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Review for Residents
Radiology



             Robert T. Bramson, MD                     Interpretation of Chest
             N. Thorne Griscom, MD
             Robert H. Cleveland, MD                   Radiographs in Infants with
             Published online before print
               10.1148/radiol.2361041278
             Radiology 2005; 236:22–29
                                                       Cough and Fever1
             1
               From the Department of Radiol-             An understanding of the appearance of the infant chest radiograph requires an
             ogy, Children’s Hospital, Boston,            understanding of the anatomy and the physiologic, immunologic, and pathologic
             300 Longwood Ave, Boston, MA
             02115. Received July 22, 2004; revi-         processes in the infant’s chest. The authors describe the features of the infant chest
             sion requested September 22; revi-           that most influence the appearance of the chest radiograph in infants with cough
             sion received November 10; accepted          and fever. They discuss why confusion sometimes occurs when radiology residents
             December 10. Address correspon-
             dence to R.T.B. (e-mail: robert.bramson
                                                          and general radiologists familiar with adult chest radiographs first evaluate the
             @childrens.harvard.edu).                     infant chest radiograph. The radiographic appearance of acute inflammation does
             ©   RSNA, 2005                               not look the same in infants as it does in older children and adults. The hallmark of
                                                          inflammatory lung disease in the infant chest is air trapping on the chest radiograph.
                                                          ©   RSNA, 2005




                                                       EDITOR’S NOTE: Please see the January 2005 From the Editor, where this new feature, Review for
                                                       Residents, was announced.

                                                       Radiology residents have often expressed to us their frustration and confusion when
                                                       attempting to interpret chest radiographs of infants. Radiologists not trained in pediatric
                                                       radiology find terms like air trapping, peribronchial thickening, bronchiolitis, lower re-
                                                       spiratory tract infection, and peribronchial pneumonia confusing (1). Pediatric radiolo-
                                                       gists have, in fact, conflicting definitions of these terms and varying opinions about their
                                                       meaning. The authors hope to clarify the relationship between the pathologic changes
                                                       within the infant chest and their radiographic appearance, explaining in pathophysiologic
                                                       terms why the infant chest looks the way it does in inflammatory airways diseases.
                                                          An understanding of the infant chest radiograph requires a review of how embryology,
                                                       anatomy, physiology, pathology, immunology, and the physics of fluid mechanics influence
                                                       its appearance. This knowledge is critical in the interpretation of the infant chest radiograph.


                                                       EMBRYOLOGY AND ANATOMY

                                                       We will summarize the science that explains the appearance of the infant chest, with the
                                                       caveat that universal agreement on the details does not exist. All of the generations of the
                                                       airways have developed by the time the fetus reaches the 16th week of gestational age.
                                                       There are about 22 generations of airways, depending on how the last generation is
                                                       counted and where the count is performed. Near the lung hila, there may be as few as 10
                                                       generations of airways before the gas-exchange units—the respiratory bronchioles and
                                                       alveolar sacs—are reached. In the lung periphery, there may be as many as 25 generations
                                                       of airways before the gas-exchange units are reached. As the child grows and becomes an
                                                       adult, the airways grow in length and diameter but not in number (2– 4) (Fig 1).
                                                          The alveoli, the gas-exchange units, develop after the airways. They start proliferating
                                                       about the 29th week of gestational age. By the 40th week of gestation, there are approx-
                                                       imately 20 million alveoli in the newborn lung, although the precise number is debated.
                                                       The mature lung contains approximately 300 million alveoli; that number is reached at
                                                       about 8 years of age (2). The alveoli then increase in size, and their lining gets progressively
                                                       thinner as the child becomes an adult. The total alveolar surface area is 70 – 80 m2 in the
                                                       adult. In the newborn infant, the total alveolar surface area is only about 3 m2. The ratio
                                                       of the alveolar surface area to the body surface area is more than three times as great in the
                                                       adult as in the newborn (5). Thus, the infant is at a distinct disadvantage, compared with

            22
During expiration, the airways narrow           of the peripheral airways to the resistance
            ESSENTIALS                                    and the cross-sectional area decreases.         of flow is considerably greater in infants
                                                          This normal variation in luminal size is        than in adults, even in normal circum-
            ●   Most respiratory infections are caused    accentuated in the infant because the           stances (4).
                by viruses in infants and children        support tissues around the airways are             When breathing at 16 times per
Radiology


