WestJB_Restrictivediseases_

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COMMONWEALTH OF AUSTRALIA

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c.

S) ~ e n r u [ t ~ y e I J ) D s e ~ e SDiseases of the LungParenchymaStructure o the Alveolar Wall

Cell TypesType I Epithelial CellType 2 Epithelial CellAlveolar MacrophageFibroblast

InterstitiumDiffuse Interstitial Pulmonary Fibrosis

PathologypqthogenesisClinical Features. Pulmonary Function

Veiltilatory Gapacity and,Mf!fhanics,t

Clinical FeaturesPulmonary Function

Hypersensitivity PneumonitisPathologyClinical FeaturesPulmonary Function

Interstitial Disease Caused y Drugs,Poisons, and RadiationCollagen DiseasesLymphangitis Carcinomatosa

i s e a ~ e s of the leuraPneumothorax

Spontaneous PneumothoraxTension Pneumothqraxeneumothorax Complicating Lung

8

q a s E X t ; h a n g ~ ; : ' : ~ . : , . . ; , : , Disease


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82 PART II Function of

Restrictive diseases are those in which the expansion of the lung is restricted eitherbecause of alterations in the lung parenchyma or because of disease of the pleura,the chest wall, or the neuromuscular apparatus. They are characterized by areduced vital capacity and a small resting lung volume usually), but the airwayresistance related to lung volume) is not increased. These diseases are thereforedifferent from the obstructive diseases in their pure form, although mixed restric-tive and obstructive conditions can occur.

C Il SEASES OF THE LUNG PARENCHYMAThis term refers to the alveolar tissue of the lung. A brief review of the structureof this tissue is pertinent.Strudure o the lyeolar WallFigure 5-1 shows an electron micrograph of a pulmonary capillary in an alveolarwall. (25) The various structures through which oxygen passes on its way from thealveolar gas to the hemoglobin of the red blood cell are the layer of pulmonary surfactant not shown in this preparation), alveolar epithelium, interstitium, capillaryendothelium, plasma, and erythrocyte.ell Types

The various cell types have different functions and different responses to injury.Type Epithelial CellThis is the chief structural cell of the alveolar wall; its long protoplasmic extensions pave almost the whole alveolar surface (Figure 5-0. The main function ofthis cell is mechanical support. It rarely divides and is not very active metabolically. When type 1 cells are injured, they are replaced by type 2 cells, which latertransform into type 1 cells.Type 2 Epithelial CellThis is a nearly globular cell (Figure 5-2) (26) that gives little structural supportto the alveolar wall but is metabolically active. The electron micrograph showsthe lamellated bodies that contain phospholipid. This is formed in the endoplasmic reticulum, passed through the Golgi apparatus, and eventually extrudedinto the alveolar space to form surfactant. (See Respiratory Physiology: TheEssentials, 7th ed., p. 99.) After injury to the alveolar wall, these cells rapidlydivide to line the surface and then later transform into type 1 cells. A type 3 cellhas also been described, but it is rare and its function is unknown.lveQlarMacrophage

This scavenger cell roams around the alveolar wall phagocytosing foreign particlesand bacteria. The cell contains lysozymes that digest engulfed foreign matter.FibroblastThis cell synthesizes collagen and elastin, which are components of the interstitiumof the alveolar wall. After various disease insults, large amounts of these materialsmay be laid down. This results in interstitial fibrosis.


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CHAPTER 5 Restrictive Diseases 8

PL

FIGURE 5 1 Electron Micrograph of Portion of an Alveolar Wall. EP epithelium; COLcollagen; PL plasma; RBe red blood cell; EN endothelial cell; IN interstitium x 6300).(From Weibel ER. Morphological basis of alveolar-capillary gas exchange. Physio/ Rev 1973;53:419-495.nterstitium

This fills the space between the alveolar epithelium and the capillary endothelium. Figure 5-1 shows that it is thin on one side of the capillary, where it consistsonly of the fused basement membranes of the epithelial and endothelial layers.On the other side of the capillary, the interstitium is usually wider and includesfibrils of type I collagen. The thick side is chiefly concerned with fluid exchangeacross the endothelium, whereas the thin side is responsible for most of the gasexchange see Figure 6-0.


