Is the patient's breathing aided by the action of the accessory muscles? Use of the accessory muscles is one of the earliest signs of airway obstruction. In respiratory distress, the trapezius and sternocleidomastoid muscles contract during inspiration. The accessory muscles assist in ventilation;they raise the clavicle and anterior chest to increase the lung volume and produce an increased negative intrathoracic pressure. This results in retraction of the supraclavicular fossae and intercostal muscles. An upward motion of the clavicle of more than 5 mm during respiration is associated with severe obstructive lung disease.
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