Medical Rounds

Reading the Chest X-Rayby Frank Thomas, MD and Irene Tocino, MD

IntroductionWith the evolution of aeromedical

transport services a variety of personnelhave been used to transport critically illpatients. Currently, physicians, flightnurses, paramedical technicians andEMTs are used for such transports.Physicians, because of their medicaltraining, have been taught the propermethodology of reading the x-ray, whileflight nurses and other paramedicalpersonnel frequently lack the skill or theexperience necessary in reading the chestx-ray.

The purpose of this article is tooutline for the flight nurse andparamedical personnel a methodology inreading the chest x-ray. However, flightnurses and paramedics are urged to seekadditional references and hands-onexperience in reading the chest x-ray todevelop the skills required to effectivelyread the chest x-ray.

Proper recognition of the chest x-raymay initiate lifesaving procedures forpatient transport, such as chest tubes tobe inserted into patients with suspectedpneumothorax. The chest x-ray may alsoallow identification of pathologicallesions such as dissecting aorticaneurysms, ARDS, orhemopneumothorax which could requireadditional modes of therapy beforedeparture of the transport team from thereferring hospital.

The anterior-posterior chest x-rayA detailed and orderly schematical

review of a chest x-ray should 1) identify

Table 1READING THE CHEST X-RAY

Patient 's NameSoft Tissues and NeckDiaphragmBonesTracheaMediastinumHeartPulmonary VasculatureLung FieldsLines and Tubes

10 HOSPITAL AVIATION, JUNE 1987

the patient's name to insure that theproper x-ray is being visualized, 2)examine the soft tissues and neck 3)inspect the diaphragm and subdia­phragmatic structures 4) survey the bonystructures of the chest x-ray, 5) observethe trachea and its position, 6) delineatethe mediastinum and its structures, 7)note the heart, its size and position, 8)assess the pulmonary vascular system, 9)examine the lungs and their fields, and10) insure that all lines placed in thepatient entering into the thorax or into theneck have been evaluated as to theirposition and location. It is only throughthis systematic overview that the mosteffective means of x-ray interpretationwill occur.

Soft tissues and neckWhen examining the patient's soft

tissue and neck, the observer should lookfor evidence of subcutaneous air whichmay indicate the presence of apneumothorax, or a pneumomediastinum.Skinfolds should be noted so as not to beconfused with a suspected pneumo­thorax. Localized soft tissue thickeningin the soft tissue areas of the chest wallmay indicate a rib fracture or hematomasoccurring from blunt trauma.Generalized soft tissue thickening isfrequently observed with excessiveextracellular edema.

Diaphragm and subdiaphragmaticstructures

The right hemidiaphragm is usually1-3 em higher than the left herni-

Table 2SIGNS OF AORTIC RUPTURE

Widened med iastinumDeviated NG-tubePleural effusionFractured ribs, 1 or 2Deviated tracheaDownward left main bronchusIndistinct aortic knobPleural capping

diaphragm. The diaphragm edge shouldbe clearly outlined from the mediastinalstructures to one costophrenic angle.Failure to see the diaphragm outlinedusually indicates that either pleural orpulmonary disease exists.

An examination for elevateddiaphragms might indicate diaphragmaticrupture. A ruptured diaphragm usuallyoccurs with blunt trauma to the lowerchest and upper abdomen. Ninety-fivepercent of ruptured diaphragms willinvolve the right hemidiaphragm. Ribfractures and spleen injuries arecommonly associated with a ruptureddiaphragm.

Several findings, such as pleuraleffusion or herniation of the abdominalcontents into the chest cavity, shouldmake one suspect the potential for aruptured diaphragm. However, becauseof the association of pleural effusion witha ruptured diaphragm, it is often difficultto visualize the herniation. In addition itis usually difficult to determine whetherthe bowel shadows are above or belowthe diaphragm.

