Air Leak

Excerpt

Air leak (AL) is a clinical phenomenon associated with the leakage or escape of air from a cavity that contains air into spaces that usually, under normal circumstances, do not have air. The terminology air leak syndrome (ALS) is the presence of air leak with associated symptoms of respiratory distress.

Air containing cavities include

Upper Airway

1. Tracheobronchial tree

2. Sinuses

3. Ethmoid sinus

4. Frontal sinus

5. Maxillary sinus

Gastrointestinal Tract

1. Esophagus

2. Stomach

3. Small intestine

4. Large intestine

The escape of air from air containing cavity to non-air containing cavity can create a condition where some vital organs in the non-air containing cavity can be compressed, creating life-threatening conditions. These life-threatening conditions can be created as a result of compression of the lung or major blood vessels. When the lung or major blood vessels are flattening by the presence of air, gas exchange or blood flow can be severely compromised.

The presence of air in spaces that it is not "supposed" to be is prefixed with the word “pneumo.”

1. Pneumothorax - the presence of air in the pleural cavity

2. Pneumopericardium - the presence of air in the pericardial sac

3. Pneumoperitoneum – the presence of air in the peritoneal cavity

4. Subcutaneous emphysema – the presence of air in the subcutaneous tissue

The presence of air in the pleural cavity that is associated with the collapse of the lung (Pneumothorax) has clinical significance because of the risk of airway collapse. If the major blood vessels are compressed with the presence of air in the pleural cavity, a clinical condition call tension pneumothorax can ensue. This is a medical emergency that requires immediate medical attention.

Pneumothoraxes Classifications

Spontaneous pneumothorax

These occur without any precipitating event and is divided into two following groups:

1. Primary spontaneous pneumothorax occurs on healthy, non-diseased lungs.

2. Secondary spontaneous pneumothorax develops from lungs that are diseased with changes in the parenchymal structures.

Traumatic pneumothorax

These pneumothoraxes occur from traumatic injury to the lung and pleura space. The traumatic injury may be direct or indirect.

Iatrogenic

In critically ill patients, iatrogenic pneumothorax causing an air leak can occur from the following conditions:

1. Barotrauma and volutrauma – Aggressive use of high pressure or volume on patients placed on mechanical ventilation or high-frequency oscillatory ventilation, especially for patients with acute respiratory distress syndrome; respiratory distress syndrome can lead to the development of air leak or ALS.

2. The placement of a subclavian central line - This can lead to the introduction of air into the pleural cavity creating pneumothoraxes and air leaks.

3. Surgical interventions - When on the lung, heart, and mediastinal structures, these can create air leak syndrome.

Determination of the Presence of an Air Leak

To quantify the amount of air leak in a patient connected to a chest tube, the patient is asked to cough, and the water column and the water seal column in the chest tube drainage system are observed. If there are no air bubbles, the pleural cavity is devoid of air. The presence of air bubbles signifies the presence of air leaks. If the amount of air bubbles is the same in quantity, this might signify the presence of a significant leak or an active leak. On the contrary, a gradual reduction in the amount of the bubble is indicative of a small leak or a passive leak.

After thoracic surgery, especially resection of the lung, warm sterile saline is instilled into the thoracic cavity. The resected lung is usually insufflated with air to a peak pressure of around 30 mmHg, and the resected section of the lung is then checked for the presence of air leak.

Macchiarini et al. suggested a way to classify the air leak

1. Grade 0 - No leak

2. Grade I - Countable bubbles

3. Grade II - Streams of bubbles

4. Grade III - Coalesced bubbles

After lung resection, air leak that persists for more than five days postoperatively is defined as a prolonged air leak (PAL).