The triple concave sign is mainly seen in the supraclavicular fossa, suprasternal fossa and intercostal space depression during inspiration. The main causes of trismus are obstruction of the upper airway or the large airway, such as acute inflammation of the pharynx, acute pharyngitis, acute tonsillar hypertrophy, and obstruction of the trachea and main bronchus. For tracheal and main bronchial obstruction, foreign body aspiration is more common clinically, such as children suddenly aspirating while eating candy bars, or tumor lesions of the trachea or bronchi. In elderly people who are bedridden for a long time, attention should also be paid to the sputum plug in their airways. Therefore, for middle-aged and elderly people who are bedridden for a long time and have a poor cough reflex, attention should be paid to good airway wetting to avoid the appearance of phlegm clots blocking the airway, thus endangering the patient’s life. In addition, insufficient power of inspiration and a very weak state of the body can also lead to truncal signs. Therefore, the trigeminal sign should be analyzed on a case-by-case basis. Tricuspidity is very common in clinical practice, and it is also very critical and should be treated urgently.