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8 PART II Function ofthe Diseasecntirig:

FIGURE 5 2 Electron Micrograph of Type 2 Epithelial Cell x 10,000). Note the lamellated bodies LB), large nucleus, and microvilli arrows), which are mainly concentratedaround the edge of the cell, and cytoplasm rich in organelles. The inset at top right is a scanning electron micrograph showing the surface view of a type 2 cell With its characteristicdistribution of microvilli x 3400). From Weibel ER Gil J Structure-function relationships atthe alveolar level. In: West JB. ed. Bioengineering Aspects of the Lung. New York: MarcelDekker, 1977.)

Interstitial tissue is found elsewhere in the lung, notably in the perivascularand peribronchial spaces around the larger blood vessels and airways and in theinterlobular septa. The interstitium of the alveolar wall is continuous with thatin the perivascular spaces (see Figure 6-1) and is the route by which fluid drainsfrom the capillaries to the lymphatics.

iffuse Interstitial Pulmonary FibrosisThe nomenclature this condition is confusing. Synonyms include idiopathicpulmonary fibrosis, interstitial pneumonia, and cryptogenic fibrosing alveolitis.Some physicians reserve the term "fibrosis" for the late stages of the disease. Thechanges in pulmonary function are described in detail because they are typical ofmany of the other conditions alluded to later in this chapter.


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'CHA >TER 5 Restrictive Diseases 8

athologyThe principal feature is thickening of the interstitium of the alveolar walLInitially there is infiltration with lymphocytes and plasma cells. Later, fibroblastsappear and lay down thick collagen bundles (Figure 5-3). (27) These changesmay be dispersed irregularly within the lung. In some patients, a cellular exudateconsisting of macrophages and other mononuclear cells is seen within the alveoliin the early stages of the disease. This is called desquamation. Eventually, thealveolar architecture is destroyed and the scarring results in multiple air-filledcystic spaces formed by dilated terminal and respiratory bronchioles, so-calledhoneycomb lung.athogenesisThis is unknown, although in some cases there is evidence of an im)TIunologic

reaction.

FIGUR 5 3 Electron Micrograph from a Patient with Diffuse Interstitial Fibrosis. Notethe thick bundles of collagen. COL collagen; ALV alveolar space; RBC red blood cell;PL plasma. Compare Figure 5-1. (From Gracey DR, Divertie MD, Brown AL, Jr Alveoiar-capillarymembrane In idiopathic interstitial pulmonary fibrosis. Electron microscopic study of 14cases. Am Rev Respir Dis 1968;98:16-21.


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8 PART II Function of t h ~

linical FeaturesThe disease is not common and tends to affect adults in late middle age. Thepatient often presents with dyspnea with rapid, shallow breathing. The dyspneatypically becomes more significant on exercise (compare Figure 3-4). An irritating, unproductive cough is often present.On examination, mild cyanosis may be seen at rest in severe cases. It typicallyworsens on exercise. Fine crepitations are usually heard throughout both lungs,especially toward the end of inspiration. Finger clubbing is common. The chestradiograph shows a reticular or reticulonodular pattern, especially at the bases.Patchy shadows near the diaphragm may be caused by basal collapse. Late in thedisease, a honeycomb appearance is often seen; this is caused by multiple airspaces surrounded by thickened tissue.Cor pulmonale or pneumonia may complicate the picture, and the patientmay develop respiratory failure terminally. The diseases often progress insidiously, although an acute form does occur, as originally described by Hamman andRich. (28)

Pulmonary FundionVentilatory apacity nd MechanicsSpirometry typically reveals a restrictive pattern (see Figure 1-2). The FYC ismarkedly reduced but the gas is exhaled rapidly so that although the FEY l is low,the FEY /FYC % may exceed the normal value. The almost square shape of theforced expiratory spirogram is in striking contrast to the obstructive pattern(compare Figure 4-15). The FEF z5- 75 is normal or high. The flow-volume curvedoes not show the scooped-out shape of obstructive disease, and the flow rate isoften higher than normal when related to absolute lung volume. This is shownin Figure 1-5, where it can be seen that the downslope of the curve for restrictivedisease lies above the normal curve.

All lung volumes are reduced, including the TLC, FRC, and RY, but therelative proportions are more or less preserved. The pressure-volume curve of thelung is flattened and displaced downward (see Figure 3-1), so that at any givenvolume, the transpulmonary pressure is abnormally high. The maximum elasticrecoil pressure that can be generated at TLC is typically higher than normaLAirway resistance is normal or low when related to lung volume.