                younger than 24 months and lead to        more compliant and allow more narrow-           minute, the adult has 3.75 seconds to
                the pathophysiologic changes of air       ing during expiration. Compared with an         move his or her diaphragm through the
                trapping.                                 adult, the number of alveoli is relatively      full course of inspiration and expiration.
                                                          low in the infant, and the proportion of        When breathing at 40 times per minute,
            ●   Hyperinflation may be the only radio-
                                                          the lung involved in air transport (the         the infant has only 1.5 seconds for this
                logic clue to illness.
                                                          airways) is relatively high. In the adult,      diaphragm movement. The infant in-
            ●   Bacterial pneumonia can have the          80% of the airways are bigger than 2 mm         creases oxygen exchange primarily by in-
                same appearance in adults and in-         in diameter. The smaller peripheral air-        creasing the respiratory rate. When this
                fants.                                    ways in adults account for less than 20%        happens, the diaphragm must change di-
            ●   The radiographic appearance reflects       of the total resistance to the flow of air. In   rection more frequently and either move
                                                          the infant lung, the peripheral airways         faster or not move as far during each
                the pathologic process occurring in the
                                                          are considerably smaller, and the resis-        excursion. During periods of respiratory
                respiratory system.
                                                          tance to air flow owing to these small           distress, these all occur.
                                                          airways is 50% of the total resistance (4)         The level of the diaphragm seen on
                                                          (Fig 2).                                        chest radiographs is determined by sev-
                                                                                                          eral things. At all ages, the level of the
            the adult and older child, in his or her                                                      diaphragm depends on how deep an in-
            reserve of alveolar surface area for gas      PHYSIOLOGY                                      spiration the patient has made when the
            exchange. The alveolar walls contain the                                                      radiograph was obtained. The adult usu-
            pulmonary capillaries, which form a gi-       Growth is proportionately more rapid in         ally takes a deep breath when requested,
            ant blood surface area for the exchange       infancy than at any other time of post-         and the diaphragm level is determined
            of respiratory gases (4).                     natal life. The metabolic requirements for      by voluntary action. The infant does not
               The adult lung and that of the older       that growth include large amounts of ox-        voluntarily take a deep breath and hold it
            child have communications between             ygen (6). However, as previously men-           for a chest radiograph. The technologist
            the alveoli, the pores of Kohn (intraal-      tioned, the adult lung has a ratio of sur-      must guess and acquire the radiograph
            veolar pores), and the channels of Lam-       face area of the pulmonary capillary bed        when the infant appears to have
            bert (bronchoalveolar channels). These        (gas-exchange area) to body surface area        achieved maximum inspiration. If the in-
            allow collateral air drift between the        that is more than three times as large as       fant diaphragm moves through the en-
            airspaces and are far fewer in infants.       that in the newborn infant (5).                 tire respiratory cycle in only 1.5 seconds,
            Their relative absence influences the             The healthy newborn infant breathes          or even less time when the rate reaches
            appearance of radiographs in infants          40 times per minute. The healthy adult          60 breaths per minute, the technologist
            with lower respiratory infection, as will     breathes 16 times per minute. The high          has little time to make a correct guess.
            be explained later (4).                       demand for oxygen in the healthy infant         The diaphragm sits at a level determined
               The structure of the chest wall in the     plus the relatively small gas-exchange          by the resistance to flow of air through
            infant differs from that in the adult. The    area per unit of body surface area taxes        the airways. Figure 3 depicts lung vol-
            infant’s ribs and adjacent soft tissues are   the respiratory system much more in the         umes and diaphragm movement during
            more elastic and compliant. As the child      infant than in the adult. This is one of        respiration, first in health and then in
            grows, the soft tissues and ribs become       the causes of the relative tachypnea of         disease, when air trapping has led to an
            stiffer (6). Watching a baby breathe          healthy infants. Infants compensate for         increase in residual volume (8).
            makes this obvious. The infant moves his      increased oxygen demand primarily by               Normally, the dome of the right hemi-
            or her chest wall in and out more than        increasing their respiratory rate (4,7).        diaphragm at inspiration is projected at
            the adult does, particularly when in re-         Resistance to the flow of air through         about the level of the sixth anterior rib
            spiratory distress. The more marked com-      the airways is higher in the infant than in     on a chest radiograph. A normal lateral
            pliance of the soft tissues of the infant     the adult. This is both because the com-        chest radiograph will show a domed,
            thorax allows retractions of those tissues    pliance of the tissues surrounding the in-      rounded configuration of the diaphragm.
            between the ribs. The lack of stiffness in    fant airways makes it easier for the air-       Figure 4 shows the typical configuration
            the soft tissues requires more work dur-      ways to narrow during normal expiration         of the diaphragm on anteroposterior and
            ing breathing. When the infant is in re-      and because of the higher percentage of         lateral chest images in a healthy small
            spiratory distress, this increased work be-   small airways in the infant lung (4). The       infant.
            comes more obvious. The sight of a sick       resistance of the flow of air through a
            infant struggling to breathe can be fright-   cylinder, such as an airway, is described
            ening, and the grunting and retractions       by the Poiseuille law. A quick summary          IMMUNOLOGY AND
            graphically demonstrate the increased         of this law is that the resistance to the       PATHOLOGY
            work of breathing. In contrast, adults        flow of air through the airways varies in-
            with pneumonia do not work particu-           versely with airways radius to the fourth       Growing children are exposed to many
            larly hard moving air in and out of their     power (4). Thus, a tiny decrease in the         infectious organisms and need to de-
            lungs unless the pneumonia is extensive.      diameter of the airways leads to a marked       velop immunity to them. The average
               During inspiration, the intrathoracic      increase in resistance to the flow of air. As    adult inhales more than 9000 L of air per
            airways increase in cross-sectional area.     previously mentioned, the contribution          day; the infant, much less (4). A multi-

            Volume 236     Number 1                                                            Chest Radiographs in Infants with Cough and Fever   23
hunger causes retractions and grunting
                                                                                                              as they work to overcome this resis-
                                                                                                              tance.
                                                                                                                 Infants breathing at 60 or more times
                                                                                                              per minute have less time to move the
Radiology



                                                                                                              diaphragm through its inspiratory-expi-
                                                                                                              ratory cycle. They have only 1 second,
                                                                                                              sometimes less, for each breath. The dia-
                                                                                                              phragm tends to move in a narrow range
                                                                                                              because of the resistance to the flow of air
                                                                                                              through their small airways (Fig 3).
                                                                                                                 The dead space in the upper airways
                                                                                                              cannot be reduced and remains constant.
                                                                                                              However, it gets more difficult to propel
                                                                                                              the dead-space air back up and out of the
                        Figure 1. Diagram shows gas exchange that occurs in the respiratory                   mouth because of the increased resis-
                        bronchiole and alveolar sac. In the lung periphery there may be as
                                                                                                              tance in the peripheral airways. As the
                        many as 25 generations of airways before the respiratory bronchiole is
                        reached or as few as 10 (near the hila), depending on where the count                 rising diaphragm pushes the air out of
                        is performed. Inset shows how a distal bronchiole may become nar-                     the lungs, it must almost immediately
                        rowed with edema and mucus during inflammation.                                        contract to start inspiration. The inspira-
                                                                                                              tion starts before the usual volume of air
                                                                                                              has been expelled. Because of the diffi-
            tude of organisms enter the airways             all of these lower respiratory tract infections   culty of pushing all the air out during
            along with this inspired air. The organ-        in the attempt to avoid the confusion in          expiration, the lungs are at a more ex-
            isms that infect the respiratory tract in       terminology.                                      panded state when inspiration starts
            infancy are usually viral. The most severe         Radiologists should be aware that the          again—that is, there is an increase in re-
            diseases in the lower respiratory tract are     nomenclature is confusing. Heated de-             sidual volume, and there is air trapping
            caused by the parainfluenza viruses and          bates may occur between physicians                (Fig 3). The lungs are at a high volume
            the respiratory syncytial virus (9,10).         who use different definitions for these            even at the end of expiration. On a radio-
            These are also among the most common            terms. We suggest that radiologists use           graph, the diaphragm is projected at a
            organisms to infect the infant’s respira-       the terms and definitions generally em-            level lower than the sixth anterior rib (Fig
            tory tract (9 –11). Adults have some im-        ployed by the referring clinicians and            6), and the diaphragm leaves are flat-
            munity to most of these organisms be-           be alert to the problem of confusion.             tened. The radiologist will notice that
            cause they were exposed to them as                 During these respiratory viral infec-          there is an increase in the transverse di-
            children and developed an immunity. Al-         tions, the airways react in several ways,         ameter of the chest and a flattened dia-
            though adults may be infected and trans-        most notably with bronchoconstriction             phragm on an anteroposterior projec-
            mit these viruses to others, they usually       and increased secretion of mucus (12).            tion. On a lateral image, there is flatten-
            become no more than mildly ill. Infants         These two factors have the effect of nar-         ing of the diaphragm, and the sternum
            have not yet developed substantial im-          rowing the cross-sectional area of the            may be bowed upward and outward (Fig
            munity to these viruses and often get sick      airways—particularly the small airways            7). Some radiologists gauge hyperaera-
            because of them, especially the parainflu-       (12th generation airways or smaller) (Fig         tion by counting posterior ribs, particu-
            enza and respiratory syncytial viruses.         5). These airways, which already contrib-         larly if the radiograph is obtained with
               The terminology for lower respiratory        ute 50% of the total airways resistance,          the patient in an apical lordotic position.
            tract infections in infants is confusing.       suddenly have a marked decrease in av-            Those who use posterior ribs in this situ-
            For example the definition of bronchioli-        erage radius. Since resistance is inversely       ation usually believe the diaphragm is
            tis varies with local pediatric usage. Some     proportional to the fourth power of the           located at the level of the eighth poste-
            physicians limit the term bronchiolitis to      radius, this has the effect of greatly in-        rior rib during normal inspiration (8).
            respiratory syncytial virus infection in        creasing the total resistance to air flow             To diagnose air trapping, the dia-
            children. Affected children may have re-        through the airways.                              phragm needs to be flattened on both
            tractions, tachypnea, air hunger, and ex-                                                         anteroposterior and lateral projections. If
            treme respiratory distress. Other children                                                        the lung volume is high on one radio-
            of a similar age may have the same clin-        RADIOLOGIC FINDINGS                               graph and normal on the other, then the
            ical findings, but respiratory syncytial vi-                                                       high-volume projection happened to be
            rus cannot be cultured; some pediatri-          As was mentioned earlier, the primary             exposed at a moment of an unusually
            cians also call this bronchiolitis. Other       way for the infant to increase ventila-           deep breath. If the diaphragm is well
            physicians may call all these clinical find-     tion is to increase his or her respiratory        domed on the other view, then the infant
            ings pneumonia, but still others are un-        rate. Infants in respiratory distress due         is able to move air out of his or her lungs
            comfortable with that term because, to          to viral infection often breathe 60 – 80          during expiration and there is no air trap-
            them, pneumonia means airspace con-             times per minute. Their air hunger can            ping.
            solidation on a chest radiograph. Some-         be recognized by the use of the acces-               To summarize, these sick infants
            times the term peribronchial pneumonia or       sory respiratory muscles. The increased           breathe faster and work harder to
            interstitial pneumonia is used to differen-     work of breathing is largely caused by            breathe, their airways narrow during ex-
            tiate this airways infection from airspace      the increased resistance to the flow of            piration, and the greatly increased air-
            pneumonia. Some individuals simply call         air through the small airways. Their air          ways resistance severely impedes the flow

