A collapsed lung, or pneumothorax, occurs when air enters the space surrounding the lung. Pressure exerted by the air pocket causes partial or complete lung deflation, depending on the size of the air leak. Penetrating chest and lung injuries and medical procedures that create an opening in the chest wall are the most frequent causes of pneumothorax. Less commonly, air sacs of the lungs rupture causing air accumulation in the chest. Pneumothorax can disrupt the normal anatomical position and function of the chest structures.
Tracheal Deviation
The windpipe, or trachea, transports air to the lungs. Normally, the trachea rests in the midline, extending from the voice box into the chest where it divides and enters the lungs. A large pneumothorax can push the trachea out of position toward the side of the chest opposite the air pocket, notes Penn State College of Medicine's Milton S. Hershey Medical Center. Tracheal deviation is an ominous sign, indicating the need for emergency treatment of the collapsed lung.
Mediastinal Shift
The mediastinum is the region in the middle of the chest that contains the heart, the major blood vessels entering and exiting the heart, the thymus gland, the esophagus and a number of lymph nodes and nerves. A large pneumothorax exerts pressure on the mediastinum, potentially shifting the position of the heart and other structures away from the air pocket, notes the Harvard Medical School reviewed patient information website InteliHealth.
A mediastinal shift due to pneumothorax frequently proves life threatening. Dislocation of the heart and its associated blood vessels can significantly decrease the volume of blood flowing into the heart. A rapid loss of blood pressure ensues, which may lead to cardiac arrest. Immediate release of the pressurized air pocket is required to restore normal blood flow to the heart. This is typically accomplished by inserting a large needle into the chest to withdraw the accumulated air, allowing the heart to move back into its normal position.
Hyperexpansion of the Chest
Tension pneumothorax is a severe form of collapsed lung in which the hole permitting airflow into the chest cavity acts as a one-way valve, facilitating airflow into the chest, but preventing air escape. The chest cavity air pocket rapidly expands with tension pneumothorax, causing progressively increasing pressure against the chest structures, explains the critical care professionals' website Trauma.org. As the volume of air in the chest cavity increases, the chest becomes abnormally expanded. Severe hyperexpansion of the chest may signal impending respiratory and cardiac arrest. Emergency release of the air in the chest is required to stave off a potentially fatal outcome.