A ruptured diaphragm should besuspected in any patient with an elevateddiaphragm. The placement of anasogastric tube frequently helps with thediagnosis of a ruptured diaphragm. Thenasogastric tube is observed to be withinthe stomach, and coiled within thethoracic cavity. SUbdiaphra~matic

structures, such as a ruptured spleen withblood between the diaphragm and organarea, can likewise elevate the diaphragm.

BonesThe bones of the chest x-ray are next

examined. The examination should

Table 3SIGNS OF PNEUMOTHORAX

Displaced trachea or heartSubcutaneous airFractured ribsRadiolucencyEnlarged chest cavityLobar collapse

Medical Rounds

include an examination of the shoulders, trachea, makesure that the endotracheal an indication of pneumomediastinum.cervical, and thoracic vertebral bodies. tube is placedat leastone to two inches The mostobviousair shadowis oftenIn addition the clavicle,ribs and sternum above the carina. This will avoid along the left mainpulmonary arteryandshouldbe examined for fractures and inadvertent placement of the adjacentto the left hilum, the aorticknobdislocations. endotracheal tubedownthe right and the left heartborder.

Each rib shouldbe examined for mainstem bronchus duringhead flexion. The causes of a widemediastinumfractures or associated swelling or The carinais foundat the area wherethe maybe due to suddendecelerationhematoma in the adjacentskinfoldareas. left and the right bronchus join together. injuries producing shearing stresses uponIntercostal spaceswhenreferring to the the majorvessels. An acutewideningplacement of chest tubesarc numbered Mediastinum mediastinum indicates accumulation ofaccording to the rib abovethem. The rightborderof the mediastinum bloodor other fluid. Bleeding from theFractured ribs can be an indicatorof and its superiormargin is formed by the arteriesor veinsis themost frequentsignificant blunt trauma. This is innominate arteryor vein. It is usually cause. Mediastinal widening canbe veryparticularly true in first and secondrib straightor slightly outwardly curved. A difficultto interpretin the elderly wherefractures. predominant innominate vein is theaorta is frequently dilatedand

Associated injuriessuchas a indication of excessive fluidoverload. tortuous.laceration of the lower trachea or Belowthe innominate vein is the right In examining the widenedbronchus, lowercervicalspine injuries, lunghilum. The rightatrium forms the mediastinum, one shouldremember thatgreat vessel damageand injuryto the lowerright mediastinal border. The theanterior-posteriorfilm in thesupinebrachial plexus,should furthersuggest ascending aorticarch usually does not position frequently is normally observedthe possibility of major thoracic injury. form the borderon the rightaspectof the to be wider thana posterior-anterior chest

The lower three ribs, whenseen with mediastinum, however withsevere x-ray. To determine the progression of afractures, may be evidencethat injuryhas tortuous aortas, one maysee thisaortic widened mediastinum a seriesof chestx-occurred to the liver, spleenor kidney. arch extendinto theright borderaspects raysshouldbe takenfrom thesameFractures of any ribs can result in of themediastinum. positionand distance. Mediastinalpenetrating wounds of the heart and the The left borderis wherethe superior widening of over 11 cm shouldsuggestalungs. The mostcommon ribs that arc margin is formed by the left subclavian majormediastinal vessel injury.fractured arc ribs four through nine. To artery. The aorticarchformsa rounded In an aorticdissection, the contourofexaminethe ribs, look for lossof the convexity and sometimes can be theaorticknob is frequently indistinct.continuity of the cortexof the rib. There highlighted in elderlypeopleby the The trachea is frequently displaced to theis usually a step-down across the fracture calcium formations found within it. The rightand the left mainbronchus issite and the bone endsappeardense aorticknobshouldbe welldefined and frequently displaced inferiorly from thebecause of the overlapat the fracturesite. approximately 2-3 em in diameter. The bleedingsite. Withaorticbleeding,Frequently swelling is seenor observed left pulmonary arteryand the hilum of bloodcan dissectpleurally and be seenasin the soft tissueareas. the left lungare observed inferiorly to the "pleuralcapping"over the left lungapex.