            24   Radiology   July 2005                                                                                                      Bramson et al
Radiology




                      Figure 2. (a) Diagram shows that during normal inspiration and expiration, there is dilation and collapse of the airways.
                      This is most obvious in distal airways. Collapse in infant airways is greater than that in adult airways because cartilaginous
                      soft tissues supporting the airways are more compliant in children. This is illustrated on (b) a lateral chest radiograph of an
                      infant obtained near the end of normal expiration. The trachea (arrows) collapses to a much smaller diameter during normal
                      expiration.



            of air. The air trapping revealed by the
            increase in lung volume on the chest ra-
            diograph is the best available indicator of
            inflammatory lung disease in infancy.
            Hyperinflation may be the only radio-
            logic clue to illness in these children. The
            alveoli are usually clear, and there is
            none of the airspace consolidation asso-
            ciated with classic bacterial pneumonia
            in adults.
               The radiologist should not become
            wedded to the relationship of the dia-
            phragm to the sixth anterior rib, but this
            finding does serve as a useful rule of
            thumb. An experienced pediatric radiol-
            ogist quickly recognizes hyperaeration at                      Figure 3. Graph depicts lung volumes at inspiration and expiration.
            a glance without counting ribs. A less                         Line on the left shows lung volume at expiration (A) and inspiration
            experienced observer will find the sixth                        (B), as well as maximum expiration (C) and inspiration (D) during
            anterior rib to be a helpful landmark.                         normal quiet respiratory cycles. The line on the right shows that
                                                                           when peripheral small-airways resistance is high (a, b), then residual
               There are often additional signs of in-                     volume (RV) is increased. This is the air trapping depicted on radio-
            flammatory disease of the small airways.                        graphs of infants with small-airways disease. c     Maximum expira-
            Edema and mucus in these airways can                           tion, d    maximum inspiration, ERV        expiratory reserve volume,
            cause peripheral atelectasis. Small plugs                      IRV     inspiratory reserve volume, TLC     total lung capacity, TV
            in many small airways produce many                             tidal volume, VC vital capacity. (Reprinted, with permission, from
            small patches of atelectasis. If enough of                     reference 7.)
            these small patches accumulate in one
            region, a patch of atelectasis shows up on
            a chest radiograph (Fig 8). The abnormal         cept that the interstitial lung tissues look       bronchial cuffing or peribronchial thickening
            appearance is often difficult to define, ex-       prominent. Some observers call this peri-          or bronchial wall thickening. Sometimes

            Volume 236    Number 1                                                                  Chest Radiographs in Infants with Cough and Fever    25
Radiology




                      Figure 4. (a) Anteroposterior radiograph of normal chest in a 4-month-old child referred because of a possible fractured
                      clavicle. (b) Lateral radiograph in the same infant shows rounded configuration of the diaphragm (arrows).



                                                                                                              As the infant improves, interesting
                                                                                                           things happen. The diaphragm returns to
                                                                                                           a more normal level, but the radiograph
                                                                                                           may show increasing patches of atelecta-
                                                                                                           sis. This can confuse pediatricians and
                                                                                                           radiologists alike. Perhaps as the hyper-
                                                                                                           expansion of the lung decreases, some
                                                                                                           alveoli kept open by the air trapping now
                                                                                                           succumb and collapse, leading to an ap-
                                                                                                           pearance of increased atelectasis. In real-
                                                                                                           ity, the child is improving even though
                                                                                                           the radiograph may look mildly worse.