All these results are consistent with the pathologic appearance of fibrosisof the alveolar walls (Figures 2-5 and 5-3). The fibrous tissue reduces the distensibility of the lung just as a scar on the skin reduces its extensibility. As aresult, the lung volumes are small, and abnormally large pressures are requiredto distend the lung. The airways may not be specifically involved. but theytend to narrow as lung volume is reduced. However, airway resistance at agiven lung volume is normal or even decreased because the retracti Ie forcesexerted on the airway walls by the surrounding parenchyma are abnormallyhigh (Figure 5-4). The pathologic correlate of this is the honeycomb appearance caused by the dilated terminal and respiratory bronchioles surrounded bythickened scar tissue.


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B l i I l l [ l J E i i l l i l l l i i l l l ~ i r J ~ I ~ ; ; , : ~ ' ~ C I : l , e ; p T E R 5 Restrictive Diseases 87

Normal Emphysema FibrosisFIGUR 5 4 Airway Caliber in Emphysema and Interstitial Fibrosis. In emphysema, theailWays tend to collapse because of the loss of radial traction. By contrast, in fibrosis, radialtraction may be excessive, with the result that ailWay caliber is large when related to lungvolume,

Gas xchangeThe arterial az and Peoz are typically reduced and the pH is normal. The hypoxemia is usually mild at rest until the disease is advanced. However, on exercise,the az often falls dramatically and cyanosis may be evident. In well establisheddisease, both the physiologic dead space and physiologic shunt are increased.

The relative contribution of diffusion impairment and ventilation-perfusionVA/OJ inequality to the hypoxemia of these patients has long been debated. Itis natural to argue that the histologic appearances shown in Figures 2-5 and 5-3slow the diffusion of oxygen from the alveolar gas to the capillary blood becausethe thickness of the barrier may be increased many fold compare Figure 5-l .Jnaddition, the increasing hypoxemia during exercise is consistent with the mechanism of impaired diffusion because exercise reduces the time spent by the redcell in the pulmonary capillary Figure 2-4).

However, we now know that impaired diffusion is not the chief cause of thehypoxemia in these conditions. First, the normal lung has enormous reserves ofdiffusion in that the Paz of the blood nearly reaches that in alveolar gas early inits transit through the capillary see Figure 2-4). In addition, these patients have

Features of Pulmonary Fundion in D i f ( u s , ~ h l t e j ~ t i J 1 ~ i F i b r o s i s,'Dyspnea with shallow, rapid breathing

Reductions in all lung volumesFEV/FVC ratio normal or even increased ,AilWay resistance nOf\llal or low when relatedio.lung'volumeReduced lung complianceVery negative intrapleural pressure arTLC ,Arterial hypoxemia chiefly 9l.1e to VA el i n e q u ~ j j t y Z ; ~ ,Diffusion impairment possibly contributing 'tothe:hYR0l'emiaduring exercise. . ,.', . .,.{_.,. filNormal or low artenal Pco; > I : . , . ~ " , 'Reduced diffusing capac:;ity for carbon m o n o ~ i ~ eIncreased pulmonary vascular resistance,


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PART II Function of the Diseased lung,

substantial inequality of ventilation and blood flow within the lung. How couldthey not with the disorganization of architecture shown in Figures 2-5 and 5-3?The inequalities have been demonstrated by single-breath nitrogen washoutsand measurements of topographical function with radioactive gases.

To apportion blame for the hypoxemia between the two possible mechanisms,it is necessary to measure the degree of A Q inequality and determine howmuch of the hypoxemia is attributable to this. This has been done by using themultiple inert gas elimination technique in a series of patients with interstitiallung disease. (29) Figure 5-5 shows that at rest the hypoxemia could be adequately explained by the degree of \lA Q inequality in these patients. However,Figure 5-6 shows that on exercise, the observed alveolar P02 was conSistentlybelow the value predicted from the measured amount of \lAIC . inequality, andthus an additional cause of hypoxemia must have been present. Most likely thiswas diffusion impairment in these patients. However, hypoxemia caused bydiffusion impairment was only evident on exercise, and even then it accountedfor only about one-third of the alveolar-arterial difference for Poz.

The low arterial Peo2 in these patients (typically in the middle or low 30s)occurs despite the evident \lAIC . inequality and is caused by increased ventilation to the alveoli (compare Figure 2-9). The cause of the increased ventilationis uncertain. There is some evidence that the control of ventilation is abnormalbecause of stimulation of receptors within the lung (see later text). Stimulationof the peripheral chemoreceprors by the arterial hypoxemia may also be a factor.The arterial pH is usually normal at rest but may increase considerably on exerciseas a result of the hyperventilation and consequent respiratory alkalosis (compareFigure 3-4), al though metabolic acidosis caused by lactic add accumulation mayalso occur. In terminal respiratory failure, the pH may fall.

