Accessory muscles of respiration – muscles other than the diaphragm and intercostal muscles that may be used for labored breathing. The sternocleidomastoid, spinal, and neck muscles may be used as accessory muscles of respiration; their use is a sign of an abnormal or labored breathing pattern.

Adventitious breath sounds – abnormal breath sounds heard when listening to the chest. Adventitious sounds may include crackles or rales, rhonchi or wheezes, or pleural friction rubs. Adventitious sounds do not include sounds produced by muscular activity in the chest wall or noises made by a stethoscope on the chest wall.

Ataxic breathing – also known as Biot's breathing, is characterized by unpredictable irregularity.

Barrel chest – a condition characterized by increased anterior-posterior chest diameter caused by increased functional residual capacity due to air trapping from small airway collapse. A barrel chest is frequently seen in patients with chronic obstructive diseases, such as chronic bronchitis and emphysema.

Cheyne-Stokes respirations – a breathing pattern characterized by a period of apnea, followed by gradually increasing depth and frequency of respirations.

Consolidation – the replacement of air in the lungs with fluid or a mass.

Crackles – an adventitious breath sound heard on ausculating the chest, produced by air passing over airway secretions. A crackle is a discontinuous sound, as opposed to a wheeze, which is continuous. Crackles are known as fine or coarse and are also known as rales.

Fremitus – a vibration felt while a patient is speaking and the examiner's hand is held against the chest.

Intercostal retractions – visible use of the muscles between the ribs (intercostal muscles) to aid in breathing. Intercostal retractions are a sign of labored breathing.

Kussmal breathing – a very deep gasping type of respiration associated with severe diabetic acidosis and coma.

Kyphosis – a deformity in the normal posterior shape of the spine, producing a humpback appearance.

Nasal flaring – intermittent outward movements of the nostrils with each inspiration; indicates an increase in the work needed to breathe.

Pleura – a serous membrane covering both lungs and the walls of the thorax and diaphragm.

Pursed lip breathing – partial closing of the lips to allow air to be expired slowly; used by patients with chronic obstructive pulmonary disease.

Sibilant rhonchi – a high pitched wheeze; musical and squeaky adventitious breath sound.

Scoliosis – a lateral curvature of the spine.

Sonorous rhonchi - a lower pitched wheeze; snoring or moaning adventitious breath sound.

Stridor – a high-pitched harsh sound heard during inspiration. Stridor is caused by obstruction of the upper airway.

Wheeze - an adventitious or abnormal breath sound heard when listening to the chest as a person breathes. Wheezes are continuous and musical sounding, and usually caused by airway obstruction from swelling or secretions. Wheezes can be high or low pitched, and are also known as rhonchi.