                                                                                                           CAVEATS

                                                                                                           The changes we have described are the
                                                                                                           most common ones in lower-airways in-
                                                                                                           flammatory disease in infancy. Most re-
                                                                                                           spiratory infections in this age group are
                                                                                                           caused by viruses and lead to the patho-
                                                                                                           physiologic changes described. Yet, just
                        Figure 5. Diagram shows that during viral infection, airways secrete               like adults, infants can also get bacterial
                        increased amounts of mucus and become edematous, particularly in                   infections. In those cases, the radio-
                        smaller peripheral airways. This narrows the airways, and that nar-
                                                                                                           graphic appearance mimics that seen on
                        rowing is accentuated during attempts at expiration.
                                                                                                           a chest radiograph in an adult with bac-
                                                                                                           terial pneumonia. Air bronchograms,
                                                                                                           consolidation, and some volume loss in
            the radiologist looks at the airways end       change than does thickening of the air-         the consolidated segment usually do not
            on. If the radiologist thinks the walls        ways that are identifiable on a radio-           confuse radiology residents and general
            of these airways (usually of the third,        graph. The patches of peripheral atelecta-      radiologists, even when seen in infants.
            fourth, or fifth generation) look thicker,      sis may shift when the infant coughs and        Pneumonia looks the same in adults,
            he or she will use the term peribronchial      dislodges small mucus plugs. Therefore,         and, when bacterial, it can look that way
            thickening or bronchial wall thickening. In    the radiographic appearance may change          in infants too. Infants with bacterial
            reality, thickening of the smaller air-        from image to image. Hyperinflation, how-        pneumonia can have pleural effusions
            ways (12th generation or higher) has a         ever, remains the major clue to inflamma-        and adenopathy. Children are not im-
            far more deleterious effect on gas ex-         tory small-airways disease (12).                mune to the types of pulmonary infec-


            26   Radiology   July 2005                                                                                                    Bramson et al
Radiology




                     Figure 6. (a) Anteroposterior radiograph shows hyperinflated lungs with suggestion that peribronchial markings are too
                     prominent. (b) Lateral radiograph shows flat slope to the diaphragm, with none of the rounded configuration seen in Figure
                     4b. The diaphragm now has a straight-line slope rather than a rounded configuration.




                     Figure 7. (a) Anteroposterior radiograph of infant chest shows hyperinflated appearance characteristic of infant inflamma-
                     tory airways disease. Hemidiaphragm domes are projected at level of the seventh anterior rib or lower. (b) Lateral radiograph
                     of hyperinflated chest shows diaphragm has a straight (not domed) slope.



            tions that older children and adults con-       sometimes produce an unusual and dis-             are fewer pores of Kohn and channels of
            tract. Nevertheless, viruses are the most       concerting appearance because of the an-          Lambert. Therefore, exudate that accu-
            common cause of respiratory infections          atomic features mentioned earlier. The            mulates in the alveoli does not spread to
            in infants (10).                                infant does not have a well-developed             adjacent alveoli as easily as in the adult.
               Bacterial pneumonia in infancy can           system of collateral ventilation—there            The limits of the inflammatory process


            Volume 236   Number 1                                                                 Chest Radiographs in Infants with Cough and Fever   27
Radiology




                      Figure 8. Respiratory syncytial virus infection in a child. (a) Anteroposterior radiograph shows prominent peribronchial
                      markings. (b) Patches of atelectasis (arrow) are best seen on lateral projection of the hyperinflated lungs. Scattered patches of
                      atelectasis tend to follow peribronchial and perivascular structures in a child with respiratory syncytial virus infection.



                                                                                                                 cause a round pneumonia can look like a
                                                                                                                 neoplasm (13). Several children have
                                                                                                                 been referred to us with the suspicion of
                                                                                                                 a primary or metastatic neoplasm, but
                                                                                                                 they really had pneumonia with an un-
                                                                                                                 usual spherical appearance (Fig 9).
                                                                                                                    Other disease processes can produce air
                                                                                                                 trapping and hyperaeration of the lungs.
                                                                                                                 Increased fluid in the interstitial spaces
                                                                                                                 can compress the small airways and cause
                                                                                                                 an increase in small-airways resistance.
                                                                                                                 Enlarged heart chambers and pulmonary
                                                                                                                 vessels can also compress airways. There-
                                                                                                                 fore, severe cardiac disease and increased
                                                                                                                 fluid load can lead to radiographs that
                                                                                                                 show air trapping. Older infants can and
                                                                                                                 do aspirate foreign bodies into their air-
                                                                                                                 ways; this may cause focal air trapping
                                                                                                                 or atelectasis. Reactive airways disease,
                                                                                                                 which does occur in infants, can cause air
                                                                                                                 trapping at any age. Certain chronic lung
                                                                                                                 diseases such as cystic fibrosis and bron-
                             Figure 9. Anteroposterior chest radiograph displays round                           chopulmonary dysplasia demonstrate
                             pneumonia (arrow). Child had a fever of 104°F (40°C), abdom-                        air trapping on radiographs. Tachypnea
                             inal pain, and a cough.                                                             from a variety of other causes, such as
                                                                                                                 acidosis, fever, and sometimes even fear,
                                                                                                                 will produce the appearance of air trap-
            are difficult to define in adults unless            takes the appearance of a spherical con-           ping secondary to the mechanism of
            they border on a pleural surface. In in-          solidation—a “round pneumonia”. The                rapid breathing (4).
            fants and younger children, however, the          inflammatory cells are confined under a                 Nevertheless, most infants who acutely
            exudate tends to be trapped in the alve-          mild degree of pressure, and these infants         develop respiratory distress have a viral
            oli, unable to spread through the pores of        often have a high fever; 104°F or 105°F            illness. The appearance of the radiograph
            Kohn. Sometimes, because of the lack of           (40°C or 41°C) is typical. The radio-              reflects the pathologic process occurring
            collateral air drift openings, the exudate        graphic appearance can be alarming be-             in the respiratory system. An understand-


            28   Radiology   July 2005                                                                                                            Bramson et al
ing of the appearance of the infant chest         4. O’Brodovich H, Haddad G. Functional ba-          9. Denny F. Acute lower respiratory tract in-
            radiograph requires an understanding of              sis of respiratory pathology and disease. In:       fection: general considerations. In: Tauss-
                                                                 Chernick V, Boat T, eds. Kendig’s disorders         ing L, Landau L, eds. Pediatric respiratory
            the underlying pathologic process. Hyper-            of the respiratory tract in children. 6th ed.       medicine. St Louis, Mo: Mosby, 1999.
            aeration of the lungs is often the earliest,         Philadelphia, Pa: Saunders, 1998; 27–73.        10. Dubois D, Ray C. Viral infections of the
            and sometimes the only, radiographic              5. Dunnill MS. Postnatal growth of the lung.           lower respiratory tract. In: Taussing L,
            sign that the infant has a viral infection           Thorax 1962; 17:329 –333.                           Landau L, eds. Pediatric respiratory medi-
Radiology



