Secretion Clearance Techniques

[Guest guest]

Hi Amy,

here are more articles from Joanne Schum about the subject. I haven't

read them yet myself, but hope they fit to the one I sent before.

Peace

Torsten

Secretion Clearance Techniques: Absence of Proof or Proof of Absence?

Healthy lungs clear mucus from the airways via the mucociliary

escalator.

When the mucociliary escalator is challenged in disease, secretions

are

cleared with the cough reflex. Acute and chronic respiratory diseases

are

commonly associated with increased respiratory secretions due to

increased mucus production, impaired mucociliary transport, or a weak

cough. However, it is unknown whether increased respiratory secretions

contribute to the deterioration of respiratory function, or whether

this

is merely a symptom associated with the progression of the disease.

Moreover, increased mucus expectoration does not necessarily imply

mucus

stasis in the airways.

Clinicians and patients are troubled by respiratory secretions, and

standard practice calls for efforts to clear these from the lungs. An

important proportion of respiratory therapists' time is spent in

efforts

to remove secretions from the lower respiratory tract. For patients

with

diseases such as cystic fibrosis a great deal of each day can be spent

using techniques designed to enhance secretion clearance. In recent

years

a variety of techniques for secretion clearance have become available.

Many of these techniques are described in this issue of RESPIRATORY

CARE.

Despite clinical enthusiasm for many of these by both clinicians and

patients, there is sparse high-level evidence demonstrating benefit

from

many of these techniques. As pointed out by others1-14 and me,15 there

are a number of methodologic limitations of published reports of

secretion clearance techniques. Most studies are small and use

crossover

designs (rather than randomized parallel designs). Sham therapy was

not

used in most studies -- often one technique was compared to another

(for

example, chest physiotherapy vs positive expiratory pressure). Many

studies were limited to short-term outcomes such as sputum clearance

with

a single treatment session. It might be argued that short-term

outcomes

are irrelevant and that the focus should be on long-term outcomes

such as

disease progression, quality of life, and patient satisfaction.

Conducting a methodologically strong study (ie, placebo-controlled

prospective randomized trial) with an adequate sample size and

important

outcomes (eg, disease progression, morbidity, mortality) is difficult.

Such a study would be expensive and industrial support is not likely.

Moreover, secretion clearance is an integral component of disease

management for patients with increased sputum production, raising

serious

ethical concerns about placebo-controlled studies. I have always

found it

intriguing that a new drug to improve secretion clearance must pass

through the usual Phase 1 through Phase 3 approval process, whereas a

new

device is not subjected to the same scrutiny.

Is absence of proof the same as proof of absence? Does the lack of

evidence mean lack of benefit? Is the lack of evidence due to study

methodology, or is there really no benefit from many techniques used

to

enhance secretion clearance? Although we should not be dogmatic about

endorsing a therapy with absence of proof of its benefit, we must also

not be dogmatic about abandoning a therapy because of absence of

proof of

its benefit -- absence of proof is not proof of absence. In fact,

from a

methodological and statistical standpoint, absence of proof is very

difficult to prove. Given a lack of evidence, I suggest the following

clinical hierarchy of questions when considering secretion clearance

therapy for a patient.

1. Is there a pathophysiologic rational for use of the therapy?

Is

the patient experiencing difficulty clearing secretions? Are retained

secretions affecting lung function in an important way, such as gas

exchange or lung mechanics? Remember that the production of large

amounts

of sputum does not necessarily mean that the patient is experiencing

difficulty clearing sputum.

2. What is the potential for adverse effects from the therapy?

Which

therapy is likely to provide the greatest benefit with the least harm?

3. What is the cost of the equipment for this therapy? Some

devices

are very expensive.

4. What are the preferences of the patient? Lacking evidence that

any technique is superior to another, patient preference is an

important

consideration.

When a decision is made to try a secretion clearance technique, an n-

of-1

trial can be conducted.16-18 For example, imagine that a decision is

made

to try positive expiratory pressure therapy for a patient with cystic

fibrosis. The clinician and patient agree that a clinically useful

outcome measure is sputum production. A 12-week trial is designed.

For 1

week, the only sputum clearance technique used is huff coughing. For a

second week, positive expiratory pressure (in addition to huff

coughing)

is used, as provided by the manufacturer. For a third week, the

positive

expiratory pressure device is used with pressure set at such a low

level

that it is probably sub-therapeutic (sham therapy). The patient is

naive

to the therapy and does not know whether the device should be used

with

or without the high-pressure setting. The order of treatments is

randomized (the patient flips a coin) and the sequence is repeated 4

times. Each day, the sputum produced during the therapy session is

weighed. A diary is also kept, in which events such as chest

infections

are logged. At the end of 12 weeks the results are analyzed (this may

include statistical analysis), reviewed together by the clinician and

patient, and a collaborative decision is made regarding the benefit of

the therapy. In this manner an objective decision is made regarding

the

benefits of the therapy for this individual patient.

