADHERENCE: THE WEAKEST LINK

The relationship between adherence to treatment and successful disease management is obvious. Without consistent use, all therapies are futile. Although the value of airway clearance is firmly established, treatments are frequently neglected. The explanation is self-evident: when treatment requirements are unreasonable, the burden of compliance becomes unbearable. Choices must be made. Unpleasant and overwhelming treatments are the first to go.

IMPROVED TREATMENT ADHERENCE

HFCWO therapy meets all the criteria of an effective and time-efficient airway clearance method. All lobes of the lungs are treated at the same time. Therapy is easy; many users require no assistance. Special positioning and breathing techniques are not required. HFCWO reduces the burden of care. Each treatment is usually accomplished in 15-20 minutes; aerosolized medications may be used at the same time. Because HFCWO therapy is adapted to accommodate busy lifestyles and hectic schedules, it is associated with improved treatment adherence.

Good outcomes depend upon realistic treatment plans. For this reason, the importance of choosing the airway clearance method most suitable for your child cannot be over stressed.

TECHNIQUE-DEPENDENT METHODS

AUTOGENIC DRAINAGE

DEFINITION: Autogenic drainage, or "self-drainage,"
is an airway clearance technique that
employs diaphragmatic breathing and controlled
coughing techniques to mobilize secretions by
varying levels of breathing.

THEORY: AD is believed to improve mucus clearance
from the peripheral airways due to airway caliber
changes in combination with special breathing
techniques. The goal is to help patients balance
their maximal expiratory flows so that mucus is
moved from dynamically unstable small airways
into the more rigid central airways, from which it
can be expectorated.

TECHNIQUE: Autogenic drainage utilizes a series
of controlled breathing exercises at three lung
volumes, each of which facilitates a different
phase of secretion clearance.
 1. Slow, maximum inspirations at low lung
    volumes to "loosen" mucus from peripheral
    airways
 2. Mid-lung volumes to "collect" mucus in
    central airways
 3. Slow, high-volume deep breaths to
    "expel" the mucus followed by cough
The entire three-phase breathing sequence is
repeated until mucus has been cleared thoroughly.
An average treatment is performed twice daily
for sessions of approximately 30-45 minutes.
Those who are able to learn the technique, do not
suffer from acute respiratory disease, can control
their breathing, and possess the physical stamina
to complete two sessions daily may use AD.

ADVANTAGES:
* Requires no equipment
* May be used independently
* Requires no postural positioning
* May be performed while seated
* Does not induce wheezing

DISADVANTAGES:
* Unsuitable for children under 8
* Technique-dependent
* Very difficult to master; requires significant
  mental acuity and mind-body awareness
   * Many hours of training required
   * Must be motivated, alert, able to interpret
     tactile and auditory signals
   * Requires specific physical strengths
   * Ability to control rate and volume of breaths
   * Adequate ventilatory muscle function
   * Adequate cough function
   * Physical stamina
   * Too demanding for use during acute exacerbations
* Time consuming

CPT WITH MECHANICAL PERCUSSOR

DEFINITION: A mechanical percussor can assist in
the delivery of chest physiotherapy (CPT), an airway
clearance technique that combines percussion
of the chest wall, strategic positioning of the body
for mucus drainage, and cough and breathing
techniques

THEORY: Percussion of various areas of the
chest and back transmits shock waves through
the chest wall, loosening secretions in the airways.
If the patient is properly positioned, the
loosened secretions will then drain into the upper
airways, where they can be expectorated using
coughing and huffing techniques.

TECHNIQUE: The patient is placed in a position
that facilitates secretion drainage from the lobe
about to be percussed.
* The percussor is moved over one lobe of the
  lung for approximately five minutes
* The patient is encouraged to employ coughing
  and huffing techniques
This process is repeated so that each segment of the
lung is percussed, with the patient assuming a position
appropriate for drainage of secretions from the
lobe receiving percussion

ADVANTAGES:
* May be suitable for children over 2 yrs of age
* Reduces physical effort required of caregiver
* May be self-administered to limited areas of
  chest wall
* As effective as properly administered manual CPT

