Causes of Lung Injuries

There are two main types of lung injuries: direct and indirect.

Direct lung injuries are caused by infections, chemicals, and trauma that directly affect the lung, including:

Pneumonia, a severe lung infection
Severe acute respiratory syndrome (SARS), a type of pneumonia
Pulmonary aspiration, the inhalation of vomit or salt water, such as from a near drowning
Inhalation of harmful smoke or fumes
Trauma to the lung, such as puncture wounds
Ventilators, machines that help people breathe, but can sometimes injure the lungs
An indirect lung injury is caused by another condition elsewhere in the body. These include:

Sepsis, where bacteria infect the bloodstream.
Severe bleeding from an injury or multiple blood transfusions.
Major trauma, such as a severe blow to the chest or head during a car accident.
Acute pancreatitis, a condition in which the pancreas (a gland that releases enzymes and hormones) becomes irritated or infected.
Fat embolism, a condition in which fat blocks an artery, which can result from a physical injury such as a broken bone.
Drug overdose
Burns
A lung injury can cause a collapsed lung or develop into acute respiratory distress syndrome -- two potentially life-threatening conditions.

What Is a Collapsed Lung (Pneumothorax)?

When the muscles of the chest and diaphragm contract they expand the chest, causing the lungs to inflate. Like a balloon, the lungs stretch as they inflate. When you exhale, the muscles relax, and like a balloon that's been released the lungs spring back. But if the air escapes from the lung and into the chest around the lung, the lung can collapse inside the chest. This can occur from the bursting of a weak spot of the lung, either from another medical condition, infection, or cancer. Or it could be caused by a puncture of the lung such as from a fractured rib.

Another condition called atelectasis is like a collapse of the lung, but the air doesn't escape into the chest. Rather the air sacs in the lung don't adequately expand when taking a breath. This can be caused by mucus plugging or a tumor blocking the airway. Or more commonly it can occur after an operation or by lying immobile for long periods.

To help prevent atelectasis, stop smoking six to eight weeks before surgery. Breathe deeply and cough often after a surgery. Also follow directions about moving, exercising, and changing positions after surgery.

source: webmd