Respiratory Muscles: Functional Evaluation

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