Chest trauma: EMS assessment and treatment
The injuries from blunt or penetrating chest trauma can cause life-threatening disruption to perfusion, ventilation or both
At 0200 hours Medic 772 is dispatched for a report of a "man down." The crew arrives to find a young male on the sidewalk, apparently sleeping and lying on his side. Knowing that the area is frequented by homeless people, the crew made an attempt to awaken him, first verbally and then with a painful stimulus. The man responded by grunting and feebly trying to push them away. With resignation, the medics lift the patient onto their gurney and wheeled him into their unit.
Under the bright lights of the patient care compartment, the crew noted the man was neatly dressed, although his jacket was torn and his shoes were missing. As they disrobed the patient, they determined that the patient was dyspneic, with rapid breathing. The pulse oximeter provided an initial reading of 79 percent on room air. Auscultation of the chest revealed near-absent lung sounds over the right side. Jugular venous distention was noted, and radial pulses were weak and thready.
Introduction to chest trauma
The thoracic, or chest area of the body contains major organs and structures essential to human survival and well-being. Chest injuries range from minor abrasions and contusions, to major blunt and penetrating traumatic events that cause compromise to the airway, breathing and/or perfusion. It is critical that EMS providers rapidly recognize and, when necessary, treat and transport chest injuries without delay.
Scope of the problem
Over 100,000 people die from trauma every year in the U.S. . Approximately 16,000 deaths occur from chest trauma annually . The most common cause of blunt force chest injuries is the motor vehicle crash, accounting for 70-80 percent of such injuries .
The most common causes of penetrating trauma are from stabbing and gunshots. Together they make up almost 20 percent of all major trauma cases .
Thoracic cavity anatomy and physiology
The thoracic or chest cavity is cylindrical in shape, and contains organs of the cardiovascular, respiratory and gastrointestinal systems. Twelve pairs of ribs connect posteriorly to the spinal column vertebrae with bands of ligaments that hold them in place. The first rib pair lies just under the clavicles. Anteriorly, the first seven rib pairs directly connect to the sternum through cartilaginous attachments. These are called true ribs, compared to the remaining five pairs of false ribs which do not attach directly to the sternum. In addition, the last two pairs of false ribs are known as floating ribs, as they do not attach to the sternum at all. This rather intricate connection of bones and ligaments provide the ribcage with strength, yet provide elasticity to allow the chest cavity to expand and contract during ventilation.
In between each rib is an intercostal space, consisting of muscle and connective tissue that, when stimulated by the respiratory center, contracts and pulls the ribs outward. Just below each rib lies a bundle of arteries, veins and nerves. The rest of the bony structure of the chest includes the clavicles, scapula and the spinal column.
The thoracic cavity is separated from the abdominal cavity by the diaphragm, a broad structure of muscle and fibrous tissue that is responsible for most of the effort of normal breathing. At rest, the superior position of the diaphragm is at the level of the fifth intercostal space. The diaphragm will move downward 1-2 cm in normal breathing, but can move up to 10-12 cm (3.9-4.7 inches) with deep inspiration.
The diaphragm and intercostal muscles provide most of the effort of normal breathing, as well as the beginning stages of respiratory distress. As breathing difficulty worsens, accessory muscles, such as the sternocleidomastoid and scalene in the neck, contract to elevate the upper portion of the ribcage. Abdominal muscles can also be used during active exhalation, as might occur during periods of severe bronchoconstriction.
The interior wall of the chest cavity is lined with the parietal pleural membrane. A second visceral pleural membrane covers the lungs and other structures lying within the cavity. In between the parietal and visceral pleural membranes is the pleural space that is normally filled with serous fluid that allows both pleural membranes to slide past each other easily.
The majority of the pleural cavity is filled with the lungs, heart and great vessels. In addition, most of the liver, the stomach and superior portion of the large intestines reside just below the diaphragm. The mediastinum is a distinct space between the two lungs and contains the heart, great vessels, esophagus, trachea and the thymus and chest lymph nodes.
Pathologies of blunt and penetrating trauma
Both blunt and penetrating trauma mechanisms can cause minor to severe injury patterns to the chest cavity, due to the large number of vascular-rich organs and structures.
Blunt force trauma results from mechanisms of injury such as falls, motor vehicle crashes and assaults with blunt objects. The energy generated from the motion of the object is transmitted first against the skin, muscle and bones of the chest, then into the organs contained within the chest cavity itself.
This energy transfer can result in one of two injury patterns:
1. Compression, where an organ is deformed causing tearing or rupture; or deceleration, where the organ is attached to an anchor point within the chest moves abruptly, causing shearing and stretching. An example of a deceleration injury is the shearing of the aorta by the ligamentum arteriosum, which normally holds the aorta upright in the chest but slices through it after a major front-end impact.
2. Penetrating trauma differs from blunt in that an object such as a bullet, knife or other object physically penetrates the skin, creating a temporary or permanent opening. The energy associated with penetrating trauma is more narrowly focused than blunt force trauma, and can be carried deep into the chest cavity. Depending upon the mechanism of injury, the generated forces may be so great as to cause compression of tissue surrounding the entrance wound. This is caused by cavitation and can result in serious damage to areas not directly injured by the penetrating object. For soft tissues such as the lung, cavitational forces can be devastating, causing major bleeding and loss of alveoli needed for adequate gas exchange during breathing.
Chest trauma injury patterns
Chest trauma can be broadly categorized into two areas: injuries that cause significant blood loss, and those that compromise ventilation. Major disruption to either perfusion or ventilation poses an immediate life threat to the victim. Patients can also succumb from significant infections due to a perforated esophagus or stomach, punctured lungs or ruptured trachea.
