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Thorac Surg Clin 17 (2007) 57-61

Blunt Traumatic Lung InjuriesDaniel L. Miller, MDa,*, Kamal A. Mansour, MDb

a Section of Genera/ Thoraeic Surgery. Deparlment of Surgery. Emory Universily and The Emory Clínic.

1365 C/iflon Road NE, AI/anla. GA 30322, USAbEmory University Schoo/ of Medicine, 1365 C/iflOn Road NE. AI/anla. GA 30322. USA

The first detailed description of chest traumaappeared in the Edwin Smith Papyrus in ancientEgypt circa 1600 BC [I]. In the fifth century BC,Hippocrates described hemoptysis after rib frac-tures. He recognized that hemoptysis indicated in-jury to the underlying lung, which was a moresevere injury than a simple rib fracture [2]. Ap-proximately one third of ali patients admitted tomajor trauma centers in the United States sustainserious injuries to the chest. The lungs, which oc-cupy a large portion of the chest cavity and lie inclose proximity to the bony thorax, are injured inthe majority of these patients directly or indi-rectly. A significant number of lung injuries arealso associated with trauma to other critical tho-racic structures. This article discusses blunt

trauma injuries of the lung, which include pulmo-nary contusions, hematomas, lacerations, andpulmonary vascular injuries.

Pulmonary contusion

Pulmonary contusion is the most commoninjury seen in association with thoracic trauma[3]. It occurs in 30% to 75% of patients sustainingmajor chest injuries [4]. Pulmonary contusion isseen with blunt and penetrating wounds but ismost common after motor vehicle accidents

when the chest strikes the steering wheel or cardoor. The incidence of pulmonary contusionsmay be decreasing because of supplementary re-straint systems, known as airbags, installed inUS automobiles. Air bags supplement the safety

* Corresponding author.E-mail address:daniel.miller@emoryhealthcare.org

(D.L. Miller).

belt by reducing the chance that the occupant'supper body will strike the vehicle's interior.They aIso help reduce the risk of serious injuryby distributing crash forces more evenly acrossthe occupant's body. This decrease in lung injurieshas been evident at Grady Memorial Hospital inAtlanta, Georgia, one of the busiest level I traumacenters in the United States. From January I,200I through Oecember 31, 2006, a total of8780 patients were admitted to the Emory Univer-sity Trauma Service; 989 patients (lI %) had anassociated lung injury related to their trauma. Pul-monary contusions can also occur after falls fromgreat heights or from blast injuries.

Isolated pulmonary contusions are encoun-tered much less commonly than are contusionsassociated with other thoracic and nonthoracic

injuries. Because pulmonary contusions are socommonly associated with other injuries, thepathophysiology of the associated injuries, theresuscitative and therapeutic measures that arenecessary for their treatment, and the effects ofaspiration, infection, and adult respiratory dis-tress syndrome (AROS) on the lung parenchymahave clouded the understanding of isolated pul-monary contusion.

Pathology

Wagner and colleagues [5]presented convincingevidence based on CT scan findings and limitedpathologic material that a pulmonary lacerationwith resultant hemorrhage into adjacent alveolarspaces, rather than alveolar capillary wall injury,is the basis for the development of pulmonary con-tusions. They described four types of lacerationsthat are associated with pulmonary contusions.Type I lacerations are the result of compression

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of the elastic chest wall that causes the underlyingair-filled lung to rupture. Type 11lacerations resultfrom compression of the lower chest wall thatcauses a sudden displacement of the lower lobeacross the vertebral column and that producesa shearing tear in the adjacent lung. Type 111lacer-ations are small peripheral lacerations that aredose to rib fractures and are thought to be pene-trating injuries caused by the ends of the fracturedribs. Type IV lacerations are tears caused by sud-den chest wall compression that displaces thelung inwardly next to thick pleuropulmonary ad-hesions. Type I is the most commonly encounteredlaceration and is almost always seen in patientswho are younger than 40 years of age. Type 111lacerations are the next most commonly seen andusually occur in older patients.

Diagnosis

Blunt trauma to the chest, falls, and blastinjuries should ali suggest the possibility thata pulmonary contusion may occur. Dyspnea,tachypnea, hemoptysis, cyanosis, and hypotensionare frequently seen. Physical examination may beunrevealing; however, in the presence of a severecontusion, inspiratory rales and decreased breathsounds may be found. A chest radiograph showssingular or multiple patchy alveolar infiltratescaused by intra-alveolar hemorrhage [6]. Thesepatchy infiltrates can coalesce into homogenousinfiltrates that involve a lobe or an entire lung.CT scans of the chest have been shown to bemore sensitive in demonstrating the changes seenwith pulmonary contusions than are routine chestradiographs [5]. In patients with pulmonary con-tusions, arterial Pa02, alveolar arterial oxygengradients, and pulmonary compliance are usuallyabnormally low. Hyperventilation may induce hy-pocapnia and respiratory alkalosis [7]. If the con-tusion is massive or if aspiration, infection, orARDS develops, carbon dioxide may be retainedand respiratory acidosis may ensue.