aorticarch. The left ventricle forms the A periaortic shadowmaybe observed inTrachea lowerleft mediastinum border. the widening mediastinum. Nasogastric

The tracheais situated in the midline Whenexamining the mediastinum, tubedisplacement from the rightof theexceptfor a very slightshift to the right one shouldlook for evidence of air midlineis a helpful indication of aat the levelof the aorticarch. The right within the mediastinum. Suchair may possibleaorticaneurysm.and left mainbronchus can often be result from a tear in theesophagus ordetected. The trachea position is most tracheal bronchial tree. Subcutaneous air The heartimportant in givingevidence of a or retroperitoneal air maybe an The examination of the heartpossible collapseof a lowerlobe. With indication thata pneumomediastinum has predominantly includes an assessment ofcollapseof a pulmonary lunglobe the occurred from a ruptured esophagus or its size and its position in relationship totrachea frequently shifts to the side of the tracheal bronchial tree. the chest. If thechest x-raywas notlesion. On the other hand,a tension The signsof finding a takenon full inspiration, the heartmaypneumothorax will cause the trachea to pneumomediastinum include streaks of look biggerand the diaphragms may lookshift away from the side of the radial lucency in the mediastinum. A hazy. Even with anterior-posterior chestpneumothorax. radial lucentair shadowmedialto the x-rays, the normal heartshouldnot take

In all cases whenexamining the lungand adjacent to the cardiacborderis up more than half of the chestcavity.However, patientswithhistory ofcongestive heart failurewill frequently

Table 5haveenlarged hearts. Enlarged hearts

Table4 SIGNS OF EFFUSiONshouldbe notedwhenexamining the

SIGNS OF LOBAR COLLAPSE chestx-ray. Acutecardiactamponade

Blunted diaphragmoftencannotbe observed by merely

Displaced trachea or heart Opaque pleural spacelooking at thechest x-ray. It is

Decreased chest cavity Fluid in lung fissuresdiagnosed by clinical examination in

Opaque lung without bronchograms Mediastinal shiftconjunction with echocardiography.

HOSPITAL AVIATION, JUNE 198711

Normal chest radiograph. The mediastinum has normal width, sharp aortic knob,and narrow right para tracheal line.

Pulmonary vasculatur eHilar shadows are due to pulmonary

arteries and veins. The normal left hilumis slightly larger than the right. Largepulmonary vessels can indicate increasedpulmonary vascular flow or significantpulmonary vascular disease present in theperiphery to cause pulmonaryhypertension. Left-sided congestiveheart failure and pulmonary embolismarc frequently associated with increasedpulmonary arteries .

LungsThe only structures identified within

the normal lungs are the blood vessels.The walls of certain bronchi can be seenon end and usually are observed asvacant small "doughnut holes" whenexamining them on end. Thickenedbronchial lumens can be observed inpatients with acute exacerbation ofasthma. Blood vessels will show anorderly decrease in the diameter from thehilar out.

In the supine chest x-ray, increasedblood flow through the pulmonaryarteries is observed in the superiorsegments of the lung. Usually only theminor fissure is visible on the normalchest x-ray. Evidences of transversefissures and major fissures areindications that fluids may exist in thepleural space and that the fluid istracking up through these fissures.

Each lung field should be comparedto the other. The intrathoracic shadowsor lucencies arriving in or projecting overthe lungs arc observed in intcrpulmonarydisease. Collapsed lobes arc usuallydistinguishable from infiltrates byobserving a diminished amount of lungspace to the side of the collapsed lobe.Further, collapsed lower lobe isfrequently differentiated from infiltrationby lacking the "air-bronchograms" whichare frequently seen when interstitial fluidsurround the bronchi. Aspirationpneumonia or other infiltrative processesoccurri ng from bacterial infectionsfrequen tly demonstrate a haziness whichmay obstruct cardiac silhouettes,mediastinal silhouettes or thediaphragmatic silhouettes on the chest x­ray.

