What is accessory muscles

accessory muscles muscles of the shoul¬der girdle and chest wall that (in addition to the intercostal muscles and the diaphragm) are utilized by people with *respiratory dis¬tress to help the flow of air in and out of the lungs. Use of these muscles can be a sign of the degree of difficulty that the patient is in, for example in cases of asthma or *air-way obstruction. .