The diffusing capacity for carbon monoxide is often strikingly reduced in thesepatients to the neighborhood of 5 ml/min per mm Hg (normal value 25-30 depending on age and stature). This may be a useful diagnostic pointer: if the diffusingcapacity is not low, the diagnosis should be regarded with suspicion. The reductionis caused in part by the thickening of the blood-gas barrier (Figure 2-5). In addition,the blood volume of the pulmonary capillaries decreases because many of the vesselsare obliterated by the fibrotic process. A further factor in the lower measured diffusing capacity is probably the V",/Q inequality, which causes uneven emptying ofthe lung. The diffusing capacity should not be taken to reflect only the properties ofthe blood-gas barrier.

xercisePatients with mild diffuse interstitial fibrosis may show much more evidence ofimpaired pulmonary function on exercise than at rest. The changes shown inFigure 3-4B are typical, although this patient had hypersensitivity pneumonitis(see later text). Note that the maximal O 2 intake and Oz output were severelylimited compared with the normal values of Figure 3-4A. The increase in ventilation on exercise was greatly exaggerated. This exaggeration was chietly causedby the high rate of breathing, which rose to over 60 breaths per minute duringma:dmal exercise.


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0 20 40 60 80 100 120Measured arterial P02 (mm Hg)

FIGUR 5-5 Study of the Mechanism of Hypoxemia in a Series of Patients withInterstitial Lung Disease. This figure shows that the arterial POL predicted from the patternof VA/a inequality agreed well with the measured arterial po). Thus at rest, all of the hypoxemia could be explained by the uneven ventilation and blood flow.

g 800'D.. 60

~ I.\l" 40u'0 20D..

0

CHAPTER 5 Restrictive Diseases 89120 I IREST I

~ 100 r _/ARegressionline

/ AInspired gas Air,'0'0


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9 P RT II Function o tHe

As a result of the high ventilation, which was out proportion to theincrease in O 2 uptake and COzoutput, the alveolar and arterial fell and thealveolar Paz rose. However, as noted earlier, the arterial fell, thus increasingthe alveolar-arterial difference for Paz. This result can be explained partly by theimpaired diffusion characteristics of the lung Figure 5-6). However, most of thehypoxemia on exercise was caused by VA/Q inequality.

One factor that tends to reduce the arterial Paz on exercise is the abnormallysmall rise in cardiac output. These patients typically have an increased pulmonary vascular resistance. This is particularly evident on exercise, during whichthe pulmonary artery pressure may rise substantially. The high resistance iscaused by obliteration of much of the pulmonary capillary bed by the interstitialfibrosis see Figure 2-5). nother factor is hypertrophy of vascular smooth muscleand consequent narrowing of the small arteries. It is important ro appreciate thatan abnormally low cardiac output in the presence of VA/Q inequality can causehypoxemia. One way of looking at this is that a low cardiac output results in alow Paz in the mixed venous blood see Chapter 9). As a consequence, a lungunit with a given VA/Q will oxygenate the blood less than when the mixedvenous Paz is normal.

The importance of this factor can be seen if we consider some results obtainedin out laboratory in a patient with interstitial lung disease. During exercise thatraised the O 2 uptake from about 300 to 700 ml/min, the arterial Paz fell from50 to 35 mm Hg. The rise in cardiac output was only from 4.6 to 5.7 L/min; thenormal value for this level of exercise is approximately 10 L/min. As a result, thePaz in the mixed venous blood fell to 17 mm normal value is approximately35 mm Hg). Calculations show that if the cardiac output had increased to10 L/min and the pattern ofVA/Q inequality remained unchanged), the arterialPaz would have been some 10 mm Hg higher.

If the diffusing capacity for carbon monoxide is measured in these patientsduring exercise, it typically remains low whereas it may double or triple in normalsubjects.onuol of VenUlaUon

We have already seen that these patients typically have shallow rapid breathing,especially on exercise. The reason for this is not certain, but it is possible that thepattern is caused by reflexes originating in pulmonary irritant receptors or J juxtacapillary) receptors. former lie in the bronchi or in the epithelial liningand may be stimulated by the increased traction on the airways caused by theincreased elastic recoil of the lung Figure 5-4). The Jreceptors are in the alveolar walls and could be stimulated by the fibrotic changes in the interstitium. Nodirect evidence of increased activity of either receptor is yet available in humans,but work in experimental animals suggests that it could cause rapid shallowbreathing.