When examining the lungs forpneumothorax, caution is necessary tomake sure that the breast precordialmuscles, nipples and skin lumps havebeen excluded in evaluating the lungs.These overlying structures can frequently

14 HOSPITAL AVIATION, JUNE 1987

Medical Rounds

be misleading. In addition a commonmistake for the novice individual readingthe chest x-ray is to interpret the scapulaas a potential pneumothorax. Skinfoldscan likewise mimic a pneumothorax butcan be differentiated from pneumothoraxsince the markings frequently extend pastthe chest wall border.

Pneumothorax arc commonly causedby traumatic or spontaneous injuries.The signs of a pneumothorax include airin the pleural space that is moreradiolucent than to the lung adjacent to itand a lack of lung markings laterally. If

the lung has decreased volume, oneshould look for the line of pleura that areseparated by air from me chest wall,mediastinum or diaphragm. Byfollowing the lung markings to theperiphery along the involved side one candetect the separation of pleura from thechest wall.

A lack of lung markings does notmake the diagnosis of pneumothorax,since lung markings are often not seen inthe lung apex. Also, in emphysematouspatients, the lung markings are markedlydecreased in the periphery. Frequently

Medical Rounds

Supine chest radiograph in patient with aortic rupture:1- Widening of right para tracheal stripe;2- Obscuration of aortic knob;3- Displacement of nasogastric tube and trachea towards the right of the middle line;4- Downward displacement of left main bronchus;5- Apical cap

I

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an increase in the sharpness in thecontour of the mediastina] structures maybe the only evidence of pneumothoraxadjacent to the mediastinum.

Often the only indication of thepneumothorax may be increasedradiolucency of the lung field which isdue to the thin layer of anterior air whichis overlying the lung (Table 2). Thesesigns, although subtle, are frequently

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missed by the novice radiologist.Pneumothorax detection may be moreobvious on a film taken on expiration.Subcutaneous air provides indirectevidence that pneumothorax is present.When a pneumothorax is under tension,one will frequently see the trachea andmediastinum shift away from the side ofthe tension pneumothorax. Flatteneddiaphragm, increased radiolucency, and

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collapse of the lobe can be observed onthe affected side of the tensionpneumothorax.

Pleura] effusions when observed inthe lung are usually caused from blood,pus, exudate or a transudate. The size ofa pleural effusion include fluid in thepleural cavity. This fluid has the sameappearance whether the fluid is atransudate, exudate, pus, or blood. Freefluid is forced around the outer surface ofthe lung and the earliest evidence ofpleural effusion is in the subpulmonicregion in the erect position of a chest x­ray in the pleural sac between the lungand the diaphragm.

On most hemothorax there isgeneralized haziness of the hemithorax,and an abrupt stoppage of the vessels atthe level of the diaphragm. Thediaphragm will often flatten out Themedial aspects will be the first affected,the lateral aspects being the last to beaffected. New air bronchograms can be

' :seen in pleural fluid. In the supineposition of the dependent portion of thepleural cavity the fluid may be seen totrack up along the posterior and lateralwalls of the chest x-ray.

The hemothorax has a uniformdensity and often the outlining of thediaphragm is indistinct Massive pleuraleffusions can cause a mediastinal shift.Hemothorax is frequently caused bylaceration of the lung, intercostal vesselsand the great vessels or diaphragm.

The signs of hemothoraxradiographically are identical to that ofthe pleural effusion. The hemothoraxinjury is usually self-limiting. It isimportant to have an upright film ifpossible. In the supine position almost aliter of blood may produce only a slightdiffuse increase in the density over theinvolved hemothorax. Massive orpersistent bleeding suggests mediastinalblood or an intercostal injury hasoccurred.

