Page 132 - Biomedical Engineering and Design Handbook Volume 1, Fundamentals

CHAPTER 5

BIOMECHANICS OF THE

RESPIRATORY MUSCLES

Anat Ratnovsky
Afeka College of Engineering, Tel Aviv, Israel

Pinchas Halpern
Tel Aviv Medical Center, Tel Aviv, Israel, and Sackler School
of Medicine, Tel Aviv University, Tel Aviv, Israel
David Elad
Tel Aviv University, Tel Aviv, Israel

5.1 INTRODUCTION 109 5.4 MODELS OF CHEST WALL MECHANICS 115
5.2 THE RESPIRATORY MUSCLES 109 REFERENCES 120
5.3 MECHANICS PERFORMANCE OF
RESPIRATORY MUSCLES 111

5.1 INTRODUCTION

The respiratory tract provides passageways for airflow between environmental air, rich in oxygen,
and the gas exchange region within the pulmonary alveoli. Periodic pumping of gas in and out of the
lungs is controlled by contractions of the respiratory muscles that rhythmically change the thoracic
volume and produce the pressure gradients required for airflow. In this chapter, which is largely
based on a recent review in a special issue on respiratory biomechanics (Ratnovsky et al., 2008), we
will review techniques for assessment of the biomechanical performance of the respiratory muscles
and biomechanical models of chest wall mechanics.

5.2 THE RESPIRATORY MUSCLES

The respiratory muscles are morphologically and functionally skeletal muscles. The group of inspi-
ratory muscles includes the diaphragm, external intercostal, parasternal, sternomastoid, and scalene
muscles. The group of expiratory muscles includes the internal intercostal, rectus abdominis, external
and internal oblique, and transverse abdominis muscles. During low breathing effort (i.e., at rest) only
the inspiratory muscles are active. During high breathing effort (i.e., exercise) the expiratory muscles
become active as well.

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