Despite the clinical observation that retained secretions are

detrimental

to respiratory function and despite anecdotal associations between

secretion clearance and improvements in respiratory function, there

is a

dearth of high-level evidence to support any secretion clearance

technique. This is problematic, given that secretion clearance is an

important aspect of respiratory care practice. Although lack of

evidence

does not mean lack of benefit, it is desirable to have better

evidence to

support the practice. Appropriately powered and methodologically sound

research is desperately needed. This provides an opportunity for

respiratory therapists to conduct research on a very important aspect

of

our practice. For the effective therapy of our patients and for the

efficient use of health care resources, it is incumbent upon us to

improve the scientific basis for secretion clearance techniques.

Dean R Hess PhD RRT FAARC

Department of Respiratory Care

Massachusetts General Hospital

Harvard Medical School

Boston, Massachusetts

New Horizons in Respiratory Care: Airway Clearance Techniques

It was an honor to co-chair the 17th Annual New Horizons Symposium at

the

American Association for Respiratory Care's International Respiratory

Congress in San , Texas, on December 2, 2001. The New Horizons

Symposium has been a landmark feature of the meeting for 17 years.

This

full-afternoon session provides a comprehensive, focused, and

multi-dimensional exploration of a key aspect of the practice of

respiratory care, usually reviewing areas of evolving clinical

practice.

In many instances the manuscripts from the symposium are then

published

in a special issue of RESPIRATORY CARE.

Airway mucus is a critically important host defense. Normal mechanisms

for mobilization of secretions include mucociliary transport,

autocephalad flow (secretions moving toward the central airway during

normal breathing), and cough. Mucus hypersecretion and impaired mucus

clearance can be serious problems, leading to discomfort, dyspnea,

airway

obstruction, atelectasis, infection, bronchiectasis, and pulmonary

disability. As respiratory care has evolved as a profession, airway

secretion clearance has always been part of our scope of practice.1-4

Terms such as " bronchial hygiene " and " pulmonary toilet " have been

used

to characterize the process of assisting patients to clear airway

secretions. Too often, however, those terms have been associated only

with postural drainage, percussion and vibration, or mechanical

aspiration of the airways in acutely ill patients.

Over the past 40 years we have come to better understand the

mechanisms

of airway clearance in health and disease, and this has led to the

development of devices and techniques to assist in secretion removal.

The

amount and quality of evidence from rigorously conducted, randomized

clinical trials in support of these diverse techniques varies widely.5

However, most of the techniques are based on physiologic rationale and

are at least supported by case studies.2

This year's New Horizons Symposium began with a review of

the " Physiology

of Airway Mucus Clearance " (Bruce Rubin). The major bronchial hygiene

techniques were reviewed in " Positioning Versus Postural Drainage "

(Jim

Fink), " Airway Physiology, Autogenic Drainage, and Active Cycle of

Breathing " (Craig Lapin), " Positive Pressure Techniques " (Jim Fink),

and

" High-Frequency Oscillation of the Airway and Chest Wall " (Mike

Mahlmeister and Jim Fink). Kathy son discussed " Airway Clearance

Strategies for the Pediatric Patient " and presented strategies for

introducing these techniques as the patient develops from infancy

through

to adulthood. then reviewed key practice considerations

for

the intubated patient in or out of the intensive care unit in " Airway

Clearance Techniques for the Patient with an Artificial Airway. " Dr

Rubin's review of " The Pharmacologic Approach to Airway Clearance:

Mucoactive Agents " then summarized the state of the art for medical

management of secretion retention.

As we concluded the symposium it was clear that we had not addressed

one

potentially valuable method of airway clearance: ultra-low-frequency

airway oscillation, better known as the Insufflator/Exsufflator (Fig.

1).

This device has been studied for more than 50 years. Evidence suggests

that it is an effective method to assist airway clearance in

debilitated

patients or in those with severe neuromuscular weakness.

The symposium participants agreed that although there may be few data

to

unequivocally support the use of many of these techniques, there is

strong observational evidence that suggest that many of these

techniques

can have a role in mobilizing secretions, reducing dyspnea, and

helping

patients maintain patent airways. Selection of a " best " technique is

currently more of an art than a science and depends greatly on the

patient's underlying condition, level of functioning and

understanding,

and ability and willingness to perform the technique and integrate it

into normal daily routines. For the clinician, the decision diagrams

in

Figure 2 represent one approach for technique selection. Education is

key

to the success of any technique. The better a patient understands a

technique the better chance the patient has of adopting it

appropriately.

Future research needs to better define and refine techniques in use

and

to incorporate good study designs in well-powered clinical trials that

use meaningful outcomes. As an example, although often measured, the

volume of expectorated sputum is of limited or no value in determining

the clinical effectiveness of these devices and techniques. Measuring

the

frequency of protocol-defined exacerbations, antibiotic use, unplanned

physician visits, hospitalizations, or missed days of work or school

appears to be of greater clinical and scientific relevance. The more

that

we as a profession invest in learning, teaching, and studying these

techniques, the greater the chance that our patients can benefit from

their use.

B Fink MSc RRT FAARC

Fellow, Respiratory Science

Aerogen Incorporated

San Francisco, California

Bruce K Rubin MEngr MD FAARC

Department of Pediatrics

Wake Forest University School of Medicine

Winston-Salem, North Carolina