                                                              6. Mortola J. Comparative aspects of neona-            cine. St Louis, Mo: Mosby, 1999.
            involving the lower airways.                         tal respiratory mechanisms. In: Haddad G,       11. Gern J. Virus-induced inflammation in air-
                                                                 Abman S, Chernick V, eds. Chernick-Mel-             ways. In: Haddad G, Abman S, Chernick V,
                                                                 lin: basic mechanisms of pediatric respira-         eds. Chernick-Mellins: basic mechanisms
            References                                           tory disease. 2nd ed. Hamilton, Ontario,            of pediatric respiratory disease. 2nd ed.
             1. Coblentz C, Babcook C, Alton D, Riley B,         Canada: Decker, 2002; 171–178.                      Hamilton, Ontario, Canada: Decker, 2002;
                Norman G. Observer variation in detecting     7. Lawson E. Respiratory control after birth.          518 –527.
                the radiologic features associated with          In: Chernick V, Mellin R, eds. Basic mech-      12. Swischuk LE, Hayden CK Jr. Viral vs. bac-
                bronchiolitis. Invest Radiol 1991; 26:115–       anisms of pediatric respiratory disease: cel-       terial pneumonia infection in children (is
                118.                                             lular and integrative. Philadelphia, Pa:            roentgenographic differentiation possi-
             2. Reid L. Lung growth in health and disease.       Decker, 1991; 288 –302.                             ble?). Pediatr Radiol 1986; 16:278 –284.
                Br J Dis Chest 1984; 78:113–134.              8. Griscom NT, Wohl M, Kirkpatrick J. Lower        13. Rose R, Ward B. Spherical pneumonias in
             3. Hislop A, Reid L. Lung development in rela-      respiratory infections: how infants differ          children simulating pulmonary and medi-
                tion to gas exchange capacity. Bull Physio-      from adults. Radiol Clin North Am 1978;             astinal masses. Radiology 1973; 106:179 –
                pathol Respir (Nancy) 1973; 9:1317–1343.         16:367–387.                                         182.




            Volume 236     Number 1                                                                  Chest Radiographs in Infants with Cough and Fever       29

