In the last ten years considerable attention has been devoted to the role of the respiratory muscles in disease, and especially in respiratory failure. The importance of this vital pump has been highlighted by numerous studies on the activity and failure or fatigue of these muscles in man. These studies have mainly focused attention on the diaphragm, which represents the most important component of the respiratory pump. The action of skeletal muscles is usually analyzed in terms of three variables: force, length and velocity. In the respiratory system, the forces produced by the respiratory muscles are not directly measured. What is measured is pressure (transdiaphragmatic pressure for the diaphragm), which is the force developed divided by the surface area over which the force acts. Similarly, changes in length are inferred from changes in lung volume, and velocity from the rate of this change, or flow . Measurement of transdiaphragmatic pressure (Pdi) is the basis for assessment of diaphragmatic function.
KeywordsChronic Obstructive Pulmonary Disease Patient Respiratory Muscle Esophageal Pressure Pleural Pressure Esophageal Balloon
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