The rapid s4allow pattern of breathing reduces the respiratory work inpatients with reduced lung compliance. However, it also increases ventilation ofthe anatomic dead space at the expense of the alveoli, so a compromise must bereached.


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I I l 1 m [ ; j r J l l l I ~ I I I I I I I I I I ~ ~ ~ ~ ~ ~ \ i J j ~ ~ I ~ ~ : ~ ~ : : f { , ~ s t r l c t l e Dise\, ses 9

Other Types o Parenchymal Restridive iseaseThe changes ih pulmonary function in diffuse interstitial pulmonary fibrosis weredealt with at some length because this disease serves as a prototype for otherforms of parenchymal restrictive disease. These diseases are now consideredbriefly h e ~ e and differences in their pattern of pulmonary function are discussed(Figure 5-7).SarcoidosisThis disease is characterized by the presence of granulomatous tissue having acharacteristic histologic appearance. It often occurs in several organs.athology

The characteristic lesion is the noncaseating epithelioid granuloma composed oflarge hist iocytes with giant cells and lymphocytes. This lesion may occur in thelymph nodes, lungs, skin, eyes, lrver, spleen, and elsewhere. In advanced pulmonary disease, fibrotic changes in the alveolJlr walls are seen.athogenesis

This is unknown, although an immunologic basis appears likely. One possibilityis that an unknown antigen is recognized by an alveolar macrophage, and thisresults in activation of a T lymphocyte and the production of interleukin-2. Theactivated macrophage may also release various products that stimulate fibroblasts, thus explaining the deposition of fibrous tissue in the interstitium.

FIGUR 5 ~ 7 Chest Radiograph of a Patient with Interstitial Pulmonary Fibro?is. Notethe small contracted lung and rib cage and: the raised diaphragms (compare the normalappearance in Figure 4-SA .


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9 PART II

linical FeaturesF ~ U : r stages of sarcoidosis can be identified. (30)

tage 0: These patients have no obvious intrathoracic involvement,although a CT scan may show enlarged mediastinal lymph nodes(lymphadenopathy) .

tage 1: There is bilateral hilar adenopathy often with right paratrachealadenopathy. This is often accompanied by erythema nodosum of the legs.Arthritis, uveitis, and parotic gland enlargement may also occur. There areno disturbances of pulmonary function.

tage 2: The pulmonary parenchyma is also involved, the most commonradiologic appearance being widespread mottled shadows, most significantin the mid and upper zones. Symptoms include breathlessness and a dry,4nproductive cough. tage 3: Here there are pulmonary infiltrates without adenopathy. Fibrosis isseen predominantly in the upper lobes, a ld cavities or bullae may be present.

Pulmonary FunctionThere is no impairment of function in stages 0 and 1 of the disease. In stages2 and 3, typical changes of the restrictive type are seen, although the radiographicappeara,nce sometimes suggests more interference with function than actually exists.

Ultimately, significant pulmonary fibrosis may develop, with a severe restrictive pattern of function. All Jung volumes are small, but the FEY/ PVC % ispreserved. Lung compliance is strikingly reduced, the pressure-volume curvebeing flattened and shifted downward and to the right (see Figure 3-1). The resting arterial POI is low and often falls considerably on exercise. The arterial OIis normal or low, although, terminally, it may rise as respiratory failure supervenes. The diffusing capacity for carbon monoxide (transfer factor) is reducedsignificantly. Cor pulmonale may develop in advanced disease.

ypersensitivity PneumonitisThis is also known as extrinsic allergic alveolitis. t is a hypersensitivity reactionaffecting the lung pa:r;enchyma that occurs in response to inhaled organic dusts.A good example is farmer's lung. The exposure is usually occupational and heavy.The disease is an example of type 3 hypersensitivity (or combination of types3 and 4), and precipitins can be demonstrated in the serum.