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Cough and fever

  • 1. Review for Residents Radiology Robert T. Bramson, MD Interpretation of Chest N. Thorne Griscom, MD Robert H. Cleveland, MD Radiographs in Infants with Published online before print 10.1148/radiol.2361041278 Radiology 2005; 236:22–29 Cough and Fever1 1 From the Department of Radiol- An understanding of the appearance of the infant chest radiograph requires an ogy, Children’s Hospital, Boston, understanding of the anatomy and the physiologic, immunologic, and pathologic 300 Longwood Ave, Boston, MA 02115. Received July 22, 2004; revi- processes in the infant’s chest. The authors describe the features of the infant chest sion requested September 22; revi- that most influence the appearance of the chest radiograph in infants with cough sion received November 10; accepted and fever. They discuss why confusion sometimes occurs when radiology residents December 10. Address correspon- dence to R.T.B. (e-mail: robert.bramson and general radiologists familiar with adult chest radiographs first evaluate the @childrens.harvard.edu). infant chest radiograph. The radiographic appearance of acute inflammation does © RSNA, 2005 not look the same in infants as it does in older children and adults. The hallmark of inflammatory lung disease in the infant chest is air trapping on the chest radiograph. © RSNA, 2005 EDITOR’S NOTE: Please see the January 2005 From the Editor, where this new feature, Review for Residents, was announced. Radiology residents have often expressed to us their frustration and confusion when attempting to interpret chest radiographs of infants. Radiologists not trained in pediatric radiology find terms like air trapping, peribronchial thickening, bronchiolitis, lower re- spiratory tract infection, and peribronchial pneumonia confusing (1). Pediatric radiolo- gists have, in fact, conflicting definitions of these terms and varying opinions about their meaning. The authors hope to clarify the relationship between the pathologic changes within the infant chest and their radiographic appearance, explaining in pathophysiologic terms why the infant chest looks the way it does in inflammatory airways diseases. An understanding of the infant chest radiograph requires a review of how embryology, anatomy, physiology, pathology, immunology, and the physics of fluid mechanics influence its appearance. This knowledge is critical in the interpretation of the infant chest radiograph. EMBRYOLOGY AND ANATOMY We will summarize the science that explains the appearance of the infant chest, with the caveat that universal agreement on the details does not exist. All of the generations of the airways have developed by the time the fetus reaches the 16th week of gestational age. There are about 22 generations of airways, depending on how the last generation is counted and where the count is performed. Near the lung hila, there may be as few as 10 generations of airways before the gas-exchange units—the respiratory bronchioles and alveolar sacs—are reached. In the lung periphery, there may be as many as 25 generations of airways before the gas-exchange units are reached. As the child grows and becomes an adult, the airways grow in length and diameter but not in number (2– 4) (Fig 1). The alveoli, the gas-exchange units, develop after the airways. They start proliferating about the 29th week of gestational age. By the 40th week of gestation, there are approx- imately 20 million alveoli in the newborn lung, although the precise number is debated. The mature lung contains approximately 300 million alveoli; that number is reached at about 8 years of age (2). The alveoli then increase in size, and their lining gets progressively thinner as the child becomes an adult. The total alveolar surface area is 70 – 80 m2 in the adult. In the newborn infant, the total alveolar surface area is only about 3 m2. The ratio of the alveolar surface area to the body surface area is more than three times as great in the adult as in the newborn (5). Thus, the infant is at a distinct disadvantage, compared with 22
  • 2. During expiration, the airways narrow of the peripheral airways to the resistance ESSENTIALS and the cross-sectional area decreases. of flow is considerably greater in infants This normal variation in luminal size is than in adults, even in normal circum- ● Most respiratory infections are caused accentuated in the infant because the stances (4). by viruses in infants and children support tissues around the airways are When breathing at 16 times per Radiology younger than 24 months and lead to more compliant and allow more narrow- minute, the adult has 3.75 seconds to the pathophysiologic changes of air ing during expiration. Compared with an move his or her diaphragm through the trapping. adult, the number of alveoli is relatively full course of inspiration and expiration. low in the infant, and the proportion of When breathing at 40 times per minute, ● Hyperinflation may be the only radio- the lung involved in air transport (the the infant has only 1.5 seconds for this logic clue to illness. airways) is relatively high. In the adult, diaphragm movement. The infant in- ● Bacterial pneumonia can have the 80% of the airways are bigger than 2 mm creases oxygen exchange primarily by in- same appearance in adults and in- in diameter. The smaller peripheral air- creasing the respiratory rate. When this fants. ways in adults account for less than 20% happens, the diaphragm must change di- ● The radiographic appearance reflects of the total resistance to the flow of air. In rection more frequently and either move the infant lung, the peripheral airways faster or not move as far during each the pathologic process occurring in the are considerably smaller, and the resis- excursion. During periods of respiratory respiratory system. tance to air flow owing to these small distress, these all occur. airways is 50% of the total resistance (4) The level of the diaphragm seen on (Fig 2). chest radiographs is determined by sev- eral things. At all ages, the level of the the adult and older child, in his or her diaphragm depends on how deep an in- reserve of alveolar surface area for gas PHYSIOLOGY spiration the patient has made when the exchange. The alveolar walls contain the radiograph was obtained. The adult usu- pulmonary capillaries, which form a gi- Growth is proportionately more rapid in ally takes a deep breath when requested, ant blood surface area for the exchange infancy than at any other time of post- and the diaphragm level is determined of respiratory gases (4). natal life. The metabolic requirements for by voluntary action. The infant does not The adult lung and that of the older that growth include large amounts of ox- voluntarily take a deep breath and hold it child have communications between ygen (6). However, as previously men- for a chest radiograph. The technologist the alveoli, the pores of Kohn (intraal- tioned, the adult lung has a ratio of sur- must guess and acquire the radiograph veolar pores), and the channels of Lam- face area of the pulmonary capillary bed when the infant appears to have bert (bronchoalveolar channels). These (gas-exchange area) to body surface area achieved maximum inspiration. If the in- allow collateral air drift between the that is more than three times as large as fant diaphragm moves through the en- airspaces and are far fewer in infants. that in the newborn infant (5). tire respiratory cycle in only 1.5 seconds, Their relative absence influences the The healthy newborn infant breathes or even less time when the rate reaches appearance of radiographs in infants 40 times per minute. The healthy adult 60 breaths per minute, the technologist with lower respiratory infection, as will breathes 16 times per minute. The high has little time to make a correct guess. be explained later (4). demand for oxygen in the healthy infant The diaphragm sits at a level determined The structure of the chest wall in the plus the relatively small gas-exchange by the resistance to flow of air through infant differs from that in the adult. The area per unit of body surface area taxes the airways. Figure 3 depicts lung vol- infant’s ribs and adjacent soft tissues are the respiratory system much more in the umes and diaphragm movement during more elastic and compliant. As the child infant than in the adult. This is one of respiration, first in health and then in grows, the soft tissues and ribs become the causes of the relative tachypnea of disease, when air trapping has led to an stiffer (6). Watching a baby breathe healthy infants. Infants compensate for increase in residual volume (8). makes this obvious. The infant moves his increased oxygen demand primarily by Normally, the dome of the right hemi- or her chest wall in and out more than increasing their respiratory rate (4,7). diaphragm at inspiration is projected at the adult does, particularly when in re- Resistance to the flow of air through about the level of the sixth anterior rib spiratory distress. The more marked com- the airways is higher in the infant than in on a chest radiograph. A normal lateral pliance of the soft tissues of the infant the adult. This is both because the com- chest radiograph will show a domed, thorax allows retractions of those tissues pliance of the tissues surrounding the in- rounded configuration of the diaphragm. between the ribs. The lack of stiffness in fant airways makes it easier for the air- Figure 4 shows the