Treatment

Patients with pulmonary contusions should behospitalized for careful monitoring because theycan become critically ill rapidly. Oxygen should beadministered as necessary to maintain arterialoxygen saturation greater than 90%. Patient-controlled analgesia, intravenous or epidural,should be used as necessary to control pain.Vigorous chest physiotherapy is important tokeep the airway dear and help prevent the

development of atelectasis. If ventilation is in-adequate, intubation and mechanical ventilationare indicated. If large volumes of fluid arenecessary for resuscitation, a pulmonary arterycatheter should be positioned so that pulmonaryartery pressures and pulmonary capillary wedgepressures can be measured.

The use of steroids and antibiotics is contro-versial. Some authorities advocate the use of highdoses of steroids for a short time, whereas othersbelieve that the use of steroids is not indicated [8].Prophylactic antibiotics are used in some institu-tions; in others, antibiotics are used only whenevidence of infection is present.

Pulmonary contusions are not innocuous in-juries. In one series, 11% of patients with severeisolated pulmonary contusions died, whereas themortality rate was much higher (22%) in patientswith associated injuries [9]. ARDS developed in17% of patients with isolated pulmonary contu-sions and in 78% of patients with two or more si-multaneous associated injuries in other series [10].

Pulmonary lacerations

Pulmonary parenchymal lacerations, althoughseen more commonly after penetrating chesttrauma, are also seen after blunt trauma. Al-though blood vessels and tracheobronchial pas-sages may be disrupted, pneumothorax is in manycases the major problem, and bleeding is of minorconsequence. If the laceration involves the visceralpleura and the communication with the pleuralspace remains patent, hemothorax, pneumotho-rax, or hemopneumothorax results. If the visceralpleura is tom but quickly seals, blood, air, or bothcan accumulate within the parenchyma and resultin the development of a hematoma, cyst, or a cystcontaining blood.

As a result of high-speed motor vehidecrashes, extensive pulmonary lacerations, occa-sionally with volvulous or torsion of the lung, arebeing encountered with increasing frequency.Such lacerations often are centrally located, areassociated with severe chest wall injuries andpulmonary contusion, and disrupt large vesselsand major bronchi.

Pulmonary hematoma

Pulmonary lacerations resulting from blunt orpenetrating injuries may fill with blood, forminga pulmonary hematoma. The reported incidence

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of hematomas developing in pulmonary contu-sions has ranged from 4% to Ii % [5,11]. Becausehematomas are recognized infrequently in clinicalsituations, the true incidence is likely to be less.Despite an unimpressive radiographic appear-ance, the injury represents a significant collectionof intraparenchymal blood. It may not becomevisible radiographically for 24 to 72 hours aftertrauma resuscitation, during which time it in-creases insidiously. Pulmonary hematomas gener-ally do not interfere with gas exchange, nor dothey produce significant intrapulmonary shunting.Nevertheless, a pulmonary hematoma is a majorrisk facto r for infection and lung abscess forrna-tion [12].The use of CT scans perrnits more accu-rate evaluation of hematomas than conventionalradiographs. On CT scans, hematomas havebeen found to shrink less than 0.5 cm in 3 weeks,whereas on conventional radiographs, they are re-ported to resolve within 2 to 4 weeks of injury [5].In the absence of previous radiographs, serialfilms, or serial CT scans demonstrating the evolu-tion of the hematoma, the exact nature of the nod-ule or lesion may be unclear, and the possibility ofa neoplasm must be considered. If the nodule re-mains stable after 4 weeks, showing no evidenceof resolution, fine-needle aspiration of the noduleor surgical excision should be perforrned to estab-lish the nature of the lesion [13].

Management

In most cases, pulmonary lacerations healpromptly after chest tube insertion without anysignificant long-Iasting ill effects. Peripherallacer-ations encountered at operation can be oversewn(pneumonorrhaphy), stapled, or wedged out.Extensive lacerations may be centrally locatedand may disrupt major vessels and bronchi. Re-sultant massive bleeding, large air leaks, and,although rarely seen, bronchopulmonary venousfistulas resulting in systemic air embolizationrequire immediate operation. Proceeding to a tho-racotomy is deterrnined by the urgency of thissituation, location of the injury, and structurespresumed to be involved. Lately, more traumacenters are using thoracoscopy as a diagnostic ortherapeutic procedure for pulmonary lacerations[14,15]; however, if a thoracotomy is required, hi-lar compression with the fingers and then witha large vascular clamp, such as a Satinsky orcurved DeBakey, is used to control bleeding andair leak and to stop systemic air embolization.When the hilum is controlled, if embolization

has occurred, air is aspirated from the left sideof the heart, aorta, and coronary arteries. Thevascular and bronchial injuries are then repaired,if possible, and the laceration is left open anddrained with appropriately placed chest tubes.

