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Shortness of breath,
the distressful sensation of uncomfortable breathing, occurs
in people with pulmonary disease when the work of the breathing
muscles is increased or the capacity of the breathing muscles
to do this work is decreased. In people with pulmonary disease,
many activities may lead to shortness of breath.
There are two types
of lung disease that are characteristic of several neuromuscular
diseases. Obstructive lung disease affects the lung itself,
as in asthma and emphysema. Restrictive lung disease, occurring
in disorders with muscle weakness, spine deformity and obesity,
is caused by weakness of the muscles of respiration. Inspiration
and expiration are the two parts of normal respiration. The
major inspiratory muscle is the diaphragm, while the most
active expiratory muscles are the abdominal and internal intercostal
(chest) muscles.
In the health care
setting, we often evaluate a person's activity tolerance by
their ability to walk or ride a bicycle. Arm activities are
also important to people with pulmonary diseases. In fact,
the shortness of breath--limited ability to perform arm activities
is often a response leading to disability. Individuals with
severe COPD report a marked increase in the sensation of shortness
of breath when performing daily tasks requiring arm use, particularly
unsupported arm use, such as bathing and lifting. To reduce
or avoid intolerable levels of shortness of breath with arm
use, individuals limit their activity.
Responses to reduced
activity, in turn, are muscle deconditioning and general disability.
Reduced arm activities also may lead to emotional and social
alterations, such as reduction in life satisfaction, increased
anxiety, depression, alteration in self-care strategies, and
enhanced dependency necessitating an increase in social support.
Breathing is a complex
phenomenon, carried out by many muscles of the torso and neck.
During periods of increased breathing demand, the work to
be done by the breathing muscles may be shifted among these
muscles to prevent muscle fatigue. The breathing muscles,
in turn, have multiple roles. They maintain ventilation, and
they carry out other motor functions as well. For example,
torso muscles maintain upper body posture, assist in torso
motion and support, and contribute to ventilation. Ordinarily,
the breathing muscles are capable of maintaining ventilation
and additional motor functions. However, when the breathing
muscles are required to perform other motor functions, their
capacity to assist in breathing is reduced.
Similar to all other
activities, unsupported arm activity leads to an increase
in the need for oxygen and other breathing gas exchange in
the lungs. Unsupported arm activity also creates a unique
challenge in pulmonary disease, because it places both breathing
and other motor function burdens on the breathing muscles.
During unsupported arm activity, therefore, the breathing
muscles are required to perform two roles: the maintenance
of breathing, and the stabilization of the chest wall in support
of arm weight (resulting in limited activity). This may be
likened to the use of muscles of the face that have multiple
roles, such as speech, smiling and chewing, of which only
one role can be carried out at a time. When a person with
pulmonary disease performs an activity but needs the same
muscles for breathing, shortness of breath ensues.
Rehabilitation strategies
may improve arm activity endurance and enhance functional
ability in pulmonary disease. Persons with pulmonary disease
can pace the performance of arm activities in relation to
the breathing cycle in an effort to decrease shortness of
breath. Individuals with pulmonary disease report less difficulty
with arm activity performed in phase with inspiration than
with arm activity performed with expiration. An additional
strategy to improve unsupported arm function includes arm
exercise training. A simple and inexpensive unsupported arm
training exercise is to perform lightweight dowel rod lifts
from waist to shoulder level. The addition of weights to the
rods can be used to increase the resistance as tolerance grows.
Training strategies should be implemented as early as possible
in the disease course, for they may delay, limit, or prevent
reduced arm activity tolerance in pulmonary disease.
Many activities of daily living require the use of unsupported arm exercise. The inability to perform such tasks can lead to severe disability in persons with pulmonary disease. Unsupported arm activity leads to increases in breathing muscle work and recruitment to maintain torso position. Treatment strategies to improve unsupported arm activities include unsupported arm exercise training. Additional research, involving persons with COPD, to identify mechanisms of reduced unsupported arm activity may lead to better understanding of the reluctance to perform routine arm activities, as well as to the development of more treatment strategies to improve arm exercise endurance and functional ability.