typical configuration the soft tissues requires more work dur- ways to narrow during normal expiration of the diaphragm on anteroposterior and ing breathing. When the infant is in re- and because of the higher percentage of lateral chest images in a healthy small spiratory distress, this increased work be- small airways in the infant lung (4). The infant. comes more obvious. The sight of a sick resistance of the flow of air through a infant struggling to breathe can be fright- cylinder, such as an airway, is described ening, and the grunting and retractions by the Poiseuille law. A quick summary IMMUNOLOGY AND graphically demonstrate the increased of this law is that the resistance to the PATHOLOGY work of breathing. In contrast, adults flow of air through the airways varies in- with pneumonia do not work particu- versely with airways radius to the fourth Growing children are exposed to many larly hard moving air in and out of their power (4). Thus, a tiny decrease in the infectious organisms and need to de- lungs unless the pneumonia is extensive. diameter of the airways leads to a marked velop immunity to them. The average During inspiration, the intrathoracic increase in resistance to the flow of air. As adult inhales more than 9000 L of air per airways increase in cross-sectional area. previously mentioned, the contribution day; the infant, much less (4). A multi- Volume 236 Number 1 Chest Radiographs in Infants with Cough and Fever 23
  • 3. hunger causes retractions and grunting as they work to overcome this resis- tance. Infants breathing at 60 or more times per minute have less time to move the Radiology diaphragm through its inspiratory-expi- ratory cycle. They have only 1 second, sometimes less, for each breath. The dia- phragm tends to move in a narrow range because of the resistance to the flow of air through their small airways (Fig 3). The dead space in the upper airways cannot be reduced and remains constant. However, it gets more difficult to propel the dead-space air back up and out of the Figure 1. Diagram shows gas exchange that occurs in the respiratory mouth because of the increased resis- bronchiole and alveolar sac. In the lung periphery there may be as tance in the peripheral airways. As the many as 25 generations of airways before the respiratory bronchiole is reached or as few as 10 (near the hila), depending on where the count rising diaphragm pushes the air out of is performed. Inset shows how a distal bronchiole may become nar- the lungs, it must almost immediately rowed with edema and mucus during inflammation. contract to start inspiration. The inspira- tion starts before the usual volume of air has been expelled. Because of the diffi- tude of organisms enter the airways all of these lower respiratory tract infections culty of pushing all the air out during along with this inspired air. The organ- in the attempt to avoid the confusion in expiration, the lungs are at a more ex- isms that infect the respiratory tract in terminology. panded state when inspiration starts infancy are usually viral. The most severe Radiologists should be aware that the again—that is, there is an increase in re- diseases in the lower respiratory tract are nomenclature is confusing. Heated de- sidual volume, and there is air trapping caused by the parainfluenza viruses and bates may occur between physicians (Fig 3). The lungs are at a high volume the respiratory syncytial virus (9,10). who use different definitions for these even at the end of expiration. On a radio- These are also among the most common terms. We suggest that radiologists use graph, the diaphragm is projected at a organisms to infect the infant’s respira- the terms and definitions generally em- level lower than the sixth anterior rib (Fig tory tract (9 –11). Adults have some im- ployed by the referring clinicians and 6), and the diaphragm leaves are flat- munity to most of these organisms be- be alert to the problem of confusion. tened. The radiologist will notice that cause they were exposed to them as During these respiratory viral infec- there is an increase in the transverse di- children and developed an immunity. Al- tions, the airways react in several ways, ameter of the chest and a flattened dia- though adults may be infected and trans- most notably with bronchoconstriction phragm on an anteroposterior projec- mit these viruses to others, they usually and increased secretion of mucus (12). tion. On a lateral image, there is flatten- become no more than mildly ill. Infants These two factors have the effect of nar- ing of the diaphragm, and the sternum have not yet developed substantial im- rowing the cross-sectional area of the may be bowed upward and outward (Fig munity to these viruses and often get sick airways—particularly the small airways 7). Some radiologists gauge hyperaera- because of them, especially the parainflu- (12th generation airways or smaller) (Fig tion by counting posterior ribs, particu- enza and respiratory syncytial viruses. 5). These airways, which already contrib- larly if the radiograph is obtained with The terminology for lower respiratory ute 50% of the total airways resistance, the patient in an apical lordotic position. tract infections in infants is confusing. suddenly have a marked decrease in av- Those who use posterior ribs in this situ- For example the definition of bronchioli- erage radius. Since resistance is inversely ation usually believe the diaphragm is tis varies with local pediatric usage. Some proportional to the fourth power of the located at the level of the eighth poste- physicians limit the term bronchiolitis to radius, this has the effect of greatly in- rior rib during normal inspiration (8). respiratory syncytial virus infection in creasing the total resistance to air flow To diagnose air trapping, the dia- children. Affected children may have re- through the airways. phragm needs to be flattened on both tractions, tachypnea, air hunger, and ex- anteroposterior and lateral projections. If treme respiratory distress. Other children the lung volume is high on one radio- of a similar age may have the same clin- RADIOLOGIC FINDINGS graph and normal on the other, then the ical findings, but respiratory syncytial vi- high-volume projection happened to be rus cannot be cultured; some pediatri- As was mentioned earlier, the primary exposed at a moment of an unusually cians also call this bronchiolitis. Other way for the infant to increase ventila- deep breath. If the diaphragm is well physicians may call all these clinical find- tion is to increase his or her respiratory domed on the other view, then the infant ings pneumonia, but still others are un- rate. Infants in respiratory distress due is able to move air out of his or her lungs comfortable with that term because, to to viral infection often breathe 60 – 80 during expiration and there is no air trap- them, pneumonia means airspace con- times per minute. Their air hunger can ping. solidation on a chest radiograph. Some- be recognized by the use of the acces- To summarize, these sick infants times the term peribronchial pneumonia or sory respiratory muscles. The increased breathe faster and work harder to interstitial pneumonia is used to differen- work of breathing is largely caused by breathe, their airways narrow during ex- tiate this airways infection from airspace the increased resistance to the flow of piration, and the greatly increased air- pneumonia. Some individuals simply call air through the small airways. Their air ways resistance severely impedes the flow 24 Radiology July 2005 Bramson et al
  • 4. Radiology Figure 2. (a) Diagram shows that during normal inspiration and expiration, there is dilation and collapse of the airways. This is most obvious in distal airways. Collapse in infant airways is greater than that in adult airways because cartilaginous soft tissues supporting the airways are more compliant in children. This is illustrated on (b) a lateral chest radiograph of an infant obtained near the end of normal expiration. The trachea (arrows) collapses to a much smaller diameter during normal expiration. of air. The air trapping revealed by the increase in lung volume on the chest ra- diograph is the best available indicator of inflammatory lung disease in infancy. Hyperinflation may be the only radio- logic clue to illness in these children. The alveoli are usually clear, and there is none of the airspace consolidation asso- ciated with classic bacterial pneumonia in adults. The radiologist should not become wedded to the relationship of the dia- phragm to the sixth anterior rib, but this finding does serve as a useful rule of thumb. An experienced pediatric radiol- ogist quickly recognizes hyperaeration at Figure 3. Graph depicts lung volumes at inspiration and expiration. a glance without counting ribs. A less Line on the left shows lung volume at expiration (A) and inspiration experienced observer will find the sixth (B), as well as maximum expiration (C) and inspiration (D) during anterior rib to be a helpful landmark. normal quiet respiratory cycles. The line on the right shows that when peripheral small-airways resistance is high (a, b), then residual There are often additional signs of in- volume (RV) is increased. This is the air trapping depicted on radio- flammatory disease of the small airways. graphs of infants with small-airways disease. c Maximum expira- Edema and mucus in these airways can tion, d maximum inspiration, ERV expiratory reserve volume, cause peripheral atelectasis. Small plugs IRV inspiratory reserve volume, TLC total lung capacity, TV in many small airways produce many tidal volume, VC vital capacity. (Reprinted, with permission, from small patches of atelectasis. If enough of reference 7.) these small patches accumulate in one region, a patch of atelectasis shows up on a chest radiograph (Fig 8). The abnormal cept that the interstitial lung tissues look bronchial cuffing or peribronchial thickening appearance is often difficult to define, ex- prominent. Some observers call this peri- or bronchial wall thickening. Sometimes Volume 236 Number 1 Chest Radiographs in Infants with Cough and Fever 25