The term "extrinsic" implies that the etiologic agent is external and can beidentified, in contrast to "intrinsic" fibrosing alveoli tis (diffuse interstitial fibrosisdiscussed above), where the cause is unknown. Farmer's lung is due to the sporesof thermophilic Actinomyces in moldy hay. Bird breeder's lung is caused by avianantigens from feathers and excreta. Air conditioner's lung and bagassosis (in sugarcane workers) are also recognized. .PathologyThe alveolar walls are thickened and infiltrated with lymphocytes, plasma cells,and occasional eosinophils together with collections of histiocytes that, in someareas, form sma U granulomas The small bronchioles are usually affected andthere may be exudate in the lumen. Fibrotic changes occur in advanced cases.


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"'P: APTER 5 Restrictive iseases 9

Clinical FeaturesThe disease occurs in either acute or chronic forms. In the former, symptoms ofdyspnea, fever, shivering, and cough appear 4-6 hours after exposure and continuefor 24 48 hours. The patient is frequently dyspneic at rest, with fine crepitationsthroughout both lung fields. The disease may also occur in a chronic form withoutprior acute attacks. These patients present with progressive dyspnea, usually overa period of years. In the acute form, the chest radiograph may be normal, butfrequently a military nodular infiltrate is present. In the chronic form, fibrosis ofthe upper lobes is common.Pulmonary FundionIn well-developed disease, the typical restrictive pattern is seen. This includesreduced lung volumes, low compliance, hypoxemia that worsens on exercise,normal or low arterial Peoz, and a reduced diffusing capacity. In the early stages,variable degrees of airway obstruction may be present.Interstitial Disease Caused by Drugs Poisons nd RadiationVarious drugs may cause an acute pulmonary reaction, which can proceed tointerstitial fibrosis. These drugs include busulfan (used in the treatment ofchronic myeloid leukemia), the antibiotic nitrofurantoin, the cardiac antiarrhythmic agent amiodarone, and the cytostatic drug bleomycin. Other antineoplastic drugs can also cause fibrosis. Oxygen in high concentrations causes acutetoxic changes with subsequent interstitial fibrosis (see Figure 5-3). Ingestion ofthe weedkiller paraquat results in the rapid development of lethal interstitialfibrosis. Therapeutic radiation causes acute pneumonitis followed by fibrosis iflung is included in the field.Collagen DiseasesInterstitial fibrosis with a typical restrictive pattern may be found in patientswith systemic sclerosis (generalized scleroderma). Dyspnea is often severe andout of proportion to the changes in radiologic appearance or lung function.Other connective r.issue diseases that may produce fibrosis include systemic lupuserythematosus and rheumatoid arthritis.Lymphangitis CarclnomatosaThis refers to the spread of carcinoma tissue through pulmonary lymphatics and maycomplicate carcinomas, chiefly of the stomach or breast. Dyspnea is prominent, andthe typical restrictive pattern of lung function may be seen.

DISE SES f THn PLEURPneumothoraxAir can enter the pleural space either from the lung or, less commonly, throughthe chest wall as the result of a penetrating wound. The pressure in theintrapleural space is normally subatmospheric as a result of the elastic recoilforces of the lung and chest walL When air enters the space, the lung collapses


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and the rib cage springs out. (See Respiratory Physiology: he Essentials 7th ed.,p. 104.) These changes are evident on a chest radiograph (Figure 5-8), whichshows partial or complete collapse of the lung, overexpansion of the rib cage anddepression of the diaphragm on the affected side, and sometimes displacement ofmediastinum away from the pneumothorax. These changes are most evidentif the pneumothorax is large, particularly if a tension pneumothorax is present(see text).

pontaneous PneumothoraxThis most common form of pneumothorax is caused by the rupture of a small blebon the surface of the lung near the apex. t typically occurs in tall young malesand may be related to the high mechanical stresses that occur in the upper zoneof the upright lung (see Figure 3-5). The presenting symptom is often sudden painon one side accompanied by dyspnea. On auscultation, breath sounds are reducedon the affected side and the diagnosis is readily confirmed by a radiograph.

The pneumothorax gradually absorbs because the sum of the partial pressures inthe venous blood is considerably less than atmospheric pressure. Recurrent attacksmay need surgical treatment to promote adhesions between the two pleural surfaces.

FIGUR 5 8 Chest Radiograph Showing a Large Right-Sided Spontaneous Pneumothorax.Note the small, collapsed right lung, depression of the right hemidiaphragm, and overexpansionof the rib cage on the right.


