Intercostal muscle action inferred from finite-element analysis.

Area of Science:

• Respiratory Mechanics
• Biomechanics
• Anatomy

Background:

• The mechanical actions of external and internal intercostal muscles, crucial for human respiration, remain debated.
• Understanding these actions is vital for respiratory physiology and clinical applications.

Purpose of the Study:

• To investigate the mechanical actions of intercostal and other rib cage muscles.
• To clarify the role of muscle activation extent in determining intercostal muscle function.

Main Methods:

• Utilized three-dimensional finite-element analysis on an isolated canine rib cage model.
• Incorporated anatomic and mechanical measurements from canine subjects.
• Simulated forces applied to intercostal muscles across various spatial extents.

Main Results:

• Applying force to a single interspace caused ribs to be pulled together.
• Widespread activation of external intercostal muscles induced inspiratory motion.
• Widespread activation of internal intercostal muscles induced expiratory motion.
• Simulations of parasternal intercostal, levator costae, and transversus thoracis muscles yielded expected rib and sternum movements.

Conclusions:

• The functional role of intercostal muscles is contingent upon the spatial extent of their activation.
• Finite-element models effectively explain observed intercostal muscle actions in both single and multiple interspace scenarios.
• This study clarifies the controversial mechanical actions of intercostal muscles in respiration.