Torsion or volvulous of the lobe or lungsuggested by atypically oriented lobar collapsealso necessitates prompt diagnosis and operation.At thoracotomy, the involved lobe or lung isuntwisted and observed to ensure viability. Ifthere is any question about its viability, the lobeor lung should be resected. Otherwise, the in-volved lobe should be stapled, if possible, to anadjacent lobe to prevent retwisting.

If a pulmonary hematoma or pulmonarycontusion is identified at the time of thoracotomy,the surgeon should resist the temptation to resectthe involved lung. Despite the gross appearance,there is rarely an indication for resection of aninjured lung, unless there is associated significantinjury to the airway or pulmonary vessels [16].

Pulmonary vascular injury

Vascular injury within the pulmonary paren-chyma occurs within a low pressure system com-pressed by the surrounding parenchyma. Suchhemorrhage generally stops with complete expan-sion of the lung [16,17]; however, uncorrected in-jury to the main pulmonary arteries or veins or totheir principie lobar branches is usually lethalfrom rapid exsanguination because these structuresbleed freely into the pleural space. Major pulmo-nary vascular injuries usually result from suddendeceleration. Mortalities rates for pulmonary arte-rial or venous injuries exceed 75%; therefore, themajority of these patients rarely survive longenough to reach a trauma center.

Management

If a major pulmonary vascular injury is di-agnosed or suspected, control may be obtained atthe pulmonary hilum by clamping the entirehilum. Through a thoracotomy incision, the hilumof the lung is grasped firrnly with one hand as thesurgeon uses the other hand to apply a longvascular clamp across the entire pulmonary hilum.This maneuver excludes the main pulmonaryartery and veins from the circulation, may preventexsanguination, and provides time for the anes-thesiologist to resuscitate the patient. If there isa significant amount of blood in the airway,a double-Iumen endotracheal tube or a bronchial

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blocker may be used to protect the opposite lungfrom aspiration of blood. Next, the vascularinjury should be isolated and repaired usingstandard vascular techniques [18]. If a lobar pul-monary artery is irreparable, it may be ligatedwithout fear of pulmonary necrosis. The bron-chial blood supply is usually sufficient to maintainparenchymal viability. If the venous drainage toa parenchymal region must be sacrificed, the in-volved parenchyma should be resected to preventinfarction of that portion of the lung secondary tovenous obstruction [18].

Video-assisted thoracic surgery or thoracoscopy

Although most chest traumas do not requirea major operation, tube thoracostomy remains thebasis of treatment. Patients who would have

required a thoracotomy in the past may actuallybenefit from a less invasive surgical technique toperform diagnostic and therapeutic proceduresafter blunt chest trauma. Improvements in in-strumentation, especially endoscopic staplers andcameras, and endoscopic surgical techniques haveexpanded the indications for video-assisted tho-racic surgery (VATS) or thoracoscopy in thediagnosis and treatment of diseases within thechest; however, the use ofVATS remains contro-versial in trauma patients. Early publicationsexplored the use of VATS in patients sustainingthoracic trauma [19,20]. The results were encour-aging, but the series reported a small number ofcases. In 1999, a meta-analysis of the use of thor-acoscopy in trauma was published that involved28 studies and more than 500 patients. The com-plication rate was 2% and the missed injury rate0.8%. The most important benefit was that 62%of patients did not require a thoracotomy or lap-arotomy for diagnosis or treatment of their tho-racic injuries [21]. VATS is an accurate andeffective modality in the evaluation and manage-ment of hemodynamically stable patients who ex-perience thoracic injuries. One should have a lowthreshold to perform an open procedure if the sit-uation arises. A reiative stable thoracic traumapatient can become extremely unstable at any mo-ment; therefore, one should be prepared to pro-ceed with a thoracotomy immediately. Cautionshould also be taken in the thoracic traumapatient with multiple injuries, especially severeintra-abdominal injuries.

Blunt thoracic trauma continues to be a signif-icant cause of morbidity and mortality in the

United States. A comprehensive evaluation ofthese patients is needed to improve their survival.Understanding the lung injuries that can occurre1ated to blunt chest trauma is essential toimproved outcomes. The use of VATS in bluntthoracic trauma has improved the diagnosis andmanagement of patients with life-threateningpulmonary injuries.

References

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Classification of parenchymal injuries of the lung.Radiology 1998;167:77-82.

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[17] Beall AC, Crawford HW, Debakey ME. Consid-erations in the management of acute traumatichemothorax. J Thorac Cardiovasc Surg 1966;52:351-60.

[18] Carr RE. Injuries to the pu1monary parenchyma andvasculature. In: Daughtry DC, editor. Thoracictrauma. Boston: Little Brown; 1980.

[19] Smith RS, Fry WR, Tsoi EKM, et aI. Preliminary re-port on videothoracoscopy in the evaluation and

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Reprinted from Thoracic Surgery Clinincs 2007; 17(1):57-61, vi. Miller DL, Mansour KA. Blunt traumatic lung injuries. Copyright 2007@ EIsevier, Inc.

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