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m ~ f ~ . ; ' i . I I . ~ J ~ i ~ : : : ,C8APTER 5 Restrictive Diseases 9

pontaneous PneumothoraxTypically occurs in young people in their 20sAccompanied by dyspnea, painGrad_ually absorbed by the bloodRecurrent attacks may require surgeryTension pneumothorax is a medical emerg.ency. , .

Tension PneumothoraxIn a small proportion of spontaneous pneumothoraces, the communicationbetween the lung and the pleural space functions as a check valve. As a consequence, air enters the space during inspiration but cannot escape during expiration. The result is a large pneumothorax in which the pressure may considerablyexceed atmospheric pressure and thus interfere with venous return to the thorax.This medical emergency is recognized by increasing respiratory distress, tachycardia, and signs ofmediastinal shift, such as tracheal deviation and movement ofthe apex beat. The radiograph is usually diagnostic. Treatment consists of relieving the pressure by inserting a tube through the chest walL This tube is connectedto an underwater seal that allows air to escape from the chest but not to enter it.Pneumothorax omplicating Lung iseaseThis occurs in a variety of conditions, including rupture of a bulla in OPD or acyst in advanced fibrotic disease. It also sometimes occurs during mechanical ventilation w i ~ h high airway pressures (see Chapter 10, Mechanical Ventilation ).Pulmonary FunctionAs would be expected, a pneumothorax reduces the FEV and FVC. In practice,pulmonary function tests are rarely helpful in treating these patients because theradiograph is so infortnative.Pleural ffusionThis refers to fluid rather than air in the pleural space. It is not a disease iri itsown right, but it frequently accompanies serious disease and an explanationshould always be sought.

The patient often reports dyspnea if the effusion is large and there may bepleuritic pain from the n d e ~ l y i n g disease. The chest signs are often informativeand i n l ~ d e reduced movement of the chest on the affected side, absence ofbreath sounds, and dullness to percussion. The radiograph is diagnostic.

Pleural effusions can be divided into exudates and ttansudates according towhether their protein content is high or low. In addition, the lactic dehydrogenase(LDH) concentration tends to be higher in transudates. Exudates typically occurwith malignancies and infections, whereas transudates complicate severe heartfailure and other edematous states. It is often necessary to aspirate an effusion, buttreatment should be directed at the underlying cause. Pulmonary function isimpaired as in pneumothorax, but the measurements are not required in practice.


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96 PART II Function of the Diseased lung __ , ~ ; ; ; ; ~ i ' i ~ i t l j i D " J i j ~ I .

Variants of pleural effusion include empyema (pyothorax), hemothorax, andchylothorax, which refer to the presence of pus, blood, and lymph, respectively,in the pleural space,

Pleural ThickeningOccasionally, a long-standing pleural effusion results in a rigid, contractedfibrotic pleura that splints the lung and prevents its expansion. This can resultin a severe restrictive type of functional impairment, particularly if the disease isbilateral. Surgical stripping may be necessary.

DISE SES OF TtgE CHEST W LLScoliosisBony deformity of the can cause restrictive disease. Scoliosis refers to lateralcurvature of the spine and kyphosis to posterior curvature. Scoliosis is more serious,especially if the angulation is high in the vertebral column. It is frequently associated with a backward protuberance of the ribs, giving the appearance of anadded kyphosis. In most cases, the cause is unknown, although the condition isoccasionally caused by bony tuberculosis or neuromuscular disease.

The patient initially reports dyspnea on exertion; breathing tends to be rapidand shallow. Hypoxemia later develops, and eventually carbon dioxide retentionand cor pulmonale may supervene. Bronchitis is common if the patient smokes.

Pulmonary function tests typically show a reduction in all lung volumes. Airwayresistance is nearly nonnal if related to lung volume. However, there is inequalityof ventilation, partly of airway closure in regions. Parts of thelung are compressed and there are often areas of atelectasis.

The hypoxemia is caused by ventilation-perfusion inequality. In advanceddisease, a reduced ventilatory response to CO2 can be demonstrated. Thisreduction reflects the increased work of breathing caused by deformity of thechest wall. Not only is the chest wall stiff, but also the respiratory muscles operateinefficiently. pulmonary vascular bed is restricted, causing a rise in pulmonary artery pressure, which is exaggerated by the alveolar hypoxia, Venouscongestion and peripheral edema may develop. patient may succumb to anintercurrent pulmonary infection or respiratory failure.