DISADVANTAGES:
* Technique-dependent
   * Success depends upon skill and reliability of
     caregiver
   * Cannot reach all lobes of the lung
* Labor-intensive
   * User or Caregiver must possess strength
     and endurance sufficient to manage
     mechanical device effectively and to position
     patient or self on slant board
* Mentally impaired, physically uncooperative, or
  severely spastic patients are difficult to treat effectively
* Requires physical tolerance
   * Contraindications arising from anatomical
     deformity, transient hypoxemia associated with
     postural drainage, predisposition to gastro-esophageal
     reflux, inability to perform breathing
     techniques, etc., preclude use of CPT.
   * Technology-dependent patients may be
     unable to tolerate positioning
* Costly if professionally administered
* Time consuming

FLUTTER[R] VALVE

DEFINITION: The Flutter[R] valve is a hand-held
mucus clearance device designed to combine positive
expiratory pressure (PEP) with high frequency
airway oscillations. The device resembles a pipe
with an inner cone leading to a loosely supported
steel ball covered by a perforated cap.

THEORY: Exhalation through the Flutter[R] device is
thought to create oscillations at the airway opening
which cause transient increases in airflow. The
weight of the steel ball housed within the device provides
intermittent positive expiratory pressure (PEP),
which, together with the airway oscillations, vibrates
the airway walls and loosens secretions. Accelerated
expiratory flow rates move secretions centrally.

TECHNIQUE: Using controlled breathing techniques,
the user exhales through the Flutter[R]
valve, building pressure in the airways and in the
passageway beneath the enclosed steel ball until
the ball begins to move and some air escapes.
When the technique is performed correctly, the
ball oscillates rapidly, opening and closing air
pathways, thus producing vibrations that resonate
throughout the bronchial tree. The position
or angle of the device determines the intensity
of airway vibration. Cough and huff techniques
are used to expectorate mucus from the
central airways.

ADVANTAGES:
* Self-administered
* Portable
* May be used by some young children (age 5 and up)
* May be performed while seated
* Direct costs low
* May enhance treatment adherence among suitable users

DISADVANTAGES:
* Technique dependent
* Unsuitable for children < 5 yrs
* Requires adequate cognitive function
   * Ability and motivation to concentrate
   * Ability to master breathing techniques
* Requires specific physical attributes:
   * Ability to inhale and exhale adequately
   * Good motor control; unsuitable for spastic
     individuals
   * Adequate bulbar and facial muscle function
   * No incompatible facial deformities
* Adverse effects may include discomfort,
  fatigue and shortness of breath, possibly
  reducing compliance.

INTRAPULMONARY PERCUSSIVE
VENTILATION (IPV)

DEFINITION: Intrapulmonary percussive ventilation
(IPV) involves the use of a pneumatic
device to deliver mini bursts of positive pressure
to the airways via a mouthpiece. It is designed
to treat patchy atelectasis while mobilizing and
clearing secretions.

THEORY: High frequency puffs of air are
believed to open atelectatic alveoli and deliver air
behind mucus plugs, helping to dislodge them.
Use of the device may also enhance delivery of
aerosolized medications to the airways.

TECHNIQUE: During inspiration, the patient or
caregiver depresses a button that triggers delivery
of up to 300 bursts of air per minute. The
button is released during expiration. A treatment
time of twenty minutes is recommended.

ADVANTAGES:
* May be self-administered by some users
* Requires no positioning
* May be suitable for children over 5 years of age

DISADVANTAGES:
* Technique-dependent
* Requires adequate cognitive function unless
  patient has artificial airway or is on a ventilator
   * Ability and motivation to concentrate
   * Ability to master breathing techniques
* Requires specific physical attributes
   * Adequate motor control; unsuitable for
     spastic individuals
   * No incompatible facial deformities
* Home use of IPV devices sparsely researched
* Adverse effects may include discomfort and
  shortness of breath, possibly reducing compliance

POSITIVE EXPIRATORY PRESSURE (PEP)

DEFINITION: Positive expiratory pressure (PEP)
is an airway clearance technique administered
by applying a mechanical pressure device to
the mouth.

THEORY: PEP therapy is based upon the theory
that prolonged exhalation against a positive
pressure functions to stabilize smaller airways as
air is pushed beyond retained secretions. With
the small airways thus supported, expiratory airflow
mobilizes mucus towards more rigid, central
airways. Mucus can then be cleared using cough
or other forceful clearance maneuvers.

TECHNIQUE: The patient exhales through a flow
resistor held in place by a tight-fitting mask or
mouthpiece, which creates a backpressure in the
lungs. The patient then performs a "huff" cough
or forced expiratory technique (FET).
Aerosolized medications can be administered
during the inspiratory portion of the PEP protocol.
If performed properly and sufficient pressure
is generated, peripheral airways remain open and
secretions are mobilized.