The heart, lungs, great vessels (aorta, vena cava, pulmonary veins and arteries) and liver will hemorrhage quickly if punctured or lacerated. The chest cavity can hold several liters of blood (hemothorax), displacing the lungs and other organs. Bleeding inside lung tissue (pulmonary contusion) can cause a ventilatory mismatch, compromising adequate gas exchange at the alveolar/capillary interface.
Blunt force trauma to the heart can cause a myocardial contusion, resulting in decreased cardiac output, dysrhythmia or myocardial infarction. Additionally, even a small amount of blood leaking from injured myocardium into the pericardial sac that surrounds the heart can result in a cardiac tamponade that compresses against the heart chambers, reducing stroke volume capacity and cardiac output.
Air that enters the chest cavity through any means, other than through the mouth and nares can result in potential catastrophe. Normally the pleural space is virtually nonexistent, allowing for normal chest excursion during breathing. Air that enters through a penetrating wound or a rupture in the lung tissue can create an actual space (pneumothorax) that results in the loss of negative pressure during inspiration. This can cause part of the lung to collapse and stop exchanging carbon dioxide and oxygen causing a ventilatory mismatch.
If the wound remains open eventually air pressure equalizes between the inside of the chest and the environment. However, if the wound closes after inspiration, air becomes trapped inside the chest, unable to escape into the atmosphere. Over time, the pressure inside the chest rises, causing a tension pneumothorax to form. The pressure acts as a balloon, forcing the lung on the side of injury to collapse. Additionally, the mediastinum shifts toward the unaffected side, placing pressure on the other lung, heart and great vessels. As this occurs, cardiac output falls, resulting in hypotension. Hypoxia, hypercarbia and hypoperfusion cause significant altered mental status. This condition is lethal if not corrected.
Air can also enter the mediastinum directly creating a pneumomediastinum. Air can escape from the area, leaking into the soft tissue of the chest and causing subcutaneous emphysema to form under the skin of the face, neck and chest. A patient may show a rapid onset of what appears to be edema in these locations; palpation might result in a "Rice Krispies" sound. Auscultation of heart tones might reveal Hamman's sign, crunchy, raspy noises timed to the heart beat.
The presence of air and blood in the chest is not uncommon. Patients with significant blunt and/or penetrating trauma will often have a combination of the two patterns, such as a pneumohemothorax.
Multiple ribs, each broken in two or more places, may cause a part of the ribcage to separate from the chest wall, creating a flail segment. If the segment is small, the intercostal muscles will "self splint" the area. However, a large segment will "float" and move in the opposite (paradoxical) direction of normal chest excursion. This can also create a ventilatory mismatch, as the lung is unable to expand normally.
Chest trauma assessment and treatment
Because the potential for serious harm is high, assessment of the chest occurs during the primary assessment.
1. Primary assessment treatments
Based on the mechanism of injury, consider manual stabilization of the cervical spine until a more complete spinal exam can be accomplished. Establish and maintain a patent airway while determining the patient's level of consciousness using the AVPU scale. If the patient is not fully awake or alert, manual airway positioning and basic airway adjuncts such as an OPA or NPA may be needed. Suctioning an airway filled with blood or emesis may be necessary.
2. Seal chest wounds
Any open chest wound should be sealed as soon as it is found, using the palm of a gloved had at first, followed by an occlusive dressing. Using a commercially prepared product such as an Asherman or Bolin chest seal, or a multifunction pad or electrode may be preferable to the often-taught three-sided seal, as the latter may not adhere to the skin well due to blood or diaphoresis .
3. Relieve tension pneumothorax
Tachypnea, hypopnea (shallow breathing) and accessory muscle use are key indicators of respiratory distress or failure. Expose the chest and auscultate lung fields immediately. Diminished sounds over one side may indicate a loss of lung capacity, either from a hemothorax, pneumothorax or both.
Inspect the neck and chest area. Jugular venous distension may indicate greater than normal pressure within the chest cavity, possibly related to a developing tension pneumothorax. Hyperinflation of the chest over one side is another sign related to a tension pneumothorax. If the patient's mental status worsens and blood pressure falls, a decompression of the tension pneumothorax using a long, large gauge angiocatheter is needed to relieve the excessive pressure in the chest.
4. Control hemorrhage
Control any major external bleeding immediately with direct pressure. It will be difficult to create a pressure dressing, as is more commonly seen with extremity injuries. Manual pressure may be needed to stop the bleeding. Recognize that the chance of active bleeding inside the chest is significant and emergent transport to a trauma center is needed.
5. Package for transport
Unless there are clear signs of neurological deficit, avoid placing the patient with penetrating chest trauma in spinal precautions. Being supine may worsen respiratory distress and delay transport. Similarly, EMS providers can use a standardized spinal clearance protocol based on NEXUS criteria to spinal immobilize patients with blunt trauma injuries.
In general, on-scene management of chest trauma should be done with BLS interventions, with the intent to begin transport to a trauma center as soon as feasible. With the exception of the needle decompression, other advanced level procedures are best done while en route.
Case study follow-up
After careful inspection of the chest wall, a small incision wound was noted in the patient's right side, along the mid-axillary line, just under the inferior rib. With little bleeding, the wound was almost unnoticeable. Blood pressure was noted to be 82/68. An occlusive dressing was applied to the site, which did not improve the patient's condition. Given the patient's altered mental status, absent lung sounds, the presence of jugular venous distension and hypotension, a needle decompression was performed on the right side of the chest at the second intercostal space. The patient's respiratory effort began to improve, and oxygen saturation levels rose. At the trauma center, a chest X-ray confirmed the presence of a right sided pneumothorax that was likely a tension pneumothorax earlier. The patient suffered significant blood loss from a lacerated liver and hemothorax, but was successfully discharged after two weeks week in surgical ICU.
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