Chapter 1 General Approach to the Critically Ill Patient
5 Define paradoxic respirations and accessory muscle use. What is their significance?
Normal breathing involves simultaneous rise and fall of the abdomen and chest wall.
A patient with paradoxic respirations has asynchrony of abdominal and chest wall movement. With inspiration, the chest wall rises as the abdomen falls. The opposite occurs with exhalation.
Accessory muscle use refers to the contraction of the sternocleidomastoid and scalene muscles with inspiration. These patients have increased work of breathing, which is the amount of energy the body consumes for the work of the respiratory muscles. Most patients use accessory muscles before they have development of paradoxic respirations. Without support from a mechanical ventilator, patients with paradoxic respirations or increased work of breathing will eventually have respiratory muscle fatigue, hypoxemia, and hypoventilation.