SYMPTOMS

What is the three concave sign?

The three concave sign (also known as Hoover's sign) was first reported by Charles Franklin Hoover in the 1920s.

It is a typical clinical sign of respiratory diseases, characterized by visible inward retractions of the suprasternal fossa, supraclavicular fossa, and intercostal spaces during inspiration. The presence of this sign usually indicates severe airway obstruction.

Why does the three concave sign appear in severe airway obstruction?

The human respiratory tract, also called the airway, consists of cartilages with certain tension. During inhalation and exhalation, the diameter of the airway remains relatively stable.

During inhalation, the thoracic cavity generates transient negative pressure, allowing external air to rapidly enter the lungs. At this point, the pressure difference between the thoracic cavity and the external environment is small, maintaining a balanced state without localized retractions.

However, if the airway diameter significantly narrows—due to obstruction (e.g., foreign objects) or swelling in the laryngeal area—the resistance during inhalation increases sharply. When the thoracic cavity produces strong negative pressure, only a small amount of air can pass through the narrowed airway. The resulting large pressure gradient between the external environment and the thoracic cavity compresses the softer tissues (suprasternal fossa, supraclavicular fossa, and intercostal spaces) inward, forming the three concave sign.

TREATMENT

How to relieve three-concave sign?

Once the three-concave sign appears, it indicates a respiratory emergency. Typically, it can only be relieved by clearing the airway obstruction. Therefore, seeking medical attention promptly is essential.

If the three-concave sign is caused by a foreign object in the airway, while calling 120, you can use the Heimlich maneuver to expel the obstruction. It is recommended to learn the Heimlich maneuver in advance for emergencies.

How to prevent the three-concave sign?

Daily precautions vary depending on the cause.

• For patients with chronic obstructive pulmonary disease (COPD), follow the doctor's medication instructions to control disease progression and avoid acute COPD episodes.
• Avoid eating too quickly and refrain from talking while eating. Especially for children, ensure they eat and play under adult supervision, use age-appropriate toys without small parts, and avoid foods like jelly, sausages, whole grapes, peanuts, and other nuts. These precautions help prevent airway obstruction by foreign objects.
• For asthma patients, follow the doctor's prescribed asthma medications regularly to maintain symptom control and avoid exposure to asthma triggers or environments.
• To prevent allergic laryngeal edema, avoid known allergens. Be particularly cautious when using antibiotics or consuming potentially allergenic foods.

DIAGNOSIS

Which department should be consulted for three depressions sign?

If the patient's condition is urgent, they should visit the emergency department. For less severe cases, the respiratory medicine department is appropriate.

Under what circumstances should a patient with three depressions sign seek medical attention?

The three depressions sign is a warning symptom, indicating severe respiratory obstruction and constituting a medical emergency. Immediate hospital evaluation and treatment are recommended in such cases.

In certain critical situations, such as airway foreign bodies or allergic laryngeal edema, the condition is even more urgent. The principle for seeking medical care in these cases is: as quickly and as nearby as possible.

What examinations and treatments might a patient with three depressions sign require after arriving at the hospital?

Doctors may choose different examinations or treatments based on the underlying cause of the three depressions sign.

• Possible examinations include: lung CT, bronchoscopy, echocardiography, laryngoscopy, and hematological tests such as blood gas analysis or allergen testing.

• Possible treatments include: anti-allergy therapy, anti-infection therapy, tracheotomy, anti-heart failure measures, etc.

For example, if the patient is a child with no history of asthma who suddenly develops inspiratory three depressions sign, the priority is to rule out airway foreign bodies. If the patient can still maintain breathing and oxygen supply, CT or other relevant examinations may be performed first to assess the foreign body. However, if severe airway obstruction with hypoxia or suffocation is present, emergency interventions like bronchoscopy or tracheotomy may be required.

POTENTIAL DISEASES

In which diseases is three depression sign commonly seen?

Common diseases that can cause three depression sign include:

• Chronic Obstructive Pulmonary Disease (COPD): In the end stage with severe airway obstruction, it may lead to three depression sign.
• Foreign body aspiration: This is more common in children, usually caused by small objects accidentally entering (choking) the airway, leading to airway obstruction.
• Asthma attack: During acute asthma episodes, it may cause bronchospasm, narrowing of the tracheal diameter, and difficulty breathing.
• Congestive heart failure.
• Laryngeal edema: This is more likely to occur in people with allergic constitutions. Allergic reactions can cause edema in various organs, and swelling in the throat area can block the airway, leading to severe breathing difficulties.
• Severe pneumonia or bronchitis: These can also cause airway obstruction and are more common in children.
• Other less common conditions: Such as diphtheria, bilateral diaphragmatic paralysis, pleural effusion, pneumothorax, etc.