Abstract
The respiratory muscles are essential components of the pump that move air in and
out of the lungs. The function of the respiratory muscles is intimately linked with
their anatomical arrangement and their histological and biochemical composition. Diseases
that affect the respiratory system invariably affect the muscles and their work. More
often the end result is a decrease in the force the muscles can generate, and in some
extreme cases the development of muscle fatigue. Compromise in the function can be
initially assessed by simple history, especially positional dyspnea. Determination
of the respiratory rate, and observation of the thoraco-abdominal displacement in
the upright and supine position complement the initial evaluation. Measurement of
spirometry in the sitting and the supine position, and determination of lung volumes
and blood gases help direct attention to the respiratory muscles. Decreased strength
is confirmed by measuring inspiratory and expiratory forces. Decreased endurance can
also be measured with relatively simple stools. The addition of esophageal and gastric
pressures, EMG and thoracoabdominal movements add certainty to the evaluation. The
near future incorporation of MRI to the dynamic evaluation of respiratory muscle function
will add a new dimension to our capacity to evaluate their function. This monograph
systematically reviews these accepted concepts and offers the readers a tool to enhance
their knowledge in this important area of respiration.
Key Words:
respiratory muscles - muscle fatigue - respiratory muscle testing
