Thoracic Trauma - Flail Segment and Pulmonary Contusions

Flail Segment

 

 

 

 

Flail Chest

 

 

A flail chest occurs when a segment of the thoracic (rib) cage is separated from the rest of the chest wall. This is usually defined as at least two fractures per rib (producing a free segment), in at least two ribs. A segment of the chest wall that is flail is unable to contribute to lung expansion. Large flail segments will involve a much greater proportion of the chest wall and may extend bilaterally or involve the sternum. In these cases the disruption of normal pulmonary mechanics may be large enough to require mechanical ventilation

 

.The main significance of a flail chest however is that it indicates the presence of an underlying pulmonary contusion. In most cases it is the severity and extent of the lung injury that determines the care need and the possible requirement for mechanical ventilation. Thus the management of flail chest consists of standard management of the rib fractures and of the pulmonary tusions underneath.

 

Diagnosis

Most significant chest wall injuries will be identified by physical examination. Bruising, grazes or seat-belt signs are visible on inspection, and palpation may reveal the crepitus associated with broken ribs. Awake patients will complain of pain on palpation of the chest wall or on inspiration.

A flail chest is identified as paradoxical movement of a segment of the chest wall - ie indrawing on inspiration and moving outwards on expiration. This is often better noted by palpation than by inspection.

 

Pulmonary Contusion

 

 

 

 A pulmonary contusion is an injury to lung tissue, leading to edema and blood collecting in alveolar spaces and loss of normal lung structure & function. This blunt lung injury develops over the course of 24 hours, leading to poor gas exchange, increased pulmonary vascular resistance and decreased lung compliance. There is also a significant inflammatory reaction to blood components in the lung, and 50-60% of patients with significant pulmonary contusions will develop bilateral Acute Respiratory Distress Syndrome (ARDS).

 

Acute respiratory distress syndrome (ARDS) is a life-threatening lung condition that prevents enough oxygen from getting to the lungs and into the blood. Infants can also have respiratory distress syndrome.

Causes

ARDS can be caused by any major direct or indirect injury to the lung. Common causes include:

• Breathing vomit into the lungs (aspiration)
• Inhaling chemicals
• Lung transplant
• Pneumonia
• Septic shock (infection throughout the body)
• Trauma

ARDS leads to a buildup of fluid in the air sacs (alveoli). This fluid prevents enough oxygen from passing into the bloodstream.
The fluid buildup also makes the lungs heavy and stiff, which decreases the lungs' ability to expand. The level of oxygen in the blood can stay dangerously low, even if the person receives oxygen from a ventilator through a endotracheal tube.

 

Pulmonary contusions occur in approximately 20% of blunt trauma patients and it is the most common chest injury in children. The reported mortality ranges from 10 to 25%, and 40-60% of patients will require mechanical ventilation. The complications of pulmonary contusion are ARDS, as mentioned, and respiratory failure, atelectasis.

 

(Atelectasis (at-uh-LEK-tuh-sis) is a condition in which one or more areas of your alveoli collapse or don't inflate properly. If only a small area or a few small areas of the alveoli are affected, you may have no signs or symptoms.

If a large area or several large areas of the alveoli are affected, they may not be able to deliver enough oxygen to your blood.)

 

Diagnosis

 

Pulmonary contusions are rarely diagnosed on physical examination. The mechanism of injury may suggest blunt chest trauma, and there may be obvious signs of chest wall trauma such as bruising, rib fractures or flail chest. These suggest the presence of an underlying pulmonary contusion. Crackles may be heard on auscultation but are rarely heard in the emergency room and are non-specific.

Severe bilateral pulmonary contusions may present with hypoxia - but more usually hypoxia develops as the pulmonary contusions blossom or as a result of subsequent ARDS.

 

In hospital radiological testing (plain chest x-ray or CAT scan) is best way to diagnose a pulmonary contusion.