Ankylosing SpondylitisIn this disease unknown etiology, there is a gradual but relentless onset of immobility of the vertebral joints and fixation of the ribs. As a result, the movement ofthe chest wall is grossly reduced. There is a reduction of FVC and TLC, but theFEV /FYC percent and the airway resistance are normal. The compliance of thechest wall may fall and there is often some uneven ventilation, probably secondaryto the reduced lung volume. The lung itself remains nonnal in nearly all cases, anddiaphragmatic movement is preserved. Respiratory failure does not occur.


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CHAPTER 5 Restrictive Diseases 9

NEUROMUS(UlAR DISORDERSDiseases affecting the muscles of respiration or their nerve supply includepoliomyelitis, Guillain-Barre syndrome, amyotrophic lateral sclerosis, myastheniagravis, and muscular dystrophies (see Table 2-1 and Figure 2-3). All these diseasescan lead to dyspnea and respiratory failure. The inability of the patient t take ina deep breath is reflected in a reduced FVC, TLC, inspiratory capacity, and FEV j .

It should be remembered that the most important muscle of respiration is thediaphragm, and patients with progressive disease often do not report dyspneauntil the diaphragm is involved. By then their ventilatory reserve may beseverely compromised. The progress of the disease can be monitored by measuringthe FVC and the blood gases. The maximal inspiratory and expiratory pressures thatthe patient can develop are also reduced. Assisted ventilation (see Chapter 10,"Mechanical Ventilation") may become necessary.KEY CONCEPTS1. Diffuse interstitial pulmonary fibrosis is an example of restrictive lung disease

characterized by dyspnea, reduced exercise tolerance, small lungs, andreduced lung compliance.

2. The alveolar walls show marked infiltration with collagen and destructionof capillaries.3. Airway resistance is not increased; indeed a forced expiration can result in

abnormally high flow rates because of the increased radial traction on theairway.

4. Diffusion of oxygen across the blood-gas barrier is impeded by the thickening and may result in hypoxemia, especially on exercise. However, ventilation perfusion inequality is the major factor in the impaired gasexchange.5. Other restrictive disorders are caused by diseases of the pleura or chestwall, or neuromuscular disease.

QUESTIONS _1 The type II alveolar epithelial cell:

A. Provides most of the structural support for the normal alveolar wall.B Cannot multiply.C Is formed when a type I epithelial cell divides.D Secretes surfactant.E Is metabolically inactive.

2. Histologic changes in diffuse interstitial pulmonary fibrosis typicallyinclude:A Infiltration of the alveolar wall with lymphocytes and plasma cells.B Breakdown of many alveolar walls.C Mucous gland hypertrophy in the bronchi.D Mucous plugging of airways.E Increased volume of the pulmonary capillary bed.


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9 PART II Functipn of

3. Features of diffuse interstitial pulmonary fibrosis include:A. Cough productive of copious sputum.B. Hemoptysis.C. Rhonchi in both lungs.D. Dyspnea especially on exercise.E. Depressed diaphragms on the radiograph.

4 Pulmonary function tests in diffuse interstitial pulmonary fibrosis typically.A. Increased FEY1B. Increased FYC.C. Increased FEY\/FYC .D. Increased TLCE. Increased airway resistance when related to lung volume.

5. The arterial hypoxemia of a patient with diffuse interstitial pulmonaryfibrosis:A. Typically worsens on exercise.B. Is chiefly caused by diffusion impairment.C. Is associated with a large increase in diffusing capacity during exercise.D. Is usually associated with carbon dioxide retentionE. Is improved during exercise because of the abrormally large increase

in cardiac output.6. In a patient with diffuse interstitial fibrosis of the lung, the maximal

expiratory flow rate at a given lung volume may be higher than in anormal subject because:A. Expiratory muscles have a large mechanical advantage.B. Airways have a small diameter.C. Dynamic compression of the airways is more likely than in a normal

subject.D. Radial traction on the airways is increased.E. Airway resistance is increased.

7. The diffusing capacity for carbon monoxide in a patient with diffuseinterstitial lung disease:A. Is typically substantially increased.B. Shows an abnormally large increase during exercise.C. Is unaffected by thickening of the blood-gas barrier.D. Is reduced in part because of obliteration of pulmonary capillaries.E. Falls only late in the disease.

8. Features of pneumothorax include:A. t reduces the volume of the chest wall on the affected side.B. t causes an increased blood flow in the affected lung.C. When present in the tension form it is a medical emergency.D. Spontaneous pneumothorax is mainly seen in older women.

WestJB_Restrictivediseases_

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