ADVANTAGES:
* May be self-administered by some users
* Requires no postural positioning
* May be used by alert, cooperative children over
  4 years of age
* Portable
* May be used during both acute illness exacerbations
  by some patients

DISADVANTAGES:
* Unsuitable for uncooperative individuals
* Requires specific cognitive abilities
   * Ability to manage mechanical components
     of the device
* Requires specific physical attributes
   * Ability to maintain mouth feel, pursed lips,
     taut cheeks unless applied to trach tube
   * Ability to generate sufficient expiratory force
* Compliance may be adversely affected by:
   * Inability to tolerate tight-fitting face mask
   * Physical effort and consequent fatigue
   * Time requirements

EMERSON[TM] IN-EXSUFFLATOR

DEFINITION: A mechanical device that delivers a
positive pressure breath (insufflation) followed
by negative pressure (exsufflation) for the purpose
of stimulating a secretion-clearing cough.
The device is intended to aid individuals whose
cough function is ineffective

THEORY: The application of positive pressure to
the airway, followed by a rapid transition to negative
pressure will produce a high expiratory flow
from the lungs, thus stimulating a secretion-mobilizing
cough effect

TECHNIQUE: Using a facemask, mouthpiece, or
an adaptor applied to an endotracheal or tracheostomy
tube, positive pressure is delivered
gradually to the airway; then shifted rapidly to a
negative pressure. A cough is thus stimulated,
mobilizing secretions to permit clearance by
expectoration or suctioning.

ADVANTAGES:
* May be self-administered by some users
* May be used where weak cough function is the
  sole impediment to normal secretion clearance
* May replace oral or nasopharyngeal suctioning
  in some patients

DISADVANTAGES:
* Technique-dependent
* Requires motivation and cooperation by caregiver
* Not a "complete" airway clearance method
  except where "weak" cough is the only defect
  of the mucociliary clearance mechanism

TECHNIQUE-INDEPENDENT AIRWAY CLEARANCE THERAPY HIGH FREQUENCY CHEST WALL OSCILLATIONS (HFCWO) A.K.A. HIGH FREQUENCY CHEST COMPRESSION (HFCC): THE VEST[TM] AIRWAY CLEARANCE SYSTEM

DEFINITION: The Vest[TM] Airway Clearance System consists of an inflatable vest, which covers the chest and is attached with hoses to an air-pulse generator. The generator rapidly inflates and deflates the vest, gently compressing and releasing the chest wall from five to 25 times per second. This process is called high-frequency chest wall oscillation, or HFCWO.

THEORY: Oscillation of the chest wall creates an expiratory airflow bias that moves secretions toward the trachea; it also results in transient increses in airflow at low lung volumes, improving gas-liquid interactions to mobilizing mucus. HFCWO has also been found to decrease sputum viscosity, making it easier to move.

TECHNIQUE: The vest is fastened around the patient's chest, and air hoses are attached to both the vest and the generator. Frequency and pressure knobs may be adjusted on the generator; commonly prescribed protocol involves performing most of the therapy at frequencies of 11-15 Hz. After the generator has been turned on, the patient or a caregiver begins the oscillations by depressing the hand/foot control. Five to ten minute periods of oscillations are alternated with pauses for coughing, huffing or suctioning to clear secretions from the trachea.

ADVANTAGES

* Technique independent

* HFCWO therapy is passive

* Requires no active participation by user

* Requires little physical effort or special skill from either independent users or caregivers

* Permits simultaneous engagement in other activities such as reading, TV viewing, computer use

* Clinical trials reported in peer-reviewed literature demonstrate equivalence or superiority to professionally administered CPT for both secretion clearance and maintenance or improvement of pulmonary function

* Associated with diminution/resolution of atelectasis 

* May be self-administered by many users

* Treats all lobes of the lungs simultaneously

* May be used in conjunction with other therapies, including aerosol treatments

* Extensive support programs provided by manufacturer

* Training

* Follow-up

* Reimbursement assistance

* System carries lifetime warranty

* Associated with direct and indirect cost savings

* Associated with increased treatment adherence

* Associated with quality-of-life gains

DISADVANTAGES

* Unsuitable for infants and most children under 2 years of age

Jane Braverman, PhD, has a background in basic medical research and clinical laboratory medicine. Formerly an Assistant Professor of the History of Medicine at the University of Minnesota, Dr. Braverman now works in the field of biotechnology for Advanced Respiratory, Inc., in St. Paul, MN.