Lung contusions usually occur froma traumatic injury. These aredistinguished from other forms ofinfiltrates in that they are usually non-segmental and provide a homogeneousconsolidation within 4-6 hours after theinjury. Often a hemothorax and ribfractures arc associated with a lungcontusion injury.

Pneumonia is caused by infections oraspiration. What helps to distinguishpneumonia from lung contusions is thatlobar consolidation usually produces an

HOSPITAL AVIATION, JUNE 198715

Supine chest radiograph after blunt chest trauma: Arrows point out large leftsubpulmonic pneumothorax. Arrowheads point out diffuse subcutaneousemphysema bilaterally, as well as pneumomediastinum secondary to trachealrupture. Observe the very large size of the balloon of the endotracheal tube cuff.

opaque lobe with air bronchograms.Because of the silhouette signs,boundaries between the affected lung andthe adjacent heart and lung, mediastinumand diaphragm will be invisible. Thesekinds of legions are segmental andpatchy in their appearance.

Atelectasis, which is collapse of lungtissue, is usually due to bronchialobstruction, pneumothorax, or pleuraleffusions, but rarely pulmonary emboli.In examining for atelectasis, one shouldlook for the shadow of collapse of the

Medical Rounds

lobe or lobes and a displacement of otherstructures to take up the space normallyoccupied by the lobe. Consolidationalmost always accompanies anobstructive lobar collapse. Theobstructed lobe will enlarge and movetoward the collapsed lobe. In collapse ofthe whole lung, the entire hemothorax isopaque and there is mediastinal andtracheal shift to the side of the collapse.Collapse also occurs due to air or fluid inthe pleural cavity.

Pulmonary edema is caused from a

multitude of problems includingcirculatory problems from hydrostaticpressures resulting from acute leftventricular failure , and occasionally fromcapillary leak syndrome such as adultrespiratory distress syndrome. Forpulmonary edema one almost alwaysfinds bilateral involvement involving allthe lobes. Frequently one observes abutterfly or bat-like appearance in thepulmonary vascular bed.

Edema can vary from lobe to lobe.Pulmonary edema is often confused withpneumonia, however the difference isusually that pulmonary edema will comeon acutely and leave acutely aftertreatment. Similarly, capillary leaksyndromes such as acute ARDS ordrowning may mimic hydrostaticpulmonary edema. The presence ofKerley B-lines indicates hydrostaticpulmonary edema. In addition, unlikehydrostatic pulmonary edema, capillaryleak syndromes are not associated withcardiac enlargement or pleural effusions.

Finally, one may be able to interpretfrom the chest x-ray the evidence ofpulmonary emboli. In such cases with anemboli in the pulmonary vascular bedone sees an increased area ofradiolucency in the lung. This is due to adecreased vascularity on the affected sideof the pulmonary embolism. The hilarshadows may become enlarged due todilatation of the pulmonary artery.

SummaryAlthough a brief discussion and

review of the chest x-ray is presented, itis hoped that a stimulus has beenprovided to flight crew members who arcfrequently not using the chestx-ray inevaluation of the transport of critically illpatients. With practice and much work,flight nurses and paramedical technicianscan become fairly good in examining theacute changes occurring in the chest x­ray and thereby make appropriateassessments and decisions concerning thepatient prior to transport and upon arrivalto transport to a tertiary care center.

Irene Tocino, MD is a radiologist at LOSHospital.and Clinical Assistallt Professor of Radiology atthe University of Utah . Salt Lake Cily. Utah. She is wellrecognized as an expert in intensi ve care chest radiology.

Frank Thomas. MD is the Medical Director of LifeFligh t and Co-Director of the Shock/frauma ICU at LOSHospital, an Assistant Professor of Medicine al theUniversity of Ula.'t Coll ege of Medicine, and President­elect of ASIIDEAMS. lie is well recognized as an expertin aeromedical transport.

HOSPITAL AVIATION. JUNE 1987 17