  • 5. Radiology Figure 4. (a) Anteroposterior radiograph of normal chest in a 4-month-old child referred because of a possible fractured clavicle. (b) Lateral radiograph in the same infant shows rounded configuration of the diaphragm (arrows). As the infant improves, interesting things happen. The diaphragm returns to a more normal level, but the radiograph may show increasing patches of atelecta- sis. This can confuse pediatricians and radiologists alike. Perhaps as the hyper- expansion of the lung decreases, some alveoli kept open by the air trapping now succumb and collapse, leading to an ap- pearance of increased atelectasis. In real- ity, the child is improving even though the radiograph may look mildly worse. CAVEATS The changes we have described are the most common ones in lower-airways in- flammatory disease in infancy. Most re- spiratory infections in this age group are caused by viruses and lead to the patho- physiologic changes described. Yet, just Figure 5. Diagram shows that during viral infection, airways secrete like adults, infants can also get bacterial increased amounts of mucus and become edematous, particularly in infections. In those cases, the radio- smaller peripheral airways. This narrows the airways, and that nar- graphic appearance mimics that seen on rowing is accentuated during attempts at expiration. a chest radiograph in an adult with bac- terial pneumonia. Air bronchograms, consolidation, and some volume loss in the radiologist looks at the airways end change than does thickening of the air- the consolidated segment usually do not on. If the radiologist thinks the walls ways that are identifiable on a radio- confuse radiology residents and general of these airways (usually of the third, graph. The patches of peripheral atelecta- radiologists, even when seen in infants. fourth, or fifth generation) look thicker, sis may shift when the infant coughs and Pneumonia looks the same in adults, he or she will use the term peribronchial dislodges small mucus plugs. Therefore, and, when bacterial, it can look that way thickening or bronchial wall thickening. In the radiographic appearance may change in infants too. Infants with bacterial reality, thickening of the smaller air- from image to image. Hyperinflation, how- pneumonia can have pleural effusions ways (12th generation or higher) has a ever, remains the major clue to inflamma- and adenopathy. Children are not im- far more deleterious effect on gas ex- tory small-airways disease (12). mune to the types of pulmonary infec- 26 Radiology July 2005 Bramson et al
  • 6. Radiology Figure 6. (a) Anteroposterior radiograph shows hyperinflated lungs with suggestion that peribronchial markings are too prominent. (b) Lateral radiograph shows flat slope to the diaphragm, with none of the rounded configuration seen in Figure 4b. The diaphragm now has a straight-line slope rather than a rounded configuration. Figure 7. (a) Anteroposterior radiograph of infant chest shows hyperinflated appearance characteristic of infant inflamma- tory airways disease. Hemidiaphragm domes are projected at level of the seventh anterior rib or lower. (b) Lateral radiograph of hyperinflated chest shows diaphragm has a straight (not domed) slope. tions that older children and adults con- sometimes produce an unusual and dis- are fewer pores of Kohn and channels of tract. Nevertheless, viruses are the most concerting appearance because of the an- Lambert. Therefore, exudate that accu- common cause of respiratory infections atomic features mentioned earlier. The mulates in the alveoli does not spread to in infants (10). infant does not have a well-developed adjacent alveoli as easily as in the adult. Bacterial pneumonia in infancy can system of collateral ventilation—there The limits of the inflammatory process Volume 236 Number 1 Chest Radiographs in Infants with Cough and Fever 27
  • 7. Radiology Figure 8. Respiratory syncytial virus infection in a child. (a) Anteroposterior radiograph shows prominent peribronchial markings. (b) Patches of atelectasis (arrow) are best seen on lateral projection of the hyperinflated lungs. Scattered patches of atelectasis tend to follow peribronchial and perivascular structures in a child with respiratory syncytial virus infection. cause a round pneumonia can look like a neoplasm (13). Several children have been referred to us with the suspicion of a primary or metastatic neoplasm, but they really had pneumonia with an un- usual spherical appearance (Fig 9). Other disease processes can produce air trapping and hyperaeration of the lungs. Increased fluid in the interstitial spaces can compress the small airways and cause an increase in small-airways resistance. Enlarged heart chambers and pulmonary vessels can also compress airways. There- fore, severe cardiac disease and increased fluid load can lead to radiographs that show air trapping. Older infants can and do aspirate foreign bodies into their air- ways; this may cause focal air trapping or atelectasis. Reactive airways disease, which does occur in infants, can cause air trapping at any age. Certain chronic lung diseases such as cystic fibrosis and bron- Figure 9. Anteroposterior chest radiograph displays round chopulmonary dysplasia demonstrate pneumonia (arrow). Child had a fever of 104°F (40°C), abdom- air trapping on radiographs. Tachypnea inal pain, and a cough. from a variety of other causes, such as acidosis, fever, and sometimes even fear, will produce the appearance of air trap- are difficult to define in adults unless takes the appearance of a spherical con- ping secondary to the mechanism of they border on a pleural surface. In in- solidation—a “round pneumonia”. The rapid breathing (4). fants and younger children, however, the inflammatory cells are confined under a Nevertheless, most infants who acutely exudate tends to be trapped in the alve- mild degree of pressure, and these infants develop respiratory distress have a viral oli, unable to spread through the pores of often have a high fever; 104°F or 105°F illness. The appearance of the radiograph Kohn. Sometimes, because of the lack of (40°C or 41°C) is typical. The radio- reflects the pathologic process occurring collateral air drift openings, the exudate graphic appearance can be alarming be- in the respiratory system. An understand- 28 Radiology July 2005 Bramson et al
  • 8. ing of the appearance of the infant chest 4. O’Brodovich H, Haddad G. Functional ba- 9. Denny F. Acute lower respiratory tract in- radiograph requires an understanding of sis of respiratory pathology and disease. In: fection: general considerations. In: Tauss- Chernick V, Boat T, eds. Kendig’s disorders ing L, Landau L, eds. Pediatric respiratory the underlying pathologic process. Hyper- of the respiratory tract in children. 6th ed. medicine. St Louis, Mo: Mosby, 1999. aeration of the lungs is often the earliest, Philadelphia, Pa: Saunders, 1998; 27–73. 10. Dubois D, Ray C. Viral infections of the and sometimes the only, radiographic 5. Dunnill MS. Postnatal growth of the lung. lower respiratory tract. In: Taussing L, sign that the infant has a viral infection Thorax 1962; 17:329 –333. Landau L, eds. Pediatric respiratory medi- Radiology 6. Mortola J. Comparative aspects of neona- cine. St Louis, Mo: Mosby, 1999. involving the lower airways. tal respiratory mechanisms. In: Haddad G, 11. Gern J. Virus-induced inflammation in air- Abman S, Chernick V, eds. Chernick-Mel- ways. In: Haddad G, Abman S, Chernick V, lin: basic mechanisms of pediatric respira- eds. Chernick-Mellins: basic mechanisms References tory disease. 2nd ed. Hamilton, Ontario, of pediatric respiratory disease. 2nd ed. 1. Coblentz C, Babcook C, Alton D, Riley B, Canada: Decker, 2002; 171–178. Hamilton, Ontario, Canada: Decker, 2002; Norman G. Observer variation in detecting 7. Lawson E. Respiratory control after birth. 518 –527. the radiologic features associated with In: Chernick V, Mellin R, eds. Basic mech- 12. Swischuk LE, Hayden CK Jr. Viral vs. bac- bronchiolitis. Invest Radiol 1991; 26:115– anisms of pediatric respiratory disease: cel- terial pneumonia infection in children (is 118. lular and integrative. Philadelphia, Pa: roentgenographic differentiation possi- 2. Reid L. Lung growth in health and disease. Decker, 1991; 288 –302. ble?). Pediatr Radiol 1986; 16:278 –284. Br J Dis Chest 1984; 78:113–134. 8. Griscom NT, Wohl M, Kirkpatrick J. Lower 13. Rose R, Ward B. Spherical pneumonias in 3. Hislop A, Reid L. Lung development in rela- respiratory infections: how infants differ children simulating pulmonary and medi- tion to gas exchange capacity. Bull Physio- from adults. Radiol Clin North Am 1978; astinal masses. Radiology 1973; 106:179 – pathol Respir (Nancy) 1973; 9:1317–1343. 16:367–387. 182. Volume 236 Number 1 Chest Radiographs in Infants with Cough and Fever 29